Four novel isostructural coordination polymers {[M(H′L)2(H2O)2]·2DMF} [M =Zn(II), Cd(II), Mn(II) and Co(II)] built using a nitrogen and oxygen donor azo ligand: Crystal structures and fluorescence studies

Abstract

When the ligand HH′L was treated with different transition metal salts at room temperature, four new isostructural coordination polymers, {[Zn(H′L)2(H2O)2]·2DMF}n (1), {[Cd(H′L)2(H2O)2]·2DMF}n (2), {[Mn(H′L)2(H2O)2]·2DMF}n (3), and {[Co(H′L)2(H2O)2]·2DMF}n (4) (HH′L=2-hydroxy-5-(pyridin-4-ylazo)-benzoic acid) were formed. These polymers were characterized by IR spectroscopy, elemental analysis, powder X-ray diffraction (PXRD) and thermogravimetric analysis (TGA), in addition to X-ray crystallography. X-ray single crystal studies revealed that 1–4 are 1D coordination polymers that are further extended by weak interactions to afford 3D coordination polymers. All the complexes show high thermal stability after losing coordinated and lattice solvent molecules in the temperature range 80–200°C. Upon excitation at 344nm, complexes 1–4 exhibit solid-state luminescence at room temperature.