Vibrational spectra of germanium-carbon clusters in solid Ar: identification of the nu4(sigma(u)) mode of linear GeC5Ge

Observation of Aromatic Three-Membered Rings in Ge3C and Ge3O via Photoelectron Spectroscopy and Theoretical Calculations

The structures and chemical bonding of Ge₃C^- and Ge₃O^- as well as their neutrals are explored with anion photoelectron spectroscopy and theoretical calculations. The vertical detachment energies of Ge₃C^- and Ge₃O^- are measured to be 1.51 ± 0.04 and 2.00 ± 0.04 eV, respectively. It is found that Ge₃C^-/0 have a C_2v symmetric planar structure with the C atom interacting with three Ge atoms. Ge₃O^-/0 have the O atom interacting with two Ge atoms of the triangular Ge₃ unit. Ge₃O^- has a C_s symmetric nonplanar structure, while Ge₃O has a C_2v symmetric planar structure. Theoretical results show that the multiconfigurational effects in Ge₃C^-/0 and Ge₃O^-/0 are insignificant. Chemical bonding analyses reveal that there exist the C-Ge₃ π_⊥ orbital interaction and two π aromatic Ge₂C units in Ge₃C. There are O-Ge₃ π_⊥ orbital interaction and one doubly aromatic Ge₃ unit in Ge₃O, but the π_⊥ orbital interaction is relatively weak.

Generation and structural characterization of Ge carbides GeCn (n = 4, 5, 6) by laser ablation, broadband rotational spectroscopy, and quantum chemistry

Following the recent discovery of T-shaped GeC₂, rotational spectra of three larger Ge carbides, linear GeC₄, GeC₅, and GeC₆ have been observed using chirped pulse and cavity Fourier transform microwave spectroscopy and a laser ablation molecule source, guided by new high-level quantum chemical calculations of their molecular structure. Like their isovalent Si-bearing counterparts, Ge carbides with an even number of carbon atoms beyond GeC₂ are predicted to possess ¹Σ ground electronic states, while odd-numbered carbon chains are generally ³Σ; all are predicted to be highly polar. For the three new molecules detected in this work, rotational lines of four of the five naturally occurring Ge isotopic variants have been observed between 6 and 22 GHz. Combining these measurements with ab initio force fields, the Ge-C bond lengths have been determined to high precision: the derived values of 1.776 Å for GeC₄, 1.818 Å for GeC₅, and 1.782 Å for GeC₆ indicate a double bond between these two atoms. Somewhat surprisingly, the spectrum of GeC₅ very closely resembles that of a ¹Σ molecule, implying a spin-spin coupling constant λ in excess of 770 GHz for this radical, a likely consequence of the large spin-orbit constant of atomic Ge (∼1000 cm^-1). A systematic comparison between the production of SiC_n and GeC_n chains by laser ablation has also been undertaken. The present work suggests that other large metal-bearing molecules may be amenable to detection by similar means.

Gas-Phase Spectroscopic Detection and Structural Elucidation of Carbon-Rich Group 14 Binary Clusters: Linear GeC3Ge

Guided by high-level quantum-chemical calculations at the CCSD(T) level of theory, the first polyatomic germanium-carbon cluster, linear Ge2C3, has been observed at high spectral resolution in the gas phase through its remarkably complex fundamental antisymmetric C-C stretching mode ν3 located at 1932 cm(-1). The observation of a total of six isotopic species permits the derivation of a highly accurate value for the equilibrium Ge-C bond length. The present study suggests that many more Ge-C species might be detectable in the future using a combination of laser-ablation techniques for production and high-resolution infrared and/or microwave techniques for spectroscopic detection.

Infrared observation of linear GeC3 trapped in solid Ar

Linear GeC(3) has been synthesized and its vibrational spectrum observed for the first time. The cluster was detected by Fourier transform infrared spectroscopy when the products from the dual laser ablation of either a pair of carbon and germanium rods or a single, sintered germanium-carbon rod were trapped in solid Ar at approximately 10 K. Comparison of (13)C isotopic shift measurements with the predictions of density functional theory calculations at the B3LYP/cc-pVDZ level has resulted in the identification of the nu(1)(sigma) and nu(2)(sigma) modes of linear GeC(3) at 1903.9 and 1279.6 cm(-1), respectively. For the related group IV clusters, this result is in contrast to SiC(3) for which two cyclic isomers have been observed but similar to C(4) for which only the linear isomer has been observed spectroscopically.

FTIR identification of the nu4(sigmau) and nu6(piu) modes of linear GeC3Ge trapped in solid Ar

GeC 3Ge was previously (1) produced by the dual laser ablation of germanium and carbon rods, and the nu 3(sigma u) carbon-carbon stretching fundamental was assigned at 1920.7 cm (-1). This paper presents results from new experiments that have enhanced the production of the molecule via laser ablation of a single sintered germanium-carbon rod, thus enabling the identification of two additional infrared active vibrational fundamentals. Ge participates strongly in one of these, the nu 4(sigma u) mode, and the corresponding Ge isotopic shifts reported here are the first for a germanium-carbon species. GeC 3Ge was produced by trapping the products from the laser evaporation of the Ge-C rod, in solid Ar at approximately 10 K, and recording the FTIR (Fourier transform infrared) spectra. Comparison of (70,72,73,74,76)Ge and (13)C isotopic shift measurements with the predictions of density functional theory calculations (DFT) at the B3LYP/cc-pVDZ level confirms the identification of the nu 4(sigma u) stretching fundamental at 735.3 cm (-1) and the nu 6(pi u) bending fundamental at 580.1 cm (-1) for linear GeC 3Ge.

Fourier transform infrared observation of the nu3(sigmau) vibration of NiC3Ni in solid Ar

The Fourier transform infrared spectrum of linear NiC(3)Ni was observed by trapping the vapor produced from the dual ablation of nickel and carbon rods with Nd:YAG (yttrium aluminum garnet) lasers in solid Ar at approximately 10 K. Measurements of (13)C isotopic shifts have enabled the identification of the nu(3)(sigma(u)) vibrational fundamental at 1950.8+/-0.2 cm(-1), an asymmetric carbon stretching mode. Experimental results are in good agreement with the predictions of density functional theory at the B3LYP6-311G(*) level. Theoretical results suggest that the molecule is slightly floppy. Although other nickel carbide clusters have been studied theoretically or observed by photoelectron spectroscopy or mass spectrometry, this is the first report on the structure of NiC(3)Ni and its vibrational spectrum.

Fourier transform infrared observation of the nu1(sigma) mode of linear CoC3 trapped in solid Ar

Fourier transform infrared (FTIR) and density functional theory (DFT) isotopic studies on cobalt-carbon species have resulted in the detection of linear CoC3. Dual laser ablation of carbon and cobalt rods, followed by trapping the products in solid Ar at approximately 10 K, produced the CoC3 chain. FTIR measurements of 13C isotopic shifts are in good agreement with the predictions of DFT calculations using the B3LYP and BPW91 functionals and the 6-311+G(3df) basis set, confirming the assignment of the nu1(sigma) fundamental of linear CoC3 at 1918.2 cm(-1).