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.