Parent, unsubstituted porphycene and its two derivatives: 2,7,12,17-tetra-n-propylporphycene and 2,7,12,17-tetra-t-butylporphycene were substituted at the meso position with amino and nitro groups. These two families of porphycenes were characterized in detail with respect to their spectral, photophysical, and tautomeric properties. Two trans tautomers of similar energies coexist in the ground electronic state, but only one form dominates in the lowest excited singlet state. Absorption, magnetic circular dichroism (MCD), and emission anisotropy combined with quantum-chemical calculations led to the assignment of S₁ and S₂ transitions in both tautomers. Compared with the parent porphycene, the S₁–S₂ energy gap significantly increases; for one tautomeric form, the effect is twice as large as for the other. Both amino- and nitroporphycenes emit single fluorescence; previously reported dual emission of aminoporphycenes is attributed to a degradation product. Introduction of bulky t-butyl groups leads to a huge decrease in fluorescence intensity; this effect, arising from the interaction of the meso substituent with the adjacent t-butyl moiety, is particularly strong in the nitro derivative.

中文翻译：

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氨基和硝基卟啉的光物理学和互变异构现象的光谱研究

母体、未取代的卟啉及其两个衍生物：2,7,12,17-四正丙基卟啉和 2,7,12,17-四叔丁基卟啉在中间位置被氨基和硝基取代。这两个系列的卟啉在光谱、光物理和互变异构特性方面进行了详细表征。两种能量相似的反式互变异构体共存于基电子态，但只有一种形式在最低激发单线态中占主导地位。吸收、磁圆二色性 (MCD) 和发射各向异性与量子化学计算相结合导致了 S ₁和 S _2的分配两种互变异构体的转变。与母体卟啉相比，S ₁ –S ₂能隙明显增大；对于一种互变异构形式，效果是另一种的两倍。氨基卟啉和硝基卟啉都发出单一荧光；先前报道的氨基卟啉的双重排放归因于降解产物。大体积叔丁基的引入导致荧光强度大幅下降；这种效应由内消旋取代基与相邻的叔丁基部分的相互作用引起，在硝基衍生物中尤为强烈。