Role of carboxyl group in the coordination of metals in organic structures

Abstract

In the present work COOH was tested in order to assess its role in the coordination between Li, Na, K, Rb, Ca and Zn and organic structure. HF/3-21G∗ ∗ was used to study the histidine-H+ complex as a model molecule. Li, Na, K, Rb, Ca and Zn were coordinated with histidine instead of hydrogen bonding of COOH group. The effect of such coordination is followed in terms bond distances, bond angle and the vibrational characteristics of COOH group. The calculated total dipole moments were increased on going from histidine to Rb coordinated histidine. The same behavior was also noticed for the C O stretching. The bond length LC-O was increased while the LC-O was decreased as a result of coordination. The change in the geometry of COOH was also changing the symmetric stretching vibration of COOH into asymmetric stretching vibration.