A theoretical study of subphthalocyanine and its nitro- and tertbutyl-derivatives

Abstract

The unsubstitute subphthalocyanine (SubPc) and their tertbutyl- ( tertbutyl-SubPc) and nitro-(nitro-SubPc) derivatives have been theoretically studied at Hartree–Fock (HF) and Density Functional Theory (DFT) levels using STO-3G and 6-31G basis sets. The geometric optimization of the molecules was carried out. The calculated geometry for SubPc agrees with experimental X-ray data. No significant geometrical changes with respect to SubPc were observed in the tertbutyl-SubPc and nitro-SubPc macrocycles. B–Cl distance systematically changes with the electron donor/acceptor properties of the peripheral substituents. The calculated dipole moments reproduce very well the experimental values, whereas the atomic charges reveal the polar character of the SubPc macrocycle. An extensive study of some frontier orbitals was performed. The present calculations reproduce the breakdown of Gouterman's four-orbital model in SubPcs, this effect being less dramatic in the DFT description. The nodal patterns for the two highest occupied molecular orbitals and the two lowest unoccupied molecular orbitals obtained from different computational methods exhibit important differences, but in general an explanation for some of the most important aspects of the chemical reactivity of the SubPcs can be put forward.