Sodium and lithium one-dimensional coordination polymers with 1H-indazole-3-carboxylic acid: Crystal structures, vibrational spectra and DFT calculations

Abstract

Sodium(I) and lithium(I) one-dimensional coordination polymers, [Na(IND3CAH)(IND3CAH2)]n (1) and [Li(IND3CAH)(H2O)]n (2), with 1H-indazole-3-carboxylic acid (IND3CAH2) have been synthesized and investigated by a single crystal X-ray diffraction and vibrational spectroscopy. In compound 1, both the O-deprotonated (IND3CAH−) and neutral (IND3CAH2) forms of the acid act as the tridentate ligands and are bound with Na+ via two oxygen atoms and the 1H-indazole nitrogen atom forming polymeric chains. Each Na+ ion is six-coordinate in a distorted octahedral geometry (NaO4N2). In compound 2, the Li+ ion is five-coordinate (LiO4N) and the coordination sphere is intermediate between square-pyramid and trigonal-bipyramid. The deprotonated IND3CAH− ion acts as the bidentate ligand coordinated to Li+ ion via one carboxylate oxygen atom and the 1H-indazole nitrogen atom. In contrast to 1, the carboxylate group exhibits the monoatomic bridging mode. In addition, the oxygen atom of the water molecule also links two adjacent Li+ ions. The bridging ligands lead to the formation of polymeric ribbons of edge-sharing O4N distorted pyramids. Intermolecular NH⋯O and OH⋯O hydrogen bonds have a distinctive effect on crystal packing of the title compounds. The IR and Raman spectra of 1 and 2 in the solid state confirm the results from X-ray analysis. Vibrational spectra of the ligand IND3CAH2 and its deuterated derivative (IND3CAD2) have been measured and assigned based on DFT calculations.