The molecular and electronic structure, as well as the electronic absorption spectrum of Tc2(O2CCH3) 2Cl4 were studied by multiconfigurational quantum chemical methods. The computed ground state geometry is in excellent agreement with the experimental structure determined by single crystal X-ray diffraction (SCXRD). The total bond order (i.e., 3.20) is consistent with the presence of a moderately strong quadruple Tc-Tc bond and is the largest bond order reported so far for a multiple Tc-Tc bonded complex. Effective bond order analysis indicates stronger π and δ bonds for Tc2(O 2CCH3)2Cl4 (i.e., 1.71 for π and 0.59 for δ) than for Tc2Cl82- (i.e., 1.68 for π and 0.47 for δ). The electronic absorption spectrum was recorded in dichloromethane and shows three distinct bands in the range 10 000-35 000 cm-1. Assignment of the bands, as well as their excitation energies and intensities were performed at the CASSCF/CASPT2 level of theory. The lowest energy band corresponds to the δ → δâ̂ - transition; the next higher energy bands are attributed to δ → πâ̂ - and π → δâ̂ - transitions, respectively.
Bibliographical noteFunding Information:
Funding for this research was provided by a SISGR Grant from the US Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. 47824B. The computational part of this study was supported by the Chemical Sciences, Geosciences, and Biosciences Division, Office of Basic Energy Sciences, Office of Science, Heavy Elements Chemistry Program, US Department of Energy, under Grant DE-SC002183. The authors thank Trevor Low and Julie Bertoia for outstanding health physics support.
- Electronic structure
- Metal-metal bonds
- Optical spectroscopy