Singlet-Triplet Energy Gaps in Divalent C2H2M and C2H6M (M = C, Si, Ge, Sn and Pb)

Abstract

Singlet-triplet energy gaps in cyclopropeneylidene, 1_C, and propaneylidene, 2_C, are calculated and compared with their analogues 1_M and 2_M (M = Si_-s vs. Si_-t), (M = Ge_-s vs. Ge_-t), (M = Sn_-s vs. Sn_-t) and (M = Pb_-s vs. Pb_-t); at B3LYP/6-311++G** level of theory. The change order of energy gaps between triplet (t) and singlet (s) states, ΔG_t-s for 1_M is: 1_Si > 1_C > 1_Ge > 1_Sn > 1_Pb while for 2_M, the opposite order is obtained: 2_Pb > 2_Sn > 2_Ge > 2_Si > 2_C (calculated via B3LYP/6-311++G**). Energy gaps, IG_t-s, of 1_M and 2_M appear linearly proportional to the size of the group 14 divalent elements (M) and the ∠ C-M-C angle.