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Artikelaktionen

Nanodiamonds (Diamondoids)

Diamondoids (nanometer-sized, hydrogen-terminated diamond hydrocarbons, nanodiamonds) are emerging as complementary materials to fullerenes and carbon nanotubes. In contrast to the latter, nanodiamonds are available in large quantities from crude oil, are chemically well-defined, and of high purity. Nanodiamonds are likely to share some of the unique properties of macroscopic diamond that are very attractive for a number of applications. One of the challenges with these novel building blocks is their selective and preparatively useful C–H bond functionalization. We have developed a variety of such approaches yielding numerous derivatives that can now be utilized for applications including platforms for organocatalysis and, in particular, organic molecular electronics.
Directors: Univ.-Prof Peter R. Schreiner, Prof. Andrey A. Fokin
Nanodiamonds (Diamondoids)

Current work:

 

From isolated molecules to a van-der-Waals crystal: A theoretical and experimental analysis of a trishomocubane and a diamantane dimer in the gas and in the solid phase. Functionalized Nanodiamonds, part 59. Christoph Tyborski, Reinhard Meinke, Roland Gillen, Tobias Zimmermann, Andre Knecht, Torbjörn Rander, Robert Richter, Andrea Merli, Andrey A. Fokin, Tetyana V. Koso, Vladimir N. Rodionov, Peter R. Schreiner, Thomas Möller, Christian Thomsen, and Janina Maultzsch J. Chem. Phys. 2017, 147, 044303. DOI: 10.1063/1.4994898

The electronic properties of sp2/sp3 diamondoids in the crystalline state and in the gas phase are presented. Apparent differences in electronic properties experimentally observed by resonance Raman spectroscopy in the crystalline/gas phase and absorption measurements in the gas phase isolated diamondoids to a van-der-Waals crystal.gifwere investigated by density functional theory computations. Due to a reorganization of the molecular orbitals in the crystalline phase, the HOMO (highest occupied molecular orbital) and LUMO (lowest unoccupied molecular orbital) energy gaps are lowered significantly by 0.5 eV–1 eV. The π → π∗ transition is responsible for large absorption in both gas and crystalline phases. It further causes a large increase in the Raman intensity of the C=C stretch vibration when excited resonantly. By resonance Raman spectroscopy we were able to determine the C=C bond length of the trishomocubane dimer to exhibit 1.33 Å in the ground and 1.41 Å in the excited state.

 

 

Chiral Building Blocks Based on 1,2-Disubstituted Diamantane. Functionalized Nanodiamonds, part 58. Andrey A. Fokin,* Alexander E. Pashenko, Vladyslav V. Bakhonsky, Tatyana S. Zhuk, Lesya V. Chernish, Pavel A. Gunchenko, Andrey O. Kushko, Jonathan Becker, Raffael C. Wende and Peter R. Schreiner*
Synthesis 2017, 49, 2003–2008. DOI: 10.1055/s-0036-1588694

Nanodiamonds part 58The reaction of 1-hydroxydiamantane with elemental bromine leads to consecutive cage opening and re-closure, thereby providing a straightforward approach to the class of previously unknown 1,2-disubstituted diamondoid derivatives. Functional group exchange gave, among others, chiral bidentate ligands 1,2-dihydroxy- and 1,2-diaminodiamantane. The latter was enantioseparated on gram scale with ee >98% through a single crystallization with (+)-tartaric acid.

 

 

Vertical-Substrate MPCVD Epitaxial Nano-diamond Growth. Functionalized Nanodiamonds, part 57. Yan-Kai Tzeng, Jingyuan Linda Zhang, Haiyu Lu, Hitoshi Ishiwata, Jeremy E. P. Dahl, Robert M. K. Carlson, Hao Yan, Peter R. Schreiner, Jelena Vuckovic, Zhi-Xun Shen, Nicholas A. Melosh, Steven Chu
Nano Lett. 2017, 17, 1489–1495. DOI: 10.1021/acs.nanolett.6b04543

Nanodiamonds57.gif

Color center-containing nanodiamonds have many applications in quantum technologies and biology. Diamondoids, molecular-sized diamonds have been used as seeds in chemical vapor deposition (CVD) growth. However, optimizing growth conditions to produce high crystal quality nanodiamonds with color centers requires varying growth conditions that often leads to ad-hoc and time-consuming, one-at-a-time testing of reaction conditions. In order to rapidly explore parameter space, we developed a microwave plasma CVD technique using a vertical, rather than horizontally oriented stage-substrate geometry. With this configuration, temperature, plasma density, and atomic hydrogen density vary continuously along the vertical axis of the substrate. This variation allowed rapid identification of growth parameters that yield single crystal diamonds down to 10 nm in size and 75 nm diameter optically active center silicon-vacancy (Si-V) nanoparticles. Furthermore, this method may provide a means of incorporating a wide variety of dopants in nanodiamonds without ion irradiation damage.

 

 

Hybrid metal–organic chalcogenide nanowires with electrically conductive inorganic core through diamondoid-directed assembly. Functionalized Nanodiamonds, Part 54. Hao Yan, J. Nathan Hohman, Fei Hua Li, Chunjing Jia, Diego Solis-Ibarra, Jeremy E. P. Dahl, Robert M. K. Carlson, Boryslav A. Tkachenko, Andrey A. Fokin, Peter R. Schreiner,* Yufeng Liang, Taheo Roy Kim, Thomas Devereaux, Zhi-Xun Shen,* and Nicholas A. Melosh,*
Nature Mat. 2017, 16, 349–357. DOI: 10.1038/nmat4823

Controlling inorganic structure and dimensionality through structure-directing agents is a versatile approach for new materials synthesis that has been used extensively for metal–organic frameworks and coordination polymers. However, the lack of ‘solid inorganic cores requires chargeNanodiamonds part 54 transport through single-atom chains and/or organic groups, limiting their electronic properties. Here, we report that strongly interacting diamondoid structure-directing agents guide the growth of hybrid metal–organic chalcogenide nanowires with solid inorganic cores having three-atom cross-sections, representing the smallest possible nanowires. The strong van der Waals attraction between diamondoids overcomes steric repulsion leading to a cis configuration at the active growth front, enabling face-on addition of precursors for nanowire elongation. These nanowires have band-like electronic properties, low effective carrier masses and three orders-of-magnitude conductivity modulation by hole doping. This discovery highlights a previously unexplored regime of structure-directing agents compared with traditional surfactant, block copolymer or metal–organic framework linkers.

 

 

Defying Stereotypes with Nanodiamonds: Stable Primary Diamondoid Phosphines. Functionalized Nanodiamonds, part 56. Oana Moncea, Maria A. Gunawan, Didier Poinsot, Hélène Cattey, Jonathan Becker, Raisa I. Yurchenko, Ekaterina D. Butova, Heike Hausmann, Marina Šekutor, Andrey A. Fokin,* Jean-Cyrille Hierso,* and Peter R. Schreiner*
J. Org. Chem. 2016, 81, 8759–8769. DOI: 10.1021/acs.joc.6b01219


Nanodiamonds part 56Direct unequal C–H bond difunctionalization of phosphorylated diamantane was achieved in high yield from the corresponding phosphonates. Reduction of the functionalized phosphonates provides access to novel primary and secondary alkyl/aryl diamantane phosphines. The prepared primary diamantyl phosphines are quite air stable compared to their adamantyl and especially alkyl or aryl analogues. This finding is corroborated by comparing the singly occupied molecular orbital energy levels of the corresponding phosphine radical cations obtained by density functional theory computations.

 

 

Peptide-Functionalized Sn/S Clusters. Niklas Rinn, Jan-Philipp Berndt, Annikka Kreher, Natalie Brüll, Radim Hrdina, Matthias Reinmuth, Peter R. Schreiner and Stefanie Dehnen*
Organometallics 2016, 35, 3215–3220. DOI: 10.1021/acs.organomet.6b00561


Abstract Image

 

We report the first successful attachment of peptides to tin sulfide clusters. For proof of principle, H-l-Phe hydrazide and Boc-protected dipeptide hydrazides (Boc-l-Ala-l-Ala hydrazide and Boc-l-Val-l-Phe hydrazide) were reacted with keto-functionalized tin sulfide clusters [(R1Sn)4S6] (A; R1 = CMe2CH2C(O)Me) and [(R1Sn)3S4Cl] (B). In the first case, we obtained single crystals of an amino acid functionalized Sn/S cluster, [R22Sn4S5] (1; R2 = (CMe2CH2C(Me)N2C(O)CH(CH2Ph)NC(Me)CH2CMe2), formed after inorganic cluster rearrangement and intramolecular condensation of the amino acid ligand. By means of NMR spectroscopic investigations and ESI/LIFDI mass spectrometry, we demonstrate that both dipeptides are attached to B under retention of the original cluster architecture to yield [(R3Sn)3S4Cl] (2; R3 = CMe2CH2C(NNH-Ala-Ala-Boc)Me) and [(R4Sn)3S4Cl] (3; R4 = CMe2CH2C(NNH-Phe-Val-Boc)Me), as evident from mass spectrometric data of their cations [(R3Sn)3S4]+ (2+) and [(R4Sn)3S4]+ (3+).

 

 

[2](1,3)Adamantano[2]-(2,7)pyrenophane, a Hydrocarbon with a Large Dipole Moment. Functionalized Nanodiamonds, part 55. Paul Kahl, Jan P. Wagner, Ciro Balestrieri, Jonathan Becker, Heike Hausmann, Graham J. Bodwell and Peter R. Schreiner
Angew. Chem. Int. Ed. 2016, 55, 9277-9281. DOI: 10.1002/anie.201602201

The fusion of the sp3-hybridized parent diamondoid adamantane with the sp2-hybridized pyrene results in a hybrid structure with a very large dipole moment which arises from bending the pyrene moiety. Presented herein is the synthesis, study of the electronic and optical properties, as well as the dynamic behavior of this new hydrocarbon.

 

 

Hybrid group IV nanophotonic structures incorporating diamond silicon-vacancy color centers. Functionalized Nanodiamonds, part 52.
Jingyuan Linda Zhang, Hitoshi Ishiwata, Thomas M. Babinec, Marina Radulaski, Kai Müller, Konstantinos G. Lagoudakis, Jeremy E. P. Dahl, Robert Edgington, Veronique Souliére, Gabriel Ferro, Andrey A. Fokin, Peter R. Schreiner, Zhi-Xun Shen, Nick Melosh and Jelena Vukovic
Nano Lett. 2016, 15, 212–217. DOI: 10.1021/acs.nanolett.5b03515

Functionalized Nanodiamonds Part 52We demonstrate a new approach for engineering group IV semiconductor-based quantum photonic structures containing negatively charged silicon-vacancy (SiV) color centers in diamond as quantum emitters. Hybrid diamond-SiC structures are realized by combining the growth of nano- and microdiamonds on silicon carbide (3C or 4H polytype) substrates, with the subsequent use of these diamond crystals as a hard mask for pattern transfer. SiV color centers are incorporated in diamond during its synthesis from molecular diamond seeds (diamondoids), with no need for ion-implantation or annealing. We show that the same growth technique can be used to grow a diamond layer controllably doped with SiV on top of a high purity bulk diamond, in which we subsequently fabricate nanopillar arrays containing high quality SiV centers. Scanning confocal photoluminescence measurements reveal optically active SiV lines both at room temperature and low temperature (5 K) from all fabricated structures, and, in particular, very narrow line widths and small inhomogeneous broadening of SiV lines from all-diamond nanopillar arrays, which is a critical requirement for quantum computation. At low temperatures (5 K) we observe in these structures the signature typical of SiV centers in bulk diamond, consistent with a double lambda. These results indicate that high quality color centers can be incorporated into nanophotonic structures synthetically with properties equivalent to those in bulk diamond, thereby opening opportunities for applications in classical and quantum information processing.



Ultralow effective work function surfaces using diamondoid monolayers. Functionalized Nanodiamonds, part 51.
Karthik T. Narasimha, Chenhao Ge, Jason D. Fabbri, William Clay, Boryslav A. Tkachenko, Andrey A. Fokin, Peter R. Schreiner, Jeremy E. Dahl, Robert M. K. Carlson, Z. X. Shen, Nicholas A. Melosh
Nature Nanotech. 2016, 11, 267–272. DOI: 10.1038/nnano.2015.277

Electron emission is critical for a host of modern fabrication and analysis applications including mass Functionalized Nanodiamonds Part 51spectrometry, electron imaging and nanopatterning. Here, we report that monolayers of diamondoids effectively confer dramatically enhanced field emission properties to metal surfaces. We attribute the improved emission to a significant reduction of the work function rather than a geometric enhancement. This effect depends on the particular diamondoid isomer, with [121]tetramantane-2-thiol reducing gold's work function from ∼5.1 eV to 1.60 ± 0.3 eV, corresponding to an increase in current by a factor of over 13,000. This reduction in work function is the largest reported for any organic species and also the largest for any air-stable compound1, 2, 3. This effect was not observed for sp3-hybridized alkanes, nor for smaller diamondoid molecules. The magnitude of the enhancement, molecule specificity and elimination of gold metal rearrangement precludes geometric factors as the dominant contribution. Instead, we attribute this effect to the stable radical cation of diamondoids. Our computed enhancement due to a positively charged radical cation was in agreement with the measured work functions to within ±0.3 eV, suggesting a new paradigm for low-work-function coatings based on the design of nanoparticles with stable radical cations.

 

 

Template Synthesis of Linear Chain Nanodiamonds Inside Carbon Nanotubes from Bridgehead-Halogenated Diamantane Precursors. Funtionalized Nanodiamonds, part 50.
Yusuke Nakanishi, Haruka Omachi, Natalie A. Fokina, Ryo Kitaura, Peter R. Schreiner, Jeremy E. P. Dahl, Robert M. K. Carlson, and Hisanori Shinohara
Angew. Chem. Int. Ed. 2015, 54, 10802–10806. DOI: 10.1002/anie.201504904
Highlights: a) Noted as hot paper (top 10% of all Angewandte publications); b) Nanodiamonds lined up in ChemistryViews, September 02, 2015; c) Auffädelung von Nanodiamanten auf chemie.de, September 03, 2015

Linear Chain Nanodiamonds

A simple method for the synthesis of linear-chain diamond-like nanomaterials, so-called diamantane polymers, is described. This synthetic approach is primarily based on a template reaction of dihalogen-substituted diamantane precursors in the hollow cavities of carbon nanotubes. Under high vacuum and in the presence of Fe nanocatalyst particles, the dehalogenated radical intermediates spontaneously form linear polymer chains within the carbon nanotubes. Transmission electron microscopy reveals the formation of well-aligned linear polymers. We expect that the present template-based approach will enable the synthesis of a diverse range of linear-chain polymers by choosing various precursor molecules. The present technique may offer a new strategy for the design and synthesis of one-dimensional nanomaterials.

 

 

Transition metal complexes with cage-opened diamondoidtetracyclo[7.3.1.14,14.02,7]tetra-deca-6,11-diene. Functionalized Nanodiamonds, part 49.
Lars Valentin, Anja Henss, Boryslav A. Tkachenko, Andrey A. Fokin, Peter R. Schreiner, Sabine Becker, Christian Würtele, and Siegfried Schindler
J. Coord. Chem. 2015, 68, 3295–3301. DOI: 10.1080/00958972.2015.1071802

 

Cage-opened diamondoid tetracyclo[7.3.1.14,12.02,7]tetradeca-6,11-diene forms complexes with AgNO3 and CuCl. The latter crystallized from acetonitrile in polymeric form [Cu2Cl2(CH3CN)(diene)]n; in the presence of 2,2′-bipyridine, a double-charged monomeric Cu(I)-complex [Cu2(bipy)2(diene)]2+ formed. Both complexes were structurally characterized through X-ray crystal diffraction analysis.
Copper(I) complexes with the diamantane diene tetracyclo[7.3.1.14,12.02,7]tetradeca-6.11-diene (6) have been prepared and an interesting crystal structure, [Cu2(bipy)2(6)]2+ (hydrogen atoms, anions, and solvent molecules are omitted for clarity), was obtained.

Transition metal complexes

 

 

Inverted Carbon Geometries: Challenges to Experiment and Theory.

Matthias Bremer, Harald Untenecker, Pavel A. Gunchenko, Andrey A. Fokin, and Peter R. Schreiner
J. Org. Chem. 2015, 80, 6520–6524. DOI: 10.1021/acs.joc.5b00845
Highlights: a) Clare Tovee, Cambridge Structural Database (CCDC), June 18, 2015; b) Steven Bachrach, Computational Organic Chemistry, July 6, 2016.

Inverted Carbon Geometries.gif

Disproving a long C–C-bond textbook example: The reported 1.643 Å C–C bond in 5-cyano-1,3-dehydroadamantane was redetermined and “only” amounts to 1.584 Å. While this value is well reproduced with ab initio methods, some common DFT approaches perform poorly and are only consistent with CCSD(T)/cc-pVTZ optimizations for noninverted carbons. Large deviations from experiment were also found for other molecules with atypical electron density distributions, e.g., cubane, bicyclo[2.2.0]hexane, and bicyclo[2.1.0]- and bicyclo[1.1.1]pentane, thereby presenting challenging structures for some DFT implementations.

 

 

Toward an Understanding of Diamond sp2-Defects with Unsaturated Diamondoid Oligomer Models. Tatyana S. Zhuk, Tatyana Koso, Alexander E. Pashenko, Ngo Trung Hoc, Vladimir N. Rodionov, Michael Serafin, Peter R. Schreiner and Andrey A Fokin

J. Am. Chem. Soc. 2015, 137, 6577–6586. DOI: 10.1021/jacs.5b01555

Diamond sp2-Defects

Nanometer-sized doubly bonded diamondoid dimers and trimers, which may be viewed as models of diamond with surface sp2-defects, were prepared from corresponding ketones via a McMurry coupling and were characterized by spectroscopic and crystallographic methods. The neutral hydrocarbons and their radical cations were studied utilizing density functional theory (DFT) and ab initio (MP2) methods, which reproduce the experimental geometries and ionization potentials well. The van der Waals complexes of the oligomers with their radical cations that are models for the self-assembly of diamondoids, form highly delocalized and symmetric electron-deficient structures. This implies a rather high degree of σ-delocalization within the hydrocarbons, not too dissimilar to delocalized π-systems. As a consequence, sp2-defects are thus also expected to be nonlocal, thereby leading to the observed high surface charge mobilities of diamond-like materials. In order to be able to use the diamondoid oligomers for subsequent surface attachment and modification, their C—H-bond functionalizations were studied, and these provided halogen and hydroxy derivatives with conservation of unsaturation.

 

 

The functionalization of nanodiamonds (diamondoids) as a key parameter of their easily controlled self-assembly in micro- and nanocrystals from the vapor phase. Functionalized Nanodiamonds, part 43. Maria A. Gunawan, Didier Poinsot, Bruno Domenichini, Sébastien Chevalier, Céline Dirand, Andrey A. Fokin, Peter R. Schreiner, and Jean-Cyrille Hierso
Nanoscale
2015, 7, 1956-1962. DOI: 10.1039/C4NR04442H. Open Access.

Self-Assembly in Micro- and Nanocrystals

We detail herein readily accessible processes to control previously unobserved robust self-assemblies of nanodiamonds (diamondoids) in micro- and nanocrystals from their mild vapor deposition. The chemical functionalization of uniform and discernible nanodiamonds was found to be a key parameter, and depending on the type of functional group (hydroxy, fluorine, etc.) and its position on the diamondoid, the structure of the discrete deposits can vary dramatically. Thus, well-defined anisotropic structures such as rod, needle, triangle or truncated octahedron shapes can be obtained, and self-assembled edifices of sizes ranging from 20 nm to several hundred micrometers formed with conservation of a similar structure for a given diamondoid. Key thermodynamic data including sublimation enthalpy of diamondoid derivatives are reported, and the SEM of the self-assemblies coupled with EDX analyses and XRD attest the nature and purity of nanodiamond crystal deposits. This attractive method is simple and outperforms in terms of deposit quality dip-coating methods we used. This vapor phase deposition approach is expected to allow for an easy formation of diamondoid nanoobjects on different types of substrates.

 

 

Beyond the Corey Reaction II: Dimethylenation of Sterically Congested Ketones. Anastasiya V. Barabash, Ekaterina D. Butova, Igor M. Kanyuk, Peter R. Schreiner, and Andrey A. Fokin
J. Org. Chem.
2014, 79, 10669–10673. DOI: 10.1021/jo502021x
Highlight:
selected as “Editor’s choice” and made open access by the journal. Listed as one of the five most accessed JOC articles in 2014.

Dimethylenation of Sterically Congested Ketones

Bulky methyl ketones show significantly decreased reactivities toward the Corey-Chaykovsky methylenation reagent dimethylsulfoxonium methylide (DMSM). The excess of base and temperature increase opens an alternative reaction channel that instead leads to the corresponding cyclopropyl ketones. Computations suggest that the initial reaction step involves the methylene group transfer from DMSM on the ketone enolate followed by the intramolecular cyclization. The key step is associated with a barrier of 22 ± 3 kcal mol–1 and is driven by exothermic elimination of DMSO.

 

 

Unconventional Molecule-Resolved Current Rectification in Diamondoid-Fullerene Hybrids. Functionalized Nanodiamonds, part 44. Jason C. Randel, Francis C. Niestemski, Andrés R. Botello-Mendez, Warren Mar, Georges Ndabashimiye, Sorin Melinte, Jeremy E. P. Dahl, Robert M. K. Carlson, Ekaterina D. Butova, Andrey A. Fokin, Peter R. Schreiner, Jean-Christophe Charlier, and Hari C. Manoharan 
Nature Commun. 2014, 5, #4877. DOI: 10.1038/ncomms5877.
Highlights:


The unimolecular rectifier is a fundamental building block of molecular electronics. Rectification in single molecules can arise from electron transfer between molecular orbitals displaying asymmetric spatial charge distributions, akin to p–n junction diodes in semiconductors. Here we report a novel all-hydrocarbon molecular rectifier consisting of a diamantane–C60 conjugate. By linking both sp3 (diamondoid) and sp2 (fullerene) carbon allotropes, this hybrid molecule opposingly pairs negative and positive electron affinities. The single-molecule conductances of self-assembled domains on Au(111), probed by low-temperature scanning tunnelling microscopy and spectroscopy, reveal a large rectifying response of the molecular constructs. This specific electronic behaviour is postulated to originate from the electrostatic repulsion of diamantane–C60 molecules due to positively charged terminal hydrogen atoms on the diamondoid interacting with the top electrode (scanning tip) at various bias voltages. Density functional theory computations scrutinize the electronic and vibrational spectroscopic fingerprints of this unique molecular structure and corroborate the unconventional rectification mechanism.


Selective Preparation of Diamondoid Phosphonates. Functionalized Nanodiamonds, part 44. Andrey A. Fokin, Raisa I. Yurchenko, Boryslav A. Tkachenko, Natalie A. Fokina, Maria A. Gunawan, Didier Poinsot, Jeremy E. P. Dahl, Robert M. K. Carlson, Michael Serafin, Hélène Cattey, Jean-Cyrille Hierso, and Peter R. Schreiner
J. Org. Chem. 2014, 79, 5369–5373. DOI: 10.1021/jo500793m

Selective Preparation of Diamondoid Phosphonates
We present an effective sequence for the preparation of phosphonic acid derivatives of the diamondoids diamantane, triamantane, [121]tetramantane, and [1(2,3)4]pentamantane. The reactions of the corresponding diamondoid hydroxy derivatives with PCl3 in sulfuric or trifluoroacetic acid give mono- as well as didichlorophosphorylated diamondoids in high preparative yields.


Synthesis of Substituted Adamantylzing Reagents Using a Br/Mg-Insertion in the Presence of ZnCl2 and their Subsequent Functionalization. Christoph Sämann, Vasudevan Dhayalan, Peter R. Schreiner, and Paul Knochel*

Org. Lett. 2014, 136, in press. DOI: 10.1021/ol500781j.

Synthesis of Substituted Adamantylzinc Reagents Using a Mg-Insertion in the Presence of ZnCl2 and Further Functionalizations

The LiCl-mediated Mg-insertion in the presence of ZnCl2 allows an efficient synthesis of adamantylzinc reagents starting from the corresponding functionalized tertiary bromides. The highly reactive adamantylzinc species readily undergo a broad variety of functionalizations such as Negishi cross-couplings, Cu(I)-catalyzed acylations and allylations, and 1,4-addition reactions leading to the expected products in excellent yields. Furthermore, the adamantyl moiety could be introduced as α-substituent in terthiophene, increasing its solubility due to the higher lipophilicity and the prevention of π-stacking.

 

Diamondoid hydrozones and hydrazides: sterically demanding ligands for Sn/S cluster design. Functionalized Nanodiamonds, part 42. Beatrix E. K. Barth, Boryslav A. Tkachenko, Jens P. Eußner, Peter R. Schreiner, and Stefanie Dehnen*

Organometallics 2014, 33, 1678–1688. DOI: 10.1021/om500014z.

Diamondoid Hydrazones and Hydrazides

A series of new adamantane and diamantane hydrazides was synthesized and coupled with organo-functionalized Sn/S clusters of the general type [R1Sn4S6] (R1 = CMe2CH2COMe) to form diamondoid-decorated Sn/S clusters. The new ligand precursors as well as the resulting hybrid compounds were analyzed by NMR spectroscopy, mass spectrometry, and single-crystal X-ray diffraction, and first insights were gained in the installation of sterically highly demanding and at the same time rigid mono-, di-, and trifunctionalized diamondoid ligands on tetrelchalcogenide cages.



Functionalization of Homodiamantane: Oxygen Insertion Reactions Without Rearrangement with Dimethyldioxirane. Functionalized Nanodiamonds, part 42. Andrey A. Fokin,* Tanya S. Zhuk, Alexander E. Pashenko, Valeriy V. Osipov, Pavel A. Gunchenko, Michael Serafin, Peter R. Schreiner,*

J. Org. Chem. 2014, 79, 1861–1866. DOI: 10.1021/jo4026594

Functionalization of Homodiamantane: Oxygen Insertion Reactions Without Rearrangement with Dimethyldioxirane. Functionalized Nanodiamonds, part 42.

Homodiamantane bromination and nitroxylation are accompanied by contraction of the seven-membered ring to give the corresponding substituted 1-diamantylmethyl derivatives. In contrast, CH-bond hydroxylations with dimethyldioxirane retain the cage and give both apically and medially substituted homodiamantanes. The product ratios are in accord with the barriers for the oxygen insertion computed with density functional theory methods only if solvation is included through a polarizable continuum model. B3LYP-D3 and M06-2X computations with a 6-31G(d,p) basis set on the oligomeric van der Waals complexes predict the potential of homodiamantane derivatives for surface modifications with conformationally slightly flexible diamondoid homologues.

 

UV resonance Raman analysis of trishomocubane and diamondoid dimers. Functionalized Nanodiamonds, part 38. Reinhard Meinke, Robert Richter, Andrea Merli, Andrey A. Fokin, Tetyana V. Koso, Vladimir N. Rodionov, Peter R. Schreiner, Christian Thomsen, Janina Maultzsch J. Chem. Phys. 2014, 140, 034309-1–5. DOI: 10.1063/1.4861758

We present resonance Raman measurements of crystalline trishomocubane and diamantane dimers containing a C=C double bond. Raman spectra were recorded with excitation energies between 2.33 eV and 5.42 eV. The strongest enhancement is observed for the C=C stretch vibration and a bending mode involving the two carbon atoms of the C=C bond, corresponding to the B wagging mode of ethylene. This is associated with the localization of the π-HOMO and LUMO and the elongation of the C=C bond length and a pyramidalization of the two 2-hybridized carbon atoms at the optical excitation. The observed Raman resonance energies of the trishomocubane and diamantane dimers are significantly lower than the HOMO-LUMO gaps of the corresponding unmodified diamondoids.

 

Efficient preparation of apically substituted diamondoid derivatives. Functionalized Nanodiamonds, part 39. Paul Kahl, Boryslav A. Tkachenko, Anatoliy A. Novikovsky, Jonathan Becker, Jeremy E. P. Dahl, Robert M. K. Carlson, Andrey A. Fokin,* and Peter R. Schreiner* Synthesis 2014, 46,787–798; DOI: 10.1055/s-0033-1338583

Efficient preparation of apically substituted diamondoid derivatives. Functionalized Nanodiamonds, part 39

We present an effective three-step chromatography-free sequence for the preparation of apical monohydroxy derivatives of diamantane, triamantane, and [121]tetramantane from the corresponding bis-apical diols utilizing tert-butyldimethylsilyl chloride as the monosilylating agent. The procedure was successfully applied to the monoprotection of several other aliphatic and aromatic diols. Additionally, 9-aminodiamantan-4-carboxylic acid, which has significant potential in medicinal and material sciences, was prepared through Ritter reaction of 4,9-dihydroxydiamantane in trifluoroacetic acid.


Diamondoids: Functionalization and subsequent applications of perfectly defined molecular cage hydrocarbons. Functionalized Nanodiamonds, part 41. Maria A. Gunawan, Jean-Cyrille Hierso,* Didier Poinsot, Andrey A. Fokin, Natalie A. Fokina, Boryslav A. Tkachenko, and Peter R. Schreiner,* New. J. Chem. 2014, 38, 28–41. DOI: 10.1039/c3nj00535f.

Diamondoids: functionalization andThe term “diamondoid” describes cage hydrocarbon molecules that are superimposable on the diamond lattice. Diamondoids that are formally built by face-fusing of adamantane units, namely diamantane, triamantane, tetramantane, etc., have fascinated chemists since the beginning of the last century. The functionalization of these perfectly defined (C,H)-molecules is described here. Thus, diamondoid halides and diamondoid alcohols are first rank precursors for amino and phosphine-substituted diamondoids that have proved to be highly useful in therapeutic applications and metal catalysis, respectively. The extent of functionalization and polyfunctionalization achieved for adamantane and diamantane, and the synthesis and applications of the resulting organohybrids are illustrated, revealing their high potential in fields such as organocatalysis, polymers, molecular electronics and mechanics.


Covalent Attachment of Diamondoid Phosphonic Dichlorides to Tungsten Oxide Surfaces. Functionalized Nanodiamonds, part 40. Fei Hua Li, Jason D. Fabbri, Raisa I. Yurchenko, Alexander N. Mileshkin, James N. Hohmann, Hao Yan, Honyuan Yuan, Ich C. Tran, Trevor Willey, Michael Bagge-Hansen, Jeremy E. P. Dahl, Robert M. K. Carlson, Andrey A. Fokin, Peter R. Schreiner, Zhi-Xun Shen, Nicholas A. Melosh* Langmuir 2013, 29, 9790–9797. DOI: 10.1021/la401781e

Covalent Attachment of DiamondoidDiamondoids (nanometer-sized diamond-like hydrocarbons) are a novel class of carbon nanomaterials that exhibit negative electron affinity (NEA) and strong electron–phonon scattering. Surface-bound diamondoid monolayers exhibit monochromatic photoemission, a unique property that makes them ideal electron sources for electron-beam lithography and high-resolution electron microscopy. However, these applications are limited by the stability of the chemical bonding of diamondoids on surfaces. Here we demonstrate the stable covalent attachment of diamantane phosphonic dichloride on tungsten/tungsten oxide surfaces. X-ray photoelectron spectroscopy (XPS) and Fourier-transform infrared (FTIR) spectroscopy revealed that diamondoid-functionalized tungsten oxide films were stable up to 300–350 °C, a substantial improvement over conventional diamondoid thiolate monolayers on gold, which dissociate at 100–200 °C. Extreme ultraviolet (EUV) light stimulated photoemission from these diamondoid phosphonate monolayers exhibited a characteristic monochromatic NEA peak with 0.2 eV full width at half-maximum (fwhm) at room temperature, showing that the unique monochromatization property of diamondoids remained intact after attachment. Our results demonstrate that phosphonic dichloride functionality is a promising approach for forming stable diamondoid monolayers for elevated temperature and high-current applications such as electron emission and coatings in micro/nano electromechanical systems (MEMS/NEMS).


Exploring covalently bound diamondoid particles with valence photoelectron spectroscopy. Functionalized Nanodiamonds, part 37. Tobias Zimmermann, Robert Richter, Andre Knecht, Andrey A. Fokin, Tetyana V. Koso, Lesya V. Chernish, Pavel A. Gunchenko, Peter R. Schreiner, Thomas Möller, and Torbjörn Rander

J. Chem. Phys. 2013, 139, 084310-084316. DOI: 10.1063/1.4818994

We investigated the valence electronic structure of diamondoid particles in the gas phase, utilizing valence photoelectron spectroscopy. The samples were singly or doubly covalently bonded dimers or trimers of the lower diamondoids. Both the bond type and the combination of bonding partners are shown to affect the overall electronic structure. For singly bonded particles, we observe a small impact of the bond on the electronic structure, whereas for doubly bonded particles, the connecting bond determines the electronic structure of the highest occupied orbitals. In the singly bonded particles a superposition of the bonding partner orbitals determines the overall electronic structure. The experimental findings are supported by density functional theory computations at the M06-2X/cc-pVDZ level of theory.


The Lipophilic Bullet Hits the Targets: Medicinal Chemistry of Adamantane Derivatives. Functionalized Nanodiamonds, part 27. Lukas Wanka, Khalid Iqbal, and Peter R. Schreiner* Chem. Rev. 2013, 113, 3516–3604. DOI: 10.1021/cr100264t.

Listed as one of the 10 most accessed articles 03/2013.

The Lipophilic Bullet


Evidence of Diamond Nanowires Formed inside Carbon Nanotubes from Diamantane Dicarboxylic Acid. Jinying Zhang, Zhen Zhu, Yanquan Feng, Hitoshi Ishiwata, Yasumitsu Miyata, Ryo Kitaura, Jeremy E. P. Dahl, Robert M. K. Carlson, Natalie A. Fokina, Peter R. Schreiner, David Tomanek, Hisanori Shinohara Angew. Chem. Int. Ed.  2013, 52, 3717–3721. Angew. Chem. 2013, 125, 3805–3809. DOI: 10.1002/anie.201209192. Designated as a “Hot paper”;

Highlights: a) Inside cover of this issue; b) Phys.org, March 6, 2013. c) Chemie.de, March 2013. d) Innovations Report, March 6, 2013. d) TechniScience, March 2013. e) e! Science News, March 6, 2013.

f) GIT Laboratory Journal, March 2013.

Evidence of Diamond NanowiresCarbon is a girl′s best friend: Carbon-based nanowires have been produced during thermal annealing of diamantane-4,9-dicarboxylic acid in carbon nanotubes under hydrogen atmosphere (see scheme). HR-TEM images, Raman spectra, and structural transformations observed under an intense electron beam suggest that the as-produced carbon-based nanowires are sp3 diamond nanowires, consistent with our computational results.

 

 

 

 

Preparative Synthesis of Vinyl Diamondoids. Functionalized Nanodiamonds, part 36. Andrey A. Fokin,* Ekaterina D. Butova, Anastasiya V. Barabash, Nhan N. Huu, Boryslav A. Tkachenko, and Peter R. Schreiner* Synth. Commun. 2013, 43, 1772–1777.

We describe a convenient four-step preparation of 1- vinyl adamantane, 1- vinyl diamantane, and 4,9-divinyl diamantane from the respective diamondoid acetic acids in 50–80% isolated yields involving esterification, reduction, and hydrobromination/dehydrobromination.
Supplemental materials are available for this article. Go to the publisher's online edition of Synthetic Communications® to view the free supplemental file.

Preparative Synthesis of Vinyl Diamondoids


Electronic structure tuning of diamondoids through functionalization. Torbjörn Rander, Matthias Staiger, Robert Richter, Tobias Zimmermann, Lasse Landt, David Wolter, Jeremy E. P. Dahl, Robert M. K. Carlson, Boryslav A. Tkachenko, Natalie A. Fokina, Peter R. Schreiner, Thomas Möller, and Christoph Bostedt J. Chem. Phys. 2013, 135, 024310 (1–7).

We investigated the changes in electronic structures induced by chemical functionalization of the five smallest diamondoids using valence photoelectron spectroscopy. Through the variation of three parameters, namely functional group (thiol, hydroxy, and amino), host cluster size (adamantane, diamantane, triamantane, [121]tetramantane, and [1(2,3)4]pentamantane), and functionalization site (apical and medial) we are able to determine to what degree these affect the electronic structures of the overall systems. We show that unlike, for example, in the case of halobenzenes, the ionization potential does not show a linear dependence on the electronegativity of the functional group. Instead, a linear correlation exists between the HOMO-1 ionization potential and the functional group electronegativity. This is due to localization of the HOMO on the functional group and the HOMO-1 on the diamondoid cage. Density functional theory supports our interpretations.

 

Photocathode Device using Diamondoid and Cesium Bromide Films. William A. Clay, Juan R. Maldonado, Piero Pianetta, Jeremy E. P. Dahl, Robert M. K. Carlson, Peter R. Schreiner, Andrey A. Fokin, Boryslav A. Tkachenko, Nicolas A. Melosh, Zhi-Xun Shen,

Appl. Phys. Lett. 2012, 101, 241605/1–5. DOI: 10.1063/1.4769043.

A photocathode structure is presented that shows promise for use in high brightness electron sources. The structure consists of a metal substrate, a monolayer of a diamondoid derivative, and a thin film of cesium bromide. Diamondoid monolayers reduce the energy spread of electron emitters, while cesium bromide increases the yield and stability of cathodes. We demonstrate that the combined structure retains these properties, producing an emitter with lower energy spread than the corresponding cesium bromide emitter (1.06 eV versus 1.45 eV) and higher yield and stability than un-coated diamondoid emitters.

 

Diamondoid coating enables disruptive approach for chemical and magnetic imaging with 10 nm spatial resolution. Hitoshi Ishiwata, Yves Acremann, Andreas Scholl, Olav Hellwig, Elisabeth Dobisz, Andrew Doran, Boryslav A. Tkachenko, Andrey A. Fokin, Peter R. Schreiner, Jeremy E. P. Dahl, Robert M. K. Carlson, Nicolas A. Melosh, Zhi-Xun Shen, Hendrik Ohldag Appl. Phys. Lett. 2012, 101, 163101. DOI: 10.1063/1.4756893.

Diamondoids are unique molecular nano-materials with diamond structure and fascinating properties such as negative electron affinity and short electron mean free paths. A thin layer of diamondoids deposited on a cathode is able to act as an electron monochromator, reducing the energy spread of photo-emitted electrons from a surface. This property can be applied effectively to improve the spatial resolution in x-ray photoemission electron microscopy (X-PEEM), which is limited by chromatic aberration of the electron optics. In this paper, we present X-PEEM measurements reaching the technological relevant spatial resolution of 10 nm without the need of expensive and complex corrective optics. Our results provide a simple approach to image surface chemical and magnetic information at nanometer scales by employing diamondoids.

 

Stable Alkanes Containing Very Long Carbon-Carbon Bonds. Andrey A. Fokin, Lesya V. Chernish, Pavel A. Gunchenko, Evgeniya Yu. Tikhonchuk, Heike Hausmann, Michael Serafin, Jeremy E. P. Dahl, Robert M. K. Carlson, and Peter R. Schreiner

J. Am. Chem. Soc. 2012, 134, 13641–13650. DOI: 10.1021/ja302258q.

Stable Alkanes Containing Very Long Carbon-Carbon BondsThe metal-induced coupling of tertiary diamondoid bromides gave highly sterically congested hydrocarbon (hetero)dimers with exceptionally long central C–C bonds of up to 1.71 Å in 2-(1-diamantyl)[121]tetramantane. Yet, these dimers are thermally very stable even at temperatures above 200 °C, which is not in line with common C–C bond length versus bond strengths correlations. We suggest that the extraordinary stabilization arises from numerous intramolecular van der Waals attractions between the neighboring H-terminated diamond-like surfaces. The C–C bond rotational dynamics of 1-(1-adamantyl)diamantane, 1-(1-diamantyl)diamantane, 2-(1-adamantyl)triamantane, 2-(1-diamantyl)triamantane, and 2-(1-diamantyl)[121]tetramantane were studied through variable-temperature 1H- and 13C NMR spectroscopies. The shapes of the inward (endo) CH surfaces determine the dynamic behavior, changing the central C–C bond rotation barriers from 7 to 33 kcal mol–1. We probe the ability of popular density functional theory (DFT) approaches (including BLYP, B3LYP, B98, B3LYP-Dn, B97D, B3PW91, BHandHLYP, B3P86, PBE1PBE, wB97XD, and M06-2X) with 6-31G(d,p) and cc-pVDZ basis sets to describe such an unusual bonding situation. Only functionals accounting for dispersion are able to reproduce the experimental geometries, while most DFT functionals are able to reproduce the experimental rotational barriers due to error cancellations. Computations on larger diamondoids reveal that the interplay between the shapes and the sizes of the CH surfaces may even allow the preparation of open-shell alkyl radical dimers (and possibly polymers) that are strongly held together exclusively by dispersion forces.

 

Nanodiamonds in Sugar Rings: An Experimental and Theoretical Investigation of Cyclodextrin-Nanodiamond Inclusion Complexes. Functionalized Nanodiamonds, part 31. Jens Voskuhl, Mark Waller, Sateesh Bandaru, Boryslav A. Tkachenko, Carlo Fregonese, Birgit Wibbeling, Peter R. Schreiner,* and Bart Jan Ravoo*

Org. Biomol. Chem. 2012, 10, 4524–4530. Highlight: Inside cover of this issue.

Nanodiamonds in sugar ringsWe report on the noncovalent interactions of nanodiamond carboxylic acids derived from adamantane, diamantane, and triamantane with β- and γ-cyclodextrins. The water solubility of the nanodiamonds was increased by attaching an aromatic dicarboxylic acid via peptide coupling. Isothermal titration calorimetry experiments were performed to determine the thermodynamic parameters (Ka, ΔH, ΔG and ΔS) for the host–guest inclusion. The stoichiometry of the complexes is invariably 1 : 1. It was found that Ka, ΔG and ΔH of inclusion increase for larger nanodiamonds. ΔS is generally positive, in particular for the largest nanodiamonds. β-Cyclodextrin binds all nanodiamonds, γ-cyclodextrin clearly prefers the most bulky nanodiamonds. The interaction of 9-triamantane carboxylic acid shows one of the strongest complexation constants towards γ-cyclodextrin ever reported, Ka = 5.0 × 105 M−1. In order to gain some insight into the possible structural basis of these inclusion complexes we performed density functional calculations at the B97-D3/def2-TZVPP level of theory.

 

Synthesis of Diamondoid Carboxylic Acids. Functionalized Nanodiamonds, part 30. Natalie A. Fokina, Boryslav A. Tkachenko, Jeremy E. P. Dahl, Robert M. K. Carlson, Andrey A. Fokin, and Peter R. Schreiner* Synthesis 2012, 44, 259–264.

Diamondacid

Procedures for the synthesis of apical mono-, di-, and tricarboxylic acids of triamantane, [121]tetramantane, and [1(2,3)4]pentamantane, apical diacetic acids of diamantane and triamantane, as well as medial propionic acids of diamantane and triamantane were elaborated starting from the corresponding alcohols and bromides. The obtained diamondoid acids were characterized as their methyl ester derivatives.

 

Overcoming Extremely Long C–C Alkane Bond Lability through Attractive Dispersion Forces. Functionalized Nanodiamonds, part 29. Peter R. Schreiner,* Lesya V. Chernish, Pavel A. Gunchenko, Evgeniya Yu. Tikhonchuk, Heike Hausmann, Michael Serafin, Sabine Schlecht, Jeremy E. P. Dahl, Robert M. K. Carlson, and Andrey A. Fokin* Nature 2011, 477, 308–311.

Longest C-C Bond
 

Steric effects in chemistry are a consequence of the space required to accommodate the atoms and groups within a molecule, and are often thought to be dominated by repulsive forces arising from overlapping electron densities (Pauli repulsion). An appreciation of attractive interactions such as van der Waals forces (which include London dispersion forces) is necessary to understand chemical bonding and reactivity fully. This is evident from, for example, the strongly debated origin of the higher stability of branched alkanes relative to linear alkanes and the possibility of constructing hydrocarbons with extraordinarily long C-C single bonds through steric crowding. Although empirical bond distance/bond strength relationships have been established for C-C bonds (longer C-C bonds have smaller bond dissociation energies), these have no present theoretical basis. Nevertheless, these empirical considerations are fundamental to structural and energetic evaluations in chemistry, as summarized by Pauling as early as 1960 and confirmed more recently. Here we report the preparation of hydrocarbons with extremely long C-C bonds (up to 1.704 Å), the longest such bonds observed so far in alkanes. The prepared compounds are unexpectedly stable--noticeable decomposition occurs only above 200 °C. We prepared the alkanes by coupling nanometre-sized, diamond-like, highly rigid structures known as diamondoids. The extraordinary stability of the coupling products is due to overall attractive dispersion interactions between the intramolecular H•••H contact surfaces, as is evident from density functional theory computations with and without inclusion of dispersion corrections.

 

Diamondoid-modified DNA. Functionalized Nanodiamonds, part 28.

Yan Wang, Boryslav A. Tkachenko, Peter R. Schreiner,* and Andreas Marx*

Org. Biomol. Chem. 2011, 9, 7482–7490.

Diamondoid-DNAWe prepared novel C5-modified triphosphates and phosphoramidites with a diamondoid functionally linked to the nucleobase. Using primer extension experiments with different length templates we investigated whether the modified triphosphates were enzymatically incorporated into DNA and whether they were further extended. We found that all three modified nucleotides can be incorporated into DNA using a single-nucleotide incorporation experiment, but only partially using two templates that demand for multiple incorporation of the modified nucleotides. The modified phosphoramidites were introduced into oligonucleotides utilizing DNA synthesizer technology. The occurring oligonucleotide structures were examined by circular dichroism (CD) and melting temperature (Tm) measurements and were found to adapt similar helix conformations as their unmodified counterparts.

 

Synthesis of Higher Diamondoids and Implications of Their Formation in Petroleum. Jeremy E. P. Dahl,* J. Michael Moldovan, Zhibin Wei, Paul A. Lipton, Peter Denisevich, Shengao Liu, Peter R. Schreiner,* and Robert M. K. Carlson Angew. Chem. Int. Ed. 2011, 49, 9881–9885.

Synthesis of Higher Diamondoids

Could chemistry be as easy as A + B = C? En route to laboratory diamond synthesis: We show that higher diamondoids form from lower ones in experiments mimicking petroleum cracking. The yields are low but can be significantly improved by the addition of isobutane or isobutene. Rather than through superacid-catalyzed carbocation rearrangement reactions – long assumed to be responsible for diamondoid growth – our experiments take place via free-radical mechanisms that are akin to CVD growth giving microcrystalline diamond. Indeed, we used higher diamondoids as seeds to grow CVD diamond, and it should be possible to synthesize larger nanodiamonds and perhaps even diamond using diamondoids as seeds.

 

Negative-electron-affinity diamondoid monolayers as high-brilliance source for ultrashort electron pulses. S. Roth, D. Leuenberger, J. Osterwalder, J.E. Dahl, R.M.K. Carlson, B.A. Tkachenko, A.A. Fokin, P.R. Schreiner, M. Hengsberger Chem. Phys. Lett. 2010, 495, 102-108.

Diamondoids are nanometer-sized, hydrogen terminated diamond-like molecules consisting of fused adamantane units. The thiolated diamondoid [121]tetramantane-6-thiol shows negative electron affinity behavior, i.e. population of unoccupied states directly leads to spontaneous electron emission. We present time-resolved photoemission data from self-assembled monolayers of [121]tetramantane-6-thiol in order to shed light on the emission process: A photon energy threshold for electron emission of 5.6–5.8 eV was observed, and the electron affinity was estimated to be -0.21 to -0.57 eV for Ag and Au substrates, respectively. Electrons are emitted after excitation in the metal substrate through the molecular orbitals within a few femtoseconds.  Negative-electron-affinity Diamondoid


Molybdenum(VI) Oxide-Organic Frameworks (MOOFs), a New Series of Coordination Hybrids Constructed with Bitopic 1,2,4-Trialzole Linkers. Andrey B. Lysenko, Ganna A. Senchyk, Jörg Lincke, Daniel Lässig, Andrey A. Fokin, Peter R. Schreiner, Harald Krautscheid, and Konstantin V. Domasevitch Dalton Trans. 2010, 39, 4223–4231.

Molybdenum(VI)-(MOOFs)A series of molybdenum(VI) oxide-organic solids were prepared by hydrothermal reactions employing N-donor tectons, which combine two 1,2,4-triazol-4-yl sites separated by representative aliphatic spacers (ethylene, tr2eth; 1,3-propylene, tr2pr; trans-1,4-cyclohexanediyl, tr2cy; diamondoid 1,3-adamantanediyl, tr2ad; 1,6- and 4,9-diamantanediyls, 1,6-tr2dia and 4,9-tr2dia) and heterofunctional 5-[4-(1,2,4-triazol-4-yl)phenyl]tetrazole (trtz). In all the compounds the 1,2,4-triazol-4-yl group acts as a short-distance N1,N2-bridge between two Mo ions (Mo-N 2.36–2.50 Å). The 3D framework structure is based upon pseudo-41 helices  ([Mo4O12(tr2eth)2] 1, [Mo2O6(tr2cy)] 3) or sinusoidal chains ([Mo2O6(tr2pr)] 2, [Mo2O6(tr2ad)]•6H2O 4, [Mo2O6(4,9-tr2dia)]•0.5H2O 5) of vertex-sharing MoO4N2 octahedra, while the bitopic organic ligands manifest a dual role as connectors for two adjacent octahedra and as links between separate 1D inorganic subtopologies. For linear, lengthy tectons tr2cy and 4,9-tr2dia two identical frameworks interpenetrate. In [MoO3(trtz)] 7, the 41 helices aggregate into 3D tetragonal framework (five-fold interpenetrated) by hydrogen bonding between the tetrazole groups. 2D structure of [Mo4O12(1,6-tr2dia)]•2H2O 6 is influenced by very bulk aliphatic portion of the ligands, which connect chains of edge-shared octahedra MoO5N (Mo-N 2.346(2), 2.456(2) Å).

 

Experimental and Theoretical Studies of the Absorption Properties of Thiolated Diamondoids. Lasse Landt, Christoph Bostedt, Thomas Möller, Roland Mitric, Jeremy E. P. Dahl, Robert M. K. Carlson, Boryslav A. Tkachenko, Andrey A. Fokin, Peter R. Schreiner, Alexander Kulesza, and Vlasta Bonacic-Koutecky J. Chem. Phys. 2010, 132, 144305.

Nanoscale hybrid systems are a new class of molecular aggregates that offer numerous new possibilities in materials design. Diamondoid thiols are promising nanoscale building blocks for such hybrid systems. They allow the incorporation of functional groups and the investigation of their effects on the unique materials’ properties of diamondoids. Here we combine experimental data with ab initio theory to explore the optical properties of diamondoid thiols and their dependence on size and shape. Agreement between theoretically and experimentally obtained absorption spectra allows the identification of the nature of the optical transitions that are responsible for some photophysical and photochemical processes. We show that the optical properties of diamondoid thiols in the deep UV regime depend on the functionalization site but are largely size independent. Our findings provide an explanation for the disappearance of diamondoid UV photoluminescence upon thiolation for smaller diamondoids. However, our theoretical results indicate that for larger diamondoid thiols beyond the critical size of six diamondoid cages the lowest energy transitions are characterized by diamondoidlike states suggesting that UV luminescence may be regained.

 

thioad

 

Diamondoid Phosphines – Selective Phosphorylation of Nanodiamonds. Hartmut Schwertfeger, Mareike Machuy, Christian Würtele, Jeremy E. P. Dahl, Robert M. K. Carlson, Andrey A. Fokin, and Peter R. Schreiner Adv. Synth. Cat. 2010, 352, 609–615.

phosph_diam
 
The diamondoids (nanodiamonds) diamantane and triamantane were selectively converted into diorganophosphinic acid chlorides by reacting them with phosphorus trichloride under Friedel-Crafts-like conditions. The di-diamondoid phosphinic acid chlorides were subsequently reduced with trichlorosilane to give the hitherto unknown corresponding di-diamondoid phosphines. These diamondoid phosphinic acid chlorides and phosphines are of great utility as starting materials in organo-element and coordination chemistry due to their extraordinary rigidity and steric bulk.

 

Synthesis of Diamondoid Nitro Compounds from Amines with m-Chlorobenzoic Acid. Hartmut Schwertfeger, Christian Würtele, and Peter R. Schreiner

Synlett 2010, 493–495.


We report the synthesis of diamondoid nitro derivatives via the selective oxidation of the corresponding amines using m-chloroperbenzoic acid in 1,2-dichloroethane as solvent.

 

nitrodiam

 

Synthetic Routes to Aminotriamantanes, Topological Analogues of the Neuroprotector Memantine. Andrey A. Fokin, Anika Merz, Natalie A. Fokina, Hartmut Schwertfeger, Shenggao L. Liu, Jeremy E. P. Dahl, Robert M. K. Carlson, and Peter R. Schreiner 

Synthesis 2009, 909–912.

 aminotriam_1 The amino derivatives of diamantane and triamantane representing close topological analogues of the neuroprotective drug memantine were prepared via amination of the respective carboxylic acids or alcohols.

 

Synthesis of Diamantane-Derived N-Heterocyclic Carbenes (IDAd) and Applications in Catalysis. Heinrich Richter, Hartmut Schwertfeger, Peter R. Schreiner, Roland Fröhlich, and Frank Glorius Synlett 2009, 193–197.

Novel diamantyl-substituted imidazolium salts have been synthesized, characterized and, in addition, analyzed by single crystal structural analysis. The corresponding NHCs (a-IDAd and m-IDAd) have been prepared in solution and have been characterized by NMR. They exhibit increased steric demand and increased lipophilicity relative to the well-known IAd. In comparative studies, these NHCs were tested as ligands in palladium-catalyzed Sonogashira reactions of primary alkyl halides and, in addition, as catalysts in an organocatalyzed silyl enol ether formation. IDAd_1

[123]Tetramantane: Parent of a New Family of alpha-Helicenes. Peter R. Schreiner, Andrey A. Fokin, Boryslav A. Tkachenko,  Elemer Vass, Marylin Olmstead, Dieter Bläser, Roland Boese, Hans Peter Reisenauer, Jeremy E. P. Dahl, and Robert M. K. Carlson J. Am. Chem. Soc. 2009, 131, 11292–11293.


 tetraman We present a new type of alpha-helical structure based on a diamondoid (nanodiamond) framework, C2-symmetric [123]tetramantane, whose (+) and (–) isomers could be enantioseparated by HPLC techniques.  Bromination of the enantiopure hydrocarbon led to the isolation of (+)-7-bromo-[123]tetramantane, which could be crystallized and subjected to X-ray structure analysis.  By using the anomalous dispersion, we identify this compound as the P-isomer for the hydrocarbon moiety.  Experimental as well as computed ORD and VCD spectra independently and in agreement with the X-ray structure analysis give M-(–) for the configuration of the second eluted parent hydrocarbon isomer.

Photoacetylation of Diamondoids: Selectivities and Mechanism. Andrey A. Fokin, Pavel A. Gunchenko, Anatoliy A. Novikovsky, Tatyana E. Shubina, Boris V. Chernyaev, Jeremy E. P. Dahl, Robert M. K. Carlson, Alexander G. Yurchenko, and Peter R. Schreiner 
Eur. J. Org. Chem. 2009, 5153–5161.
 
diam_acet
 
The cover picture shows the photochemical generation of triplet diacetyl (butadione, center) and its highly selective C–H bond activation reactions in the functionalizations of tertiary C–H bonds. Despite several similarly reactive tertiary C–H bonds and a multitude of secondary C–H bonds with similar or even smaller bond dissociation energies (blue hydrogens on structures on the left), this reagent shows a remarkable selectivity for the apical positions of diamondoids owing to high sensitivity to steric hindrance. This gives the respective apical acetyl diamondoids (blue groups on the right) with high yields. Deuterium kinetic isotope effects and accompanying computational studies shed light on the rate-determining C–H bond activation step.

Oxygen-Doped Nanodiamonds: Synthesis and Functionalizations.
Andrey A. Fokin, Tatyana S. Zhuk, Alexander E. Pashenko, Pavlo O. Dral, Pavel A. Gunchenko, Jeremy E. P. Dahl, Robert M. K. Carlson, Tatyana V. Koso, Michael Serafin, and Peter R. Schreiner
Org. Lett. 2009, 11, 3068–3071.

ox_diam Oxadiamondoids representing a new class of carbon nanoparticles were prepared from the respective diamondoid ketones via an effective two-step procedure involving addition of methyl magnesium iodide and oxidation with trifluoroperacetic acid in trifluoroacetic acid.  The reactivities of the oxacages are determined by the position of the dopant and are in good agreement with computational predictions.

 

Band Gap Tuning in Nanodiamonds: First Principle Computational Studies. Andrey A. Fokin and Peter R. Schreiner Mol. Phys. 2009, 107, 823–830.

bgap_tune_1 We present a density functional theory study on changes in band gap effects of nanodiamonds (hydrogen terminated diamond-like molecules, diamondoids) depending on size, shape, and the incorporation of heteroatom functionalities.  Strong quantum confinement effects were identified at particle sizes from 0.5 to at least 2 nm, when the band gaps of these nanodiamonds are reduced to 6.7 eV.  Octahedral and tetrahedral nanodiamonds show the same trends in band gap narrowing, and it is the dimension rather than the shape/morphology of the nanodiamonds that alters the band gaps.  Band gap tuning through external (by C–H bond substitution) or internal (by replacing CH or CH2 moieties) doping is non-additive for the same dopant.  Push-pull doping, with electron donating and electron withdrawing groups is most effective and reduces the band gaps of diamondoids to that of bulk diamond.  Further reductions down to 1–2 eV are conceivable with charged external substituents.  The combination of increasing the size of the nanodiamond and push-pull doping are likely to make these materials highly valuable for semiconductor applications.

Selective Preparation of Diamondoid Fluorides. Harmut Schwertfeger, Christian Würtele, Heike Hausmann, Jeremy E. P. Dahl, Robert M. K. Carlson, Andrey A. Fokin, and Peter R. Schreiner Adv. Synth. Cat. 2009, 351, 1041–1054.
 
The selective fluorination of diamantane, triamantane, [121]tetramantane, and [1(2,3)4]pentamantane bromides and alcohols was achieved by using the fluorinating agents AgF and DAST. Various mono-, di-, tri- and even tetrafluorinated diamondoid derivatives were prepared and characterized. We were also able to prepare the amino fluoro and the fluoro alcohol of diamantane from the corresponding monoprotected diamondoid diols. These reactions can be carried out in a highly selective manner and proceed without isomerizations. The fluorinated, unequally disubstituted derivatives are valuable compounds for the exploration of electronic, pharmacological, and material properties of functionalized diamondoids.  diam_fluor

Synthesis, Characterization, and Property Evaluations of Copolymers of Diamantyl Methacrylate with Methyl Methacrylate. Carsten Sinkel, Seema Agarwal, Natalie A. Fokina, Peter R. Schreiner J. Appl. Polym. Sci. 2009, 114, 2109–2115.
 
 poly_ad This work reports the homo- and copolymerization behavior of previously unknown 4-diamantyl methacrylate (DMA) with vinyl comonomers like methyl methacrylate (MMA);the starting monomer DMA was synthesized in our laboratory using 4-diamantanol and methacryloylchloride.  The structures of the homo- and copolymers, were analyzed using NMR techniques.  DMA was found to be more reactive than MMA during copolymerization.  The reactivity ratios as determined by the Kelen-Tüdos method are rMMA = 0.58 and rDMA = 1.75.  The incorporation of a few mol% of diamantyl units into the PMMA backbone led to an increase in its thermal stability and glass transition temperature.  The polymers with 15 and 42 mol% of DMA units in the copolymers showed increased Tg values of 126 °C and 172 °C, respectively.
 
Determining Orientational Structure of Diamondoid Thiols Attached to Silver Using Near-Edge X-ray Absorption Fine Structure Spectroscopy. Trevor M. Willey, Jonathan R. I. Lee, Jason D. Fabbri,  Dongbo Wang, Michael H. Nielsen, Jason C. Randel, Peter R. Schreiner, Andrey A. Fokin, Boryslav A. Tkachenko, Natalyia A. Fokina, Jeremy E. P. Dahl, Robert M. K. Carlson, Louis J. Terminello, Nicolas A. Melosh, and Tony van Buuren J. Elec. Spec. Rel. Phenom. 2009, 172, 69–77.

Near-edge X-ray absorption fine structure spectroscopy (NEXAFS) is a powerful tool for determination of molecular orientation in self-assembled monolayers and other surface-attached molecules. A general framework for using NEXAFS to simultaneously determine molecular tilt and twist of rigid molecules attached to surfaces is presented. This framework is applied to self-assembled monolayers of higher diamondoids, hydrocarbon molecules with cubic-diamond-cage structures. Diamondoid monolayers chemisorbed on metal substrates are known to exhibit interesting electronic and surface properties. This work compares molecular orientation in monolayers prepared on silver substrates using two different thiol positional isomers of [121]tetramantane, and thiols derived from two different pentamantane structural isomers, [1212]pentamantane and [1(2,3)4]pentamantane. The observed differences in monolayer structure demonstrate the utility and limitations of NEXAFS spectroscopy and the framework. The results also demonstrate the ability to control diamondoid assembly, in particular the molecular orientational structure, providing a flexible platform for the modification of surface properties with this exciting new class of nanodiamond materials. diam_ag
 
 
Origin of the Monochromatic Photoemission Peak in Diamondoid Monolayers. W. A. Clay, Z. Liu, W. Yang, J. D. Fabbri, J. E. Dahl, R. M. K. Carlson, Y. Sun, P. R. Schreiner, A. A. Fokin, B. A. Tkachenko, N. A. Fokina, P. A. Pianetta, N. Melosh, and Z.-X. Shen
 Nano Lett. 2009, 9, 57-61.

Abstract.  Recent photoemission experiments have discovered a highly  monochromatized secondary electron peak emitted from diamondoid self-assembled monolayers on metal substrates. New experimental data and simulation results are presented to show that a combination of negative electron affinity and strong electron−phonon scattering is responsible for this behavior. The simulation results are generated using a simple Monte Carlo transport algorithm. The simulated spectra recreate the main spectral features of the measured ones.

 von Boryslav Tkachenko


Reactivities of the Prism-Shaped Diamondoids [1(2)3]Tetramantane and [12312]Hexamantane (Cyclohexamantane). A. A. Fokin, B. A. Tkachenko, N. A. Fokina, H. Hausmann, M. Serafin, J. E. P. Dahl, R. M. K. Carlson, P. R. Schreiner

Chem. Eur. J. 2009, 15, 3851-3862.

Abstract. Various functional groups have been incorporated into the structures of the naturally occurring diamondoids [1(2)3]tetramantane and [12312]hexamantane (cyclohexamantane), which represent hydrogen-terminated prism-shaped nanodiamonds. The selectivities of the C—H substitutions in [1(2)3]tetramantane depend on the reagent employed and give products substituted at either central (through bromination) or peripheral (through nitroxylation and photo-oxidation) positions. The hydrogen-coupled electron-transfer mechanism of C—H nitroxylation with the model electrophile NO2+···HNO3 was verified computationally at the B3PW91 and MP2 levels of theory by utilizing the 6-31G(d) and cc-pVDZ basis sets. The thermodynamically controlled nitroxylation/isomerization of [1(2)3]tetramantane allows the preparation of peripherally trisubstituted derivatives, which were transformed into tripod-like nanodiamond building blocks. The bromination of cyclohexamantane selectively gives the 2-bromo derivative, reproducing the chemical behavior of the {111} surface of the hydrogen-terminated diamond.
von Boryslav Tkachenko

Diamonds are a chemist’s best friend: Diamondoid chemistry beyond adamantane. Hartmut Schwertfeger, Andrey A. Fokin, and Peter R. Schreiner
Angew. Chem. Int. Ed. 2008, 47, 1022-1036. Listed as one of the most accessed articles 2008.
   
    Abstract.
  Marilyn Monroe knew that “diamonds are a girl's best friend” but, in the meantime, many chemists have realized that they are also extremely attractive objects in contemporary chemistry. The chemist's diamonds are usually quite small (herein: nanometer-sized “diamondoids”) and as a result of their unique structure are unusual chemical building blocks. Since lower diamondoids (up to triamantane) have recently become available in large amounts from petroleum and higher diamondoids (starting from tetramantane) are now also accessible from crude oil new research involving them has begun to emerge. Having well-defined structures makes these cage compounds so special compared to other nanometer-scale diamonds. Selective and high-yielding synthetic approaches to the functionalization of diamondoids gives derivatives that can find applications in, for example, polymers, coating materials, drugs, and molecular electronics.
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Monoprotection of Diols as a Key Step for the Selective Synthesis of Unequally Disubstituted Diamondoids (Nanodiamonds). Hartmut Schwertfeger, Christian Würtele, Michael Serafin, Heike Hausmann, Robert M. K. Carlson, Jeremy E. P. Dahl, and Peter R. Schreiner J. Org. Chem. 2008, 73, 7789-7792;
Highlight: Monoprotection of Diamondoid Diols. Timothy M. Swager, Eric L. Dane Synfacts 2008, 1275.
   
 Abstract.
 
The monoprotection (desymmetrization) of diamondoid, benzylic, and ethynyl diols has been achieved using fluorinated alcohols such as 2,2,2-trifluoroethanol (TFE) under acidic conditions. This practical acid-catalyzed SN1 reaction opens the door for the synthesis of novel bifunctional diamondoids. With diamantane as an example, we show that the resulting monoethers can be used to prepare selectively, for instance, amino or nitro alcohols and unnatural amino acids. These are important compounds in terms of the exploration of electronic, pharmacological, and material properties of functionalized nanodiamonds.
 
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Monochromatic Electron Emission from Diamondoid Monolayers. W. K. Yang, J. D. Fabbri, T. M. Willey, J. R. I. Lee, J. E. P. Dahl, R. M. K. Carlson, P. R. Schreiner, A. A. Fokin, B. A. Tkachenko, N. A. Fokina, W. Meevasana, N. Mannella, K. Tanaka, X. J. Zhou, T. van Buuren, M. A. Kelly, Z. Hussain, N. A. Melosh, Z.-X. Shen Science 2007, 316, 1460-1462;
Highlight: Nature Nanotechnology 2007, 2, 462-463.
    Abstract.  We found monochromatic electron photoemission from large-areaself-assembled monolayers of a functionalized diamondoid, [121]tetramantane-6-thiol.Photoelectron spectra of the diamondoid monolayers exhibiteda peak at the low–kinetic energy threshold; up to 68%of all emitted electrons were emitted within this single energypeak. The intensity of the emission peak is indicative of diamondoidsbeing negative electron affinity materials. With an energy distributionwidth of less than 0.5 electron volts, this source of monochromaticelectrons may find application in technologies such as electronmicroscopy, electron beam lithography, and field-emission flat-paneldisplays. Monochromatic Electron Emission