Self-assembled Transition Metal Coordination Frameworks of ...

_ g “FOUR
CHAPTER
Cu(II) complexes of carbohydrazone and
thiocarbohydrazone ligands: Spectral, magnetic and
anticancer studies
4.1. Introduction
The copper(II) ion is a typical transition metal ion in respect of the formation
of coordination complexes, but less typical in its reluctance to take up a regular
octahedral or tetrahedral stereochemistry [1]. Cu(H) is the most stable oxidation state
of copper, though Cu(I) and Cu(IH) are also relevant. The Cu(II) ion with 3 d 9 outer
electron configuration lacks cubic symmetry and hence exhibits distorted forms of the
basic stereochemistries such as tetrahedral, square planar, square pyramidal and
octahedral. Jahn Teller effect plays a major role in deciding the distortion effect of
stereochemistries of Cu(H) complexes. The typical distortion involved in octahedral
geometry is elongated structures with the odd electron residing in the d‘_;_}__1 orbital
resulting in four short Cu—L bonds and two trans long bonds, which are usually more
energetically favorable than the compressed structures, consistent with their more
frequent occurrence. The coordination numbers of four, five and six predominate, but
variations of each structure occur through bond-length or bond-angle distortions [1].
The Cu(II) complexes are magnetic and EPR active and have been attracted the eyes
of various research groups. Depending on the coupling between Cu(II) centers in
multinuclear complexes, the EPR and magnetic features are interesting and their
coordination chemistry have a distinct role in the progress of inorganic chemistry.
Copper(I) [2>