Theoretical prediction of vertical transition energies of diaminosilylenes and aminosubstituted disilenes

Vertical electronic transition energies of diaminosilylenes and their dimers (disilenes and nitrogen-bridged) were investigated by ab initio and density functional calculations. A good linear correlation was found between the observed UV transition energies of various silylenes and disilenes and those of model compounds calculated using the CIS and TD-DFT methods. On the basis of these computations the experimental UV absorption maximum observed for the dimer of (i-Pr₂N)₂Si: (λ_max 439 nm at 77 K), could be assigned to an Si-Si bonded dimer with an unusually long Si-Si distance of 2.472 Å, and the isomeric amino-bridged cyclic dimer could be discarded.