Novel halogenated cyclopentasilylene-2,4-dienes via DFT

In view of immense importance of silylenes and the fact that their properties undergo significant changes on substitution with halogens, here, we have used B3LYP/6-311++G** level of theory to access the effects of 1-4 halogens (X = F, Cl, Br, and I) on four unprecedented sets of cyclopentasilylene-2,4-dienes; with the following formulas: SiC4H3X ( 1(X)), SiC4H2X2 (2(X)), SiC4HX3 (3(X)), and SiC4X4 (4(X)). In going down from F to I, the singlet (s)-triplet (t) energy gap (Delta Es-t, a possible indication of stability), and band gap (Delta EH-L) decrease while nucleophilicity ( N), chemical potential (mu), and proton affinity (PA) increase. The overall order of N, mu, and PA for each X is 2(X) > 1(X) > 3(X) > 4(X). Precedence of 2(X) over 1(X) is attributed to the symmetric cross conjugation in the former. The highest and lowest N are shown by 2(I) and 4(F). The trend of divalent angle ((A) over cap) for each X is 4(X) > 1(X) > 3(X) > 2(X). The results show that in going from electron withdrawing groups (EWGs) to electron donating groups (EDGs), the Delta Es-t and Delta EH-L decrease while N, mu, and PA increase. Also, rather high N of our scrutinized silylenes may suggest new promising ligands in organometallic chemistry.