Department of Chemistry and Chemical Biology, Rensselaer Polytechnic Institute, 110 Eighth Street, Troy, New York 12180, United States.
Inorg Chem. 2012 Dec 17;51(24):13114-22. doi: 10.1021/ic301170a. Epub 2012 Dec 6.
Cu(I) catalyzed azide-alkyne cycloaddition (CuAAC) reactivity was successfully employed to synthesize three donor-acceptor energy transfer (EnT) arrays that contain one (Dyad), three (Tetrad) and four (Pentad) 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene (BODIPY) donors connected to a Zn-tetraphenylporphyrin acceptor via 1,2,3-triazole linkages. The photophysical properties of the three arrays, along with individual donor and acceptor chromophores, were investigated by UV-vis absorption and emission spectroscopy, fluorescence lifetimes, and density functional theory (DFT) electronic structure modeling. Comparison of the UV-vis absorption spectra and frontier molecular orbitals from DFT calculations of the three arrays with ZnTPP, ZnTTrzlP, and Trzl-BODIPY shows that the electronic structure of the chromophores is essentially unperturbed by the 1,2,3-triazole linkage. Time-dependent DFT (TDDFT) calculations on the Dyad reproduce the absorption spectra in THF and show no evidence of excited state mixing of the donor and acceptor. The BODIPY singlet excited state emission is significantly quenched in all three arrays, consistent with EnT to the porphyrin core, with efficiencies of 95.8, 97.5, and 97.2% for the Dyad, Tetrad, and Pentad, respectively. Fluorescence excitation spectra of the three arrays, measured at the porphyrin emission, mirror the absorption profile of both the porphyrin and BODIPY chromophores and are consistent with the Förster resonance energy transfer (FRET) mechanism. Applying Förster theory to the spectroscopic data of the chromophores gives EnT efficiency estimates that are in close agreement with experimental values, suggesting that the through-space mechanism plays a dominant role in the three arrays.
铜（I）催化的叠氮化物-炔烃环加成（CuAAC）反应成功地用于合成三个供体-受体能量转移（EnT）阵列，其中包含一个（二联体）、三个（四联体）和四个（五联体）通过 1,2,3-三唑键连接到 Zn-四苯基卟啉受体的 4,4-二氟-4-硼-3a,4a-二氮杂-s-茚并（BODIPY）供体。通过紫外-可见吸收和发射光谱、荧光寿命和密度泛函理论（DFT）电子结构建模研究了三个阵列以及单个供体和受体发色团的光物理性质。比较三个阵列与 ZnTPP、ZnTTrzlP 和 Trzl-BODIPY 的紫外-可见吸收光谱和前沿分子轨道，从 DFT 计算得出，三唑键对发色团的电子结构基本没有影响。二联体的时间依赖密度泛函（TDDFT）计算再现了 THF 中的吸收光谱，并且没有证据表明供体和受体的激发态混合。在所有三个阵列中，BODIPY 单重激发态发射都显著猝灭，这与卟啉核心的 EnT 一致，二联体、四联体和五联体的效率分别为 95.8%、97.5%和 97.2%。在卟啉发射处测量的三个阵列的荧光激发光谱反映了卟啉和 BODIPY 发色团的吸收轮廓，并与Förster 共振能量转移（FRET）机制一致。将 Förster 理论应用于发色团的光谱数据可得到 EnT 效率估计值，与实验值非常吻合，表明在三个阵列中，通过空间机制起主要作用。
