Supramolecular architectures constructed with the skeletons of zinc(II) 2,2′-bipyridine and barbiturate anion: Synthesis and characterization

Abstract

The barbiturate 1,5-dihydro-5-[5-pyrimidine-2,4(1H,3H)-dionyl]-2H-chromeno[2,3-d] pyrimidine-2,4(3H)-dione) (LH 4) 1 forms a complex with Zn(bpy)(NO 3) 2·2H 2O (bpy = 2,2′-bipyridine) of composition [Zn(bpy) 2(H 2O) 2] 2+·(LH 3) 2·7H 2O ( 2). In this structure, the ligand exists as anion ( LH 3 - ) as revealed by its single crystal X- ray crystallographic study. Packing studies of 2 provide three dimensional helical chains as secondary structure. However, its PXRD pattern shows that 2 does not retain its structure upon dehydration. Recrystallization of 2 from DMSO results in complex 3 with the composition [Zn(bpy) 2(H 2O) 2] 2+·( LH 3 - ) 2·DMSO·9H 2O assigned on the basis of its elemental analysis and its X-ray crystallography. In order to understand the role of the 2,2′-bipyridine ring in the construction of supramolecular architecture, the reaction of zinc(II) nitrate salt with 1 is carried out to provide complex 4 of composition [Zn(LH 3) 2(H 2O) 4]·4H 2O characterized by its single crystal X-ray diffraction study. Thermal, emission and photoluminescence properties of the complexes are also studied.