Long-Chain Molecular Crystals Antimony(III) Alkanethiolates Sb(SCH₂)₃ (n ≥ 12): Synthesis, Crystal and Electronic...

Currently, there is not much success in solving the molecular and crystal structures of long-chain metal alkanethiolate complexes [M(SCH₂)] at the atomic level. Taking Sb(SC₁₆H₃₃)₃ (1) as an example, we herein disclose the structural characteristics of long-chain trivalent antimony(III) alkanethiolates Sb(SCH₂)₃ (n ≥ 12) by single-crystal X-ray crystallography. Specifically, the Sb atom is three-coordinated by alkanethiolate ligands and a slightly distorted triangular pyramid SbS₃ core is formed owing to the unique intramolecular stereochemistry of three alkyl chains, namely, two of them almost parallel aligning and the third chain extending alone around the SbS₃ core. We further determine the conformation, spatial orientation and packing density of alkyl chains in 1 along with a comparison to those in other long-chain crystalline systems, and reveal the roles of intermolecular van der Waals and Sb···S secondary interactions in molecular self-assembly, which enables 1 to be a layer-structured molecular crystal with a monoclinic P2₁/c unit cell. The band structures and the atomic orbital contributions to the valence band maximum and conduction band minimum for 1 have also been evaluated by DFT calculations and rationally correlated with its optical absorption property. This study will help understand and discover new structures and structure-property relations of long-chain chemical systems.