Chemistry Faculty Work


Vibronic Spectroscopy of Unsaturated Transition Metal Complexes: CrC2H, CrCH3, and NiCH3

Document Type


Publication Date


Publication Title

Journal of Chemical Physics

Volume Number


Issue Number





Vibronically resolved resonant two-photon ionization and dispersed fluorescence spectra of the organometallic radicals CrC2H, CrCH3, and NiCH3 are reported in the visible and near-infrared wavelength regions. For CrC2H, a complicated vibronic spectrum is found in the 11 100–13 300 cm−1 region, with a prominent vibrational progression having ω′e=426.52±0.84 cm−1, ω′ex′e=0.74±0.13 cm−1. Dispersed fluorescence reveals a v″=1 level of the ground state with ΔG″1/2=470±20 cm−1. These vibrational frequencies undoubtedly pertain to the Cr–C2H stretching mode. It is suggested that the spectrum corresponds to the Ã 6Σ+←X̃ 6Σ+ band system, with the CrC2H molecule being linear in both the ground and the excited state. The related CrCH3 molecule displays a vibronic spectrum in the 11 500–14 000 cm−1 region. The upper state of this system displays six sub-bands that are too closely spaced to be vibrational structure, but too widely separated to be K structure. It is suggested that the observed spectrum is a 6E←X̃ 6A1 band system, analogous to the well-known B 6Π←X 6Σ+ band systems of CrF and CrCl. The ground state Cr–CH3 vibration is characterized by ω″e=525±17 cm−1 and ω″ex″e=7.9±6 cm−1. The spectrum of NiCH3 lies in the 16 100–17 400 cm−1 range and has ω′e=455.3±0.1 cm−1 and ω′ex′e=6.60±0.03 cm−1. Dispersed fluorescence studies provide ground state vibrational constants of ω″e=565.8±1.6 cm−1 and ω″ex″e=1.7±3.0 cm−1. Again, these values correspond to the Ni–CH3 stretching motion.



Link Out URL