Study of spectral properties of bis(1,10‐phenanthroline) silicon hexacoordinated complexes by density functional theory

Applying ab initio method the structures and UV‐vis spectra of silicon hexacoordinated compound [Si(phen) 2 (OMe) 2 ]I 2 and it's nitrate [Si(phen) 2 (OMe) 2 ](NO 3 ) 2 were calculated. On the ground of comparison of theoretical and experimental data ( 1 H NMR and electronic absorption spectra) it was shown that the theoretical method B3LYP/LanL2DZ we have used describes bis(1,10‐phenanthroline) silicon complexes reasonably well. On the basis of TDDFT calculations at B3LYP/LanL2DZ level it is predicted that [Si(phen) 2 (OMe) 2 ]I 2 compound has charge transfer band in UV‐vis spectrum at 557 nm which is associated with electron transfer from I − to phen ligand while [Si(phen) 2 (OMe) 2 ](NO 3 ) 2 doesn't have one. The absence of this band in the observed spectrum of the [Si(phen) 2 (OMe) 2 ]I 2 complex methanol solution (10 −5 M) is explained by the dissociation of the complex into ions [Si(phen) 2 (OMe) 2 ] 2+ and 2I − . We assume that this charge transfer band corresponds to peak at 400 nm in UV‐vis spectrum of [Si(phen) 2 (OMe) 2 ]I 2 thin film. The missing of such bands in UV‐vis spectrum of nitrate [Si(phen) 2 (OMe) 2 ](NO 3 ) 2 film is explained by n → p * nature of these transitions. Significant error in prediction of charge transfer band energy is due to failure of TDDFT method to yield underestimated charge transfer electronic energies. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2008