Department of Chemistry, University of Akron, Akron, Ohio 44325-3601, USA.
Inorg Chem. 2011 Aug 1;50(15):6902-9. doi: 10.1021/ic102255k. Epub 2011 Jun 24.
Nickel N-confused tetraphenylporphyrin, 1, and nickel 2-N-methyl-N-confused tetraphenylporphyrin, 1-Me, exhibit unusual sign-reversed (positive-to-negative intensities in ascending energy) MCD spectra in the Q-type band region, suggesting a rare ΔHOMO < ΔLUMO relationship between π and π* MOs in the porphyrin core. Simple and reversible deprotonation of the external NH proton in 1 dramatically changes the electronic structure of the porphyrin core into the ΔHOMO > ΔLUMO combination characteristic for the meso-(tetraaryl)porphyrins. DFT, time-dependent DFT, and semiempirical ZINDO/S calculations on 1, 1-Me, and 1(-) confirm the experimental finding and successfully explain the MCD pattern in the target compounds.
镍 N 混淆四苯基卟啉，1，和镍 2-N-甲基-N 混淆四苯基卟啉，1-Me，在 Q 型带区域表现出不寻常的符号反转（能量上升时强度由正变负）的 MCD 谱，表明在卟啉核心的π 和 π*MO 之间存在罕见的ΔHOMO <ΔLUMO 关系。1 中外部 NH 质子的简单可逆去质子化，将卟啉核心的电子结构剧烈地改变为ΔHOMO >ΔLUMO 组合，这是中（四芳基）卟啉的特征。对 1、1-Me 和 1(-)的 DFT、含时 DFT 和半经验 ZINDO/S 计算证实了实验结果，并成功地解释了目标化合物中的 MCD 模式。
