Three purine-containing metal complexes with discrete binuclear and polymeric chain motifs: Synthesis, crystal structure and luminescence

• Three purine-based inner-sphere metal complexes were hydrothermally prepared.
• The former two molecules exhibit binuclear motifs and the third one is helical chain.
• The luminescent behaviors of the complexes are curious and important.

To investigate the influences of exocyclic substituent of purine base on the coordination and recognition behavior, three new purine-based inner-sphere metal complexes, [Cd2(H2ade)2(H2O)4(btc)2]·4H2O (1), [Cd2(Hhyp)2(H2O)4(Hbtc)2]·4H2O (2), and [Cd(H2dap)(H2O)2(btc)]n (3) (Hade = adenine, Hhyp = hypoxanthine, Hdap = 2,6-diaminopurine, and H3btc = 1,2,4-benzenetricarboxylic acid), were hydrothermally synthesized and structurally characterized. The former two complexes with monodentate H2(N1, N9)ade+ cation (for 1) and H(N1, N7)hyp molecule (for 2) are centrosymmetric binuclear entities aggregated by a pair of tricarboxylate ligand. In contrast, 3 bearing a cationic H2(N1, N9)dap+ ligand has a polymeric one-dimensional helical chain extended by btc3− connectors. The side group of the purine can significantly dominate and stabilize the supramolecular network by different H-bonding recognition patterns. Additionally, these three samples with considerable thermal stability display strong emissions originated from ligand-based electron transfer, suggesting their potential application as luminescent materials.

Crystal structures, thermal stability, and luminescent properties of two centrosymmetric binuclear entities and one polymeric helical chain with different purine bases were reported. The influences of the exocyclic substituted group of the purine base on the coordination modes and hydrogen-bonding recognition patterns were also discussed.Figure optionsDownload as PowerPoint slide