Polymorphism of Two-Dimensional Semiconducting Coordination Polymers: Impact of a Lead-Sulfur Network on Photoconductivity.

Sulfur-coordinated coordination polymers (S-CPs) have unique optoelectrical properties that originate from infinite M-S bond networks. In this study, we synthesized and characterized two polymorphs of a two-dimensional (2D) Pb(II) S-CP with a formula of [Pb(tzdt)(OAc)] (Htzdt=1,3-thiazolidine-2-thione, OAc=acetate). Our findings revealed that the thermodynamic product (KGF-26) possesses quasi-2D (-Pb-S-) n layers with weak nonbonded Pb-S bonds, whereas the kinetic product (KGF-27) has intrinsic 2D (-Pb-S-) n layers with Pb-S bonds. The results of time-resolved microwave conductivity measurements and first-principles calculations confirmed that KGF-27 exhibits higher photoconductivity than KGF-26, which establishes that the inorganic (-Pb-S-) n networks with Pb-S bonds are crucial for achieving high photoconductivity. This is the first experimental demonstration of the impact of the (-M-S-) n networks in S-CPs on photoconductivity through the comparison of crystal polymorphisms.