Abstract
Ferromagnetic hydroxo–acetato bridged dicopper(II) complexes of 1,10-phenanthroline and dipyridoquinoxaline ligands show efficient hydrolytic cleavage of pUC19 DNA as evidenced from the T4 DNA ligase experiments and the binuclear complexes on reaction with bis(4-nitrophenyl)phosphate (BNPP) as a model ester show formation of trigonal bipyramidal copper(II) complexes as mono-adduct of BNPP. [Display omitted]
► The subject area is bioinorganic chemistry of nucleic acids related to nucleases. ► Hydroxo-acetato bridged dicopper(II) complexes are efficient synthetic nucleases. ► DNA hydrolysis rate has been evaluated under true Michaelis–Menten conditions. ► The hydrolytic rates compare well with those known for synthetic metallonucleases.
Ferromagnetic dicopper(II) complexes [Cu2(μ-O2CCH3)(μ-OH)(L)2(μ-L1)](PF6)2, where L=1,10-phenanthroline (phen), L1=H2O in 1 and L=dipyrido[3,2-d:2′,3′-f]quinoxaline (dpq), L1=CH3CN in 2, are prepared and structurally characterized. Crystals of 1 and 2 belong to the monoclinic space group of P21/n and P21/m, respectively. The copper(II) centers display distorted square-pyramidal geometry having a phenanthroline base and two oxygen atoms of the bridging hydroxo and acetate group in the basal plane. The fifth coordination site has weak axially bound bridging solvent molecule H2O in 1 and CH3CN in 2. The Cu···Cu distances are 3.034 and 3.046Å in 1 and 2, respectively. The complexes show efficient hydrolytic cleavage of supercoiled pUC19 DNA as evidenced from the mechanistic studies that include T4 DNA ligase experiments. The binuclear complexes form monomeric copper(II) adducts [Cu(L)2(BNPP)](PF6) (L=phen, 3; dpq, 4) with bis(4-nitrophenyl)phosphate (BNPP) as a model phosphodiester. The crystal structures of 3 and 4 reveal distorted trigonal bipyramidal geometry in which BNPP binds through the oxygen atom of the phosphate. The kinetic data of the DNA cleavage reactions of the binuclear complexes under pseudo- and true-Michaelis–Menten conditions indicate remarkable enhancement in the DNA hydrolysis rate in comparison to the control data.
