Two Cu(II) double betaine coordination polymers with different metal-organic frameworks

Two new Cu(II) coordination polymers with double betaine ligands have been prepared, and their structures have been characterized by single-crystal X-ray diffraction techniques. The structure of [Cu(L1)2](ClO4)2·2H2O 1 (L1 = 1,3-bis(pyridinio-4-carboxylato)-propane) contains 1-D cationic chains, in which the adjacent Cu(II) atoms are doubly bridged by L1 ligands in the syn-syn bis-monodentate mode. In [Cu(L2)2](ClO4)2·4H2O 2 (L2 = 1,4-bis(pyridinio-4-carboxylato)-1,4-dimenthylbenzene), the Cu(II) atoms are joined by the L2 ligands in the same coordination mode as 1 in two directions to form a 2-D grid-like framework. The crystal packing in 1 and 2 is controlled mainly by face-to-face π–π stacking interactions between pyridine rings. The thermal stability of 1 has also been investigated.