Synthesis, characterization and DNA binding studies of organoantimony(V) ferrocenyl benzoates Faiza Asghar a , Amin Badshah a, * , Afzal Shah a , Muhammad Khawar Rauf a , Muhammad Irshad Ali a , Muhammad Nawaz Tahir b , Erum Nosheen a , Zia-ur-Rehman a , Rumana Qureshi a a Department of Chemistry, Quaid-i-Azam University, Islamabad 45320, Pakistan b University of Sargodha, Department of Physics, Sargodha, Pakistan article info Article history: Received 23 May 2012 Received in revised form 4 July 2012 Accepted 15 July 2012 Keywords: Organoantimony(V) ferrocenyl benzoates Single crystal XRD Cyclic voltammetry UVeVis spectroscopy Complex-DNA interaction abstract Organoantimony(V) ferrocenyl benzoates (OFBs) [p-(C 5 H 5 FeC 5 H 4 )C 6 H 4 COO] 2 SbR 3 (R ¼ C 6 H 5 , p-CH 3 C 6 H 4 ) (3, 4) and [m-(C 5 H 5 FeC 5 H 4 )C 6 H 4 COO] 2 SbR 3 (R ¼ p-CH 3 C 6 H 4 )(5) were synthesized and characterized by FT-IR, 1 H and 13 C NMR, single crystal XRD and elemental analysis. The DNA interaction of the complexes (3e5) was investigated by UVeVis spectroscopy and cyclic voltammetry (CV). The complex-DNA binding constant was found to vary in the sequence: K 2 (4.80  10 5 ) > K 1 (2.36  10 4 ) > K 3 (1.87  10 4 ) > K 4 (6.61  10 3 ) > K 5 (6.58  10 3 ). The shift in peak potential, current and absorption maxima of OFBs in the presence of DNA revealed that CV coupled with UVeVis spectroscopy could provide a convenient way to characterize complex-DNA interaction mechanism, a prerequisite for the design of new anticancer agents and understanding the molecular basis of their action. Ó 2012 Elsevier B.V. All rights reserved. 1. Introduction Synthesis, structural aspects and antitumor activities of ferro- cenyl benzoateeantimony complexes have been the subject of intensive investigations [1e4]. Among the organometallic compounds, ferrocene has captured the utmost attention for conjugation with biomolecules due to its stability in aqueous media, large variety of derivatization, facile oxidation and the unique property of retaining simple one electron redox behavior after the introduction of substituents at the cyclopentadienyl rings [5e7]. Medicinal application of ferrocene is an active area of research and many reports have shown that ferrocenyl derivatives are endowed with interesting cytotoxic [8e10], antitumor [11,12], antifungal [13], antimalarial [14] and DNA-cleaving activities [15]. Antimony was first introduced into medicinal treatment in 16th century and gained a growing interest due to its emetic effect [16]. The organic derivatives of the element in both trivalent and pentavalent states are known which leads to many different classes of compounds that have various therapeutic and technological applications. The pentavalent antimonials became the first choice of chemotherapy due to their efficient therapeutic index and 10-fold lower toxicity than trivalent analogues [17e19]. The major clinical use of organoantimonials is in the treatment of leishman- iasis. Some organoantimony derivatives such as antimony tartrate [20] and sodium stibogluconate [21,22] have been reported to exhibit significant anti-cancer and anti-viral activities as well. Deoxyribonucleic acid, DNA, is a molecule of great biological significance since it contains all the genetic information for cellular function. The interaction of small molecules to DNA is gaining wide spread importance. This interaction may be summarized in three ways: (a) electrostatic, (b) groove binding and (c) intercalation [23,24]. A variety of analytical techniques have been used to study the drug-DNA interactions such as luminescence [25], fluorescence [26], UVevisible spectroscopy [27], and voltammetric methods [28e30]. But the electrochemical methods are most widely used due to their advantages like high sensitivity, cost effectivity, more reli- ability and fast detection ability. UVeVis spectroscopic technique is also best suited to ferrocenes owing to their intense colors. In this paper, we have synthesized organoantimony derivatives of m-fer- rocenylbenzoic acid and p-ferrocenylbenzoic acid (3e5), which contain three active centers, namely the organoantimony (V) moiety and two ferrocenyl carboxylate groups. The synthesis and charac- terization of compound (5) bis(p-ferrocenylbenzoato)tri(p-tolyl) antimony(V) have already been reported by Yu et al. [1], but crys- tallographic and electrochemical studies have not yet been reported. * Corresponding author. Tel.: þ92 5190642131; fax: þ92 5190642241. E-mail addresses: aminbadshah@yahoo.com (A. Badshah), mkhawarrauf@ yahoo.co.uk (M.K. Rauf). Contents lists available at SciVerse ScienceDirect Journal of Organometallic Chemistry journal homepage: www.elsevier.com/locate/jorganchem 0022-328X/$ e see front matter Ó 2012 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.jorganchem.2012.07.028 Journal of Organometallic Chemistry 717 (2012) 1e8