Effect of Peripheral Substituents on Luminescent Properties of the Porphyrin Platinum(II) Complexes

TL;DR: In this article, a series of porphyrin platinum(II) complexes with different peripheral substituents (PtTEMP, PtTBMP, PtOMPP and PtDMPP) were designed, synthesized and characterized, for the purpose of effectively restraining the intermolecular pi-pi interaction.

Abstract: Porphyrin platinum (IT) complexes with efficient red phosphorescent emission have attracted extensive interest due to their potential application in the organic light emitting diodes (OLEDs). However, the strong pi-pi intermolecular interactions derived from their rigid planar coordination geometry result in the occurrence of self-quenching and affect their performance. In this work, a series of porphyrin platinum(II) complexes with different peripheral substituents (PtTEMP, PtTBMP, PtOMPP and PtDMPP) were designed, synthesized and characterized, for the purpose of effectively restraining the intermolecular pi-pi interaction. Single crystal X-ray structure analysis indicated that they had ideal square-planar geometry around Pt atom, and bulky t-butyl substituent could inhibit effectively pi-pi interactions. The peripheral substituents hardly affected absorption and emission properties of the complexes, and the luminescent peaks at 646-656 nm were assigned to (LC)-L-3 phosphorescent emission. PtTBMP showed the highest emission quantum yield (0. 58) and external quantum efficiency(EQE, 6. 3%) due to strong steric effect of t-butyl. The luminous efficiency of PtDMPP with three methoxyl substitutents was better than PtOMPP with two methoxyl, the corresponding emission quantum yield were 0. 36 and 0. 29, and were 2. 4% and 1. 7%, respectively. The results indicated that the encapsulating effect of the peripheral substituents could improve luminescent efficiency of porphyrin platinum(II) complexes.