Spectroscopy and Redox Behaviour of Dicopper(II) and Dinickel(II) Complexes of Bis(cyclen) and Bis(cyclam) Ligands

Abstract

The dinuclear CuII and NiII complexes of meta‐xylyl and pyridyl biscyclen and biscyclam have been prepared and characterised in solution by means of UV/Visible spectra, electrochemical and EPR studies. X‐ray structures of copper biscyclen complexes have been obtained. The comparison of all the data shows that the potentially coordinating N(py) pyridyl atom promotes the interaction between the two metal centers, whether it is spontaneously coordinated (biscyclen complexes) or not (biscyclam ones). (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)

Coordination chemistry of a mono-dibenzofuran derivative of 1,4,7,10-tetraazacyclododecane

“…All compounds were characterized by a combination of NMR and IR spectroscopy, and mass spectrometry. The IR spectrum of L1 showed bands at 3344 cm −1 (NH stretch), 2800-2900 cm −1 (C-H stretch), 1682 cm −1 (C=O stretch), and 1600-1400 cm −1 (aromatic ring vibrations [35][36][37]. A similar trend was previously seen in the case of the analogous bis-dibenzofuran copper(II) complex, which also showed similar coordination [24].…”

Macrocycles Bearing Ferrocenyl Pendants and their Electrochemical Properties upon Binding to Divalent Transition Metal Cations

“…In previous studies on related copper(II)‐cyclen complexes, it was reported that voltammograms for the copper(II) to copper(I) process were accompanied by the partial release of the copper(I) ion . This was attributed to the incapacity of the cyclen cavity to stabilise the copper(I) ion . Hence, the chemically reversible nature of the copper(II)/copper(I) process in this study along with quasi‐reversible electron transfer deserves further comment.…”

“…In previous studies on relatedc opper(II)-cyclen complexes, it was reported that voltammograms for the copper(II)t oc op-per(I) process were accompanied by the partial releaseo ft he copper(I) ion. [16] This was attributed to the incapacityo ft he cyclen cavity to stabilise the copper(I) ion. [16] Hence, the chemically reversible nature of the copper(II)/copper(I) process in this study along with quasi-reversible electron transfer deservesf urther comment.I ti sg enerally accepted that in describing the nature of the behaviouro ft he copper(II)/copper(I) electrode process, an important criterion to consider is the impact of changes in geometry that accompany the electrontransfer process.…”

“…[16] This was attributed to the incapacityo ft he cyclen cavity to stabilise the copper(I) ion. [16] Hence, the chemically reversible nature of the copper(II)/copper(I) process in this study along with quasi-reversible electron transfer deservesf urther comment.I ti sg enerally accepted that in describing the nature of the behaviouro ft he copper(II)/copper(I) electrode process, an important criterion to consider is the impact of changes in geometry that accompany the electrontransfer process. [17] In general, copper(I) complexes adopt at etrahedralgeometry.T hus, if the copper(II) complex, whatever its geometry,i ss ufficiently flexible to allow ar apid structuralr eor-Scheme2.Schematicrepresentation of the mechanism postulated for the oxidation of 1.…”

A copper–cyclen coordination complex associated with a polyoxometalate anion: Synthesis, crystal structure and electrochemistry of [Cu(cyclen)(MeCN)][W6O19]

“…The Cu-cyclen complexes pack in such a way that a channel-like arrangement is formed in the crystal lattice of 1 (Fig. 3 [41][42][43]. Because of some conformational change/change of geometry around copper ion in the Cu-cyclen complex (e.g., from square planar to tetrahedral), the cyclen cavity cannot bind and/or stabilize the Cu 1+ oxidation state [44][45][46].…”