Conradie Jeanet, Wamser Carl C, Ghosh Abhik
Department of Chemistry, UiT─The Arctic University of Norway, N-9037 Tromsø, Norway.
Department of Chemistry, University of the Free State, P.O. Box 339, Bloemfontein 9300, Republic of South Africa.
J Phys Chem A. 2025 Feb 13;129(6):1591-1598. doi: 10.1021/acs.jpca.4c07216. Epub 2025 Jan 30.
Presented herein is a DFT/TDDFT study of -tetrakis(4-hydroxyphenyl)porphyrin (H[THPP]) and its -deprotonated tetraanionic form; the latter was modeled as both a free tetraanion and with various counterions. Based on our calculations, the experimentally observed hyperporphyrin spectra are attributed to an admixture of phenol/phenoxide character into the a-type HOMO of tetraphenylporphyrin. The admixture results in an elevation of the orbital energy of the HOMO in relation to other frontier orbitals, which accounts for the observed spectral redshifts. The calculations underscore differences in the performance of different exchange-correlation functionals. Thus, while the popular hybrid functional B3LYP greatly exaggerates the redshift of the far-red hyperporphyrin band of -deprotonated H[THPP], the range-separated functional CAMY-B3LYP predicts a more moderate redshift. The latter, however, fails to reproduce experimentally observed absorptions in the 550-600 nm range, potentially underscoring the still imperfect modeling of anionic hyperporphyrins.
本文展示了对四（4-羟基苯基）卟啉（H[THPP]）及其去质子化四阴离子形式的密度泛函理论/含时密度泛函理论（DFT/TDDFT）研究；后者被建模为自由四阴离子和带有各种抗衡离子的形式。基于我们的计算，实验观察到的超卟啉光谱归因于苯酚/苯氧离子特性混入四苯基卟啉的a型最高占据分子轨道（HOMO）中。这种混合导致HOMO的轨道能量相对于其他前沿轨道升高，这解释了观察到的光谱红移。计算结果强调了不同交换相关泛函性能的差异。因此，虽然常用的杂化泛函B3LYP极大地夸大了去质子化H[THPP]的远红外超卟啉带的红移，但范围分离泛函CAMY-B3LYP预测的红移更为适度。然而，后者未能重现实验观察到的550 - 600 nm范围内的吸收，这可能突出了阴离子超卟啉建模仍不完善的问题。
