European Journal of Biomedical and Pharmaceutical Sciences

SPECTRAL AND ELECTROCHEMICAL STUDIES OF NI (II) MACROCYCLIC COMPLEXES OF ME2 PH2 R BZO2 [14] TETRAENE-N4

*Dr. Radhey Shyam and Dr. Surekha Kannaujia

ABSTRACT

Synthesis of Ni (II) macrocyclic complexes and their spectral and redox behavior have been carried out. Different substituent on phenyl ring of macrocyclic complexes were attached and the effects of these groups R=OCH3 , Cl and NO2 were observed . the cyclic voltammetric studies showed two irreversible oxidation peals Ep (A) in the range from 0.40 to 0.80 V and from 1.00 to 1.40 Vs SCE respectively. During these studies a reversible reduction was also observed in the range 1.50 to -1.80V. Electrochemical studies showed that the oxidation process seems to be ligand based. The UV visible spectrum showed a charge transfer characteristics that may be assigned as ligand to metal. The substituted effect was also examined by means of Hammett plots of Ep (A), Ep (B) and E½ Vs 2σp which were linear and slopes of 0.21 and 0.24 respectively.[1-3] The evidence for ligand oxidation can be made by comparing potentials for oxidation of the copper (II) complexes to its nickel (II) analogue. The peal potentials occur in the same potential region but are shifted⁓0.1 V more negative. Since copper (III) is unusual oxidation sate, the shift is due to the electronic changes due to different metal centers. The larger shift (⁓0.3 V) in the positive direction for reduction of the copper complex has also been observed may due to the reduction of copper (II) to copper (I). It is also noteworthy that the redox behavior of the tetraazaannulenes complexes can be tuned by the appropriate choice of substituents attached to the macrocyclic ligand and the effect can be controlled by the precise location of the substituents.[4-6]

Keywords: Macrocyclic complexes, Electrochemical studies, and cyclic voltammetry studies.