K, Ca complexes with a sulfonic ligand: Structure and DNA-binding properties

A novel 4-(2,4-dihydroxybenzylideneamino)benzenesulfonic acid (HL), and its kalium(I), calcium(II) complexes [M(L)n]·2nH2O·Cln (M = K(1) n = 1, M = Ca(2) n = 2), have been prepared and characterized. The crystal and molecular structures of 1 and 2 were determined by single-crystal X-ray diffraction. The interaction of 1, 2 and ligand (L) with calf thymus DNA was investigated by UV–visible (UV–vis), fluorescence and viscosity measurements. Experimental results indicate that 1, 2 and L could bind to DNA via the intercalation mode, and the binding affinity of 1 is stronger than that of 2 and L. The intrinsic binding constants of 1, 2 and L were 5.60 × 105, 6.53 × 105 and 1.44 × 105 M−1, respectively. The cleavage reaction on plasmid DNA has been monitored by agarose gel electrophoresis. The results indicated that 1 and 2 could cleave pBR322 DNA.

Graphical abstractThe emission spectra of DNA–EB system (10 μM and 0.32 μM EB), λex = 500 nm, λem = 520.0–700.0 nm, in the presence of 0–40 μM complex 1. The arrow indicates the emission intensity changes upon increasing complex 1 concentration.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► A novel 4-(2,4-dihydroxybenzylideneamino)benzenesulfonic acid (HL), and its kalium(I), calcium(II) complexes [M(L)n]·2nH2O·Cln (M = K(1) n = 1, M = Ca(2) n = 2), have been prepared and characterized. ► This is the first time to report K, Ca complexes to interact DNA. Results suggest that the two complexes bound to DNA via a groove binding mode. ► The results also indicate that the complexes can cleave pBR322 DNA.