Electronic Structure and Chemical Bonding in the OTi-N2 Complexes: A Systematic ab Initio and DFT Study

Two OTi-N-2 complexes, experimentally observed in the TiO + N-2 reaction, have been theoretically studied using several density functionals as well as ab initio approaches and various basis sets. The benchmark results calculated with coupled-cluster singles, doubles, and perturbative triples CCSD(T) and sufficiently large correlation-consistent basis set were used to assess the performance of other theoretical models, especially four density functional families, pure functional, hybrid, double-hybrid, and long-range corrected ones. It has been shown that, out of twenty-three density functionals used in this work, only three functionals, namely TPSS0, LC-TPSS, and B2PLYP, are able to reproduce the CC-reference data quantitatively. Particularly, the B2PLYP double-hybrid (with or without addition of empirical dispersion) is the most promising functional, providing the closest results to the reference ones. The nature of bonding within products has been investigated using two topological techniques and a localized orbital approach.