Carbonic Anhydrase Inspired Phosphatase Model Complexes Derived from the Tripodal Ligand Tris(hydroxy-2-benzimidazolyl)amine: The Hydrolysis of p-nitrophenyl Acetate

Abstract

The water soluble ligand tris(hydroxyl-2-benzimidazolyl)amine NTB_OH was used for the preparation of a series of aqua transition metal complexes and their hydroxo derivatives of the types [NTB_OH-M(OH₂)]²⁺ 1-3 and [NTB_OH-M(OH)]⁺ 4-6 (M²⁺ = Zn²⁺, Cu²⁺, and Co²⁺]. Solid state studies of these model complexes were investigated using FT-IR spectroscopy, elemental analysis, and thermal analysis. Solution studies have also been carried out to investigate the coordination behavior of the ligand towards the metal ions as well as the evidence for the protonation/deprotonation of the coordinated water molecules. The effect of these model complexes as potential catalysts, especially the nature of metal ions on the hydrolysis of p-nitrophenyl acetate (NA), has also been investigated. The results indicate that copper(II) complex 3 is the most active hydrolytic catalyst among complexes 1–3, presumably a reflection of the effective electron-withdrawing as well as the greatest electrophilicity of cobalt(II) ion.

Keywords:

• carboxylate ester hydrolysis
• thermal analysis
• transition metal complexes
• water soluble ligand