Synthesis, crystal structures and antioxidant studies of Pd(II) and Ru(II) complexes of 2-(4-methoxyphenyltelluro) ethanol

Abstract

Pd(II) (1) and Ru(II) (2) complexes of 2-(4-methoxyphenyltelluro)ethanol (L), were synthesized using Na2 [PdCl4] and [Ru (η6-p-cymene)Cl2]2 as metal ion sources. The new complexes (1 and 2) were characterized by 1H, 13C{1H} NMR, FT-IR, UV–Visible spectroscopy and elemental analyses. Their structures were also confirmed by single crystal X-Ray diffraction. The characterizationdata revealed that the ligand L coordinated to M(II) ion as a monodentate telluroether ligand in both 1 and 2. The structure of cis-[PdCl2(L)2] (1) was square planar about Pd in which two molecules of L coordinated to palladium (II) in cis-fashion. Interestingly, two molecules of 1 were held by strong Te⋯Cl and aromatic π⋯π secondary interactions and oriented in staggered conformation with short Pd-Pd [3.1712 (5) Å] distance forming a dinuclear palladium cluster (cis-[PdCl2(L)2])2 (1)2. The complex [Ru (η6-p-cymene)Cl2(L)] (2) has half-sandwich, pueudo-octahedral structure. There exists several intermolecular hydrogen bonds of type: OH⋯Cl and OH⋯O in 1 and CH⋯Cl, CH⋯O and OH⋯Cl in 2. These interactions results in supramolecular assemblies in the new complexes 1 and 2. In-vitro antioxidant activity of L, 1 and 2 was investigated using DPPH assay. Vitamin-C was used as a standard antioxidant. All three compounds showed to exhibit antioxidant activity. The free radical scavenging activity was quantitatively expressed in terms of their IC50 values which found in the order: Vitamin-C ∼2 > L > 1.