X-ray diffraction and vibrational spectroscopic studies of indolecarboxylic acids and their metal complexes: Part VII. Indole-2-carboxylic acid and catena-poly[[diaquazinc(II)]-bis(μ2-indole-2-carboxylato-O:O′)]

The catena-poly[[diaquazinc(II)]-bis(μ2-indole-2-carboxylato-O:O′)], [Zn(I2CA)2(H2O)2]n has been synthesized and characterized by X-ray diffraction analysis and the infrared and Raman spectroscopic methods. The co-ordination of the indole-2-carboxylate anion to Zn(II) results in the formation of the [Zn(I2CA)2(H2O)2]n, in which the Zn(II) cations lie on inversion centres in space group P21/c, with water ligands in the apical sites of octahedral geometry. Moreover, the infrared and Raman spectra of indole-2-carboxylic acid (I2CA) and the infrared spectrum of deuterated derivative of indole-2-carbocylic acid (I2CA-d2) are recorded in the solid phase. The theoretical wavenumbers, infrared intensities and Raman scattering activities were calculated by density functional B3LYP and mPW1PW91 methods with the 6-311++G(d,p) basis set for I2CA and I2CA-d2 and with the 6-311++G(d,p)/LanL2DZ basis sets for the theoretical model of Zn(I2CA)2(H2O)2]n. The detailed vibrational assignment has been made on the basis of the calculated potential energy distribution for all molecules.