The quest for triplet ground state silylenes

In search of triplet ground state GeCNX germylenes (X=H, F, Cl, and Br): An ab initio and DFT study

“…The trend of curve slopes is: 2 s-X (m = À1.26) > 1 s-X (m = À0.92) > 3 s-X (m = À0.78), where m = slope. One of the significant parameters affecting the DE s-t and determining the ground state of divalent carbene like species is the magnitude of the divalent bond angle [40]. Therefore, bending potential energy curves for divalent 3 s-X and 3 t-X structures are calculated at B3LYP/6-311++G** (Fig.…”

A quest for triplet silylenes XHSi3 at ab initio and DFT levels (X=H, F, Cl and Br)

“…Energy gaps between 3 s-X and 3 t-X , calculated at CCSD(T)/6-311++G** level, appear as: DE s-t,Cl (À59.22 kcal/mol) > DE s-t,H (À44.20 kcal/mol) > DE s-t,F (35.19 kcal/mol) > DE s-t,Br (26.77 kcal/mol) (Tables 1-4). This trend demonstrates the stabilizing of singlet silylenes, due to the effects of electro-negativity, suggested by Gaspar [48]. Contrary to alkynes, the substituents attached to the Si"Si moiety are not arranged in a linear fashion.…”

From halo-azasilylenes to halo-phosphasilylenes (X-CNSi vs. X-CPSi) at ab initio and DFT levels

“…Generally, all known silylene species possess a singlet (s) ground state, in contrast to their carbene analogues which often have triplet (t) ground states. This has made the quest for triplet ground state silylenes one of the most challenging issues in the modern organosilicon chemistry [14]. Theoretical studies indicate that substituents attached to the divalent center have considerable effects on the singlet-triplet energy gaps (DE s-t ) [14][15][16].…”

“…This has made the quest for triplet ground state silylenes one of the most challenging issues in the modern organosilicon chemistry [14]. Theoretical studies indicate that substituents attached to the divalent center have considerable effects on the singlet-triplet energy gaps (DE s-t ) [14][15][16]. It has been shown that electronegative substituents increase the DE s-t , whereas electropositive substituents decrease the gap.…”