Metal complexes of general formula, [M(NNS)2] (M = Cu(II), Ni(II), Zn(II) and Cd(II); NNS'= S-2-methylbenzyl-β-N-(di-2-pyridyl)methylenedithiocarbazate (1), NNS''= S-3-methylbenzyl-β-N-(di-2-pyridyl)methylenedithiocarbazate (2) and NNS'''= S-4-methylbenzyl-β-N-(di-2-pyridyl)methylenedithiocarbazate (3) have been synthesized by reacting the respective metal acetates with the Schiff bases in an ethanol/acetonitrile mixture. negative estrogen receptor) cell lines. Only 9 was active against MCF-7 whereas 10 and 13were active against the MDA-MB-231 cell line. Cytotoxic activity was observed to be enhanced upon complexation particularly for the Ni(II) complexes.Keywords: biological activities, S-R-methylbenzyldithiocarbazate, di-2-pyridylketone, Schiff bases
IntroductionDithiocarbazate Schiff bases and their transition metal complexes [1-10] have been of considerable interest to scientists for many years as they show a wide range of therapeutic properties against various diseases, with different anti-bacterial, anti-malarial, anti-viral and anti-tumour properties [1][2][3][4][5][6][7][8][9][10]. In recent years, heterocyclic thiosemicarbazones and Schiff bases derived from S-alkyl dithiocarbazates have been considered as useful model compounds for sulphur-containing analogues of purine and pyrimidine bases [11][12][13]. The π-delocalisation of charge and the configurational flexibility of their molecular chain give rise to a great variety of coordination modes [14][15][16][17][18]. Their chemistry and pharmacological applications have been widely investigated as well [1][2][3][4][5][6][15][16][17][18].Coordination compounds, especially those that contain nitrogen-sulphur ligands are synthesized via relatively simple, cost-effective procedures and it has been observed that small changes in their structure, such as change of substituents and their chelation to different metal ions cause great changes in their bioactivities. The coordination of these compounds often lead to enhanced biological activity in several pathogenic fungi [3,[19][20][21]. Some of these metal complexes have been known to accelerate drug action and the efficacy of a therapeutic agent [1][2][3][4][5][6][19][20][21].The Schiff bases synthesized in this study are the di-2-pyridylketone Schiff bases of isomeric dithiocarbazates, S-2-methylbenzyldithiocarbazate, S-3-methylbenzyl dithiocarbazate and S-4-methylbenzyldithiocarbazate (Fig. 1). Investigations have shown that di-2-pyridylketone thiosemicarbazone and an analogue, 2-benzoylpyridine thiosemicarbazone, demonstrated marked and selective antitumour activity in vitro and also in vivo against many tumours. Di-2-pyridylketone thiosemicarbazone has also been found to possess several structural characteristics important for iron chelating efficacy and potent anti-proliferative activity, and can be further modified as anti-neoplastic agents. Iron has a crucial role in the active site of ribonuclease reductase which is the rate-limiting step of DNA synthesis. This Schiff base and other similar compounds h...
