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 Ni2+ species wereinvestigated in aqueous solution at 25 ±1 °C in I = 0.10 M (NaNO3). Speciation of Ni2+ was done in I = 0.10M (NaNO3) for knowing distribution of Ni2+ species with solution pH. Experimental data were comparedwith speciation diagram constructed from the values of hydrolysis constants of Ni2+ ion. Speciation datashowed that hexaaquanickel(II) ions took place in hydrolysis reactions through formation of [Ni(OH2)6-n(OH)n]2-n species with solution pH. According to speciation of Ni2+ and pH dependent rate constants, rateexpression can be written as: d[Ni(TMPyP)4+]/dt = (k1[Ni2+(aq)] + k2[Ni(OH)+(aq)] + k3[Ni(OH)2o(aq)] + k4[Ni(OH)3-(aq)])[H2TMPyP4+], where k1, k2, k3 and k4 were found to be k1 = (0.62 ± 0.22) ˟ 10-2; k2 = (3.60± 0.40) ˟ 10-2; k3 = (2.09 ± 0.52) ˟ 10-2, k4 = (0.53 ± 0.04) ˟ 10-2 M-1s-1 at 25 ±1 °C, respectively.Formation of hydrogen bonding between [Ni(H2O)5(OH)]+ and [H2TMPyP]4+ causes enhanced reactivity.Rate of formation of [Ni(II)TMPyP]4+ complex was to be 3.99 ˟ 10-2 M-1s-1 in I = 0.10 M, NaNO3 (25 ±1 °C). UV-Vis and fluorescence data suggested that [Ni(II)TMPyP]4+ and [H2(TMPyP)]4+ interact with DNA via outside binding with self-stacking and intercalation, respectively.
Volume 133, 2021
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