Syntheses And Characterizations Of Fluorescent Zn(?)/Cd(?)coordination Complexes Based On Polycarboxylic Acid And Nitrogen-containing Ligands

In recent years,the directional controllable synthesis of functional metal-organic coordination complexes is a hot spot for scientists due to their fascinating structures,and their extensive applications in optics,catalysis,magnetism,and electrical and so on.It is well known that the structures and properties of the complexes are closely related,and metal-organic coordination complexes is influenced by many factors in the synthesis process,for example,metal ions,organic ligands,solvents,pH,temperature and so on.Therefore,the key to the construction of novel metal-organic complexes with unique properties is to select the appropriate organic ligands and metal ions,use the appropriate synthesis methods,and effectively regulate the synthesis conditions.In this paper,polycarboxylic acid ligands: 1,1'-biphenyl-2,2',6,6'-tetracarboxylic acid?H4bptc?,and dimethyl-2,2'-dihydroxy-[1,1'-binaphthalene]-3,3'-dicarboxylate?H₂bndc?,as well as nitrogen-containing ligands: 4-?2-methyl-1H-imidazol-1-yl?benzoic acid?Hiba?were selected.The reaction of metals Zn???and Cd???with d10 closed shell under hydrothermal conditions gave rise to four cordination polymers,namely,[Zn₂?bptc?·?H₂O?₄]_n·nCH₃OH?1?,[Zn₃?bndc?₄·H₂O]_n?2?,[Zn₃?bndc?₄?2-picoline?₂]_n?3?and [Cd?iba?₂]_n?4?.The crystal structures of complexes 1-4 were defined by single crystal X-ray diffraction analysis.The results show that complexes 1 is one-dimensional chain structure,which furnishes a 2D supramolecular architecture through hydrogen bonding interactions.Complexes 2 and 3 possess two-dimensional layered structures.The solvent molecule as a guest molecule is filled in the gap between layer and layer in complexes 3.Complexes 4 is a 2D wave-shape layer structure,which can be simplified as a four-connected topological net.Interestingly,the 2D layers are further extended into a 3-fold interpenetrating 3D architecture by ?-? stacking between the phenyl and phenyl rings from adjacent layers.At the same time,elemental analysis and fluorescence properties were characterized.Fluorescence analysis showed that the four complexes exhibit interesting fluorescence properties in the solid state at ambient temperature,and compound 4 also displays a second harmonic generation?SHG?activity,which can evaluate its potential application as the second-order non-linear optic?NLO?material.