Browsing by Author "Percy, G C"

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    Isotopic labelling applied to the infrared spectra of metal complexes
    (1980) Niven, Margaret Lilian; Percy, G C; Thornton, David A
    An ir investigation of a series of 2-aminomethylpyridine complexes of first transition metal(II) perchlorates, tetrafluoroborates, halides and thiocyanates is reported. Comparisons with the spectra of related complexes of 2,2'-bipyridine and ethylenediamine together with metal-ion substitution, deuteration and ¹⁵N isotopic labelling of the amino group in 2-aminomethylpyridine enable reliable band assignments to be made. The study shows that in complexes of the type M(amp)nX₂, metal-to-amino-nitrogen stretches occur at frequencies greater than 350 cm⁻¹ , while the metal-to-pyridine-nitrogen stretches are generally below 300 cm⁻¹, the assignment of the latter being generally complicated by the presence of metal-to-halogen vibrations. In addition to an x-ray crystallographic investigation of the complex [Ni(amp)₃](BF₃ ₄)₂, considerable structural information about these complexes is obtained from correlations between the number of M-L vibrations observed in the far ir and those predicted for localized molecular point symmetries on a group theoretical basis.
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    Isotopic labelling applied to the infrared spectra of metal complexes
    (1979) Hodgson, John Betton; Thornton, David A; Percy, G C
    An investigation of a series of imidazole complexes of first transition metal (II) nitrates, perchlorates and halides is reported. Deuteration of the imidazole ring provides reliable assignments for the internal vibrations of imidazole. This technique also permits unambiguous assignments of the internal vibrations of nitrate or perchlorate by their lack of deutero-sensitivity. The infrared spectra of imidazole and its complexes are examined in order to determine the ratio vD/ vH for bands as signed to the C-H, N-H and ring modes of the heterocyclic ring. With very few exceptions, vD/vH falls within the ranges 0. 74 to 0. 84 and 0. 93 to 1. 00 for C-H and ring vibrations, respectively. The potential usefulness of the results is discussed. Assignments of the M-N and M-halide vibrations are based on the results of the deuteration studies, metal ion substitution and on halogen substitution. The number of M-L vibrations in the far-infrared satisfies the selection rules for the molecular point or site group symmetries and facilitates accurate structural assignments.