Spectroscopic and Potentiometric Analysis on Diaquo Bis(N–2–Amino–3–Methylbutayl-2,4-Pentanedionato) Copper (II) Complex

Abstract

A Schiff base was prepared from the reaction of 2 - amino - 3 – methylbutanoic acid and 2, 4 - pentanedione. The reaction of the prepared Schiff base with ethanolic solution of copper (II) chloride formed diaquo
bis( N – 2 – amino – 3 - methylbutyl - 2, 4 - pentanedionato) copper (II) complex. The Schiff base is crystalline orange yellow, has a yield of 53% and melting point of 210oC. The copper (II) Schiff base complex is crystalline greenish blue, has a yield of 73% and a decomposition temperature of 231oC. The Schiff base is soluble in most solvent
including water, but insoluble in ether. The diaquo bis( N – 2 – amino – 3 – methylbutyl - 2, 4 - pentanedionato) copper (II) complex is soluble in water, DMSO and DMF, but insoluble in most common organic solvents. The molar conductance of the copper (II) Schiff base complex determined is 33 ohm-1 cm2 mol-1. The infra-red spectral data showed bands in the range 1612 – 1636 and 1592 - 1624cm-1, assignable to v(C=N) stretching vibrations of the Schiff base and its copper (II) complex, respectively. The broad bands in the range 3278 - 3423 and 3314 - 3397cm-1 are
attributable to v(O-H) stretching frequencies in the Schiff base and it complex compound, respectively. The weak bands at 514 and 387 cm-1 are attributable to v(Cu-O) and v(Cu-N) stretching vibrations, respectively in the copper (II) Schiff base complex. The dissociation constant (pKa) of N – 2 – amino – 3 – methylbutyl – 2, 4 - pentanedione schiff base
determined is 4.55. The stability constant and Gibb’s free energy of copper (II) Schiff base complex determined are 3.9x109 and -5.46x104 Jmol-1, respectively. The ratio of copper (II) ion to N – 2 – amino – 3 – methylbutyl – 2, 4 - pentanedione determined is 1:1.