Infrared spectra and density functional calculations of triplet pnictinidene N÷ThF3, P÷ThF3 and As÷ThF3 molecules

Abstract

Thorium atoms react with NF₃, PF₃, and AsF₃ to produce the first actinide triplet state pnictinidene molecules, N÷ThF₃, P÷ThF₃, and As÷ThF₃, which are trapped in solid argon and identified from infrared spectra and comparison to computed vibrational frequencies. Density functional theory calculations for these lowest energy triplet state products converge essentially to C_3v symmetry structures. Spin density calculations show that the two unpaired electrons are mostly localized in nitrogen 2p, phosphorus 3p, or arsenic 4p orbitals. Although thorium has a small spin density, the weak degenerate π_α molecular orbitals are populated entirely from the terminal N, P, or As based on DFT natural bond orbital analysis. This is in contrast with HC÷ThF₃, which contains degenerate π_α molecular orbitals with 81% C and 19% Th character.