Ni(II) complexes with Schiff bases derived from amino sugars

Area of Science:

• Coordination Chemistry
• Carbohydrate Chemistry
• Spectroscopy

Background:

• Schiff bases derived from carbohydrates are versatile ligands in coordination chemistry.
• Understanding tautomeric and anomeric equilibria is crucial for characterizing these compounds and their metal complexes.
• Nickel(II) complexes with Schiff base ligands have applications in catalysis and materials science.

Purpose of the Study:

• To investigate the tautomeric and anomeric equilibria of a novel Schiff base derived from D-glucopyranose.
• To synthesize and characterize nickel(II) complexes of this Schiff base.
• To elucidate the coordination mode of the Schiff base ligand to the nickel(II) ion.

Main Methods:

• Proton and Carbon-13 Nuclear Magnetic Resonance (NMR) spectroscopy to study equilibria.
• Synthesis of Schiff base and its nickel(II) complexes.
• Characterization using spectroscopic methods (NMR, IR, UV-Vis) and cyclic voltammetry.

Main Results:

• The Schiff base, 2-deoxy-2-(2-hydroxybenzaldimino)-D-glucopyranose, exhibits enol-imine-keto-amine and anomeric equilibria in solution.
• A bidentate, mononuclear Ni(II) complex was successfully synthesized and characterized.
• Coordination occurs through the enol-imine tautomeric form of the Schiff base.
• The anomeric equilibrium persists in dimethyl sulfoxide solutions.
• Alternative synthesis routes for related nickel(II) complexes were explored.

Conclusions:

• The Schiff base ligand exists in multiple equilibrium forms, influencing its coordination behavior.
• Nickel(II) complexation involves specific tautomeric and anomeric configurations.
• Spectroscopic and electrochemical data confirm the structure and coordination of the Ni(II) complexes.
• The study provides insights into the coordination chemistry of carbohydrate-derived Schiff bases with transition metals.