Assembly, crystal structures, and luminescent properties of three new thiocyanate-bridging mercury(II) coordination polymers

Abstract

Two ligands, 2-{5,5-dimethyl-3-[2-(pyridin-3-yl)-ethenyl]cyclohex-2-enylidene}propanedinitrile (L1) and 2-{5,5-dimethyl-3-[2-(pyridin-2-yl)-ethenyl]cyclohex-2-enylidene}propanedinitrile (L2), were synthesized. By reaction of mercury thiocyanate with L1 and L2, respectively, coordination polymers [Hg(L1)(μ_1,3-SCN)₂]_n (1), [Hg(L1)₂(μ_1,3-SCN)₂]_n (2), and [Hg(L2)(μ_1,3-SCN)(SCN)]_n (3) with different structures and topologies were obtained. In 1, the thiocyanate shows μ_1,3-SCN bridging coordination, and adjacent Hg(II) ions are bridged by two μ_1,3-SCN ions to form an infinite chain with the remaining position of five-coordinate Hg(II) occupied by L1. In 2, the thiocyanate has the same coordination as 1. However, Hg(II) has octahedral coordination with two L1 involved in coordination. An unusual feature of 3 is the presence of two types of thiocyanates, one has a S-terminal ligand and the other has a μ_1,3-SCN bridge. The mercury(II) in 3 is four-coordinated by L2 and three thiocyanates. Luminescent properties and thermal stabilities of 1–3 were studied.

Keywords:

• Coordination polymer
• Mercury(II) thiocyanate
• Noncovalent interaction
• Crystal structure
• Self-assembly

Acknowledgments

This work was supported by Program for New Century Excellent Talents in University (China), Doctoral Program Foundation of Ministry of Education of China (20113401110004), National Natural Science Foundation of China (21271003, 21271004), the Anhui University Students Research Training Program (kyxl2012020), the Team for Scientific Innovation Foundation of Anhui Province (2006KJ007TD), the Graduate Students Innovative Program of Anhui University (10117700063), Ministry of Education Funded Projects Focus on Returned Overseas Scholar, and Education of Committee of Anhui Province (KJ2012A024, KJ2013B201).