A novel coordination polymer of 7-azaindole-3-carboxylic acid with sodium ions: crystal and molecular structures, vibrational spectra and DFT calculations

A novel two-dimensional coordination polymer, catena-poly[(mu(2)-7-azaindole-3-carboxylato-O:N)-diaqua-sodium], [Na(7AI3CAH)(H2O)(2)](n) has been synthesized and investigated by a single crystal X-ray diffraction, vibrational spectroscopy and DFT calculations. The sodium complex crystallizes in the triclinic system, space group Pi with a = 7.2226 (4), b = 7.4342 (7), c = 8.8428 (8) angstrom, alpha = 103.568 (8), beta = 93.425 (6), gamma = 91.233 (6)degrees, V = 460.42 (7) A(3) and Z = 2. The asymmetric unit contains two crystallographically independent, half occupied sodium cations surrounded by one 7AI3CAH anion and two water molecules. The O-deprotonated 7-azaindole-3-carboxylate ligand (7AI3CAH) bridges the adjacent Na ions via one oxygen atom of the carboxylate group and via the pyridine nitrogen atom of the 7-azaindole group, which is quite unusual. The sodium cations are six-coordinated in a distorted octahedral geometry, where two apical positions are occupied by two water molecules. Extensive intermolecular N-H center dot center dot center dot O and O-H center dot center dot center dot O hydrogen bonds stabilize the crystal structure of the complex. The infrared and Raman spectra of [Na(7AI3CAH)(H2O)(2)](n) were recorded in the solid state. The theoretical wavenumbers, infrared intensities, Raman scattering activities and Raman intensities were calculated at the B3LYP/6-311++G(d,p) level for a theoretical model of the title compound including an inter ligand N-H center dot center dot center dot O(aqua) interaction. A detailed vibrational assignment has been made on the basis of the calculated potential energy distribution. (C) 2017 Elsevier B.V. All rights reserved.