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: (λmax 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. © 2001 John Wiley & Sons, Inc. J Comput Chem 22: 1536–1541, 2001