Fine-Tuning of 尾-Substitution to Modulate the Lowest Triplet Excited States: A Bioinspired Approach to Design Phosphorescent Metalloporphyrinoids

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• 作者：Xian-Sheng Ke ; Hongmei Zhao ; Xiaoran Zou ; Yingying Ning ; Xin Cheng ; Hongmei Su ; Jun-Long Zhang
• 刊名：Journal of the American Chemical Society
• 出版年：2015
• 出版时间：August 26, 2015
• 年：2015
• 卷：137
• 期：33
• 页码：10745-10752
• 全文大小：582K
• ISSN：1520-5126

文摘

Learning nature鈥檚 approach to modulate photophysical properties of NIR porphyrinoids by fine-tuning 尾-substituents including the number and position, in a manner similar to naturally occurring chlorophylls, has the potential to circumvent the disadvantages of traditional 鈥渆xtended 蟺-conjugation鈥?strategy such as stability, molecular size, solubility, and undesirable 蟺鈥撓€ stacking. Here we show that such subtle structural changes in Pt(II) or Pd(II) cis/trans-porphodilactones (termed by cis/trans-Pt/Pd) influence photophysical properties of the lowest triplet excited states including phosphorescence, Stokes shifts, and even photosensitization ability in triplet鈥搕riplet annihilation reactions with rubrene. Prominently, the overall upconversion capability (畏, 畏 = 蔚路桅_UC) of Pd or Pt trans-complex is 10⁴ times higher than that of cis-analogue. Nanosecond time-resolved infrared (TR-IR) spectroscopy experiments showed larger frequency shift of 谓(C鈺怬) bands (ca. 10 cm^鈥?) of cis-complexes than those of trans-complexes in the triplet excited states. These spectral features, combining with TD-DFT calculations, suggest the strong electronic coupling between the lactone moieties and the main porphyrin chromophores and thus the importance of precisely positioning 尾-substituents by mimicking chlorophylls, as an alternative to 鈥渆xtended 蟺-conjugation鈥? in designing NIR active porphyrinoids.