Heteroleptic Cu(II) Dipyrromethene Complexes Linked via Hydrogen Bonds, Coordinative Bonds, and Covalent Bonds:  Probing the Coordination Environment by Electron Paramagnetic Resonance Spectroscopy

Abstract

meso-Phenyldipyrromethene acetylacetonato copper(II) complexes [Cu(dpm-C6H4R)(acac)] (dpm-C6H4R = phenyl-substituted dipyrromethene, acac = acetylacetonato) with different substituents R at the phenyl moiety were synthesized. These substituents determine the mode of assembly into polymeric chains, namely, via hydrogen bonds, coordinative bonds, or covalent bonds (by immobilization on a polymer). Although the primary coordination sphere around the copper center is essentially identical for all complexes reported in this study (square-planar geometry with N2O2 coordination), subtle differences due to the different microenvironments have been observed in their structures, properties, and reactivity as probed by IR spectroscopy, electron paramagnetic resonance spectroscopy, magnetic measurements, thermal analyses, density functional theory calculations, and reaction with pyridine.

Solid‐Phase Synthesis of Chiral Modular Ferrocene‐Based Peptides

“…The reaction is finished within minutes. EPR spectroscopy [16] confirms the formation of the immobilised ferricinium cation as the typical axial pattern with g ʈ = 4.30 and g Ќ = 1.99 is observed. [17] Chemical reversibility is checked on-bead by re-reduction to the neutral peptides employing CoCp 2 as reductant and UV/Vis-spectrophotometric monitoring (disappearance of the 512 nm band of CoCp 2 and development of the 400 nm absorption band of [CoCp 2 ] + ).…”

Bioinspired functional analogs of the active site of molybdenum enzymes: Intermediates and mechanisms

“…OAT from the polymer-anchored Mo(L 5 ) 2 (O) 2 to PMe 3 gives soluble OPMe 3 as shown by 31 [81]. All EPR spectra of these immobilized Mo V complexes are anisotropic even in the solvent-swollen state of the polymer suggesting a severely reduced mobility of the doubly-anchored species as compared with singly-anchored complexes [134]. The anisotropy renders observation of 95 95 Mo and thus further ascertains the presence of Mo V [81].…”

Polymer‐Supported Dioxido‐MoVI Complexes as Truly Functional Molybdenum Oxotransferase Model Systems

“…We have previously shown that singly polymer attached Cu II complexes give isotropic EPR spectra under gel-phase conditions suggesting that a single-point attachment allows for sufficient mobility. [34] However, two-point fixation seems to decrease the mobility of the anchored complexes 4b resulting in anisotropic EPR spectra even in the gel-phase at room temperature. [35] In addition this finding proves that the molybdenum species are still bound to the support as otherwise isotropic signals for soluble species would have been observed.…”