Single crystal 63Cu and 65Cu ENDOR of bis(2,4-pentanedionato)copper(II)

Electron paramagnetic resonance and electron-nuclear double resonance study of the neutral copper acceptor in ZnGeP2crystals

“…Hyperfine interactions with the neighbouring phosphorus nuclei were also present in the ENDOR spectra from the Cu 0 Zn acceptor. The c-axis EPR data in figure 1 suggested that the unpaired spin interacted nearly equally with four phosphorus ions, and we observed a set of very weak intensity 31 P ENDOR lines that supported this interpretation. This c-axis ENDOR spectrum, taken at 3290.0 G, consisted of two sets of lines (each set having three closely spaced components) centred on 54.7 MHz and split by 10.21 MHz.…”

“…These 'standard' values ENDOR Frequency (MHz) give a ratio of 1.14, while our parameters in table 1 give a ratio of 1.07. We note that, in a separate ENDOR study of copper [31], the ratio of the three experimentally determined nuclear quadrupole principal values for the two isotopes were 1.05, 1.07 and 1.07. These latter values directly agree with our experimental ratio.…”

ELDOR-detected NMR beyond hyperfine couplings: a case study with Cu(ii)-porphyrin dimers

“…48,49 In the latter case, also ENDOR was used. 50 The approach used here to determine the quadrupole coupling is analogous to that employed for nitroxides at W-band, where the coupling can be determined by analyzing a series of spectra at the high-field edge of the EPR spectrum. 37 An energy level diagram for our particular situation is shown in the ESI † (see Section S.7.1).…”

An ENDOR and DFT analysis of hindered methyl group rotations in frozen solutions of bis(acetylacetonato)-copper(ii)

“…The bis(acetylacetonato)-copper(II) complex [Cu(acac) 2 ] is one of the most extensively studied d-transition metal compounds by Electron Paramagnetic Resonance (EPR) spectroscopy (Scheme 1). [1][2][3][4][5][6][7][8][9][10][11][12][13][14] This can largely be attributed to its relative simplicity, ease of preparation and favourable stability constant, which collectively facilitate the investigation of this complex in single crystal, [1][2][3][4] frozen solution [5][6][7][8][9][10][11][12] and powder (doped Cu-Pd solid solution) 13 forms. The simple square planar arrangement of [Cu(acac) 2 ] with four oxygen donors forming the inner coordination sphere, has led to its inclusion in the Peisach and Blumberg 'truth tables', correlating trends in g/ Cu A with coordination environment for Cu(II) systems.…”

“…Whilst EPR studies of [Cu(acac) 2 ] are extremely numerous, there are surprisingly few detailed ENDOR investigations of this complex. 2,3,32,33 Analysis of the hyperfine tensors of the ligand protons can be found in a comparative single crystal and powder-frozen solution study by Baker et al, 3 and in an earlier frozen solution investigation by Kirste et al 32 A doped Cu/ Pd(acac) 2 powder was also used by Henderson et al, in their seminal angular selective ENDOR study. 33 In these papers, intense features observed in the CW ENDOR spectra were attributed to the methine and methyl group protons (the latter were assumed to be rapidly rotating in frozen solution on the EPR timescale).…”