Insight on noncovalent interactions and orbital constructs in low-dimensional antimony halide perovskites

Reported is a series of eight antimony halide perovskite derivatives synthesized from acidic aqueous solutions of antimony oxide and halogen substituted pyridines. These materials feature anionic one-dimensional antimony halide (SbX; X = Cl, Br, I) chains or ribbons charge-balanced by organic para-halopyridinium cations (XPy; X = H, Cl, Br) which assemble into three-dimensional networks via halogen and hydrogen noncovalent interactions (NCIs) between ion pairs. Computational density functional theory (DFT) based natural bonding orbital (NBO) and density of state (DOS) methods were utilized to map the band structure and quantify and categorize noncovalent interaction strength and type. Moreover, we determined the presence of hybridized intermediate bands which are responsible for the small bandgap energies within this family and arise from mixing of the halide p-states and the Sb s-states. We note that the degree of hybridization, and thus optical properties, is influenced primarily by changes about inner sphere bonding and independent of second sphere interactions. This report is the first to specifically monitor the evolution of haloantimonate(III) hybrid perovskite atomic and molecular orbitals involved in optical behavior as a function of inner and outer sphere effects.