Magnetic Coupling between Copper(II) Ions Mediated by Hydrogen-Bonded (Neutral) Water Molecules

Abstract

A new hydrogen-bonded dinuclear copper(II) coordination compound has been synthesized from the Schiff-base ligand 6-(pyridine-2-ylhydrazonomethyl)phenol (Hphp). The molecular structure of [Cu(2)(php)(2)(H(2)O)(2)(ClO(4))](ClO(4))(H(2)O) (1), determined by single-crystal X-ray diffraction, reveals the presence of two copper(II) centers held together by means of two strong hydrogen bonds, with O...O contacts of only 2.60-2.68 A. Temperature-dependent magnetic susceptibility measurements down to 3 K show that the two metal ions are antiferromagnetically coupled (J = -19.8(2) cm(-1)). This exchange is most likely through two hydrogen-bonding pathways, where a coordinated water on the first Cu, donates a H bond to the O atoms of the coordinated php at the other Cu. This strong O...H(water) bonding interaction has been clearly evidenced by theoretical calculations. In the relatively few related cases from the literature, this exchange path, mediated by a (neutral) coordinated water molecule, was not recognized.

Super–superexchange coupling through a hydrogen bond in a linear copper(II) complex, [Cu(LH)(L)]·BF4·2H2O (LH =N-tert-butyl-N-2-pyridylhydroxylamine)

“…However, hydrogen bonds characterized in super-superexchange systems are relatively rare [40]. The present exchange coupling seems comparably large despite of the presence of an additional hydrogen atom compared with the case of the known M-OÁ Á ÁO-M systems [12,[16][17][18][19][20], and furthermore, this is much larger than those of molecule-based magnets [34][35][36][37][38][39].…”

“…Very recently, Tang and co-workers reported a doubly hydrogen-bonded dinuclear copper(II) compound, which exhibited an antiferromagnetic coupling of À28 K and hydrogen-bonded OÁ Á ÁO distances of 2.601(2) and 2.685(2) Å [40]. Although the path in 1 consists of a single hydrogen bond, 1 exhibited stronger coupling (À33.2(2) K), because of the stronger hydrogen bonding in 1 as indicated by the shorter OÁ Á ÁO distance (2.4252(16) Å).…”

“…Tang et al [40] and Desplanches et al [33] have already summarized the geometrical parameters and exchange coupling parameters on the various hydrogen-bonded compounds previously reported. As they claimed, other geometrical parameters (the Cu-O-H angle, Cu-OÁ Á ÁO-Cu torsion, distance between the two basal planes, etc.)…”

In-situ improved phenol adsorption at ions-enrichment interface of porous adsorbent for simultaneous removal of copper ions and phenol

“…The surplus positive charged had strongly attractive force with the deprotonation of the phenolic oxygen to form CuAO phenolate bond [40,41]. Therefore, the increase of attractive strength between Cu 2+ /carboxylic functionalized PGMA porous monolith and deprotonation of the phenolic oxygen would promote adsorption equilibrium of phenol.…”

Mono-aqua-bridged dinuclear complexes of Cu(II) containing NNO donor Schiff base ligand: Hydrogen-bond-mediated exchange coupling

“…The magnetic exchanges between the metal ions through coordination bonds are well documented. However, exchange interactions through weak supramolecular interactions, such as hydrogen-bond bridges linking metal centers, have only been hardly recognised until recently when the density functional calculations clearly show the evidences for significant interactions through such pathways [15,23]. From the Cambridge Structural Data base, more than 120 molecular structures of copper(II) coordination compounds exhibiting dinuclear double hydrogen-bonded motif were found.…”