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Isotropic NMR Shifts in Imidazole, 2‐Methyl Imidazole and n ‐Methyl Imidazole Complexed with Copper (II) β‐Diketonates
Author(s) -
Wang SungMao,
Chen JungTso
Publication year - 1975
Publication title -
journal of the chinese chemical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.329
H-Index - 45
eISSN - 2192-6549
pISSN - 0009-4536
DOI - 10.1002/jccs.197500022
Subject(s) - chemistry , imidazole , adduct , pyridine , copper , ligand (biochemistry) , stereochemistry , medicinal chemistry , crystallography , organic chemistry , biochemistry , receptor
Isotropic nuclear magnetic resonance shifts have been measured for imidazole (Im), 2‐methyl imidazole (2MeIm) and N ‐methyl imidazole (NMeIm) adducts with Cu(AA) 2 , Cu(TFA), and Cu(HFA) 2 , where AA, TFA and HFA are anion of acetylacetone, trifluoroacetylacetone and hexafluoroacetylacetone, respectively, in deuteriochloroform solution. The pseudocontact contribution to the isotropic shifts are negligibly small and Ferrmi contact interaction is dominant in these copper complexes. The normal temperature effect and appreciable spin delocalization suggest that the imidazole and substituted imidazole adducts with Cu(chelate) 2 are all six‐coordinated octahedral complexes, and consistent with our results of spectrophotometric study. In these imidazole complexes, the magnitude of the contact shifts lie in the order Cu(HFA) 2 >Cu(TFA) 2 >Cu(AA) 2 , which is the same as that of the stability constants for the pyridine type adduct formation found from spectrophotometric studies. For a given Cu(chelate) 2 , the basicity of ligand for adduct formation is in the order NMeIm>Im>2MeIm.