We report the excited-state intramolecular charge transfer (ICT) characteristics of four tetrahydro[5] helicene-based imide (THHBI) derivatives with various electron-donating substitutes in different polarity of solvents using steady-state, time-resolved transient absorption (TA) spectroscopy. It is found that, the small bathochromic-shift of the absorption spectra but large red shift of the emission spectra for all dyes with increasing solvent polarity indicates the larger dipole moment of the excited state compared to ground state. The results of theoretical calculations exhibit the charge transfer from the terminal donors to helical backbone, which accounts for the degrees of red shift of the emission spectra from different extent of ICT nature. Time-resolved TA spectra recorded as a function of electron-donating substitutes and solvent polarity show the dye with stronger donors (THHBI-PhNPh2) in more polar solvent behaves faster excited-state ICT relaxation, leading to the formation of solvent-stabilized ICT state (ICT’ state) from the excited ICT state; The dyes (THHBI-Ph, THHBI-PhCF3 and THHBI-PhOMe) with relative weaker donors show weaker dependence on solvent polarity, and instead of that intersystem crossing (ISC) becomes possible from ICT state to triplet state.

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The photophysical properties of intramolecular charge transfer (ICT) in a novel tribranched donor-π-acceptor chromophore, triphenoxazine-2,4,6-triphenyl-1,3,5-triazine (tri-PXZ-TRZ), with thermally activated delayed fluorescence character was investigated in different aprotic solvents by steady-state spectroscopy and femtosecond and nanosecond transient absorption spectroscopy measurements. Increasing the solvent polarity led to a significant increase in the Stokes shift. The large Stokes shift in highly polar solvents was attributed to ICT properties upon excitation; this resulted in a strong interaction between the tri-PXZ-TRZ molecule and the surrounding solvent, which led to a strong solvation process. Quantum-chemical calculations and changes in the dipole moment showed that this compound has a large degree of ICT. Furthermore, an apolar environment helped to preserve the symmetry of tri-PXZ-TRZ and to enhance its emission efficiency. The femtosecond and nanosecond transient absorption spectroscopy results indicated that the excited-state dynamics of this push-pull molecule were strongly influenced by solvent polarity through the formation of a solvent-stabilized ICT state. The excited-state relaxation mechanism of tri-PXZ-TRZ was proposed by performing target model analysis on the femtosecond transient absorption spectra. In addition, the delayed fluorescence of tri-PXZ-TRZ was significantly modulated by a potential competition between solvation and intersystem crossing processes.

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reported flexible TFMSC devices could be directly mounted on the human skin to ensure the functionality of miniaturized electronics, such as artificial skins, wearable electronics, flexible sensors, and integrated circuitries. [30,31] The main challenges of designing and developing skinmountable TFMSCs are listed as follows: 1) The TFMSCs should be solid-state. The application of liquid electrolyte-based TFMSCs has been limited by possible leakage of toxic or corrosive electrolytes and undesired packaging issue. [32] 2) The TFMSCs must have high flexibility, pliability, and stretchability to fit the skin well. 3) The energy storage unit should have good capacitive properties and not be severely sacrificed by body movement. 4) The skin-mountable device must fulfill the requirement of biocompatibility. Therefore, the rational design and development of solid skin-mountable TFMSCs with excellent skin adhesion, flexibility, and security are highly appealing.In this study, solid in-plane TFMSCs were developed for skin-mountable and high efficient energy storages by using flexible medical tape with great skin adhesion. The design idea was inspired by the fact that graphite layer is easy to be coated on medical tape by a simple drawing process and then MnO 2 layer can be easily deposited on it through a mild in situ redox method, as seen in Figure 1a. We choose the highly bendable and stretchable medical tape as microscopic structural support and medical polymethyl methacrylate (MPMMA) as the skinmountable layer. Such plaster-like SCs can be directly mounted on the human skin by a simple uncovering-affixing procedure. The TFMSCs not only exhibit superior skin adhesion, stretchability, flexibility, and biocompatibility, but also possess outstanding electrochemical performances, such as exceptional rate capability and cycling stability. High flexibility enables the skin-mountable TFMSCs to maintain relatively stable capacitive properties when suffering from various deformations originating from the movements of the body. Especially, the obtained solid skin-mountable TFMSCs can be repeatedly distorted with the elbow bent from 0° to 90°, and the value of capacitance keeps more than 90% after 200 bending cycles. This may provide a robust strategy for development and application of integrated and skin-mountable energy storage devices. Figure 1b,c and Figure S1a (Supporting Information) illustrate the scanning electron microscope (SEM) images of surface morphologies of medical tape substrate with the fiber diameter of around 10-20 µm. The rough and porous surface structures of medical tape facilitate exfoliation and adhesion of the graphitic material when using a pencil to draw on it under the guide of a mould. A stripe of graphitic flakes were deposited (Figure 1d and Figure S1b, Supporting Information), which enables the formation of a continuous conducting path on the surface and the In this study, integrated plaster-like micro-supercapacitors based on medical adhesive tapes are fabricated by a simple pencil drawing process ...

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A comparative investigation on the photophysical properties and solvation-related ICT dynamics of three push-pull compounds containing different donors including carbazole, triphenylamine and phenothiazine, was performed. The steady-state spectra and theoretical calculations show the charge transfers from the central donors to the acceptors at each side. The characterization of the extent of charge transfer was determined by various means, including estimation of the dipole moment, the electron density distribution of HOMO and LUMO, CDD and change in Gibb's free energy, which show the charge transfer strength to be in the order PDHP > BDHT > PDHC. This suggests that the electron-donating ability of the donor groups plays a crucial role in the charge transfer in these compounds. The TA data show the excited-state relaxation dynamics follow a sequential model: FC→ICT→ICT'→S , and are affected by the solvent polarity. The results presented here demonstrate that the compound with a higher degree of ICT characteristic interacts more strongly with stronger polar solvent molecules, which can accelerate the solvation and spectral evolution to lower energy levels. The A-π-D-π-A architectures with prominent ICT characteristics based on carbazole, triphenylamine and phenothiazine might be potential scaffolds for light-harvesting and photovoltaic devices. These results are of value for understanding structure-property relationships and the rational design of functional materials for photoelectric applications.