OCTABROMOTETRAPHENYLPORPHYRIN AND ITS METAL DERIVATIVES - ELECTRONIC-STRUCTURE AND ELECTROCHEMICAL PROPERTIES
OCTABROMOTETRAPHENYLPORPHYRIN AND ITS METAL DERIVATIVES - ELECTRONIC-STRUCTURE AND ELECTROCHEMICAL PROPERTIES
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DOI：
10.1021/ic00002a018
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发表时间：
1991-01-23
影响因子：
4.6
通讯作者：
KRISHNAN, V
中科院分区：
文献类型：
--
作者：
BHYRAPPA, P;KRISHNAN, V
以（中四苯基卟啉）铜（II）为原料，采用新型溴化反应制备了游离碱八溴四苯基卟啉（H2OBP）。金属[V(IV)O, Co(II), Ni(II), Cu(II), Zn(II), Pd(II), Ag(II), Pt(II)]衍生物表现出有趣的电子光谱特征和电化学氧化还原性能。在H2OBP和M（OBP）衍生物中，吡咯碳上的吸电子溴取代基在卟啉的可见光波段（100 nm）和可见光波段（50 nm）产生显著的红移。低质子化常数（pK3 = 2.6和pK4 = 1.75）和大红移Soret和可见光吸收带使八溴卟啉独特。采用四轨道法定量分析了卟啉外围电负性溴取代基的影响。将MOBP衍生物的MO参数与中取代四苯基卟啉（M(TPP)）和未取代卟啉（M(P)）衍生物的MO参数进行比较，可以解释其不寻常的光谱特征。在已知的取代卟啉中，M（OBP）衍生物的构型相互作用矩阵元素是最低的，这表明溴的p轨道与环轨道的共轭增加导致环电荷离域。外围溴取代基极大地改变了卟啉的电子转移反应活性，在环和金属中心氧化还原电位中产生了大的阳极位移。与氧化电位（300 mV）的变化相比，M(OBP)s的还原电位（550 mV）的阳极位移的增加更大。这些变化是根据溴取代基的共振和感应相互作用来解释的。
The free-base octabromotetraphenylporphyrin (H2OBP) has been prepared by a novel bromination reaction of (meso-tetraphenylporphyrinato)copper(II). The metal [V(IV)O, Co(II), Ni(II), Cu(II), Zn(II), Pd(II), Ag(II), Pt(II)] derivatives exhibit interesting electronic spectral features and electrochemical redox properties. The electron-withdrawing bromine substituents at the pyrrole carbons in H2OBP and M(OBP) derivatives produce remarkable red shifts in the Soret (50 nm) and visible bands (100 nm) of the porphyrin. The low magnitude of protonation constants (pK3 = 2.6 and pK4 = 1.75) and the large red-shifted Soret and visible absorption bands make the octabromoporphyrin unique. The effect of electronegative bromine substituents at the peripheral positions of the porphyrin has been quantitatively analyzed by using the four-orbital approach of Gouterman. A comparison of MO parameters of MOBP derivatives with those of the meso-substituted tetraphenylporphyrin (M(TPP)) and unsubstituted porphine (M(P)) derivatives provides an explanation for the unusual spectral features. The configuration interaction matrix element of the M(OBP) derivatives is found to be the lowest among the known substituted porphyrins, indicating delocalization of ring charge caused by the increase in conjugation of p orbitals of the bromine onto the ring orbitals. The electron-transfer reactivities of the porphyrins have been dramatically altered by the peripheral bromine substituents, producing large anodic shifts in the ring and metal-centered redox potentials. The increase in anodic shift in the reduction potential of M(OBP)s relative to M(TPP)s is found to be large (550 mV) compared to the shift in the oxidation potential (300 mV). These shifts are interpreted in terms of the resonance and inductive interactions of the bromine substituents.