Chirality and Polarity Modulation in Semiconductive Zinc(II) Coordination Polymers Containing Thiolate-Based Ligands

Recently, chiral semiconductors have attracted considerable attention owing to their potential applicability in optoelectronics and spintronics. In this study, homochiral and heterochiral semiconductive Zn(II) coordination polymers [Zn(tbbt)((X)-mba)₂]·solvent (H₂tbbt = 4,4′-thiobisbenzenethiol, mba = methylbenzylamine, X = R, S, rac) were systematically synthesized. Single-crystal X-ray diffraction analyses revealed that KGF-57(R) and KGF-57(S) (KGF = Kwansei Gakuin framework), of type [Zn(tbbt)((X)-mba)₂]·(X)-mba, obtained from enantiopure (R)-mba and (S)-mba isomers, exhibited chiral–nonpolar homochiral one-dimensional (1D) structures with mba lattice solvents, comprising left- and right-handed helical chains, respectively. Conversely, when using (rac)-mba, two heterochiral 1D architectures were obtained depending on synthetic temperature and solvent. Specifically, KGF-57(rac) of type [Zn(tbbt)((rac)-mba)₂]·(rac)-mba·nH₂O exhibited an achiral–nonpolar heterochiral 1D structure with (rac)-mba and H₂O lattice solvents, containing alternately aligned left-handed helical chains with (R)-mba and right-handed helical chains with (S)-mba. Conversely, KGF-58(rac) with the formula [Zn(tbbt)((rac)-mba)₂] formed an achiral–polar assembly without mba lattice solvents. This structure is composed of zigzag chains with either (R)-mba or (S)-mba in a heterochiral arrangement. Time-resolved microwave conductivity measurements and first-principles calculations revealed that a series of Zn(II) coordination polymers exhibited photoconductivity originating from the Zn-thiolate-based skeleton. Furthermore, by exchanging the mba ligands coordinated to 1D Zn-thiolate chains, a reversible structural conversion accompanied by chirality and polarity variation was achieved.