Vibrational spectroscopic studies of indolecarboxylic acids and their metal complexes part VIII. 5-methoxyindole-2-carboxylic acid and its Zn(II) complex.

The complex of 5-methoxyindole-2-carboxylic acid with Zn(II) has been synthesized and characterized by the infrared and Raman spectroscopic methods. Moreover, the infrared and Raman spectra of 5-methoxyindole-2-carboxylic acid (5-MeOI2CAH) and the infrared spectrum of deuterated derivative of 5-metoxyindole-2-carboxylic acid (5-MeOI2CA-d2) are recorded in the solid phase. The theoretical wavenumbers, infrared intensities and Raman scattering activities were calculated by density functional B3LYP method with the 6-311++G(df,p) basis set for 5-MeOI2CAH and 5-MeOI2CA-d2 and with the 6-311++G(df,p)/LanL2DZ basis sets for the theoretical model of [Zn(5-MeOI2CA)(2)(H(2)O)(2)](n). The detailed vibrational assignment has been made on the basis of the calculated potential energy distribution for 5-MeOI2CAH, 5-MeOI2CA-d2 and [Zn(5-MeOI2CA)(2)(H(2)O)(2)](n). The results from natural bond orbitals (NBO) analyses for indole-2-carboxylic acid (I2CAH) and 5-MeOI2CAH are discussed.