Self-assembled Transition Metal Coordination Frameworks of ...

Chapter 4
observed [3]. Conversely, copper is an important bioelement and an active site in
several metalloenzymes and proteins. The chemistry of copper proteins involves
Cu(I), Cu(II) and Cu(III) species and also systems with more than one type of Cu is
present. The Cu atom switches between the Cu(I) and Cu(Il) states [4,5] in redox
reactions involving copper containing enzymes and is an essential factor for many of
the properties of these enzymes.
One of the most striking aspect of copper(H) coordination complexes is their
biological activity, which is of great interest in pharmacology. Cu(H) complexes of
many Schiff bases like hydrazones, semicarbazones, thiosemicarbazones, etc have
been reported to have a great variety of biological activity. Of these,
thiosemicarbazones present activities ranging from fungicide [6], bactericide [7],
antitumoral [8,9] anti-inflammatory [10], etc and are explored well by various
research groups. In most cases, the metal complexes show more activity compared to
their metal free chelating ligands. The present series of ligands can be considered as
an extension of these types of compounds with an additional binding site. Several
mono- and bis- carbohydrazone and thiocarbohydrazone ligands and some Cu(H)
complexes have been synthesized and studied along with their antimicrobial and anti­
mutagenic activity [ll]. Thiocarbohydrazones on complexation with Cu(II) are
proposed as anticancer drug analogues [12,13] like thiosemicarbazones and their
Cu(Il) complexes [14,15]. Hence we considered it worthwhile to synthesize and
characterize Cu(II) complexes of thiocarbohydrazones and their oxygen analogues
carbohydrazone complexes with a view to study their anticancer properties.
The present ligands of carbohydrazones and thiocarbohydrazones with mainly
two coordination pockets are expected to form complexes of interesting magnetic
properties. Also, it is found that the temperature dependence of magnetic
susceptibility with multinuclear Cu(lI) complexes of carbohydrazones and
thiocarbohydrazones and their EPR characteristics are least studied. There is only one
such work reported for thiocarbohydrazone [l2] and is of a dimeric dicopper(Il)
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