1D, 2D, and 2D Parallel Interpenetrated Dicarboxylato Bridged Co(II) Metal Organic Frameworks: Synthesis, Crystal Structure, Fluorescence Sensing and Band Gap Calculation

Metal organic frameworks of Co(II), {[Co(bphz)1.5(tp)(H2O)2]⋅3.2H2O}n (1), {[Co(bphz)(ip)]⋅(bphz)0.5}n (2), and [Co(bpp)(ppda)(H2O)2]n (3) [where bphz=N,N′-bis-pyridin-4-ylmethylene-hydrazine; tp=1,4-benzenedicarboxylate; ip=1,3-benzenedicarboxylate; bpp=1,3-bis(4-pyridyl)propane; ppda=1,4-phenylenediacrylate] have been synthesized and characterized by single crystal X-ray diffraction and spectroscopic studies. Complex 1 is a ladder like 1D polymeric chain, 2 is a 2D porous sheet, while 3 is a 2D parallel interpenetrated network. The band gap of complexes has been calculated using solid state reflectance spectra, and results show that complexes act as semiconductor. In dispersed methanolic solution complexes 1–3 exhibit intense fluorescence at room temperature. The complexes were tested with several aromatic compounds such as benzene, nitrobenzene, o-nitrotoluene and p-nitrotoluene, etc., in dispersed methanol medium. Results show that complex 3 selectively senses nitro aromatic compounds and this behavior has been explained on the basis of PET and RET mechanisms.