- 期刊
咪唑、2-甲基咪唑及N-甲基咪唑與8-羥基喹啉鎳(II)鹽及鈷(II)鹽加成物之氫核磁共振研究
Pmr Studies of Metal 8-Hydroquinolates Complexes with Imidazole, 2-Methy I Imidazole and N-Methy I Imidazole
摘要
本文探討咪唑（Im）、2-甲基咪唑（2-M Im）及N-甲基咪唑（N-M Im）和Ni（Ox）_2及Co（Ox）_2之加成物系在D-氯仿溶液中之接磁共振均向差移變化。從本研究可知，在此等物系，不成對電子自旋是從金屬離子主要經由σ-軌道傳遞至配位基分子之共振接核上。又從接共振吸收峯隨溫度降低而變寬及其均向差移隨溫度變化之事實，證明在本實驗溫度（17°至54°C）範圍內，游離配位基與己配位之分子間配位基交換相當快。正常之溫度效應及相當置之自旋傳遞顯示，N-MIm及2-MIm與Ni（Ox）_2之加成物皆為六配位之八面體錯化合物。至於Im系則呈現異常之混度效應，此乃是在溶液中大部分以五配位之錯化合物存在所致。電子自旋-核自旋偶合常數亦由均向差移之溫度效應關係算出。在本研究並假設Ni（Ox）_2錯化合物中之均向差移純為接觸性差移，而估計Co（Ox）_2錯化合物中之擬接觸性差移亦即偶極作用量。每一配位基氫核之擬接觸性差移之相對比值亦從其幾何因素平均值得以計算，並與實體觀察值作一比較分析。
關鍵字
無資料並列摘要
Isotropic NMR shifts have been measured for imidazole (Im), N-methyl imidazole (N-MIm) and 2-methyl inidazole (2-MIm) adducts with Ni(II) and Co(ID 8-hydroxyquinolates, respectively, in CDCI_3 solution at various temperature. Adelocalization of unpaired electron spin density from the metal ion to the resonance nuclei in lm or substituted-Im molecule through the σ-orbitals of the ligand is dominant. The linear temerature effect on the resonance line broadening and on the isotropic shifts prevailed a rapid exchange between a free ligand and a coordinated ligand in the temperature range of 17° to 54°C. The normal temperature effect and appreciable spin delocalisation suggest that the N-NIm and 2-MIm adducts with Ni (Ox)_2 are all six-coordinated octahedral complexes. The abnormal temperature effect was found for Im system because of predominant formation of five-coordinated mono-adduct, Ni(Ox)_2．Im. The electron spin-nuclear spin coupling constants were also evaluated from a linear plot of isotropic shift vs. the reciprocal of the absolute temperature. The pseudocontact contribution to the isotropic shifts for Co(Ox)_2 complexes were estimated assuming that the isotropic shifts in Ni(Ox)_2 complexes are pure contact shifts. From the average values of geometric factors for each of the ligand protons, the ratio of the relative pseudo contact shifts were calculated and compared with the observed values.