Crystal Engineering with 2-Aminopurine and 2,6-Diaminopurine Derivatives: Dimers, Metallaquartets, and Halide-Bridged Clusters

Design, synthesis, and single crystal structure elucidation of modified purine ligands 2-(2-amino-9 H -purin-9-yl) acetic acid ( L1 ) and 2-(2,6-diamino-9 H -purin-9-yl) acetic acid ( L2 ) and their interaction with certain d 10 transition metal ions is described. Copper complex 1 (C 28 H 34 Cu 2 N 22 O 19 ) afforded a two-dimensional polymeric structure composed of metallaquartets, while corresponding silver complex 2 (C 14 H 20 AgN 10 O 8 ) was formed as a discrete dimer. Complexes 3 (C 14 H 24 CdN 10 O 10 ) and 5 (C 14 H 22 CdN 12 O 8 ), cadmium complexes of L1 and L2, respectively, afforded different coordinating modes, where 3 resulted in a two-dimensional (2D) polymeric structure consisting of metallaquartets and 5 as a discrete dimeric structure, with an octahedral coordination geometry. Complex 4 ( C 14 H 13 Cl 13 Hg 6 N 10 O 8 ) afforded a unique hexanuclear, 2D polymeric structure, supported by mercury-chloride bridges, presenting as interconnected dimeric, trimeric, and hexameric mercury halide (μ 2double, μ 3triple, and μ 6six ) clusters. The potential of halide ions as bridges is interesting. We have also studied the fluorescence properties of ligand L1 and L2 along with complexes 1 – 5 .