A Unique Discrete Tetranuclear Cu %26apos;-Cu(N-N)(2)Cu-Cu %26apos; Copper(II) Complex, Built from a mu(3)-1,2,4-Triazolato-mu-carboxylato Ligand, as an Effective DNA Cleavage Agent

作者：Hernandez Gil Javier; Ferrer Sacramento^*; Castineiras Alfonso; Lloret Francesc

来源：Inorganic Chemistry, 2012, 51(18): 9809-9819.

DOI：10.1021/ic301168k

The title compound, characterized by means of an X-ray structure analysis, represents an easy example of a noncatena %26quot;1 + 2 + 1%26quot; tetranuclear copper(II) mu(3)-triazolate compound. [Cu-4(atc)(2)(dien)(4)(ClO4)(2)](ClO4)(2)center dot 2H(2)O (1), where H(2)atc = 5-amino-1,2,4-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%26apos;) 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 angstrom, Cu-Cu%26apos; = 5.686 and 6.370 angstrom, and Cu%26apos;-Cu%26apos; = 11.373 angstrom. 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%26apos; (Cu-central-Cu-pheripheral) Pairs, as defined by H = -J S2S2a - j (S1S2 + S2aS1a). 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 x 10(6) M-1 (K-app) and Delta T-m = 18.3 degrees 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 similar to 0.126 min(-1). The good reactivity of 1 toward DNA is explained from the electrostatic interactions of the cationic species produced in solution.

• 出版日期2012-9-17