Polymeric Copper(II) Paddlewheel Carboxylate: Structural Description, Electrochemistry, and DNA‐binding Studies

Abstract

A polymeric complex of copper(II) was isolated and purified from the self‐assembly of CuSO4 and 2‐phenyl acetate in aqueous medium. It was characterized through FT‐IR, UV/Vis, electron spin resonance, electrochemical solution studies, and powder and single crystal XRD techniques. The structure was revealed to consist of directly interconnected dimeric paddlewheel building units without any intervening ligand. This type of polymeric paddlewheel structures are found very rarely. Each copper is lying in a CuO5 square pyramid coordinated by four oxygen atoms in the square base while the axial oxygen belongs to the neighboring paddlewheel. Purity and uniform crystalline nature of the complex was assessed from matching theoretical and experimental powder XRD spectra. ESR spectrum consisted of a broad signal with g value = 2.2427, whereas electrochemical studies revealed diffusion controlled electron transfer processes with diffusion co‐efficient = 1.628 × 10–7 cm2·s–1. The results of spectroscopic techniques support each other. The complex afforded mixed binding mode with DNA yielding DNA‐binding constant values of 1.384 × 104 m–1 and 8.845 × 104 m–1 using absorption spectroscopy and cyclic voltammetry, respectively. The complex also exhibited significant activity against anti‐fungal strain Helminthosporium solani by inhibiting its 75 % ± 2.5 growth. The preliminary studies heralded excellent biological potential of the synthesized complex.

A binary copper(II) complex having stepped polymeric structure: Synthesis, characterization, DNA-binding and anti-fungal studies

“…6B) using the Benesi-Hildebrand equation. 10 The value of the DNA-binding constant thus calculated was 6.90×10 3 M -1 . The values of the DNA-binding constant of the complex determined through cyclic voltammetry and absorption spectroscopy were lower than the unsubstituted 2-phenylacetate copper(II) complex 10 and another minor groove binder of the copper(II) complex.…”

“…10 The value of the DNA-binding constant thus calculated was 6.90×10 3 M -1 . The values of the DNA-binding constant of the complex determined through cyclic voltammetry and absorption spectroscopy were lower than the unsubstituted 2-phenylacetate copper(II) complex 10 and another minor groove binder of the copper(II) complex. 6 However, these values are comparable to some other copper(II) complexes [Cu(dipica)(diimine)] 2+ , [Cu(L-tyrosine)(5,6-dmp)] 2+ and [Cu(imda)(diimine)] complexes (dipica is di-2--picolylamine, 5,6-dmp is 5,6-dimethyl-1,10-phenanthroline and imda is iminodiacetate).…”

“…The out of plane nature of the copper ion from the basal plane may also be the result of this restraint as it is typical of other paddlewheel structures. 10 The Cu … Cu bond distance was found to vary with the nature of the bonds around the Cu, whereby soft donor atoms around copper were found to have longer Cu … Cu separation. 11 The apical Cu-O bond (2.240 Å) is longer than the equatorial Cu-O bonds (average = = 1.9642 Å) owing to the double electron occupancy of the d z 2 orbital lying on the apical axis.…”

“…78.39 (10) The structure is composed of interconnected (through Cu-O bonds) paddlewheel units in an almost linear fashion resulting in a 1D polymeric chain (Fig. 4).…”

“…This behavior and peak ranges are typical of those observed for structurally similar copper(II) complex. 10 Some insight into the electron transfer reaction was obtained from a logarithmic plot of current and scan rate, the linearity with a slope value of 0.3 indicated a diffusion-controlled process in the three-electrode cell. 12 A parameter of prime importance in a diffusion controlled process is the diffusion coefficient D 0 , the value of which is determined using Randles-Sevcik equation.…”