Abstract
The photoswitchable boron-dipyrromethene–dithienylethene molecular dyad is introduced as a prototype for the efficient fluorescence intensity modulation on the molecular level. The functionality of the system is based on the photochromism of the dithienylethene, which facilitates an efficient on- and off-switching of a Förster-type intramolecular energy transfer between the photoexcited BODIPY donor and the dithienylethene acceptor moiety. The switching behavior and dynamics of the molecular dyad are monitored by steady state and time-resolved spectroscopic methods. A quenching efficiency of up to 96% in the off-state is observed and explained by a drastically accelerated decay of the boron-dipyrromethene excited state due to the efficient energy transfer despite the orthogonal arrangement of donor and acceptor. An energy transfer time orders of magnitude shorter than the lifetime of the boron-dipyrromethene in the open state is determined.
Highlights
Reversible fluorescence intensity modulation has attracted considerable interest in different application fields such as ultrahigh-density optical data storage[1,2,3] and ultrahigh-resolution microscopy[4,5]
In current literature the EET in photochromic systems is denoted as pcFRET because it is typically explained in the framework of the Förster mechanism
In contrast the BODIPY fluorescence is efficiently quenched in the off-state due to a fast FRET to the closed form of the DTE despite the orthogonal arrangement of the FRET pair
Summary
BODIPY–DTE dyad received: 07 April 2016 accepted: 06 June 2016 Published: 27 June 2016. The functionality of the system is based on the photochromism of the dithienylethene, which facilitates an efficient onand off-switching of a Förster-type intramolecular energy transfer between the photoexcited BODIPY donor and the dithienylethene acceptor moiety. In this study an orthogonally arranged photoswitchable BODIPY–DTE molecular dyad (Fig. 1) was investigated by steady state and femtosecond time-resolved spectroscopy. The open form of the DTE belongs to the on-state where a strong fluorescence of the photoexcited BODIPY fluorophore is observed. In contrast the BODIPY fluorescence is efficiently quenched in the off-state due to a fast FRET to the closed form of the DTE despite the orthogonal arrangement of the FRET pair. Fluorescence of the sample was measured in a 4 × 10 mm cuvette (fused silica) in 90° geometry between excitation and detection with a photomultiplier tube (Pico-Quant, PMA-C-182-M). The wavelength dependent group velocity dispersion caused by fused silica and benzene were calculated using the Sellmeier equation[34,35,36] and extended Cauchy relation[37], respectively
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