Abstract
Cocrystallization may alter material physicochemical properties; thus, the strategy of forming a cocrystal is generally used to improve the material performance for practical applications. In this study, two transition-metal complex cocrystals [Zn(bpy)(3)]H(0.5)BDC·H(1.5)BDC·0.5bpy·3H(2)O (1) and [Cu(2)(BDC)(bpy)(4)]BDC·bpy·2H(2)O (2) have been achieved using a hydrothermal reaction, where bpy and H(2)BDC represent 2,2'-bipyridine and benzene-1,3-dicarboxylic acid, respectively. Cocrystals were characterized by microanalysis, infrared spectroscopy, and UV-visible spectroscopy. Cocrystal 1 contains five components and crystallizes in a monoclinic space group P2(1)/n. The H(0.5)BDC(1.5-), H(1.5)BDC(0.5-), and H(2)O molecules construct three-dimensional H-bonding organic framework; the [Zn(bpy)(3)](2+) coordination cations and uncoordinated bpy molecules reside in channels, where two coordinated bpy ligands in [Zn(bpy)(3)](2+) and one uncoordinated bpy adopt sandwich-type alignment via π···π stacking interactions. Cocrystal 2 with four components crystallizes in a triclinic space group P-1 to form alternating layers; the binuclear [Cu(2)(bpy)(4)(BDC)](2+) cations and uncoordinated bpy molecules build the cationic layers, and the BDC(2-) species with disordered lattice water molecules form the anionic layers. Cocrystal 1 shows intense photoluminescence at an ambient condition with a quantum yield of 14.96% and decay time of 0.48 ns, attributed to the π* → π electron transition within phenyl/pyridyl rings, and 2 exhibits magnetic behavior of an almost isolated spin system with rather weak antiferromagnetic coupling in the [Cu(2)(bpy)(4)(BDC)](2+) cation.