Syntheses, characterization and antifungal activity of tris(1,10-phenanthroline)iron(ii) bis(n-r-sulfonyldithiocarbimate)zincate(ii)

Abstract

Recebido em 24/8/12; aceito em 7/1/13; publicado na web em 24/5/13Four new compounds with the general formula [Fe(phen) 3 ][Zn(RSO 2 N=CS 2 ) 2 ], where phen = 1,10-phenanthroline, R = 4-FC 6 H 4 (1), 4-ClC 6 H 4 (2), 4-BrC 6 H 4 (3) and 4-IC 6 H 4 (4), respectively, were obtained by the reaction of the appropriate potassium N-R-sulfonyldithiocarbimate (RSO 2 N=CS 2 K 2 ) and tris(1,10-phenanthroline)iron(II) sulfate, with zinc(II) acetate dihydrate in dimethylformamide. The elemental analyses and the IR data were consistent with the formation of the expected complexes salts. The 1 H and 13 C NMR spectra showed the signals for the cationic iron(II) complex and dithiocarbimate moieties. The molar conductance data were consistent with the 1:1 cation:anion complexes in 1-4. The antifungal activities of the compounds were tested in vitro against Candida albicans, Candida tropicalis and Colletotrichum gloeosporioides.Keywords: dithiocarbimates; metal complexes; antifungal activity. INTRODUCTIONFungal infections in humans have increased in recent years predominantly affecting immunocompromised patients. 1,2 Fungi from the Candida genus can infect the oral and vaginal cavities, skin and, more seriously, essential organs. 1,3 Colletotrichum gloeosporioides is known to infect a wide variety of hosts, including vegetables, field and forage crops, fruit trees, and ornamental shrubs. 4 C. gloeosporioides infections in humans can cause keratitis in healthy or immunocompromised individuals and can induce phaeohyphomycosis in patients with hematologic malignancies and iatrogenic immunosuppression. [5][6][7] Several dithiocarbamate and N-substituted dithiocarbamate complexes and salts (Scheme 1a) have been used as agrochemicals mainly due to their high efficiency in controlling plant fungal diseases, and their relatively low toxicity. 8,9 The literature reports that dithiocarbamate complexes are also active against Candida spp. 10In recent studies, we have demonstrated that the dithiocarbimate compounds A 2 [Zn(RSO 2 N=CS 2 ) 2 ] and A 2 [Sn(Bu) 2 (RSO 2 N=CS 2 ) 2 ] (A = tetrabutylammonium cation or tetraphenylphosphanium cation, Bu = n-butyl and R = 4-FC 6 H 4 , 4-ClC 6 H 4 , 4-BrC 6 H 4 and 4-IC 6 H 4 ) are active against Colletotrichum gloeosporioides. 11-13 It was also observed that the cations Bu 4 N + and Ph 4 P + were inactive.Unlike dithiocarbamate analogues, the bis(dithiocarbimate) metal(II) complexes are anionic species (Scheme 1), offering potentially useful modulation of this activity. For example, enhanced antifungal activity should be possible either by the use of active counter ions, or by varying the solubility of the salts of the complexes through the use of different cations.Considering these possibilities, the activities of some salts were tested in order to find an appropriate active cation to deepen the investigation into the antifungal potential of dithiocarbimates. This search revealed that tris(phenantholine)iron(II) perchlorate is active against Colletotrichum gloeosporioides. Here we describe the s...

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