Synthesis of new coordination polymer of zinc with structural transformation and photocatalysis

Abstract

The rational synthesis of new 3D coordination polymer, {[Zn4(H2O)2(4,4′-bipy)4 (glu)3](NO3)2}͚, P21/c (1), with octahedral zinc (II) cations as metal centre, glutarate anion as a flexible bridging ligand between the centre atoms along [1̅01] direction and 4,4′- bipyridine as a rigid connector which extending the structure to 3D two-fold interpenetrated framework is reported in this thesis. This framework is defined as an enantiomorphic two-fold interpenetrated as ‘3D solid state racemate’. Hydrogen bond is predominant in the framework which bind the coordinated water molecules and counter nitrate anions within the void. With an employment of Zn(NO3)2 as a precursor by microwave-heating, complex 1 is selectively produced. Whereas the use of ZnSO4 or Zn(CH3COO)2 the product is 2D-[Zn(4,4′-bipy)(glu)] ͚, P1̅ (2) In addition, when ZnCl2 is employed as a precursor, the different coordination polymer, 1D-[Zn(4,4′-bipy)Cl2]͚, (C2/c) (3), is produced. Therefore, counter anion from each metal salts certainly influences on the coordination framework formation. In other way, synthetic techniques also affect to the phase selectivity. The microwave-heating, microwave-assisted hydrothermal and conventional hydrothermal techniques produced very high crystallinephase pure 1 whereas the sonochemical produced phase 1 and 2 simultaneously. Coordination polymer 1 can undergo single-crystal-to-single-crystal (SCSC) transformation triggered by halide anions. All of the SCSC transformations were evidenced by PXRD and SEM/EDX. When 1 was soaked in an NaCl solution, it was transformed to 3. However, 1 can be transformed to other phases, when it was soaked in NaBr, it can be transformed to 1D-[Zn(4,4′-bipy)Br2]͚, C2/c (4) and 1D-[Zn(4,4′-bipy) Br2]͚, P212121 (5), which are polymorphs. In addition, photocatalysis for methyl orange degradation of coordination polymer 1 was studied.