David A. Thornton

N-aryl salicylaldimine complexes: Infrared and PMR spectra of the ligands and vibrational frequencies of their metal(II) chelates

Abstract The i.r. and PMR spectra of 28 N-aryl salicylaldimines are reported. Assignments of characteristic i.r. bands are derived by 15N-labelling of N-p-tolylsalicylaldimine. The PMR spectra establish that the bases exist in the phenol-imine form at room temperature in deuterochloroform and that eletron withdrawing N-aryl substituents reduce the magnetic shielding of the hydroxyl proton. The i.r. spectra of 38 Co(II), Ni(II), Cu(II) and Zn(II) chelates derived from the salicylaldimines are discussed. Assignments are based on 15N-labelling of the Cu(II) complex of N-p-tolylsalicylaldimine. Support for the νCuN assignments in the i.r. spectra of the Cu(II) chelates is provided by observing the frequency shifts induced by metal ion substitution and by varying the N-aryl substituents. Electron withdrawing substituents shift νCuN to higher frequencies which is consistent with substituent-induced Cu → N π-bonding.

Infrared spectra of N-aryl salicylaldimine complexes substituted in both aryl rings

Abstract The i.r. spectra of eight 15N-labelled complexes of N-p-tolylsalicylaldimines with substituents in the 3- and 5-positions of the salicylaldimine ring yield assignments of metal-ligand stretching frequencies (vM-L) and certain ligand vibrations. The assignments are supported by observing the effects on the spectra of metal ion substitution and substitution in the salicylaldimine and N-aryl rings. The vM-N values of complexes with common ligand substituents are metal ion dependent in the order Co Zn expected from crystal field theory. Substituent-induced shifts in vM-N are related to the resonance polar effects of salicylaldimine substituents and to the inductive effects of N-aryl substituents.

Metal complexes of pyridine: infrared and raman spectra with particular reference to isotopic labelling studies

Analyse spectrale de complexe de metaux de transition avec des derives de la pyridine. Synthese bibliographique

The infrared spectra of imidazole complexes of first transition series metal(ii) nitrates and perchlorates

Abstract The IR spectra (4000–4140 cm −1 ) of the twelve imidazole (Him) complexes [M(Him) 6 ] (NO 3 ) 2 (M = Co, Ni, Zn); [M(Him) 6 ](ClO 4 ) 2 (M = Mn, Fe, Co, Ni); [Zn(Him) s ](ClO 4 ) 2 ; [Cu(Him) 4 X 2 ] (X = NO 3 , ClO 4 ); [Zn(Him) 4 (NO 3 ) 2 ]; [Zn(Him) 4 ](ClO 4 ) 2 and their deuterated analogues are discussed. The ratio between the frequencies of corresponding bands in the deuterated and undeuterated species is used to assign the internal imidazole vibrations. The internal modes of the NO 3 − and ClO 4 − ions are discussed in relation to the known or proposed structures of the complexes. The metal-ligand vibrations are assigned on the grounds of the shifts which occur on imidazole deuteration and metal ion substitution.

Crystal field aspects of vibrational spectra

Abstract The M-O stretching frequencies of the acetylacetonates, benzoylacetonates, dibenzoylmethanates, trifluoroacetylacetonates and dipivaloylmethanates of the ions Sc(III), V(III), Cr(III), Mn(III), Fe(III) and Co(III) have been determined and shown to exhibit a correlation with d-orbital population which is consistent with the relative crystal field stabilization energies of the metal(III) ions. Band assignments are discussed and an amendment to previously suggested assignments of the C-O and C-C stretching frequencies of phenyl-substituted β-ketoenolates is proposed.

ESR studies of alkylamine complexes of copper(II) imides: the CuN42− chromophore

Abstract The ESR spectra of a number of [Cu(Im) 2 (RNH 2 ) 2 ] (Im = succinimidate, phthalimidate; RNH 2 = alkylamine) complexes have been examined. The ESR data support the essentially square planar geometries proposed for the compounds on the basis of other spectroscopic data. Covalency parameters evaluated from ESR data indicate that the unpaired electron spends only roughly 80 per cent of its time on the central copper ion. Covalency parameters for various CuN 4 complexes are shown to be more indicative of geometry than the degree of metal-ligand covalency. Limitations of ESR studies of Cu(II)-doped biological systems are discussed and an explanation based on the second-order perturbation approach to chemical bonding proposed.

Salicylaldehyde complexes: effects of metal ion substitution, ligand substitution and adduct formation on their infrared spectra

Abstract The i.r. spectra of forty-two complexes of salicylaldehyde containing the ions Co(II), Ni(II) and Cu(II) are discussed. Metal-oxygen (ν M O), aldehyde carbonyl (νCO) and phenolic carbonyl (νCO) stretching frequencies are assigned by observing the effects of metal ion substitution, substitution in the aryl ring and adduct formation on the spectra. Comparison of the spectra of the anhydrous complexes and their bis(aquo) and bis(pyridine) adducts supports existing evidence for polynuclear octahedral coordination in the anhydrous Co(II) and Ni(II) complexes. Substitution in the aryl ring of the complexes produces shifts in ν M O which are related to the resonance capacities of the substituents. Pyridine adduction causes a depletion of electron density in the CO and M −O bonds which is consistent with its π-electron acceptor properties.

Crystal field aspects of vibrational spectra: II. First-row transition metal(II) complexes with nitrogen donors

Abstract The M-N stretching frequencies and certain metal-sensitive ligand vibrations of complexes of nitrogen donors with first-row divalent transition metal ions vary with d orbital population in a way which is consistent with crystal field theory. The effects on the frequencies of tetrahedrally co-ordinated Co(II) and Zn(II) and of tetragonally distorted Cu(II) are discussed.

Infrared spectra of o-toluidine and m-toluidine complexes of Co(II), Ni(II), Cu(II) and Zn(II) halides

Abstract The infrared spectra of eighteen metal complexes of empirical formula [ML 2 X 2 ] (M = Co, Ni, Cu or Zn; L = o − or m -toluidine; X = Cl, Br or I) have been determined over the range 4000-150 cm −1 . Assignments of the internal vibrations of the amino group are based on the band shifts induced by 15 N-labelling of the nitrogen donors. Bands within the range 400–600 cm −1 are assigned to the metal-nitrogen stretching frequency ( v M-N) on the grounds of their sensitivity to 15 N-labelling and metal ion substitution and their absence of sensitivity to halide substitution. Bands within the range 350–150 cm −1 are assigned to the metal-halogen stretching frequency ( v M-X) on the basis of their sensitivity to halide and metal ion substitution and their insensitivity to 15 N-labelling. Structural aspects of the spectra are discussed and the present assignments are compared with those previously reported.

The influence of substituents on the infrared spectra of metal β-ketoenolates

Abstract The infrared spectra of complexes of Al(III), Cu(II) and K(I) with nine β-diketones reveal that co-ordination by an electropositive metal ion or the presence of strongly electron-withdrawing ligand substituents confers ionic character on the M-O bond as evidenced by a low M-O and high C-O stretching frequency. In general, for any particular co-ordinated metal ion, the M-O stretching frequencies increase in the order: hexafluoroacetylacetonates