Structural and spectroscopic study of neutral dioxides MO2 (M = B, Al, Ga, In, Tl)

Abstract

Both ab initio Hartree-Fock self consistent field (HF-SCF) with Cluster Coupled (CCSD(T)) and Density Functional Theory with B3LYP functional, high level theories are adopted for structural study of different dioxides MO2 (M = B, Al, Ga, In and Tl). A geometry optimization is performed using the avtz, aug-cc-pwcvnz (nz = tz; qz; 5z), 6–311++G** and Lanl2DZ basis sets. Vibration frequencies are reported for optimized geometries. We also report calculated M-O and O-O bond lengths, O-M-O and M-O-O, bond angles for stable isomers. Our calculations indicate that there are five possible isomers with linear or folded shapes. Some discrepancies with previous results are noted, on the other hand, according to our CCSD(T) calculations, MO2 molecule (M = B, Al and Ga) is in ground state when it is linear and symmetric O-M-O (2Πg), then in a higher energy state with the cyclic isomer (2A2, or 2A1) and in more higher state when it is dissymmetric M-O-O (2A’, 2∑+), B3LYP and CCSD(T) results agree on energetic ordering of various isomeric forms for BO2, AlO2,InO2 and TlO2 systems, while there is disagreement for GaO2, molecule. HOMO-1, HOMO, LUMO and LUMO + 1 molecular orbitals for the most stable structures are given as well. NBO analysis is performed to study the superoxide 2A2 and its stability which evolves according to electropositivity of metal along the 13th column of periodic table.