The synthesis of visible light-harvesting C60-bodipy dyads (bodipy = boron-dipyrromethene), and the study of the photophysical properties and the application of dyads as heavy-atom free organic triplet photosensitizers for tripletâtriplet annihilation (TTA) based upconversion, are reported. By attaching carbazole units to the Ï-core of the bodipy chromophore via an ethynyl linker, the absorption wavelength of the antenna in the dyads is readily tuned from 504 nm for the unsubstituted bodipy, to 538 nm (one carbazole unit, ε = 61â800 Mâ1 cmâ1) and 597 nm (two carbazole units, ε = 58â200 Mâ1 cmâ1). Upon photoexcitation at 538 nm (dyad C-1) or 597 nm (dyad C-2), intramolecular energy transfer from the antenna to the C60 unit occurs, and as a result, the singlet excited state of the C60 unit is populated. Subsequently, with the intrinsic intersystem crossing (ISC) of C60, the triplet excited state of the C60 unit is produced (ÏT up to 24.5 μs). Thus, without the need for any heavy atoms, the triplet excited state of the dyads was populated upon visible light excitation. The population of the C60-localized triplet excited state of the dyads was confirmed by nanosecond time-resolved transient difference absorption spectra and spin density analysis. The dyads were used as triplet photosensitizers for TTA upconversion and upconversion quantum yields of up to 2.9% were observed.
本研究报告介绍了可见光收集型 C60-bodipy(bodipy =
硼-二
吡咯并二酮)二元体的合成、光物理性质研究以及二元体作为无重
金属有机三重态光敏剂在基于三重态湮灭(
TTA)的上转换中的应用。通过
乙炔基连接剂将
咔唑单元连接到波地平发色团的Ï-核上,二元化合物中天线的吸收波长很容易从未被代理的波地平的 504 nm 调整到 538 nm(一个
咔唑单元,δµ = 61â800 Mâ1 cmâ1)和 597 nm(两个
咔唑单元,δµ = 58â200 Mâ1 cmâ1)。在 538 纳米(
染料 C-1)或 597 纳米(
染料 C-2)处受到光激发时,分子内能量会从天线转移到 C60 单元,从而填充 C60 单元的单激发态。随后,随着 C60 的内在系统间交叉(ISC),C60 单元的三重激发态产生(ÏT 高达 24.5 μs)。因此,无需任何重
金属原子,二元体的三重激发态就能在可见光激发下产生。纳秒时间分辨瞬时差分吸收光谱和自旋密度分析证实了二元化合物的 C60 定位三重激发态的填充。这些二元化合物被用作
TTA 上转换的三重态光敏剂,并观察到高达 2.9% 的上转换量子产率。