Ab initio geometry and anharmonic vibrational spectra of PbX2 halides and PbX2⋯L (X=F, Cl, Br, I; L=CO, N2) complexes

Equilibrium geometries of PbX2 halides and PbX2⋯L (X=F, Cl, Br, I; L=CO, N2) complexes have been determined at ab initio level with second order perturbative (MP2) treatment of electron correlation using Stevens-Basch-Krauss-Jasien-Cundari (SBKJC) relativistic effective core potentials (RECP) and basis sets. Optimized structures of PbX2⋯L complexes have Cs symmetry with end-on coordination of the ligand, and are characterized by Pb⋯C bond length within 279.9-281.6 pm, Pb⋯N distance of 273.9-278.0 pm, and Pb⋯L-L angle of 163.3-173.5o. Anharmonic vibrational spectra of PbX2 halides and PbX2⋯L complexes have been determined from ab initio MP2/SBKJC+(d) potential energy surfaces using vibrational self-consistent field (VSCF) and correlation-corrected vibrational self-consistent field (CC-VSCF) methods. Sensitivity of ν(Pb-X) and ν(L-L) stretching modes to complex formation, established from CC-VSCF anharmonic spectra, closely follows that observed in low temperature Ar matrix infrared spectra of these complexes. Anharmonic estimates of ν(Pb⋯C) and ν(Pb⋯N) stretching modes were computed at 137-131 and 149-150 cm−1, respectively.