Switching Pathways of Triplet State Formation by Twisted Intramolecular Charge Transfer

Abstract

With the aim of constructing efficient photoelectric organic materials, a pyrido[3,2-g]quinoline derivative named LA17b has been synthesized, and its photodynamic relaxation processes in solvents and films were studied by time-resolved fluorescence and femtosecond transient absorption techniques. The steady-state fluorescence spectra show pronounced red-shift with the increase of the solvent polarity as well as in binary solvent hexane/ethanol by increasing ethanol concentration. However, the strong red-shift does not lead to quenching of the fluorescence. This is explained in terms of a twisted intramolecular charge transfer (TICT) state. The TICT state of LA17b in ethanol is highly emissive with a long fluorescence lifetime: 1.1 ns. TICT state was shown to play an important role in enhancement of intersystem crossing rate. TD-DFT calculations confirm the pathways of relaxation of locally excited state via TICT and triplet states. In films, the photodynamic properties are similar to that of LA17b in hexane and the TICT state vanishes due to the rigid environment. The obtained optical properties of this molecule suggest that it can be a promising candidate for various optoelectronic applications.

Singlet Fission from Upper Excited States of Bodipy Crystalline Film and Single Crystal

“…Moreover, efficient Forster resonance energy transfer (FRET) between the heterogeneous populations of the [monomeric] molecules in an inhomogeneously broadened ensemble will further lead to quenching of the S 1 state. 22,35 In Figure 4e, the fluorescence of the crystalline film is strongly quenched as well. Combining the time-resolved fluorescence techniques of TCSPC and fs up-conversion (Figures 4f and S8), the time components of the PhBDP crystalline film were obtained: τ 1 = 6.3 ps (75%), τ 2 = 47−130 ps (15%), and τ 3 = 340−900 ps (10%).…”

“…As mentioned above, the broadening of the absorption is indicative of extended nanoaggregates with a variety of lifetimes. Moreover, efficient Förster resonance energy transfer (FRET) between the heterogeneous populations of the [monomeric] molecules in an inhomogeneously broadened ensemble will further lead to quenching of the S 1 state. , …”

“…PhBDP films were prepared by using a vacuum evaporation pump device (QHV-Z350C, Pana Instruments) at a temperature of 313 K for 5 min. The treatment of the quartz substrates before the vacuum evaporation was the same as our former work . PhBDP films involve two types (Figure S1); the film was transparent and homogeneous after preparation.…”

“…The treatment of the quartz substrates before the vacuum evaporation was the same as our former work. 22 PhBDP films involve two types (Figure S1); the film was transparent and homogeneous after preparation. After 2 h in the atmosphere, the inhomogeneous microcrystalline structures spontaneously formed.…”

Optical Chemical Sensing of Iodide Ions: A Comprehensive Review for the Synthetic Strategies of Iodide Sensing Probes, Challenges, and Future Aspects

“…On the contrary, ICT probes showed ratiometric measurements with obvious fluorescence band shifts on binding with the analytes. The ICT‐based processes can also be experienced in twisted internal charge transfer (TICT) [46] and metal‐ligand charge transfer (MLCT) [47] …”