Slow diffusion in situ ruthenium/ligand reaction: Crystal structures, fluorescence and biological properties

Abstract

Promoted by RuCl 3 .3H 2 O coordination in the mixed solvent DMF/H 2 O, diverse in situ S-S bond reactions such as S-S bond scission and S-oxidation occurred in the disulfide ligand of 2,2'-dithiodibenzoic acid acid (dtdb) to yield the new sulfinato-benzoate ligand (sb). The X-ray analysis of complexes of [Ru(phen) 2 (sb)] (1) and [Ru(bipy) 2 (sb).H 2 O] (2) revealed that in both complexes, the ruthenium ion was found to be in an octahedral geometry, coordinating to the sulfur atom, rather than the oxygen of sulfinate. The complexes were found to be active against the bacterial strains tested with MIC ranging from 14.3-261 µM. In addition, the metal complexes present strong DNA binding affinities constants in the major or minor grooves at the order of magnitude 10 3 -10 5 M −1 . The antioxidant activities of the ligand and its metal complexes were investigated through scavenging effects for DPPH in vitro, indicating that the compounds show stronger antioxidant activities than some standard antioxidants, such as ascorbic and vitamin C.Keywords: 2,2'-dithiodibenzoic acid, S-oxidation, ruthenium, bacterial strains, DNA binding, antioxidantIn situ metal/disulfide reactions under slow diffusion conditions undergo S-S mediated bond reactions, such as S-oxidation, S-S and C-S bond scission. This is a very important research field in coordination chemistry as it leads to structurally novel coordination architectures with interesting physical properties [1][2][3]. In this respect, the use of organosulfur compounds containing carboxylate groups can be attractive due to their flexibility and versatile coordinating modes of both sulfur and oxygen atoms and, generating unprecedented coordination frameworkswhich can act as linkers between inorganic moieties [4][5][6][7][8]. Up to now, a series of transition metal complexes have been found to react with 2,2'-dithiodibenzoic acid (dtdb), giving rise to 1D chains, 2D sheets or 3D network whereby the carboxylate act as monodentate or bidentate donor with or without cleavage of the S-S bond [9]. Recently, we have isolated new copper(II) coordination polymers, whereby dtdb underwent simultaneous S-S and C-S scission under slow diffusion conditions, leading to the formation of 1D coordination polymers [10]. In the presence of 1,10 phenanthroline (phen) and 2,2'bipyridine (bipy), in addition to extrusion of the sulfur atom, the oxidation of sulfur to a sulfate ion was observed. These observations, coupled with the fact that there are no reports of ruthenium complexes derived from dtdb, stimulated our interest to investigate its coordination behavior. Hence, in this work we report for the first time new coordination polymers obtained from RuCl 3 .3H 2 O and dtdb in the presence of phen and bipy, which exhibit sulfinato-benzoate units. The fluorescent, antioxidant and antibacterial properties of the complexes have also been studied, since ruthenium complexes is considered as an attractive alternative to platinum in anticancer drug design and biological applications [11][12][13]...

Photooxidation Reactions of Cyclometalated Palladium(II) and Platinum(II) Complexes

“…The Pd­(Pt)–N and Pd­(Pt)–C distances were comparable to those found in other Schiff base palladium­(II) [platinum­(II)] complexes, − while the Pd­(Pt)–S distances in the cyclometalated complexes, except for the corresponding sulfinato species, were significantly longer than those found in other palladium­(II) [platinum­(II)] thiolate complexes. , This can be explained by the strong trans influence exerted by the cyclometalated aryl carbon atom. − In contrast, the typical Pd­(Pt)–S distances in the sulfinato species can be related to the lower trans influence, suggesting that the oxygenated sulfur atom is a stronger π acceptor than the coordinated thiolato sulfur atom and more competitive with the cyclometalated aryl carbon atom for electron back-donation. The SO distances of the sulfinato species were consistent with other sulfinato metal complexes (Table S2) as well as the IR bands for SO 2 moieties (Figures S1 and S2). , …”

“…31−33 In contrast, the typical Pd(Pt)−S distances in the sulfinato species can be related to the lower trans influence, suggesting that the oxygenated sulfur atom is a stronger π acceptor than the coordinated thiolato sulfur atom 36 and more competitive with the cyclometalated aryl carbon atom for electron backdonation. The SO distances of the sulfinato species were consistent with other sulfinato metal complexes (Table S2) 37 as well as the IR bands for SO 2 moieties (Figures S1 and S2). 38,39 The absorption spectra of the cyclometalated palladium(II) and platinum(II) complexes showed the diagnostic peaks responsible for their blue color at around 600 nm (Figures S3 and S4).…”

Sulfur-center Reactivity toward Oxygenation Mediated by Ruthenium: Effective Bioactive Compounds (A Review)

“…[86][87][88] Recent research on the coordination polymers of Ru II -organosulfur compounds having benzoate group combine with sulfinate functions; their synthesis utilising RuCl 3 •3H 2 O and dtdb [2,2′-dithiodibenzoic acid], and arrangements of atoms and groups inside the polymer and chemical behaviour were described. 89 Such ruthenium sulfur compounds and their derivatives being the member of heavier platinum group metals, are found to be active component to show the in vitro cytotoxicity [90][91][92] and can become active precursor for the anticancer drug design [93][94][95] in the field of biological applications because of these components are lesser toxic for remaining healthy part of the body. 96…”