DNA Cleavage by Structurally Characterized Dinuclear Copper(II) Complexes Based on Triazine

Abstract

The reaction of 2‐chloro‐4,6‐bis(di‐2‐picolylamino)‐1,3,5‐triazine (bdpaTCl) with copper(II) perchlorate and copper(II) chloride afforded two dinuclear complexes [Cu2(μ‐bdpaTCl)(μ‐OH)2(H2O)0.5(ClO4)0.5](ClO4)1.5·(H2O)1.5 (1) and [Cu2(μ‐bdpaTCl)Cl4]·2CH3OH (2), respectively. These complexes were characterized by IR, UV/Vis, and EPR spectroscopy, single‐crystal X‐ray crystallography, and temperature dependence magnetic susceptibility measurements (2–300 K) as well as by electrochemical and molar conductivity measurements. In 1, each of the three N‐donor atoms of the binucleating bdpaTCl ligand coordinate to CuII ions, which are further bridged by two OH– anions in a distorted five‐coordinate geometry. In addition, each CuII ion forms a Cu–O semicoordinate bond with an aqua ligand or perchlorato anion. The Cu···Cu distance across the hydroxido bridges is 2.9698(11) Å. In 2, the bdpaTCl ligand acts as bis‐tridentate ligand connecting the two CuII ions, and the five‐coordinate geometry around each copper center is achieved by two terminal chloro ligands. Magnetic measurements revealed strong antiferromagnetic coupling in 1 (J = –311.2 cm–1) and very weak coupling in 2 (J = –2.4 cm–1). DNA cleavage by these two complexes has been investigated (pH = 7.0, 37 °C). Although the bridged dihydroxido complex 1 did not show any detectable cleavage for DNA, significant cleavage was observed with the tetrachloro complex 2. Under pseudo‐Michaelis–Menten kinetic conditions, the kinetic parameters kcat = 2.53 × 10–5 s–1 and KM = 1.44 × 10–4 M were determined for 2. The kcat value corresponds to a 2.5 × 106 fold rate enhancement over noncatalyzed DNA. Electrophoretic experiments conducted in the presence and absence of oxidative scavengers DMSO, KI, and NaN3, and radical promoter H2O2 provide evidence for the oxidative cleavage of DNA by hydroxy radicals and hydrogen peroxide species.

Thiocyanato-copper(II) complexes derived from a tridentate amine ligand and from alanine

“…The SP stereochemical configuration seems to be the predominant geometry in most of the Cu(II) complexes. However, it has been observed that TBP geometry was adopted by tripodal tetraamine-Cu(II) complexes that form five-membered chelate rings with Cu(II) ion [4,7,18,[20][21][22][23][24][25]. Increasing the steric hindrance on the coordinated linear tridentate amine in the five-or sixmembered chelate rings tends to cause a severe distortion from SP to TBP geometry.…”

“…ion, most likely constitute distorted TBP geometry [3,4,21]. Replacing the methylenic group(s) in TPA by ethylenic group(s) (pmea, pmap, tepa) tends to stabilize SP geometries in the Cu(II) complexes [22][23][24][25]. Partial increase in the steric environment of the coligand (Medpt, Et 2 dien) and/or increasing the length of N donor amines around the central Cu 2?…”

“…In general, five-coordinate Cu(II) species with an intermediate stereochemical environment ranging between trigonal bipyramidal (TBP) and square pyramidal (SP) were found to be the major species that are formed in solid and in solution states [3,4,[18][19][20][21][22][23][24][25]. The nature of the coligand around the central Cu 2? ion plays a crucial role in adopting one of the two geometries.…”

Guanidine Metal Complexes for Bioinorganic Chemistry and Polymerisation Catalysis

“…nuclease, whereas the μ-hydroxido shows no DNA cleavage activity. The strong magnetic coupling between the two copper centres mediated by the hydroxido ligands seems to play a fundamental role in inhibiting its reactivity [125].…”

A novel 1-D coordination Cu(II) polymer with alternating μ1,3-squarato and binucleating polypyridylamine bridges

“…The coordination geometry around the Cu(II) centers is a five-coordinate with a slightly distorted square pyramidal environment which is achieved by the three N-donor atoms of each arm of the ligand L, an oxygen atom of the bridging squarato moiety and by an oxygen atom of the ClO À 4 anion. The complex shows antiferromagnetic coupling between the squarato-bridged Cu(II) ions with J = À6.3 cm À1 .Ó 2009 Elsevier B.V. All rights reserved.The squarate dianion, C 4 O 2À 4 (3,4-dihydroxycyclobut-3-ene-1,2-dionate) is a very well known ligand that is capable of binding more than one metal ion at the same time leading to a variety of coordination modes [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] where four types were recognized known as l-1,3-(trans) [1,3-6], l-1,2-(cis) [1,3,7-11], l-1,2,3-and l-1,2,3,4- [2,[12][13][14]. It has been pointed out that the ligand does not generally act as a bis-bidentate linker for the first raw divalent transition metal ions because of its very large bite angle relative to that observed in the oxalate dianion [15].…”