Aggregation and DNA binding characteristics of tetrakis(N,N',N″,N‴-tetramethyltetra-3,4-pridino)porphyrazine cobalt(II)

Abstract

ABSTRACT:The association behavior of tetrakis(N,N´,N´´,N´´´-tetramethyltetra-3,4-pridino)-porphyrazine cobalt(II) ([Co(II) -DNA has also been studied. The binding constant (K) was obtained by analysis of optical absorption spectra of the above-mentioned complex at various DNA concentrations using SQUAD software. The value of K was estimated as 1.31 × 10 6 ± 1.174 M -1 at 25 °C. The thermodynamic parameters were calculated by vanʼt Hoff equation. The enthalpy and entropy changes were 48.77 ± 2.50 kJ.mol -1 and 280.77 ± 9.62 J.mol -1 .K -1 at 25 °C, respectively. The results indicate that the process is entropy driven suggesting that hydrophobic interactions are the main driving forces for complex formation. The increase of ionic strength due to the addition of NaCl, destabilized porphyrazine-DNA complexes, which indicates the competition of Na + ions with porphyrazine complexes for occupation of minor groove binding sites.