Editing Diamondoid

{{Short description|Various forms of carbon crystal lattices}}
In chemistry, '''diamondoids''' are generalizations of the [[carbon]] cage molecule known as [[adamantane]] (C<sub>10</sub>H<sub>16</sub>), the smallest unit cage structure of the [[diamond]] [[crystal lattice]]. Diamondoids also known as '''nanodiamonds''' or '''condensed adamantanes''' may include one or more cages (adamantane, [[diamantane]], [[triamantane]], and higher polymantanes) as well as numerous isomeric and structural variants of adamantanes and polymantanes. These diamondoids occur naturally in [[petroleum]] deposits and have been extracted and purified into large pure crystals of polymantane molecules having more than a dozen adamantane cages per molecule.<ref name="Dahl">{{cite journal |title= Isolation and Structure of Higher Diamondoids, Nanometer-Sized Diamond Molecules |first1= J. E. |last1= Dahl |first2= S. G. |last2= Liu |first3= R. M. K. |last3= Carlson |journal= [[Science (journal)|Science]] |date= 3 January 2003 |volume= 299 |number= 5603 |pages= 96–99 |doi= 10.1126/science.1078239 |pmid=12459548|s2cid= 46688135 |doi-access= free }}</ref> These species are of interest as molecular approximations of the [[diamond cubic]] framework, terminated with C−H bonds.

==Examples==
 
[[File:Diamondoids.png|center|400px|Diamondoids, from left to right [[adamantane]], [[diamantane]], [[triamantane]] and one isomer of [[tetramantane]]]]

Examples include:
* [[Adamantane]] (C<sub>10</sub>H<sub>16</sub>)
* [[Iceane]] (C<sub>12</sub>H<sub>18</sub>)
* BC-8 (C<sub>14</sub>H<sub>20</sub>)
* [[Diamantane]] (C<sub>14</sub>H<sub>20</sub>) also ''diadamantane'', two face-fused cages
* Triamantane (C<sub>18</sub>H<sub>24</sub>), also ''triadamantane''. Diamantane has four identical faces available for anchoring a new C<sub>4</sub>H<sub>4</sub> unit.
* Isotetramantane (C<sub>22</sub>H<sub>28</sub>). Triamantane has eight faces on to which a new C<sub>4</sub>H<sub>4</sub> unit can be added resulting in four [[isomer]]s. One of these isomers displays a helical twist and is therefore [[prochiral]]. The [[Axial chirality|''P'' and ''M'']] [[enantiomer]]s have been separated.
* Pentamantane has nine isomers with chemical formula C<sub>26</sub>H<sub>32</sub> and one more pentamantane exists with chemical formula C<sub>25</sub>H<sub>30</sub>
* Cyclohexamantane (C<sub>26</sub>H<sub>30</sub>)<ref>{{cite journal |first1=J. E. P. |last1=Dahl |first2=J. M. |last2=Moldowan |first3=T. M. |last3=Peakman |first4=J. C. |last4=Clardy |first5=E. |last5=Lobkovsky |first6=M. M. |last6=Olmstead |first7=P. W. |last7=May |first8=T. J. |last8=Davis |first9=J. W. |last9=Steeds |first10=K. E. |last10=Peters |first11=A. |last11=Pepper |first12=A. |last12=Ekuan |first13=R. M. K. |last13=Carlson | title= Isolation and Structural Proof of the Large Diamond Molecule, Cyclohexamantane (C<sub>26</sub>H<sub>30</sub>) | journal= Angewandte Chemie International Edition | year= 2003 | volume= 42 | pages= 2040–2044 |doi= 10.1002/anie.200250794 | pmid= 12746817 | issue= 18}}</ref>

* Super-adamantane (C<sub>30</sub>H<sub>36</sub>)

One tetramantane isomer is the largest ever diamondoid prepared by [[organic synthesis]] using a keto-[[carbenoid]] reaction to attach cyclopentane rings.<ref>{{cite journal | title=A New Approach to the Construction of Diamondoid Hydrocarbons. Synthesis of ''anti''-Tetramantane |last1=Burns |first1=W. |last2=McKervey |first2=M. A. |last3=Mitchell |first3=T. R. |last4=Rooney |first4=J. J. | journal= Journal of the American Chemical Society | volume=100 |issue=3 | pages=906–911 |year=1978 | doi=10.1021/ja00471a041}}</ref> Longer diamondoids have been formed from diamantane dicarboxylic acid.<ref>{{cite journal | journal= Angewandte Chemie International Edition | date= Mar 25, 2013 |volume=52 |issue=13 | pages=3717–3721 | title=Evidence of diamond nanowires formed inside carbon nanotubes from diamantane dicarboxylic acid |last1=Zhang |first1=J. |last2=Zhu |first2=Z. |last3=Feng |first3=Y. |last4=Ishiwata |first4=H. |last5=Miyata |first5=Y. |last6=Kitaura |first6=R. |last7=Dahl |first7=J. E. |last8=Carlson |first8=R. M. |last9=Fokina |first9=N. A. |last10=Schreiner |first10=P. R. |last11=Tománek |first11=D. |last12=Shinohara |first12=H. | pmid=23418054 | doi=10.1002/anie.201209192}}</ref> The first-ever isolation of a wide range of diamondoids from petroleum took place in the following steps:<ref name="Dahl"/> a [[vacuum distillation]] above 345&nbsp;°C, the equivalent [[atmospheric boiling point]], then [[pyrolysis]] at 400 to 450&nbsp;°C in order to remove all non-diamondoid compounds (diamondoids are thermodynamically very stable and will survive this pyrolysis) and then a series of [[high-performance liquid chromatography]] separation techniques.

In one study a tetramantane compound is fitted with [[thiol]] groups at the bridgehead positions.<ref>{{cite journal|title=Functionalized Nanodiamonds Part 3: Thiolation of Tertiary/Bridgehead Alcohols|first1= Boryslav A.|last1= Tkachenko|first2= Natalie A.|last2= Fokina|first3= Lesya V.|last3= Chernish|first4= Jeremy E. P.|last4= Dahl|first5= Shenggao|last5= Liu|first6= Robert M. K.|last6= Carlson|first7= Andrey A.|last7= Fokin|first8= Peter R.|last8= Schreiner|journal= Organic Letters |date=2006 |volume=8 |issue=9 |pages= 1767–70|doi=10.1021/ol053136g |pmid= 16623546}}</ref> This allows their anchorage to a [[gold]] surface and formation of [[self-assembled monolayer]]s (diamond-on-gold).

Organic chemistry of diamondoids even extends to ''pentamantane''.<ref>{{cite journal | last1 = Fokin | first1 = Andrey A. | last2 = Schreiner | first2 = Peter R. | last3 = Fokina | first3 = Natalie A. | last4 = Tkachenko | first4 = Boryslav A. | last5 = Hausmann | first5 = Heike | last6 = Serafin | first6 = Michael | last7 = Dahl | first7 = Jeremy E. P. | last8 = Liu | first8 = Shenggao | last9 = Carlson | first9 = Robert M. K. | year = 2006 | title = Reactivity of [1(2,3)4]Pentamantane (Td-Pentamantane): A Nanoscale Model of Diamond | journal = The Journal of Organic Chemistry | volume = 71 | issue = 22| pages = 8532–8540 | doi = 10.1021/jo061561x | pmid = 17064030 }}</ref> The medial position (base) in this molecule (the isomer [1(2,3)4]pentamantane) is calculated to yield a more favorable [[carbocation]] than the apical position (top) and simple [[bromination]] of pentamantane ''1'' with [[bromine]] exclusively gives the medial bromo derivative ''2'' which on hydrolysis in water and [[dimethylformamide|DMF]] forms the [[Alcohol (chemistry)|alcohol]] ''3''.

[[File:PentamaneChemistry.png|center|400px|Pentamane chemistry]]

In contrast [[nitrooxylation]] of ''1'' with [[nitric acid]] gives the apical [[nitrate]] ''4'' as an intermediate which is hydrolysed to the apical [[Alcohol (chemistry)|alcohol]] ''5'' due to the higher [[steric hindrance|steric demand]] of the active [[electrophilic]] {{chem|NO|2|-}}{{chem|HNO|3|+}} species. This alcohol can react with [[thionyl bromide]] to the bromide ''6'' and in a series of steps (not shown) to the corresponding [[thiol]]. Pentamantane can also react with [[tetrabromomethane]] and [[Quaternary ammonium cation|tetra-''n''-butylammonium]] bromide (TBABr) in a [[free radical reaction]] to the bromide but without selectivity.

== Origin and occurrence ==

Diamondoids are found in mature high-temperature [[petroleum]] fluids (volatile oils, condensates and wet gases). These fluids can have up to a spoonful of diamondoids per US gallon (3.78&nbsp;liters). A review by Mello and Moldowan in 2005 showed that although the carbon in diamonds is not biological in origin, the diamondoids found in [[petroleum]] are composed of carbon from biological sources. This was determined by comparing the ratios of carbon [[isotope]]s present.<ref>{{cite web|url=http://www.searchanddiscovery.net/documents/abstracts/2005research_calgary/abstracts/extended/mello/mello.htm|website=Search and Discovery|title=Petroleum: To Be Or Not To Be Abiogenic |first1=M. R. |last1=Mello |first2=J. M. |last2=Moldowan |date=2005}}</ref>

== Optical and electronic properties ==

The [[Absorption (electromagnetic radiation)|optical absorption]] for all diamondoids lies deep in the [[ultraviolet]] spectral region with optical [[band gap]]s around 6 [[electronvolt]]s and higher.<ref>{{cite journal |first1=L. |last1=Landt |first2=K. |last2=Klünder |first3=J. E. |last3=Dahl |first4=R. M. K. |last4=Carlson |first5=T. |last5=Möller |first6=C. |last6=Bostedt | title= Optical Response of Diamond Nanocrystals as a Function of Particle Size, Shape, and Symmetry | journal= Physical Review Letters | year= 2009 | volume= 103 |issue=4 | pages= 047402 |doi= 10.1103/PhysRevLett.103.047402 | bibcode=2009PhRvL.103d7402L | pmid=19659398|url=http://bib-pubdb1.desy.de/record/92624 }}</ref> The spectrum of each diamondoid is found to reflect its individual size, shape and [[molecular symmetry|symmetry]]. Due to their well-defined size and structure diamondoids also serve as a model system for electronic structure calculations.<ref>{{cite journal |first1=M. |last1=Vörös |first2=A. |last2=Gali | title= Optical absorption of diamond nanocrystals from ''ab initio'' density-functional calculations | journal= Physical Review B | year= 2009 | volume= 80 |issue=16 | pages= 161411 |doi= 10.1103/PhysRevB.80.161411|bibcode = 2009PhRvB..80p1411V }}</ref>

Many of the optoelectronic properties of diamondoids are determined by the difference in the nature of the [[HOMO/LUMO|highest occupied and lowest unoccupied molecular orbitals]]: the former is a [[bulk state]], whereas the latter is a [[surface state]]. As a result, the energy of the lowest unoccupied molecular orbital is roughly independent of the size of the diamondoid.<ref name="dmc_diamondoid">{{cite journal |first1=N. D. |last1=Drummond |first2=A. J. |last2=Williamson |first3=R. J. |last3=Needs |first4=G. |last4=Galli | title= Electron emission from diamondoids: a diffusion quantum Monte Carlo study | journal= Physical Review Letters | year= 2005 | volume= 95 |issue=9 | pages= 096801–096804 |doi= 10.1103/PhysRevLett.95.096801 | bibcode=2005PhRvL..95i6801D|arxiv = 0801.0381 | pmid=16197235|s2cid=16703233 }}</ref><ref>{{cite journal |first1=T. M. |last1=Willey |first2=C. |last2=Bostedt |first3=T. |last3=van Buuren |first4=J. E. |last4=Dahl |first5=S. G. |last5=Liu |first6=R. M. K. |last6=Carlson |first7=L. J. |last7=Terminello |first8=T. |last8=Möller | title= Molecular Limits to the Quantum Confinement Model in Diamond Clusters | journal= Physical Review Letters | year= 2005 | volume= 95 |issue=11 | pages= 113401–113404 |doi= 10.1103/PhysRevLett.95.113401 | bibcode=2005PhRvL..95k3401W | pmid=16197003|url=https://digital.library.unt.edu/ark:/67531/metadc876588/ |type=Submitted manuscript }}</ref>

Diamondoids have been found to exhibit a negative [[electron affinity]], making them potentially useful in [[Field electron emission|electron-emission]] devices.<ref name="dmc_diamondoid" /><ref>{{cite journal |first1=W. L. |last1=Yang |first2=J. D. |last2=Fabbri |first3=T. M. |last3=Willey |first4=J. R. I. |last4=Lee |first5=J. E. |last5=Dahl |first6=R. M. K. |last6=Carlson |first7=P. R. |last7=Schreiner |first8=A. A. |last8=Fokin |first9=B. A. |last9=Tkachenko |first10=N. A. |last10=Fokina |first11=W. |last11=Meevasana |first12=N. |last12=Mannella |first13=K. |last13=Tanaka |first14=X.-J. |last14=Zhou |first15=T. |last15=van Buuren |first16=M. A. |last16=Kelly |first17=Z. |last17=Hussain |first18=N. A. |last18=Melosh |first19=Z.-X. |last19=Shen | title= Monochromatic Electron Photoemission from Diamondoid Monolayers | journal= Science | year= 2007 | volume= 316 |issue=5830 | pages= 1460–1462 |doi= 10.1126/science.1141811 |pmid=17556579 |bibcode = 2007Sci...316.1460Y |url=https://cloudfront.escholarship.org/dist/prd/content/qt5h79b9nr/qt5h79b9nr.pdf |doi-access=free }}</ref>

==See also==
* Other diamond-like compounds: [[Boron nitride]]
* [[Abiogenic petroleum origin]]
* [[Nanorobot]]

==References==
{{reflist|30em}}

==External links==
* [http://www.cluster-ag.tu-berlin.de/menue/research/diamondoids/ Cluster and Nanocrystal Research Group, Technische Universität Berlin]
* [https://web.archive.org/web/20060826183233/http://www.chevron.com/moleculardiamond/diamondtech/discovery.asp Molecular Diamond Technologies, Chevron Texaco]
* [https://web.archive.org/web/20060925014642/http://www.dse.nl/~hkl/e_nano1.htm Nanotechnology and the arrival of the Diamond Age]
* [http://www.chm.bris.ac.uk/pt/diamond/diamondoids.htm Laser Raman Spectroscopy and Modelling of Diamondoids]
* [http://opus.kobv.de/tuberlin/volltexte/2010/2855/pdf/landt_lasse.pdf Electronic and Optical Properties of Diamondoids (free download)]
* [http://www.worldscientific.com/worldscibooks/10.1142/7559 Diamondoid Molecules: With Applications in Biomedicine, Materials Science, Nanotechnology & Petroleum Science]
* [http://pubs.rsc.org/is/content/articlehtml/2016/nr/c6nr00500d Diamondoid-functionalized gold nanogaps as sensors for natural, mutated, and epigenetically modified DNA nucleotides]

[[Category:Carbon nanoparticles]]
[[Category:Adamantane-like molecules]]