Suhina Tomislav, Amirjalayer Saeed, Woutersen Sander, Bonn Daniel, Brouwer Albert M
University of Amsterdam, van 't Hoff Institute for Molecular Sciences, University of Amsterdam, PO Box 94157, 1090 GD Amsterdam, The Netherlands.
Phys Chem Chem Phys. 2017 Aug 2;19(30):19998-20007. doi: 10.1039/c7cp02037f.
Molecular rotors based on meso-substituted boron-dipyrromethane (BODIPY) are widely recognized fluorescent viscosity sensors. The viscosity dependence of their fluorescence arises from an efficient excited-state deactivation process that can only occur when molecular-scale motion is not hindered. Here, we use visible and IR pump-probe spectroscopies combined with TD-DFT calculations to show that this fluorescence deactivation takes place through a fast and irreversible process which does not involve intermediate electronic states. Our data indicate that nonradiative excited-state deactivation of BODIPY molecular rotors is practically independent of solvent polarity, but strongly governed by viscoelastic/free volume properties of the local environment in both low- and high-viscosity regimes.
基于中位取代硼二吡咯甲烷（BODIPY）的分子转子是广泛认可的荧光粘度传感器。其荧光对粘度的依赖性源于一种高效的激发态失活过程，该过程只有在分子尺度的运动不受阻碍时才会发生。在此，我们结合可见和红外泵浦 - 探测光谱以及含时密度泛函理论（TD - DFT）计算表明，这种荧光失活是通过一个快速且不可逆的过程发生的，该过程不涉及中间电子态。我们的数据表明，BODIPY分子转子的非辐射激发态失活实际上与溶剂极性无关，但在低粘度和高粘度体系中都强烈受局部环境的粘弹性/自由体积性质的支配。
