Six new coordination compounds based on rigid 5-(3-carboxy-phenyl)-pyridine-2-carboxylic acid: synthesis, structural variations and properties

Six new coordination compounds Ni(cppca)(H 2 O) 4 ·2H 2 O ( 1 ), Co(cppca)(H 2 O) 4 ·2H 2 O ( 2 ), {Cd 2 (cppca) 2 (H 2 O) 5 } n ( 3 ), {[Cd 3 (cppca) 2 (H 2 P 2 O 7 )(H 2 O) 6 ]·2H 2 O} n ( 4 ), {Cu(Hcppca) 2 } n ( 5 ) and {[Mn 7 (cppca) 6 (Hcppca) 2 (H 2 O) 10 ]·2H 2 O} n ( 6 ) have been obtained by reactions of the corresponding metal salts and the rigid ligand 5-(3-carboxy-phenyl)-pyridine-2-carboxylic acid (H 2 cppca) under solvothermal conditions. All the compounds were fully characterized by single-crystal X-ray diffraction, elemental analysis, IR spectroscopy, thermal analysis and powder X-ray diffraction. The single-crystal X-ray analyses showed that compounds 1–6 have rich structural chemistry ranging from mononuclear ( 1 and 2 ), one-dimensional ( 3 and 4 ), two-dimensional ( 5 ) to three-dimensional ( 6 ) structures. Moreover, the framework of compound 6 may be simplified into a 3-nodal net with Schlafli symbol {4 2 ·6}{4 2 ·8 2 ·10 2 }{4 3 ·6 2 ·8·10 4 } 2 , which shows an unprecedented (3,4,5)-connected topology net. The fluorescent properties of compounds 3 and 4 were investigated in the solid state and in various solvent emulsions, which indicated that compounds 3 and 4 are both highly sensitive fluorescent probes for the acetone molecules. Variable-temperature magnetic susceptibility measurements indicate weak antiferromagnetic interactions between metal centers in compounds 1 , 2 , 5 and 6 .