Building thiol and metal-thiolate functions into coordination nets: Clues from a simple molecule

The simple and easy-to-prepare bifunctional molecule 2,5-dimercapto-1,4-benzenedicarboxylic acid (H4DMBD) interacts with the increasingly harder metal ions of Cu+, Pb2+ and Eu3+ to form the coordination networks of Cu6(DMBD)3(en)4(Hen)6 (1), Pb2(DMBD)(en)2 (2) and Eu2(H2DMBD)3(DEF)4 (3), where the carboxyl and thiol groups bind with distinct preference to the hard and soft metal ions, respectively. Notably, 1 features uncoordinated carboxylate groups and Cu3 cluster units integrated via the thiolate groups into an extended network with significant interaction between the metal centers and the organic molecules; 2 features a 2D coordination net based on the mercapto and carboxylic groups all bonded to the Pb2+ ions; 3 features free-standing thiol groups inside the channels of a metal-carboxylate-based network. This study illustrates the rich solid state structural features and potential functions offered by the carboxyl-thiol combination.