Department of Chemistry , Indian Institute of Technology Roorkee , Roorkee 247667 , India.
Inorg Chem. 2019 Feb 18;58(4):2514-2522. doi: 10.1021/acs.inorgchem.8b03106. Epub 2019 Feb 1.
A new series of mixed β-substituted dibenzoporphyrins were synthesized, and the effect of β-substitution on the spectral and electrochemical redox properties of the macrocycle was elucidated. The synthetic route to β-tetrasubstituted dibenzoporphyrins begins with the regioselective bromination of NiTPP(Benzo) to afford NiTPP(Benzo)Br, followed by Pd catalyzed coupling reaction to access NiTPP(Benzo)(R) (R = phenyl (Ph) and phenylethynyl (PE)). Synthesized benzoporphyrins exhibited red-shifted absorption spectral features with tunable redox properties. These benzoporphyrins displayed pronounced electronic effects of β-substituents on the macrocyclic skeleton. NiTPP(Benzo)(PE) exhibited the lowest HOMO-LUMO gap among the series due to extended π-conjugation. Intrestingly, metal-centered oxidation of Ni(II)/Ni(III) was observed for NiOPP(Benzo) and NiOPP(Benzo)Br after an initial conversion of the neutral porphyrin to its dicationic form under electrochemical conditions.
合成了一系列新型的混合β取代二苯并卟啉，并阐明了β取代对大环光谱和电化学氧化还原性质的影响。β-四取代二苯并卟啉的合成路线从 NiTPP（苯并）的区域选择性溴化开始，得到 NiTPP（苯并）Br，然后通过 Pd 催化偶联反应得到 NiTPP（苯并）（R）（R=苯基（Ph）和苯乙炔基（PE））。合成的苯并卟啉表现出红移的吸收光谱特征，同时具有可调的氧化还原性质。这些苯并卟啉显示出β-取代基对大环骨架的显著电子效应。由于扩展的π共轭，NiTPP（苯并）（PE）在该系列中表现出最低的 HOMO-LUMO 能隙。有趣的是，在电化学条件下，中性卟啉初始转化为二阳离子形式后，NiOPP（苯并）和 NiOPP（苯并）Br 观察到 Ni(II)/Ni(III)的金属中心氧化。
