title: Multifrequency cw-EPR and DFT Studies of an Apparent Compressed Octahedral Cu(II) Complex.
abstract: The syntheses and single-crystal X-ray structures of the mononuclear complexes [Cu(bmet)](ClO4)2·H2O, [Cu(bmet)]Br2·2MeCN, and [Zn(bmet)](ClO4)2·H2O (bmet = N,N'-bis(2,2'-bipyridin-6-ylmethyl)ethane-1,2-diamine) are described. All three complexes feature a central metal ion bound to all six N atoms of the bmet ligand, which displays a meridional-facial-facial-meridional (mffm) configuration. The three complexes show one N-M-N axis to be significantly shorter than the others in agreement with an apparent compressed octahedral geometry. The X-ray structures of a single crystal of [Cu(bmet)](ClO4)2·0.375H2O resolved from data recorded at different temperatures display no remarkable structural modifications. However, they all display both as a powder and, in solution, an axial g1 > g2 ≳ g3 > g(e) electron paramagnetic resonance (EPR) pattern at low temperature, which is indicative of tetragonally elongated octahedra, while at room temperature the Q-band EPR spectra display a more rhombic g1 ≳ g2 > g3 > g(e) pattern. The fully density functional theory optimized structure of the Cu(II) complexes displays significant structural modifications only along one N(imine)-M-N(amine) axis resulting in an elongated octahedral structure. Furthermore, the EPR parameters predicted from this structure are comparable to those determined experimentally from the axial EPR signal recorded at low temperature, consistent with the unpaired electron residing mainly in the {3d(x(2)-y(2))} orbital. The structural and electronic properties of [Cu(bmet)](2+) are different from those in other previously described dynamic Jahn-Teller systems. We propose that these data can be rationalized by a dynamic Jahn-Teller effect perturbed by the strain of the hexadentate bmet ligand.
authors.affiliation: Univ. Grenoble Alpes , CNRS UMR 5250, DCM, F-38000 Grenoble, France.
authors.forename: Nikita
authors.initials: N
authors.lastname: Hall
authors.affiliation: Institut des Sciences Moléculaires de Marseille, Aix Marseille Université, CNRS , Centrale Marseille, ISM2 UMR 7313, 13397 Marseille, France.
authors.forename: Maylis
authors.initials: M
authors.lastname: Orio
authors.affiliation: Univ. Grenoble Alpes , CNRS UMR 5250, DCM, F-38000 Grenoble, France.
authors.forename: Marcello
authors.initials: M
authors.lastname: Gennari
authors.affiliation: Univ. Grenoble Alpes , CNRS UMR 5250, DCM, F-38000 Grenoble, France.
authors.forename: Christopher
authors.initials: C
authors.lastname: Wills
authors.affiliation: Univ. Grenoble Alpes , CNRS UMR 5250, DCM, F-38000 Grenoble, France.
authors.forename: Florian
authors.initials: F
authors.lastname: Molton
authors.affiliation: Univ. Grenoble Alpes , CNRS UMR 5250, DCM, F-38000 Grenoble, France.
authors.forename: Christian
authors.initials: C
authors.lastname: Philouze
authors.affiliation: Institute of Fundamental Sciences and the MacDiarmid Institute for Advanced Materials and Nanotechnology, Masssey University , Private Bag 11222, Palmerston North 4442, New Zealand.
authors.forename: Geoffrey B
authors.initials: GB
authors.lastname: Jameson
authors.affiliation: School of Chemistry, University of Leeds , Woodhouse Lane, Leeds UK LS2 9JT, United Kingdom.
authors.forename: Malcolm A
authors.initials: MA
authors.lastname: Halcrow
authors.affiliation: School of Applied Sciences, Auckland University of Technology , Private Bag 92006, Auckland 1142, New Zealand.
authors.forename: Allan G
authors.initials: AG
authors.lastname: Blackman
authors.affiliation: Univ. Grenoble Alpes , CNRS UMR 5250, DCM, F-38000 Grenoble, France.
authors.forename: Carole
authors.initials: C
authors.lastname: Duboc