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Like (CO)₄, Do (CS)₄ and (CSe)₄ Have a Triplet Ground State?

Xiaoguang Bao^1,*(鲍晓光), Dr. David A. Hrovat², Weston Thatcher Borden^2,*

¹College of Chemistry, Chemical Engineering and Materials Science, Soochow University, 199 Ren-Ai Road, Suzhou Industrial Park, Suzhou, Jiangsu 215123 (P. R. China)

²Department of Chemistry and the Center for Advanced Scientific Computing and Modeling, University of North Texas, 1155 Union Circle #305070, Denton, Texas 76203-5070 (USA)

Chem. Eur. J. 2013, 19, 5687–5693.

Cyclobutane-1,2,3,4-tetraone, (CO)₄, was computationally predicted and, subsequently, experimentally confirmed to have a triplet ground state, in which a b_2g σ MO and an a_2u π MO were each singly occupied. In contrast, the (U)CCSD(T) calculations reported herein found that cyclobutane-1,2,3,4-tetrathione, (CS)₄, and cyclobutane-1,2,3,4-tetraselenone, (CSe)₄, both had singlet ground states, in which the b_2g σ MO was doubly occupied and the a_2u π MO was empty. Our calculations showed that both the longer C X distances and smaller coefficients on the carbon atoms in the b_2g and a_2u MOs of (CS)₄ and (CSe)₄ contributed to the difference between the ground states of these two molecules and the ground state of (CO)₄. An experimental test of the prediction of a singlet ground state for (CS)₄ is proposed.

链接： //onlinelibrary.wiley.com/doi/10.1002/chem.201204049/abstract