<b<The singlet-triplet energy gap in divalent three, five and seven-membered cyclic C<sub<2</sub<H<sub<2</sub<M, C<sub<4</sub<H<sub<4</sub<M and C<sub<6</sub<H<sub<6</sub<M (M = C, Si, Ge, Sn AND Pb)</b<

Total energy gaps, ∆E<sub<t–s</sub<, enthalpy gaps, ∆H<sub<t–s</sub<, and Gibbs free energy gaps, ∆G<sub<t–s</sub<, between singlet (s) and triplet (t) states were calculated for three, five and seven-membered cyclic C<sub<2</sub<H<sub<2</sub&...
Ausführliche Beschreibung

Total energy gaps, ∆E<sub<t–s</sub<, enthalpy gaps, ∆H<sub<t–s</sub<, and Gibbs free energy gaps, ∆G<sub<t–s</sub<, between singlet (s) and triplet (t) states were calculated for three, five and seven-membered cyclic C<sub<2</sub<H<sub<2</sub<M, C<sub<4</sub<H<sub<4</sub<M and C<sub<6</sub<H<sub<6</sub<M (M = C, Si, Ge, Sn and Pb) at B3LYP/6-311++G**. The singlet-triplet free energy gaps, ∆G<sub<t–s</sub<, for C<sub<2</sub<H<sub<2</sub<M (M = C, Si, Ge, Sn and Pb) are found to be increased in the order: C<sub<2</sub<H<sub<2</sub<Si < C<sub<2</sub<H<sub<2</sub<C < C<sub<2</sub<H<sub<2</sub<Ge < C<sub<2</sub<H<sub<2</sub<Sn < C<sub<2</sub<H<sub<2</sub<Pb. The ∆G<sub<t–s</sub< of C<sub<4</sub<H<sub<4</sub<M are found to be increased in the order: C<sub<4</sub<H<sub<4</sub<Pb < C<sub<4</sub<H<sub<4</sub<Sn < C<sub<4</sub<H<sub<4</sub<Ge < C<sub<4</sub<H<sub<4</sub<Si < C<sub<4</sub<H<sub<4</sub<C. Also, the ∆G<sub<t–s</sub< of C<sub<6</sub<H<sub<6</sub<M are determined in the order: C<sub<6</sub<H<sub<6</sub<Pb < C<sub<6</sub<H<sub<6</sub<Ge ≥ C<sub<6</sub<H<sub<6</sub<Sn < C<sub<6</sub<H<sub<6</sub<Si < C<sub<6</sub<H<sub<6</sub<C. The most stable conformers of C<sub<2</sub<H<sub<2</sub<M, C<sub<4</sub<H<sub<4</sub<M and C<sub<6</sub<H<sub<6</sub<M are proposed for both the singlet and triplet states. Nuclear independent chemical shifts (NICS) calculations were carried out for determination of aromatic character. The geometrical parameters are calculated and discussed. Ausführliche Beschreibung