Cd(II) Coordination Architectures with Mixed Ligands of 3-(2-Pyridyl)pyrazole and Pendant Carboxylate Ligands Bearing Different Aromatic Skeletons: Syntheses, Crystal Structures, and Emission Properties

To investigate the influences of the geometries of pendant carboxylate ligands and some intramolecular/intermolecular weak interactions on the structures of transition metal complexes, five new Cd(II) complexes, Cd 2 (H L 1 ) 2 ( L 2 ) 4 ( 1 ), Cd 2 (H L 1 ) 2 ( L 3 ) 4 ( 2 ), {[Cd 2 (H L 1 )( L 4 ) 4 (H 2 O) 2 ](H 2 O)} ∞ ( 3 ), [Cd( L 1 )( L 5 )] ∞ ( 4 ), and Cd 2 ( L 1 ) 2 (H L 1 ) 2 ( L 4 ) 2 ( 5 ) (H L 1 = 3-(2-pyridyl)pyrazole, H L 2 = benzoic acid, H L 3 = naphthalene-carboxylic acid, H L 4 = 9-anthracene-carboxylic acid, and H L 5 = isonicotinic acid), have been synthesized and structurally characterized by elemental analyses, IR spectroscopy, and single-crystal X-ray diffraction analyses. 1 and 2 have a similar dinuclear structure, which is further assembled to form a one-dimensional (1D) chain by π···π stacking and/or hydrogen-bonding interactions. 3 possesses a 1D chain structure that is further interlinked via intermolecular π···π stacking, resulting in a two-dimensional (2D) network, while 4 has a 2D (4,4) network with channel dimension of 9.34 × 9.34 Å 2 and further assembles into a three-dimensional (3D) network by interlayer π···π stacking. 5 also possesses a dinuclear structure and then forms a 2D network through intermolecular π···π stacking and C−H···O hydrogen-bonding interactions. Interestingly, 3 and 5 were obtained simultaneously in the same reaction system. The structural differences of those complexes show the influences of the geometries of the pendant carboxylate ligands. This result also shows that intramolecular/intermolecular weak interactions play important roles in the formation of coordination architectures, especially in the aspect of linking multinuclear discrete subunits or low-dimensional entities into high-dimensional supramolecular frameworks. In addition, complexes 1, 2, and 4 exhibit blue emission in the solid state at room temperature.