Evidence for Hydrogen‐Bond‐Mediated Exchange Coupling in an Aqua‐Bridged Cu^II Dimer: Synthesis, Magnetic Study and Correlation with Density Functional Calculations

Abstract

Keywords: Bridging ligands / Copper / Density functional calculations / Exchange interactions / Hydrogen bondsA rare example of a mono-aqua-bridged copper(II) dimer,, has been synthesised and its structure determined by single-crystal Xray diffraction. Each Cu II centre is in a square-pyramidal surrounding formed by a Schiff base and a terminal H 2 O ligand; a second H 2 O ligand, which acts as a bridge, is common to two metal ions. Hydrogen bonds between the H 2 O ligand and the Schiff base of the adjacent centre complete the intra-

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

“…However, to the best of our knowledge only four single [15,[20][21][22] aqua-bridged Cu(II) complexes are reported in the literature. It is interesting to note that each unit within the dimer are also connected to each other through strong H-bonds.…”

“…Although the aqua ligand usually exhibits the terminal coordination mode in copper(II) complexes, but complexes in which H 2 O acts as a bridge are also well known [15][16][17][18][19]. However, to the best of our knowledge only four single [15,[20][21][22] aqua-bridged Cu(II) complexes are reported in the literature.…”

“…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.…”

“…From the Cambridge Structural Data base, more than 120 molecular structures of copper(II) coordination compounds exhibiting dinuclear double hydrogen-bonded motif were found. Out of these compounds, the magnetic properties of only 28 have been investigated in detail [23] and only in eight of these copper(II) compounds, the double hydrogen-bonded bridge, involving (neutral) coordinated water molecules, had been considered as a possible magnetic-exchange pathway [15,[22][23][24][25][26][27][28]. Literature study shows, no clear relationship between the hydrogen-bonding features (bond distances and angles) and the magnetic properties.…”

Synthesis and Crystal Structures of Polymeric Copper(II) Complexes Derived from Tridentate Schiff Bases

“…The versatile features of metal-azido and metal-thiocyanato systems in coordination chemistry may lead to novel structures that are difficult to obtain with other bridging ligands, but a major obstacle is impossible to predict which coordination modes will be adopted by the azide and thiocyanate ligands. During the search of literature, we found that the copper(II) complexes derived from the tridentate Schiff base ligands 2-[1-(2-dimethylaminoethylimino)ethyl]phenol and N,N-dimethyl-N 0 -(1-pyridin-2-ylethylidene)ethane-1,2-diamine have been extensively studied [11][12][13][14][15], however, no complexes have been reported for the similar tridentate Schiff base ligands 2-[1-(2-methylaminoethylimino)ethyl]phenol (HL 1 ; Scheme 1) and N-methyl-N 0 -(1-pyridin-2-ylethylidene)ethane-1,2-diamine (L 2 ; Scheme 1). In continuation of the work on the azide and thiocyanate-bridged complexes with Schiff bases, a new end-to-end thiocyanato-bridged 1D polymeric copper(II) complex [CuL 1 (l 1,3 -NCS)] n (1), and a new end-on azido-bridged dimeric copper(II) complex [CuBrL 2 (l 1,1 -N 3 )] 2 (2), were synthesized and structurally characterized.…”