【摘要】 本文报道了氯化四苯基卟啉合铑(Ⅲ)均相催化的苦干饱和脂肪醇和烯丙醇的光化学脱氢反应.研究表明,底物结构不仅影响反应速率,而且可以改变反应机理从而影响反应产物;其影响方式有电子效应、立体效应和配位体振动能量转移效应.根据实验结果推断了反应的电子和激发态能量转移过程.更多还原

【Abstract】 The catalyst solution (80 ml, [cat.] = 4 × 10-4M] was irradiated in a φ50mm quartz cell with a 500W xenon lamp for over 10 hours. The experimental results showed that the rate of dihydrogen evolution from the saturate aliphatic secondary alcohols is larger than that from the primary one with the same number of carbon atoms, except pentanol. From investigations on the effects of both molecular structure of substrates and photon energy on the reaction rate, it was concluded that structure of substrates influences the reaction at least in three ways:steric effect, electronic effect, and ligand vibration energy-transfer (LVET) effect.The smaller steric hindrance and/or the stronger Lewis basic capacity of RO-favour the electron transfer from RO- to H+ through the central metal ion with the help of porphyrin ligand. The restricted C-C bond vibration in the cyclic structure is believed to be one of the reasons of the higher rate of dihydrogen evolution from cyclohexanol than that from a noncyclic substrate. For allyl alcohol other gases are evolved together with dihydrogen in the reaction. An intermediate, [(RO-)Rh(TPP) (H)]+, was suggested from the analysis of electronic absorption spectrum of the catalyst solution after a 44 h reaction. Based on the experimental results, mechanism of electron transfer and energy transfer of excited state is inferred.更多还原