title: A unique discrete tetranuclear Cu'-Cu(N-N)2Cu-Cu' copper(II) complex, built from a μ3-1,2,4-triazolato-μ-carboxylato ligand, as an effective DNA cleavage agent.
abstract: The title compound, characterized by means of an X-ray structure analysis, represents an easy example of a noncatena "1 + 2 + 1" tetranuclear copper(II) μ(3)-triazolate compound. [Cu(4)(atc)(2)(dien)(4)(ClO(4))(2)](ClO(4))(2)·2H(2)O (1), where H(2)atc = 5-amino-l,2,4-triazole-3-carboxylic acid and dien = diethylenetriamine = 1,4,7-triazaheptane, contains two copper atoms linked by a double diazinic bridge, each of which is further connected to a third and fourth copper atom (Cu') through the triply bridging triazolato ring and the bidentate carboxylato group of the atc(2-) ligands. The copper-copper distances within the tetranuclear unit are Cu-Cu = 4.059 Å, Cu-Cu' = 5.686 and 6.370 Å, and Cu'-Cu' = 11.373 Å. The compound self-assembles into a tridimensional hydrogen-bonded network to generate a MOF. 1 exhibits antiferromagnetic behavior with g = 2.10(1), J = -34.1(2) cm(-1) and j = -5.50(3) cm(-1), where J is the coupling constant of the central Cu-Cu pair and j the coupling constant of the two Cu-Cu' (Cu(central)-Cu(pheripheral)) pairs, as defined by H = -JS(2)S(2a) - j (S(1)S(2) + S(2a)S(1a)). Complex 1 has been tested as nuclease mimic. It shows good binding propensity to calf thymus DNA, with a binding constant value of 6.20 × 10(6) M(-1) (K(app)) and ΔT(m) = 18.3 °C. Moreover, the compound displays efficient oxidative cleavage of pUC18 DNA, even at low concentration, in the presence of a mild reducing agent (ascorbate), with a rate constant for the conversion of supercoiled to nicked DNA (k(obs)) of ~0.126 min(-1). The good reactivity of 1 toward DNA is explained from the electrostatic interactions of the cationic species produced in solution.
authors.affiliation: Departament de Química Inorgànica, Universitat de València, Vicent Andrés Estellés s/n, 46100-Burjassot, Valencia, Spain.
authors.forename: Javier
authors.initials: J
authors.lastname: Hernández-Gil
authors.forename: Sacramento
authors.initials: S
authors.lastname: Ferrer
authors.forename: Alfonso
authors.initials: A
authors.lastname: Castiñeiras
authors.forename: Francesc
authors.initials: F
authors.lastname: Lloret
mesh_terms: D002264:Carboxylic Acids / Q000737:chemistry*; D003300:Copper / Q000737:chemistry*; D018360:Crystallography, X-Ray; D004247:DNA / Q000187:drug effects*; D053837:DNA Cleavage / Q000187:drug effects*; D008024:Ligands; D008958:Models, Molecular; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000138:chemical synthesis / Q000737:chemistry / Q000494:pharmacology*; D010957:Plasmids / Q000187:drug effects; D014230:Triazoles / Q000737:chemistry*
chemical_list: D002264:Carboxylic Acids; D008024:Ligands; D009942:Organometallic Compounds; D014230:Triazoles; D003300:Copper; D004247:DNA