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

Graphical Abstract

Sulfur-coordinated coordination polymers (S−CPs) have unique optoelectrical properties resulting from inorganic (−M−S−)_n network structures. However, these structures have never been correlated with their electronic properties. We reveal the impact of the (−M−S−)_n networks in S−CPs on photoconductivity by comparing S−CP crystal polymorphs.

Abstract

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.