Kinetics and mechanism of formation of nickel(II)porphyrin and its interaction with DNA in aqueous medium

Kinetics between 5,10,15,20-tetrakis(N-methylpyridium-4-yl)porphyrin and Ni(2+) species were investigated in aqueous solution at 25 ±1 °C in I = 0.10 M (NaNO(3)). Speciation of Ni(2+) was done in I = 0.10 M (NaNO(3)) for knowing distribution of Ni(2+) species with solution pH. Experimental data were compared with speciation diagram constructed from the values of hydrolysis constants of Ni(2+) ion. Speciation data showed that hexaaquanickel(II) ions took place in hydrolysis reactions through formation of [Ni(OH(2))(6-n)(OH)(n)](2-n) species with solution pH. According to speciation of Ni(2+) and pH dependent rate constants, rate expression can be written as: d[Ni(TMPyP)(4+)]/dt = (k(1)[Ni(2+)((aq))] + k(2)[Ni(OH)(+)((aq))] + k(3)[Ni(OH)(2)(o)((aq))] + k(4)[Ni(OH)(3)(-)((aq))])[H(2)TMPyP(4+)], where k(1), k(2), k(3) and k(4) were found to be k(1) = (0.62 ± 0.22) × 10(-2); k(2) = (3.60 ± 0.40) × 10(-2); k(3) = (2.09 ± 0.52) × 10(-2), k(4) = (0.53 ± 0.04) × 10(-2) M(-1)s(-1) at 25 ±1 °C, respectively. Formation of hydrogen bonding between [Ni(H(2)O)(5)(OH)](+) and [H(2)TMPyP](4+) causes enhanced reactivity. Rate of formation of [Ni(II)TMPyP](4+) complex was to be 3.99 × 10(-2) M(-1)s(-1) in I = 0.10 M, NaNO(3) (25 ± 1 °C). UV-Vis and fluorescence data suggested that [Ni(II)TMPyP](4+) and [H(2)(TMPyP)](4+) interact with DNA via outside binding with self-stacking and intercalation, respectively. SYNOPSIS [Figure: see text] SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s12039-021-01945-y.