# Last edited on 2013-02-12 04:48:21 by stolfilocal ---------------------------------------------------------------------- C. S. Casari, A. Li Bassi, L. Ravagnan, F. Siviero, C. Lenardi, P. Piseri, G. Bongiorno, C. E. Bottani, and P. Milani (2004), ''Chemical and thermal stability of carbyne-like structures in cluster-assembled carbon films'' Physical Review B, volume 69, paper 075422. {{doi|10.1103/PhysRevB.69.075422}} Grow thn films (up to 200 nm) of carbon by depositing a supersonic beam of carbon clusters in vacuum on a silicon substrate. Film is porous (pore diameter peaks at 3-4 nm and presence of linear polyyine chains (as well as polycumulene and other carbon forms) detected by Raman infrared spectroscopy ---------------------------------------------------------------------- Franco Cataldo (1999), ''From dicopper acetylide to carbyne''.Polymer International, volume 48, issue 1, pages 15-22. {{doi|10.1002/(SICI)1097-0126(199901)48:1}} ---------------------------------------------------------------------- Franco Cataldo (1999), ' 'A study on the structure and electrical properties of the fourth carbon allotrope: carbyne''. Polymer International, volume 44, issue 2, pages 191–200. {{doi|10.1002/(SICI)1097-0126(199710)44:2}} ---------------------------------------------------------------------- K. Yamada, H. Kunishige, and A. B. Sawaoka (1991) ''Formation process of carbyne produced by shock compression'' Naturwissenschaften volume 78, pages 450-452 {{doi|10.1007/BF01134379}} K. Akagi, M. Nishiguchi, H. Shirakawa, Y. Furukawa, and I. Harada (1987) ''One-dimensional conjugated carbyne - synthesis and properties''. Synthetic Metals, volume 17, issues 1–3, pages 557–562. {{doi|10.1016/0379-6779(87)90798-3}} Reaction of thin-film polychloroacetylene (-CH=CCl-)''n'' in trans-gauche form with strong base in various solvents. Polyyne lengths 12 to 65 acetylene units. ---------------------------------------------------------------------- R. Eastmond, T.R. Johnson, and D.R.M. Walton (1972), ''Silylation as a protective method for terminal alkynes in oxidative couplings: A general synthesis of the parent polyynes H(C≡C)''n''H (''n'' = 4–10, 12)''. Tetrahedron, volume 28, issue 17, pages 4601–4616. {{doi|10.1016/0040-4020(72)80041-3}} T.R. Johnson and D.R.M. Walton (1972), ''Silylation as a protective method in acetylene chemistry: Polyyne chain extensions using the reagents, Et3Si(C≡C)''m''H (''m'' = 1,2,4) in mixed oxidative couplings''. Tetrahedron, volume 28, issue 20, pages 5221–5236. {{doi|10.1016/S0040-4020(01)88941-9}} {{chem|Et|3|Si}}–(C≡C)''m''–{{chem|SiEt|3}} m = 2 - liquid? bp 139 _ 140 C (0.4 mmHg) m = 3 - white solid mp 16.5 _ 17.5 C m = 4 - yellowish white crystals mp 39.5 _ 40 C; bp 120 C at 0.55 mmHg m = 5 - solution only m = 6 - dark solid at -20 C , blackens rapidly at +20 C m = 7 - solution only m = 8 - stable crystals up to -30 C, decomposes at -20 C m = 9 - solution only m = 10 - solution only m = 16 - impure solution only School of Molecular Sciences, University of Sussex, Brighton BN1 9QJ, Sussex U.K. http://dx.doi.org/, How to Cite or Link Using DOI Permissions & Reprints ---------------------------------------------------------------------- Smith PP, Buseck PR Science (New York, N.Y.) [1982, 216(4549):984-986] Type: Journal Article DOI: 10.1126/science.216.4549.984 Carbyne forms of carbon: do they exist? (PMID:17809068) Almost 15 years have passed since carbynes entered the literature as new forms of elemental carbon. They recently attracted attention as possible interstellar dust constituents and as carriers of presolar noble gases in meteorites. Their existence and that of the related mineral chaoite are questioned, and a reevaluation of previous data is suggested. ---------------------------------------------------------------------- Sara Eisler, Aaron D. Slepkov, Erin Elliott, Thanh Luu, Robert McDonald, Frank A. Hegmann, and Rik R. Tykwinski (2005), ''Polyynes as a model for carbyne: Synthesis, physical properties, and nonlinear optical response.'' Journal of the American Chemical Society, volume 127, issue 8, pages 2666–2676. {{doi|10.1021/ja044526l}} (C≡C)8 has a bent backbone. --------------------------------------------------------------------- J. Kastner, H. Kuzmany, L. Kavan, F. P. Dousek, and J. Kürti (1995) ''Reductive preparation of carbyne with high yield: An in situ raman scattering study.'' Macromolecules, volume 28, pages 344-353. {{doi|10.1021/ma00105a048}} A linear polymeric sp-hybridized carbon molecule can be derived either from a chain with alternating single and triple bonds, i.e., polyyne (poly- ethynylene): ” Abstract published in Advance ACS Abstructs, December 1, 1994. o o ~ ~ - ~ ~ ~ ~ 1 ~ ~ 1 ~ ~ ~ a - o ~ ~ ~ $ o 9 . o o 1 o with calculated bond lengths 120.7 and 137.9 pml or alternatively from a less stable chain of only double bonds (128.2 pm), i.e., polycumulene (polyethylene- diy1idene): The polyyne configuration is preferred energetically to the cumulene one because of a stabilization by the Peierls d i s t o r t i ~ n . ~ , ~ J > ~ Calculated Peierls gaps are in the range between 2 and 5 eV.7*8 In this sense polyyne is a conjugated polymer with two nelectrons per carbon atom on the backbone. Thus, it can be expected that models appropriate for sp2-conjugated polymers are applicable here as well. In contrast to infinite carbon chains, small C, mol- ecules (n 5 8) tend to exhibit a cumulene-like structure with only a slight bond alternation.1° For n even Cn molecules two ground state structures are very close in energy and may coexist: a linear and a cyclic (rhombic) structure.l0J1 C3 and other small C, molecules (n = 4-10), as well as oligoynes (H-(C=C),-H) are presum- ably linear.1°J2 The occurrence of natural carbynes has been mostly reported in rather exotic environments such as inter- stellar space, meteorites, and meteoritic craters.l S We shall further denote the reaction C-MeF (Me stands for a cation of the depicted as (1 ) product as supporting electrolyte, i.e., alkali metal in the case of the reduction by amalgams). The reaction byproduct, i.e., alkali metal fluoride (MeF), forms nanosized crystallites interspersed between the nascent carbyne chains. These crystallites are assumed to preserve sterically t o some extent the naked carbyne chains against cross-linking and chemi- cal decomposition in a reactive e n v i r ~ n r n e n t . ~ ~ ~ ~ ~ ~ ~ ~ The former reacti ---------------------------------------------------------------------- '''Linear acetylenic carbon''', also called [[polyyne|carbyne]], is an [[allotrope]] of [[carbon]] that has the chemical structure (−C≡C−)n as a repeating chain, with alternating single and triple bonds. R.B. Heimann, S.E. Evsyukov, L. Kavan, eds. (1999), ''Carbyne and carbynoid structures'' (book), page 452. Volume 21 in the series ''Physics and Chemistry of Materials with Low-Dimensional Structures'' ISBN 0-7923-5323-4 R. H. Baughman (2006), ''Dangerously Seeking Linear Carbon''. Science, volume 312, pages 1009–1110 {{doi|10.1126/science.1125999}} This form of carbon is of considerable interest to [[nanotechnology]] as its [[Young's modulus]] is forty times that of [[diamond]], the hardest known material. L. Itzhaki, E. Altus, H. Basch, S. Hoz (2005), ''Harder than diamond: Determining the cross-sectional area and Young's modulus of molecular rods''. Angewandte Chemie Int. Edition, volume 44, pages 7432–7435 {{doi|10.1002/ange.200502448}} {{pmid|16240306}} However its existence has been contested recently, on the argument that it would be extremely unstable in condensed form. ---------------------------------------------------------------------- Thomas Gibtner, Frank Hampel, Jean-Paul Gisselbrecht, and Andreas Hirsch (2002), ''End-cap stabilized oligoynes: Model compounds for the linear sp carbon allotrope carbyne''. Chemistry, a European Journal, volume 8, issue 2, pages 408–432. {{doi|10.1002/1521-3765(20020118)8:2}} Three series of differently 3,5-disubstituted α,ω-diphenylpolyynes Ar-(C≡C)n-Ar (n=2, 4, 6, 8, 10) were synthesized under optimized Cadiot–Chodkiewicz conditions, isolated and completely characterized. These compounds can be considered as model substances for the hypothetical one-dimensional carbon allotrope carbyne C∞. The longest sp-carbon chain contains 20 atoms and is therefore the longest, purely organic polyyne studied with NMR techniques. Extinction coefficients over 600 000 m−1 cm−1 represent the highest measured quantitative values for that compound class so far. Comparisons with previous investigations and electrochemical studies allow the assignment of absorption for both wavelength regions structuring the UV/Vis spectra. Based on the trends in the spectroscopic behaviour of those molecules with increasing chain length, electronic as well as the NMR properties of carbyne are predicted, in line with our previously reported results. The observed stability properties promise the synthesis of even longer polyynes. The first attempts to synthesize long sp carbon chains were undertaken by Bohlmann and Jones in the 1950s.7, 8 As they were interested in the synthesis of di-, tri-, tetra-, and pentayne containing natural compounds, they initiated the systematical synthesis of several differently end-capped series of polyacetylenes with up to ten triple bonds.8b, 9, 10 The direct correlation they observed between the size and bulkiness of the end groups and the stability of the sp carbon chains was later studied in detail by Wegner, during his investigations of topochemically controlled polymerizations of diacetylenic compounds.11 Due to the difficulty in handling the precursors to the polyynes, the classical elongation technique was only of limited scope. The synthesis of longer derivatives was possible after Walton and co-workers had introduced silylation as a protective method in acetylene coupling chemistry.12–15 With the use of triethylsilyl as a protection group during iterative symmetrical and mixed Hay coupling reactions,16 the synthesis of homologous series of unsubstituted and triethylsilyl substituted polyynes was reported,12, 13 resulting in the longest sp carbon chain known to date (Et3Si-(C≡C)16-SiEt3) which was characterized by UV/Vis spectroscopy. A general approach to the synthesis of polyynes with an odd number of C≡C bonds has been developed by Diederich et al.17 While the alternative Cadiot–Chodkiewicz method18 often has the disadvantage of giving only a low yield of the desired coupling product,7b, 18b, 19 the smooth elimination of two carbonyl groups from differently substituted 3-cyclobutene-1,2-diones under the “solution-spray flash vacuum pyrolysis” (SS-FVP) conditions allows the formation of corresponding alkynes in high yields.17 In this way, the dodecahexayne TBDMS-(C≡C)6-TBDMS (TBDMS: tert-butyldimethylsilyl) was obtained, which is the longest NMR-characterized purely organic oligoyne known to date. The synthesis of polyynes containing up to ten triple bonds, which span two redox-active, chiral rhenium fragments, is described by Gladysz and co-workers.22 The longest molecule, the decayne, which shows impressive stability even in the solid state at room temperature,22b,22c is accessed by the use of a modified Cadiot–Chodkiewicz coupling23 followed by a classic oxidative coupling reaction.24 To date, this is the longest, completely characterized polyyne bearing transition metal end groups. Gladysz's group also reports the first structurally characterized hexayne that connects two platinum metal complex fragments, showing surprising crystallographic properties.25 ==History and controversy== # @@ Kroto: In 1967 it was claimed that a new polymorph of carbon, formed only of linear chains of sp  -hybridised carbon atoms, had been synthesised.2 This claim was further propagated by others, most prominently in the journal Science  in 1978.3 # @@ # @@ pure linear sp  -carbon chain into a solid will result in an explosion as the chains, if they get close, will crosslink exothermically.  # @@ # @@ An interesting and enlightening example of this was published over # @@ 25 years ago by a group at Exxon, suggesting that a new family of # @@ even-numbered carbon clusters from about C30 to C180 exhibited # @@ properties consistent with carbyne.5 When this paper appeared I was # @@ absolutely sure that this assignment was not correct. As some will # @@ be aware, this family turned out to be the fullerenes! [Harry Kroto # @@ was one of three recipients to share the 1996 Nobel prize in # @@ chemistry for the discovery of fullerenes.] The astrophysical # @@ community in particular still seems unaware of the fact that there # @@ is absolutely no evidence for it. # @@ # @@ A carefully definitive study was carried out by Smith and Buseck # @@ more than 25 years ago and those who casually talk and write about # @@ carbyne should read it.6 The authors showed that the signals # @@ interpreted as a carbyne phase appear to be due to impurities such # @@ as mica and talc in the samples. The existence of carbyne is myth # @@ based on bad science and perhaps even wishful thinking.  # @@ 2 V I@@ Kasatochkin et al, Dokl. Chem., 1967, 177, 1031 1 W A Chalifoux and # @@ R R Tykwinski, Nature Chem., 2010, 2, 967 (DOI: 10.1038/nchem.828) # @@ # @@ 4 T R Johnson and D R M Walton, Tetrahedron, 1972, 28, 5221 # @@ 5 E A Rohlfing, D M Cox and A J Kaldor, J. Chem. Phys., 1984, 81, 3332 # @@ 6 P P K Smith and P R Busek, Science, 1982, 216, 984 # @@ 7 H W Kroto et al, Nature, 1985, 318, 162 --------------------------- Wesley Chalifoux and Rik Tykwinski, of the University of Alberta in # @@ Edmonton, succeeded in making a polyyne consisting of 44 carbon # @@ atoms - the previous longest being 28 atoms. In this way, the researchers made a number of polyynes of differing length, with the longest containing 22 acetylene units, totalling 44 carbon atoms. 'We have shown how these longer chains can be made stable,' says Tykwinski. One dimensional carbon chains get longer Simon Hadlington 19 September 2010 http://www.rsc.org/chemistryworld/News/2010/September/17091003.asp ---------------------------------------------------------------------- Synthesis of extended polyynes: Toward carbyne Wesley A. Chalifoux, Rik R. Tykwinski, Department of Chemistry, University of Alberta, Edmonton, Alberta, Canada T6G 2G2 http://dx.doi.org/10.1016/j.crci.2008.10.004, How to Cite or Link Using DOI Permissions & Reprints Abstract This account will focus on the synthesis and characterization of polyynes. After a brief discussion of synthetic tools commonly employed in the assembly of sp-hybridized carbon frameworks, a more detailed discussion of polyynes composed of at least five contiguous acetylenic units will follow. The construction of polyynes up to hexaynes is a rather well-developed area where traditional synthetic strategies are typically still useful, i.e., metal-catalyzed homo- or heterocoupling and exhaustive elimination reactions. The synthesis of longer polyynes (heptaynes, octaynes, etc.), on the other hand, can require more subtle synthetic approaches due to inherent problems of reagent compatibility and the reactive nature of many polyyne intermediates and products. A description of the innovative synthetic methods that have been used over the past decade to overcome some of these challenges will be presented. Furthermore, a review of all polyynes reported to date with a length of at least 16 sp-carbons is included, combined with an account of methods used for their characterization. Keywords Polyynes; Conjugated oligomers; Materials science; Hay coupling; Cadiot–Chodkiewicz coupling; Eglinton coupling; Fritsch–Buttenberg–Wiechell rearrangement The synthesis of polyynes arguably dates back to 1869 when Carl Glaser observed that copper(I) phenylacetylide undergoes oxidative dimerization in the presence of air to produce diphenylbutadiyne (Scheme 1a) [48]. --------------------------- Science 20 January 1995: Vol. 267 no. 5196 pp. 362-367 DOI: 10.1126/science.267.5196.362 Synthesis of Linear Acetylenic Carbon: The "sp" Carbon Allotrope Richard J. Lagow, Joel J. Kampa, Han-Chao Wei, Scott L. Battle, John W. Genge, David A. Laude, Carla J. Harper, Robert Bau, Raymond C. Stevens, James F. Haw, Eric Munson + Author Affiliations Department of Chemistry, University of Texas at Austin, Austin, TX 78712, USA. Department of Chemistry, University of Southern California, Los Angeles, CA 90089, USA. Department of Chemistry, Texas A&M University, College Station, TX 77843, USA. ABSTRACT A carbon allotrope based on "sp" hybridization containing alternating triple and single bonds (an acetylenic or linear carbon allotrope) has been prepared. Studies of small (8 to 28 carbon atoms) acetylenic carbon model compounds show that such species are quite stable (130° to 140°C) provided that nonreactive terminal groups or end caps (such as tert-butyl or trifluoromethyl) are present to stabilize these molecules against further reactions. In the presence of end capping groups, laser-based synthetic techniques similar to those normally used to generate fullerenes, produce thermally stable acetylenic carbon species capped with trifluoromethyl or nitrile groups with chain lengths in excess of 300 carbon atoms. Under these conditions, only a negligible quantity of fullerenes is produced. Acetylenic carbon compounds are not particularly moisture or oxygen sensitive but are moderately light sensitive. ---------------------------------------------------------------------- Harder than Diamond: Determining the Cross-Sectional Area and Young's Modulus of Molecular Rods Lior Itzhaki1, Eli Altus Prof.2, Harold Basch Prof.1, Shmaryahu Hoz Prof.1 Article first published online: 20 OCT 2005 DOI: 10.1002/anie.200502448 Copyright © 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim Angewandte Chemie International Edition Volume 44, Issue 45, pages 7432–7435, November 18, 2005 Hard and straight: Diamond is the hardest material known, yet polyyne—a molecular rod comprised of CC units—resists longitudinal compression with a Young's Modulus 40 times larger than diamond, whereas [n]staffanes have a Young's Modulus close to that of diamond. Mechanical engineering provides the connection between the point at which a rod buckles under longitudinal load and its cross-sectional area. *Uses an indirect definition of cross-section area based on the buckling of macroscopic rods. Not sure this is legit. Should use packing density of rods. ---------------------------------------------------------------------- Science 19 May 2006: Vol. 312 no. 5776 pp. 1009-1110 DOI: 10.1126/science.1125999 PERSPECTIVE CHEMISTRY Dangerously Seeking Linear Carbon Ray H. Baughman* + Author Affiliations It has been problematic to produce linear carbon molecules because key reactants are highly unstable and can explode. A solid state polymerization reaction avoids this problem and allows synthesis of these elusive products. Three decades ago, there was an explosion in my laboratory at Allied Chemical. We were trying to make a new phase of carbon, called linear carbon, by thermally polymerizing diiododiacetylene (C4I2) crystals and then eliminating the iodine substituent. The first step yielded less than a gram of polymerized C4I2 crystals, which had a metallic luster. Intrigued by this sample, a talented chemist forgot caution for an instant and tapped the side of a sealed ampoule with his finger. The resulting explosion of the polymerized crystals caused minor injury and spelled the end of our efforts to make linear carbon. n the old efforts at Allied Chemical and elsewhere to commercially exploit polydiacetylene single crystals, many interesting properties were found (6, 7), including some still being pursued for applications (8). The crystals have a per-chain stiffness close to that of diamond, very high coefficients for tripling the frequency of incoming light, and negative thermal expansion coefficients tunable to near zero by introducing defects. They have been deployed as mechanical stress sensors and as temperature-limit and chemical-exposure indicators. Also, the very high observed electron mobility for polydiacetylene single crystals suggests electronic device applications. Many of these properties deserve investigation for the polymer produced by Sun et al., but probably for fundamental rather than practical reasons, because poly(C4I2) chains lack the stability of more typically investigated polydiacetylenes with large organic substituents. In perhaps the most important commercial application of diacetylene polymerization, printed inks containing diacetylene microcrystals have been used as time-temperature indicators. Diacetylenes typically have an actuation energy for thermal polymerization of about 20 to 28 kcal/mol, which can be tuned to closely match the activation energy and degradation rate for important perishables, from vaccines to foodstuffs. Color changes of the diacetylene microcrystals during thermal polymerization provide a visual indication of whether a perishable product in the same thermal environment has degraded as a result of integrated time-temperature exposure (9). Over a billion of these diacetylene polymerization-based indicators have been used on individual vaccine vials since 1996 to assist disease eradication in parts of the world that do not have a reliable cold chain, by helping to ensure the delivery of viable vaccines (10). The United States Army is using these diacetylene indicators on cartons of their MREs (Meals Ready to Eat). ---------------------------------------------------------------------- The existence of this form of carbon is controversial. As substructures of larger molecules, relatively short carbon chains with the (−C≡C−)n structure ([[polyyne]]s) are well known. W. A. Chalifouxa and R. R. Tykwinsk (2009), ''Synthesis of extended polyynes: Toward carbyne''. Comptes Rendus Chimie, volume 12, issue 3, pages 341–358 {{doi| 10.1016/j.crci.2008.10.004}} In 1995, the preparation of carbyne chains with over 300 carbons was reported; they seemed to be reasonably stable as long as the terminal alkynes on the chain are capped rather than having a free acetylenic H atom. That study specifically demonstrated that the result was a carbyne-like structure rather than a fullerene. R. J. Lagow, J. J. Kampa, Han-Chao Wei, Scott L. Battle, John W. Genge, D. A. Laude, C. J. Harper, R. Bau, R. C. Stevens, J. F. Haw., E. Munson (1995), ''Synthesis of linear acetylenic carbon: The "sp" carbon allotrope''. Science, volume 267, issue 5196, pages 362–367. Bibcode 1995Sci...267..362L; {{doi|10.1126/science.267.5196.362}} However, in 2004 an analysis of a synthesized linear carbon allotrope found it to have a [[cumulene]] electronic structure—sequential [[double bond]]s along an sp-hybridized carbon chain—rather than the alternating triple–single pattern of linear carbyne. K.-H. Xue, F.-F. Tao, W. Shen, C.-J. He, Q.-L. Chen, L.-J. Wu, Y.-M. Zhu (2004), ''Linear carbon allotrope: Carbon atom wires prepared by pyrolysis of starch''. Chemical Physics Letters, volume 385, issue 5–6, pages 477–480 Bibcode 2004CPL...385..477X; {{doi|10.1016/j.cplett.2004.01.007}} A recent syrvey claimed that the properties and synthetic methods used in those studies are consistent with generation of [[fullerene]]s. H. Kroto (2010), [http://www.rsc.org/chemistryworld/Issues/2010/November/CarbyneOtherMythsAboutCarbon.asp ''Carbyne and other myths about carbon'']. RSC Chemistry World, November 2010.