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Abstract Because the thermodynamic property is closer to gasoline, advanced biofuels (C ≥ 6) are appealing for replacing non-renewable fossil fuels using biosynthesis method that has presented a promising approach. Synthesizing advanced biofuels (C ≥ 6), in general, requires the expansion of carbon chains from three carbon atoms to more than six carbon atoms. Despite some specific biosynthesis pathways that have been developed in recent years, adequate summary is still lacking on how to obtain an effective metabolic pathway. Review of biosynthesis pathways for expanding carbon chains will be conducive to selecting, optimizing and discovering novel synthetic route to obtain new advanced biofuels. Herein, we first highlighted challenges on expanding carbon chains, followed by presentation of two biosynthesis strategies and review of three different types of biosynthesis pathways of carbon chain expansion for synthesizing advanced biofuels. Finally, we provided an outlook for the introduction of gene-editing technology in the development of new biosynthesis pathways of carbon chain expansion.

Because the thermodynamic property is closer to gasoline, advanced biofuels (C ≥ 6) are appealing for replacing non-renewable fossil fuels using biosynthesis method that has presented a promising approach. Synthesizing advanced biofuels (C ≥ 6), in general, requires the expansion of carbon chains from three carbon atoms to more than six carbon atoms. Despite some specific biosynthesis pathways that have been developed in recent years, adequate summary is still lacking on how to obtain an effective metabolic pathway. Review of biosynthesis pathways for expanding carbon chains will be conducive to selecting, optimizing and discovering novel synthetic route to obtain new advanced biofuels. Herein, we first highlighted challenges on expanding carbon chains, followed by presentation of two biosynthesis strategies and review of three different types of biosynthesis pathways of carbon chain expansion for synthesizing advanced biofuels. Finally, we provided an outlook for the introduction of gene-editing technology in the development of new biosynthesis pathways of carbon chain expansion. [ABSTRACT FROM AUTHOR]

In this paper, the results of a comprehensive theoretical investigation of neutral HCnH0 and charged HCnH± chains are reported using state‐of‐the‐art compound model chemistries (W1BD, G4, CBS‐QB3, CBS‐APNO, CBS‐4M) and single point methods (including "gold standard" CCSD(T)). The properties envisaged include electronic and chemical bonding structure data, enthalpies of formation, adiabatic and vertical ionization (IP), and electron attachment (EA) energies, gas phase acidities, C−H bond strengths, and chain "deprotecting" (HCnH → H + Cn + H) energies. The best theoretical estimates based on composite models reported here for the various properties investigated agree with the available experimental data and are better than all previous theoretical estimates. To exemplify, for the enthalpies of formation, the G4 composite model achieves a RSMD (root square mean deviation) of 0.28 kcal mol−1 and a MUD (maximum unsigned deviation) of 0.45 kcal mol−1. Most importantly from the astrochemical perspective, it is predicted that the stable HCnH− anions with n≤8$n\le 8$ are nonlinear. Having sufficiently large dipole moments, the anion HCnH−cis conformers are potential candidates for detection in space via rovibrational spectroscopy. [ABSTRACT FROM AUTHOR]

Using laser-induced vaporisation to evaporate and ionise a source of curved polyaromatic hydrocarbons (carbon nanobelts), we show collision impacts between species cause mass loss and the resultant ions are catalogued via mass-spectrometry. These data are interpreted via a series of "in-silico"-simulated systematic hydrogen-loss studies using density functional theory modelling, sequentially removing hydrogen atoms using thermodynamic stability as a selection for subsequent dehydrogenation. Initial hydrogen loss results in the formation of carbyne chains and pentagon-chains while the nanobelt rings are maintained, giving rise to new circular strained dehydrobenzoannulene species. The chains subsequently break, releasing CH and C2. Alternative routes towards the formation of closed-cages (fullerenes) are identified but shown to be less stable than chain formation, and are not observed experimentally. The results provide important information on collision degradation routes of curved molecular carbon species, and notably serve as a useful guide to high-energy impact conditions observed in some astrochemical environments. [ABSTRACT FROM AUTHOR]

To be detectable in space via radio astronomy, molecules should have a permanent dipole moment. This is the plausible reason why HCnH chains are underproportionally represented in the interstellar medium in comparison with the isoelectronically equivalent HCnN chain family, which is the most numerous homologous series astronomically observed so far. In this communication, we present results of quantum chemical calculations for the HCnH family at several levels of theory: density functional theory (DFT/B3LYP), coupled-cluster expansions (ROCCSD(T)), and G4 composite model. Contradicting previous studies, we report here that linear HCnH− anion chains with sizes of astrochemical interest are unstable (i.e., not all calculated frequencies are real). Nonlinear cis and trans HCnH− anion chains turn out to be stable both against molecular vibrations (i.e., all vibrational frequencies are real) and against electron detachment (i.e., positive electroaffinity). The fact that the cis anion conformers possess permanent dipole is the main encouraging message that this study is aiming at conveying to the astrochemical community, as this makes them observable by means of radio astronomy. [ABSTRACT FROM AUTHOR]

The 2 Π g ← X 2 Σ u + electronic spectrum of C 5 + in the gas-phase with origin band at 513 nm is reported following experiments in a cryogenic ion trapping instrument. Buffer gas-cooled C 5 + ions, generated by laser vaporisation of graphite, were investigated using two action spectroscopy approaches. Laser-induced dissociation of weakly bound C 5 + − He n complexes synthesised in the trap reveal a linear dependence of the absorption energies on n allowing prediction of those of the bare ion C 5 + . These results are confirmed in two colour experiments on C 5 + , by monitoring fragmentation into the C 3 + + C 2 product channel. The data are supplemented with high-level electronic structure calculations which support the assignment of D ∞ h symmetry to the ground electronic state. These laboratory results provide the requisite data needed for spectroscopic detection of this structure in terrestrial and extraterrestrial environments. [ABSTRACT FROM AUTHOR]

The transition between gapped (semiconducting) and gapless (metallic) phases and tunability of bandgap in materials is a very lucrative yet considerably challenging goal for new-age device preparation. For bulk materials and for two-dimensional layered systems, this is a rapidly expanding field. We theoretically propose a one-dimensional pure carbon material with a tunable bandgap. We find that two parallel coupled polyyne chains show metallic behaviour with bands crossing on the Fermi level, unlike the single semiconducting chain. The number of nodal points (two) is robust under transverse and longitudinal strain, indicating the symmetry-protected nature of the metallic phase. Sliding one chain with respect to the other breaks reflection symmetry and a clear bandgap opens up at the nodes, leading to a gapped phase. By varying the slide parameter, the bandgap can be tuned efficiently. This work initiates and indicates possible topological phases of real one-dimensional materials without the involvement of edge modes.

To realise the technological potential of subnanometer graphene junctions, there is a need to understand how their electronic and spintronic properties are controlled by the carbon chains bridging their gaps. Motivated by the recent experimental efforts to form in-situ all-carbon junctions using graphene electrodes connected to carbon chains, here we systematically study a wide variety of such structures. We find that although a wide range of transport properties are possible, the junctions can be divided into a small number of categories, according to their qualitative transport properties. For example, we find that junctions bridged by even-numbered chains of carbon atoms tend to have a lower conductance than those bridged by odd-numbered atomic chains. We also find that junctions with ferromagnetically aligned electrode surface edges have a higher transmission than anti-ferromagnetically aligned ones, because ferromagnetic alignment tends to increase the transmission of one of the spin carriers. We also examine the effect of terminal rings, electrode terminal edges and the effect of saturation of edges with hydrogen on transport properties of all-carbon junctions. Just like genomics, our findings provide a complete set of information to construct junctions formed by carbon chains with desired properties for spintronic applications. [Display omitted] [ABSTRACT FROM AUTHOR]

Monoatomic carbon chains and carbyne-rich composites are promising materials for many applications from protective coatings to nanoelectronic devices. Therefore, a thorough understanding of both the atomic and electronic structure of chained carbon is important. In this study, a combination of Raman scattering and electron photoemission techniques is used to study the bonding types, electron work functions and band gaps for carbyne-containing films on copper and silicon substrates. Raman mapping shows the nonuniform distribution of sp1 hybridization across the carbon-coated area on polycrystalline copper substrate due to adhesion differences. UV-excited electron emission dependence on thickness and ambient pressure confirms the difference between the silicon- and copper-based samples. Comparison with DFT calculations performed on surface slab models allows to draw conclusions about the chained composite structure. Image 106 [ABSTRACT FROM AUTHOR]

Dear Colleagues, [...]

In recent years, environmental wastewater has become an increasingly prominent problem, and photocatalytic degradation is one of the effective means to treat waste pollutants. In this study, glycine was embedded in a tubular carbon nitride material with melamine as the parent by a supramolecular self-assembly strategy to prepare carbon chains implanted tubular graphitic carbon nitride (CTCN). The introduction of carbon chains can reduce the formation of hydrogen bonds, which is beneficial to improve the carrier transport efficiency. It can also adjust the valence band position and has better reduction performance. The thin-walled tubular structure formed by supramolecular self-assembly exposes more active sites and shortens the carrier transport distance due to the size effect, which further improves the carrier separation efficiency. The synergistic effect of the two greatly contributes to the photocatalytic performance of the material. The degradation rate of 0.3% CTCN is 8.1 times higher than that of Bulk CN, and 0.3% CTCN exhibits good stability. This solution is beneficial to optimize some existing wastewater treatment methods and has a role in environmental protection. [Display omitted] • The carbon chain improves molecular polymerization and reduces the formation of hydrogen bonds. • The highly conductive carbon chain facilitates the separation of carriers in carbon nitride. • The thin-walled tubular structure improves the optoelectronic properties of the sample. [ABSTRACT FROM AUTHOR]

We consider longitudinal nonlinear atomic vibrations in uniformly strained carbon chains with the cumulene structure ( = C = C = ) n . With the aid of ab initio simulations, based on the density functional theory, we reveal the phenomenon of π -mode softening in certain range of its amplitude for the strain above the critical value η c ≈ 11 % . Condensation of this soft mode induces the Peierls phase transition connected with doubling of the unit cell. We introduce a simple classical model without any adjustable parameters that allows one to describe quite well the properties of the π -mode softening. Besides the π -mode, two other symmetry-determined nonlinear normal modes can exist in monoatomic chains with arbitrary interparticle interactions. They correspond to tripling or quadrupling of the vibrational unit cell. Softening of these modes allows one to suppose that two new types of carbon chains (besides cumulene and polyyne) can exist with bond lengths alternation different from that of polyyne. Since the phase transitions in the strained cumulene can significantly change its electronic properties, these phenomena can be used for constructing various nanodevices. [ABSTRACT FROM AUTHOR]

We study the electronic properties of coupled parallel polyyne chains in a couple of symmetric stacking arrangements, namely the AA stacking and the AB stacking, with the single and triple carbon bonds of one chain aligned (AA) and anti-aligned (AB) with those of the other chain. Both these arrangements described by tight-binding Hamiltonians, whose parameters are calibrated by matching low energy dispersion provided by first principle calculations, fall in the BDI class of topological classification scheme. We calculate the topological invariants for all three topological phases of the system: one for the AA stacking and 2 for the AB one. In AA stacking, both the insulating and the metallic phase belongs to the same topological phase. Whereas, the model exhibits two different values of the topological invariant in the two different insulating phases (structurally differentiated by transverse strain). In this later stacking though the transition between two distinct topological phases with the closure of the gap is practically unachievable due to the requirement of the high transverse strain. We also show the existence of four non-zero energy edge modes in the AA stacking and that of two zero energy edge modes in one of the topological phases for the AB stacking., (© 2023 IOP Publishing Ltd.)

A highly selective enhancement of the optical response of the inner tubes of double-walled carbon nanotubes has been identified upon transformation of the residual C atoms inside the hollow core to linear carbon chains (LCC). By varying the growth conditions and using standardized suspensions, it has been observed that this optical response depends sensitively on the tube diameter and LCC growth yield. It is reported how the formation of LCC by postsynthesis annealing at 1400 °C leads to an increase of the photoluminescence (PL) signal of the inner tubes up to a factor of 6 for tubes with (8,3) chirality. This behavior can be attributed to a local charge transfer from the inner tubes to the carbon chains, counterbalancing quenching mechanisms induced by the outer tubes. These findings provide a viable pathway to enhance the low PL quantum yield of double-walled carbon nanotubes and proof the capability of inner tubes to exhibit photoluminescence. [ABSTRACT FROM AUTHOR]

Exponentially localized Wannier functions of cumulene are calculated from the Bloch functions obtained through a tight-binding approach. Numerical results and discussions are given for the and bands. In the latter case, the single-band Wannier functions are similar to the orbitals of a diatomic molecule, while the two-band Wannier functions resemble hybrid atomic orbitals. Contour plot of an sp-like Wannier function of cumulene. [ABSTRACT FROM AUTHOR]

Brazil has played an important role in the development and use of resonance Raman spectroscopy as a powerful characterization tool for materials science. Here we present a short history of Raman scattering research in Brazil, highlighting the important contributions to the field coming from Brazilian researchers in the past. Next we discuss recent and important contributions where Brazil has become a worldwide leader, that is on the physics of quasi-one dimensional carbon nanotubes. We conclude this article by presenting results from a very recent resonance Raman study of exciting new materials, that are strictly one-dimensional carbon chains formed by the heat treatment of very pure double-wall carbon nanotube samples.

Performance on olfactory tests can be influenced by a number of stimulus characteristics including chemical structure, concentration, perceptual similarity, and previous experience with the test odorants. Few of these parameters have been extensively characterized in the Fischer 344 rat strain. To investigate how odor quality affects perception in this rat strain, we measured how graded perceptual similarity, created by varying carbon chain length across a series of homologous alcohol pairs, influenced odor discrimination using a liquid-motivated go/no-go task. We employed an automated, liquid-dilution olfactometer to train Fischer 344 rats (N = 8) on a 2-odor discrimination task. Six odorants (1-propanol, 1-butanol, 1-pentanol, 1-hexanol, 1-heptanol, and 1-octanol) were arranged to produce 15 novel odorant pairs differing between 1 and 5 carbon atoms; testing sessions included presentation of only 1 pseudorandomly assigned pair daily (200 trials). Results show that although rats can learn to discriminate between any 2 odorant pairs, performance declines systematically as the pairs become more structurally similar and, therefore, more perceptually confusing. As such, the easier discrimination pairs produced reliable ceiling effects across all rats, whereas performance for the difficult discrimination pairs was consistently worse, even after repeated testing. These data emphasize the importance of considering odorant stimulus dimensions in experimental designs employing olfactory stimuli. Moreover, establishing baseline olfactory performance in Fischer 344 rats may be particularly useful for predicting age-related cognitive decline in this model. [ABSTRACT FROM AUTHOR]

The donor-acceptor molecule is the only molecule that features a real intrinsic rectification. However, all investigations in the last decades showed that rectification behaviors of such molecules are not promising since their rectification ratio is only on the order of 10. Use of carbon chains C n to serve as spacers is reported, along with attempts to modulate electrical behavior of the donor-acceptor molecule. Calculations using the first-principles method show that electrical behavior is indeed altered substantively, and a particular regularity can be clearly observed, i.e., a dramatic odd-even oscillation for electronic behavior with increasing carbon-chain length n. For models with even- n carbon chains, the rectification ratio is small (30), and no negative differential resistance (NDR) behavior is detected, but the rectifying performance of models with odd- n carbon chains is tremendously improved and rectification ratios on the order of 50 to 400 can be achieved, alongside a large NDR. This study thus suggests that using a suitable spacer might be an effective way to significantly boost electrical characteristics, including rectifying performance, of the donor-acceptor molecule. [ABSTRACT FROM AUTHOR]

Carbon nanotubes (CNTs) can be used as nanoreactors due to their unique hollow nanostructures. In order to prepare linear carbon chains inside CNTs, eDIPS single-wall carbon nanotubes were annealed at high temperatures from 1300 to 1500 [ABSTRACT FROM AUTHOR]

The structures, binding energies, and molecular parameters of CnF clusters (n = 1-7) have been investigated theoretically on neutral and ionic forms with the RCCSD(T)//B3LYP/aug-cc-pVTZ level of theory. It can be concluded that for the ground states the linear structures are stable only for CF, C6F, and C7F. Other neutral species of CnF(n = 2-5) are slightly bent. The variation in stability with growth of the carbon chain is flat but the ionization potential and electron affinity exhibit clear variations with the size of the clusters. Cation clusters with an even n value have triplet ground states whereas singlet ground states exist when n is odd. All anions except CF-, have singlet ground states. The alternation in stability is found in both cationic and anionic forms, but the trends are reversed. Predictions of several molecular properties may be useful in the identification of these species in the laboratory and in space. [ABSTRACT FROM AUTHOR]

Abstract: The toxic interaction of methanol, ethanol and propanol with bovine hemoglobin (BHb) at protein molecular level was studied by resonance light scattering (RLS), fluorescence, ultraviolet–visible absorption (UV–vis) and circular dichroism (CD) techniques. The experimental results showed that the three alcohols all had toxic effects on BHb and the effects increased along with the increasing alcohol dose. The results of RLS and fluorescence spectroscopy showed that alcohols can denature BHb. They changed the microenvironment of amino acid residues and led to molecular aggregation. The decreasing order of the influence is propanol, ethanol and methanol. The results of UV–vis and CD spectra revealed that alcohols led to conformational changes of BHb, including the loosening of the skeleton structure and the decreasing of α-helix in the second structure. The changes generated by propanol were much larger than those by methanol and ethanol. [Copyright &y& Elsevier]

Double-walled carbon nanotubes (DWCNTs) with high graphitization have been synthesized by hydrogen arc discharge. The obtained DWCNTs have a narrow distribution of diameters of both the inner and outer tubes, and more than half of the DWCNTs have inner diameters in the range 0.6-1.0 nm. Field electron emission from a DWCNT cathode to an anode has been measured, and the emission current density of DWCNTs reached 1 A/cm at an applied field of about 4.3 V/μm. After high-temperature treatment of DWCNTs, long linear carbon chains (C-chains) can be grown inside the ultra-thin DWCNTs to form a novel C-chain@DWCNT nanostructure, showing that these ultra-thin DWCNTs are an appropriate nanocontainer for preparing truly one-dimensional nanostructures with one-atom-diameter. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Spectroscopic characterisation of carbon chains and ions has been motivated by a general interest in understanding the electronic structure and properties and also due to their prominence in astrochemistry, combustion processes as well as molecular electronics. Various experimental and theoretical approaches have been successfully implemented over the years towards realising this goal. In the current review, we have tabulated the experimentally available data on the excited electronic states of carbon chains and derivatives containing H, N, O, S and metals. [ABSTRACT FROM AUTHOR]

Electronic transitions of the triplet chain C5H- anion were studied using detachment spectroscopy. The system detected in the vicinity of the electron detachment threshold is assigned to the b3A ← a3A transition with a dipole bound state (DBS) character. The second system measured by autodetachment spectroscopy is attributed to the c3A ← a3A Feshbach electronic transition. Negative anharmonicity of the vibrational progression built upon the low frequency CCC in-plane bending mode ν12 is observed in both DBS and Feshbach states. This indicates a barrier to linearity on the potential energy surface in both excited states. The triplet chain C5H- anion exhibits similar electronic properties to C3H-. Renner-Teller and vibronic effects between the 3A DBS and Feshbach states are inferred and may explain the stabilisation of the DBS. This interaction is weaker in C5H- than C3H- leading to smaller barrier heights on the potential energy surface. [ABSTRACT FROM AUTHOR]

Abstract: 2-Thenoyltrifluoroacetone (TTA) was grafted onto the coupling agent 3-(triethoxysilyl)-propyl-isocyanate to construct the precursor I (TTA–Si), and polymer precursors II (PVPD, PMAA and PVPDMAA) were synthesized through the addition polymerization reactions. Then precursors I and II have coordinated to the rare-earth ions with the carbonyl, carboxyl group or nitrogen atom, respectively, and after hydrolysis and copolycondensation sol–gel process, the three kinds of polymeric hybrids were obtained. FTIR, ultraviolet–visible diffuse reflection and fluorescence absorption spectra, electronic micrographs, room-temperature X-ray diffraction patterns and TG plots were characterized and the results reveal that the hybrid materials showed uniformity in the microstructure, efficient intramolecular energy transfer system and excellent characteristic emission of terbium ions under UV irradiation. [Copyright &y& Elsevier]

Several complexes containing Co3 carbonyl clusters end-capping carbon chains of various lengths are described. Pd(0)/Cu(I)-catalysed reactions between {Co3{μ3-C(C≡C)2Au(PPh3)}(μ-dppm)(CO)7 and I(C≡C)2SiMe3 or FcC≡CI gave {Co3{μ3-C(C≡C)xR}(μ-dppm)(CO)7 [x = 4, R = SiMe33; x = 3, R = Fc 8]; treatment of 3 with NaOMe and AuCl(PPh3) gave 4 [x = 4, R = Au(PPh3)]. Related preparations of Co3{μ3-C(C≡C)2[Ru(PP)Cp′]}(μ-dppm)n(CO)9−2n [PP = (PPh3)2, Cp’ = Cp, n = 1, 5; PP = dppe, Cp′ = Cp∗, n = 1, 6; 0, 7] are also described. Syntheses of bis-cluster complexes {Co3(μ-dppm)(CO)7}2(μ-Cx) (x = 14, 12; 16, 9; 18, 11; 26, 10) – the latter being the longest cluster-capped Cx chains so far described – and the mercury-bridged compounds Hg{(C≡C)xC[Co3(μ-dppm)(CO)7]}2 (x = 1, 13; 2, 14) are reported. The molecular structures of 7, 12, 13 and 14, as well as of Co3(μ3-CC≡CSiMe3)(μ-dppm)(CO)6(PPh3) (15) and Co3{μ3-CC(O)OEt}(μ-dppm)(CO)7 (16), are reported. [Copyright &y& Elsevier]

Gas phase electronic spectra allow direct comparisons between laboratory data and the wealth of astrophysical measurements that have been tabulated. Over the past decade a number of assorted carbon chain systems have been spectroscopically investigated, yielding an understanding of the transitions and trends apparent among their homologous series. This rigorous program begins with trapping unstable carbon chain ions and radicals in neon matrices, where origin bands and vibrational data are obtained. From these results one can then seek out the gas phase transitions in higher resolution in order to more accurately determine assignments and spectroscopic constants. To this purpose, laser spectroscopic methods are employed, including pulsed and cw cavity ringdown, resonant enhanced multiphoton ionisation, and more recently, a two-photon two-colour excitation/fragmentation approach to investigate trapped ions. From a comparison involving the electronic spectra of a number of carbon chain systems measured in the laboratory with diffuse interstellar band (DIB) absorptions, one concludes that species involving only a handful of carbon atoms can not be the carriers. However, larger carbon chains and ring species still remain viable. In this review, we consider which systems require further investigation, including these longer species, metal-capped chains and other cationic radicals. [ABSTRACT FROM AUTHOR]

Abstract: Multiwalled carbon nanotubes (MWCNT) have been synthesized on graphite cathodes by arc discharge in He atmosphere, either by using a catalytic Ni–Cr mixture or without catalysts. A preliminary scanning electron microscopy (SEM) investigation evidences the presence of nanotubes. Raman peaks due to longitudinal optic (LO) modes of linear carbon chains with sp hybridization (carbyne), encapsulated inside the nanotubes, occur in the wavenumber range 1780–1870 cm−1, with variable intensity and shapes, in various regions of the analysed samples, together with the typical bands of MWCNT. In some sample zones the Raman band of carbyne results very strong with respect to G band of the host MWCNT, about one order of magnitude higher than in other studies dealing with carbon chains inside nanotubes. The second order Raman scattering is also observed, with frequency values of 2LO overtones slightly lower than the exact doubling of one phonon peak. No evidence of two-phonon density of state is found for higher frequency, as expected on the basis of existing theoretical predictions. Finally, the temperature dependence of intensity and frequency of carbyne LO modes is studied up to about 1000 K, and their behaviours are consistent with a reversible change of the bond configuration from polyynic to cumulenic character. [Copyright &y& Elsevier]

Abstract: The IR and UV–vis absorptions of oxides of long carbon chains trapped in cryogenic matrices were investigated experimentally and theoretically. Some of the IR-lines were assigned to the oxides of certain carbon chains using the method of isotopic substitution of matrix material (16O2/18O2, 12CO/13CO) and the technique of selective UV–vis photo-bleaching. Our data, along with quantum chemical calculations suggest that the wavelength positions of the major UV–vis and IR absorptions of the oxides C n O, OC n O, and of the parent carbon chains C n are located in close vicinity. [Copyright &y& Elsevier]

Proto-desilylation of 1-(Me3SiC≡C)-1′-{Cp∗(dppe)RuC≡C}Fc′ (1) afforded the corresponding ethynyl derivative 2, from which the green Co2(μ-dppm)n(CO)8−2n (n= 0,1) adducts 3 and 4 were obtained. Replacement of the ethynyl proton in reactions between 2 and AuCl(PPh3), Hg(OAc)2 or FeCl(dppe)Cp∗ gave complexes 1-(RC≡C)-1′-{Cp∗(dppe)RuC≡C}Fc′ [R=Au(PPh3) 5, 1/2Hg 6, Fe(dppe)Cp∗8]; the latter gave bis-vinylidene 9 with MeI, characterised (as was 2) by a single crystal X-ray study. Oxidative coupling of 2 (CuCl/tmeda/acetone, air) gave diyne 10, while coupling of 5 with Co3(μ3-CBr)(μ-dppm)(CO)7 afforded 1-{Cp∗(dppe)RuC≡C}-1′-{(OC)7(μ-dppm)Co3(μ3-CC≡C)}Fc′ (11). Cyclic voltammetric measurements indicated that there was no significant electronic coupling between the end-groups through the ferrocene centre in any of these compounds. [Copyright &y& Elsevier]

Abstract: The quadratic stretching force constants and the harmonic stretching vibrations of linear C13 have been studied by the coupled cluster variant CCSD(T) in conjunction with large basis sets. A large absolute IR intensity of 22,218kmmol−1 is calculated for the ν 9 band. In comparison with a high-resolution spectroscopic study [T.F. Giesen, A. van Orden, H.J. Hwang, R.S. Fellers, R.A. Provencal, R.J. Saykally, Science 265 (1994) 756], the corresponding wavenumber experiences an unusually large anharmonicity contribution of 7%. [Copyright &y& Elsevier]

Accurate equilibrium (re) structures (ca. 0.0005 Å accuracy in bond lengths) have been established for linear C13 and C15 by applying a uniform correction to the results of CCSD(T) calculations with the cc-pVQZ basis set. The equilibrium bond lengths cover a small range between 1.2690 and 1.2928 Å and are indicative of strong carbon–carbon double bonds. Equilibrium structures of still longer chains may be obtained by taking the recommended re structure for C15 and inserting one or more C2 links with Re = 1.277 Å in the middle of the molecule. Both linear C13 and C15 exhibit no sign of floppiness and appear to behave like fairly normal semi-rigid molecules. Diagonal potentials for the IR active bending vibrations of both molecules have large correlation contributions between -33 and 47%, with MP2 strongly overshooting with respect to CCSD(T). Harmonic cis-bending vibrational wavenumbers and their absolute IR intensities are predicted. Since the latter are rather small, the chances of an interstellar detection of linear C13 or C15 in the far IR may be poor. [ABSTRACT FROM AUTHOR]

We have used the elimination of AuX(PR3) (X = halide, R = Ph, tol) that occurs in reactions of alkynylgold(I)–phosphine complexes with M3(μ-H)3 (μ3-CBr) (CO)9 (M = Ru, Os) to prepare the complexes M3(μ-H)3(μ3-CC≡CR)(CO)9 [M = Ru, R = Ph 2, C≡CSiMe33, Fc 4, C≡CFc 6-Ru, CC[Ru(PPh3)2Cp] 8; M = Os, R = C≡CFc 6-Os, C≡CC≡CFc 7], Fc′{(μ3-C≡CC)Ru3(μ-H)3(CO)9}25, and bis-cluster-capped carbon chain complexes {M3(μ-H)3(CO)9}2{μ3:μ3-C(C≡C)nC} (M = Ru, n = 2 9, 3 10-Ru; M = Os, n = 3 10-Os) and {(L)(OC)8(μ-H)3M3}C(C≡C)nC{Co3(μ-dppm)(CO)7} (n = 1, M = Ru, L = CO 11, PPh312-Ru/P; n = 2, L = CO 12-Ru, PPh313; M = Os, L = CO 12-Os) in good to excellent yields. X-ray structural determinations of 2–5, 6-Ru, 6-Os, 7, 9, 11, 12-Ru, 12-Os and 12-Ru/P are reported. [Copyright &y& Elsevier]

The Pd(0)/Cu(I)-catalysed reactions between Co3(μ3-CBr) (CO)9 and W(C≡CC≡CH)(CO)3Cp gives the C5 complex {Cp(OC)3W}C≡CC≡CC{Co3(CO)9} (2). Similarly, Co3(μ3-CBr)(μ-dppm)(CO)7 and W(C≡CC≡CH)(CO)3Cp or Ru(C≡CC≡CH)(dppe)Cp* give {Cp(OC)3W}C≡CC≡CC{Co3(μ-dppm)(CO)7} and {Cp*(dppe)Ru}C≡CC≡CC{Co3(μ-dppmn)(CO)7} (5). An attempt to prepare a C3 analogue from Ru(C≡CH)(PPh3)2Cp and Co3(μ3-CBr)(CO)9 gave instead the acyl derivative {Cp(Ph3P)2Ru}C≡CC(O)C{Co3(CO)8(PPh3)} (7). The X-ray structures of 2, 5 and 7 are reported: the C5 chains in 2 and 5 have an essentially unperturbed –C≡C–C≡C–C≡ formulation. [Copyright &y& Elsevier]

Abstract: The molecular geometry of cumulene chains H2CnH2 have been optimized using LCAO-SCF MO method (contracted Gaussian basis set of triple zeta valence quality TZVP and the more extended Dunning''s correlation consistent basis set aug-cc-PVDZ), density functional theory at different basis set levels, and the highly parametrized MNDO(PM3) method. The bond lengths have no remarkable alternation within the chain and converge to the asymptotic limit as the value of n is getting larger. The total charges calculated by Mulliken population analysis yield unrealistic values if the split valence basis set was employed. In contrast, using NBO analysis the net charges of the individual atoms converge very rapidly to their asymptotic limits with almost zero charges on central atoms. The comparison of the different basis set results to test the reliability of proton affinities calculated from the differences in molecular enthalpies of the parent chain and the corresponding anions was carried out. The increase of the number of Cn the chain decreases these differences asymptotically. The concept of ‘terminal charge repulsion’ is developed for the explanation of energy effects in long chains. The role of this concept in explanation of dependence of proton affinities on the chain length was discussed. The studied compounds are the best available building blocks in bimetallic compounds with useful properties in molecular electronics and nonlinear optics. [Copyright &y& Elsevier]

The products of a CS2-hydrocarbon discharge are elucidated through a combination of mass spectrometry and laser spectroscopy. Sulfur containing species are identified and their structures proposed using spectroscopic considerations. The resonant 2-color 2-photon ionization A2Π←X2Π spectrum of HC6S is presented, confirming previous non-mass selective identification. The origin band of the A2Π←X2Π transitions of HC8S and HC10S were measured at 14838.4(1) and 13333.7(5) cm−1 by cavity ringdown spectroscopy. The near linear relationship of absorption wavelength and chain length characterizes these species as molecular nanowires exhibiting cumulenic bonding. From these data HC12S is estimated to absorb at 820±5 nm. [Copyright &y& Elsevier]

We present some recent applications of microwave Fourier transform spectroscopy for the study of various molecular systems: weakly bonded complexes, carbon chains for their importance in interstellar medium or molecules of biological interest. The recent developments are presented and some perspectives are discussed. To cite this article: D. Petitprez, G. Wlodarczak, C. R. Physique 5 (2004). [Copyright &y& Elsevier]

Complexes containing a Co3 cluster linked to SiMe3, Au(PPh3), W(CO)3Cp and Fc groups by a C5 chain have been prepared by elimination of AuBr(PR3) (R=Ph, tol) in the reactions between Co3(μ3-CBr)(μ-dppm)(CO)7 and {(R3P)Au}C&z.tbnd6;CC&z.tbnd6;CX [X=SiMe3, W(CO)3Cp] or {(OC)7(μ-dppm)Co3}CC&z.tbnd6;C{Au(PPh3)} and FcC&z.tbnd6;CI (X=Fc). Subsequent auro-desilylation of the SiMe3 compound affords {(OC)7(μ-dppm)Co3}&z.tbnd6;CC&z.tbnd6;CC&z.tbnd6;C{Au[P(tol)3]}. Single-crystal X-ray structures of the W(CO)3Cp, Au{P(tol)3} and Fc complexes are reported. The C5 chain shows little departure from a formal &z.tbnd6;C&z.sbnd;C&z.tbnd6;C&z.sbnd;C&z.tbnd6;C&z.sbnd; fragment. [Copyright &y& Elsevier]

Schemes for Kekulé structure counting of linear carbon chains are suggested. Mathematical formulas, which calculate the Pauling bond order P(k, N) of a chemical bond numbered by k, are given for the carbon chain with N carbon atoms. By use of the least-squares fitting of a linearity, relationships between Pauling bond orders and bond lengths are obtained, and such correlation of the Pauling bond order–bond length can be qualitatively extended to the excited states. The relative magnitudes of Pauling bond orders in unsaturated carbon chains dominate C–C bond lengths a well as the bond length feature with the chain size increasing. © 2003 Wiley Periodicals, Inc. Int J Quantum Chem 94: 144–149, 2003 [ABSTRACT FROM AUTHOR]

Reactions of Co3(μ3-CBr)(μ-dppm)(CO)7 with {Au[P(tol)3]}2{μ-(C&z.tbnd6;C)n} (n=2–4) have given {Co3(μ-dppm)(CO)7}{μ3:μ3-C(C&z.tbnd6;C)nC} [n=2 (1), 3 (2), 4 (3)] containing carbon chains capped by the cobalt clusters. Tetracyanoethene reacts with 2 to give {Co3(μ-dppm)(CO)7}2{μ3:μ3-C(C&z.tbnd6;C)2C[&z.dbnd6;C(CN)2]C[&z.dbnd6;C(CN)2]C} (4). X-ray structural characterisation of 1, 3 and 4 are reported, that for 3 being the first of a cluster-capped C10 chain. [Copyright &y& Elsevier]

The purpose of this paper is to compare the role of UV light and of electric discharges, the two most important sources of energy on the primitive earth, in the synthesis of organic compounds out of a reducing model of that atmosphere. Since Miller's experiments in 1953, most of the experimental simulations have been performed with electric discharges, and it has been assumed that UV radiations would give similar results. In order to check this assumption we have performed both experimental simulations in our laboratory. Experimental results indicate that this assumption was wrong in a large extent. Our four main conclusions are: [ABSTRACT FROM AUTHOR]

[Display omitted] • The C atoms reassemble to generate carbon chains inside the sheet and then erupt out during the oxidation of bare MXenes. • MXenes with fewer layers have poor oxidation resistance though they could have better properties. • The eruption of is accelerated by humid environment and high temperatures. • Combining ReaxFF MD simulations and DFT calculations. The oxidation of MXenes has aroused considerable interest and attention in recent years, which is closely related to the synthesis process and environmental stability. However, there still remain many issues unclear about the oxidation of MXenes including the exquisite observation of the atomic reactions, and the influences of oxidizing gas and layer numbers. By combining reactive force field (ReaxFF) molecular dynamics simulations and density functional theory (DFT) calculations, the oxidation characteristics and mechanism of MXenes have been investigated. Herein, the oxidation of MXenes preferentially begins with O 2 adsorption on the surface Ti layers, inducing the lattice distortion of Ti layers and the fracture of Ti-C bonds. Without the constraint from Ti atoms, the free C atoms reassemble to generate carbon chains inside the sheet. Surprisingly, the chains could erupt out of the sheet although some obstruction would appear. As a result of the reformation of Ti-C bonds and the blocking of interstitial O atoms, a few chains would be stuck inside. Besides, the layer number has great effects on the oxidation kinetics. As the layer number increases, the adsorption of O 2 becomes easier but the eruption of carbon chains becomes weaker. Our findings would be instructive in enhancing corrosion resistance of MXenes and the preparation of oxidized MXenes. [ABSTRACT FROM AUTHOR]

A practically important task of synthesizing isolated carbon nanostructures can be solved by removing soluble chloride substrates. However, a reliable express characterization method to control the synthesis results is needed. In this paper, the optical reflection and absorption spectra of the linear-chain carbon (LCC) films on sodium and potassium chlorides surfaces were studied numerically using DFT modeling. In the optical absorption and reflection spectra three peaks were found that are absent in the spectra of pure substrates. Two of them observed in red and UV regions of the difference absorption spectra have been mapped to transitions between carbon states seen in the electronic DOS. Chlorine and potassium/sodium energy states have been found to contribute to the high-energy VUV peak. The bands discovered would be useful for the rapid characterization of an LCC coating and determination of the crystalline substrate orientation. • Carbon chains on chloride substrates have three optical bands Vis-UV range. • The two absorption peaks are purely intrinsic to the chained films. • Substrates energy states contribute to the UV region. • The bands discovered are useful for the characterization of a carbyne films quality. [ABSTRACT FROM AUTHOR]