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The paper addresses the spectroscopic peculiarities of polar molecular crystals and films of dimethylaminebenzylidene-1,3-indandione (DMABI). Specific visible fluorescence bands for various modifications of the system are discovered. They are identical for all excitation conditions and seem to be correlated with the structural organization of the media. The infrared excitation of these bands is shown to be a two-step process which turns into the saturating regime at higher intensities.

A series of perylenediimide-based small molecules (PDI1-PDI5) containing electron-deficient groups in the bay region were synthesized and characterized. The PDI derivatives were found to be capable of forming molecular glasses with glass transition temperatures ranging from 50 to 102 degrees C. Detailed investigations of the optical properties of the synthesized derivatives were performed and compared with those obtained from quantum chemical calculations. Optimized molecular structures of the PDI derivatives exhibited core-twisting by 16 degrees and torsional angle between the bay substituent and the perylene core in the range of 60-72 degrees. The PDI derivatives exhibited absorption maxima in the range of 2.27-2.36 eV and emission maxima in the range of 2.10-2.28 eV. The impact of the bay substituents on the emission, fluorescence quantum yield, and lifetimes in solutions and thin films was established. The red shift of emission maxima (from 2.282 to 2.095 eV) observed for various PDIs in solutions was accompanied by significant reduction in the emission quantum yield (from 0.73 to 0.44) and corresponding increase of the fluorescence lifetime (from 4.5 to 6.8 ns). This was in agreement with quantum chemical calculations indicating decrease of the radiative relaxation rate due to reduction of the oscillator strength and remarkable decrease of the torsional activation barrier. The spectral properties of the wet-casted perylenediimide films featuring different bay substituents were also studied. The variation in the emission peak (of 0.25 eV) and the considerable increase of the Stokes shift (of 0.4 eV) are explained in terms of the formation of the amorphous state. The influence of the bay substituents on the thermal and spectral properties of the films are discussed.

Fluorescence and reflectance spectra of dipolar N,N-dimethylaminobenzylidene 1,3-indandione (DMABI) molecular crystals of α and β crystallographic modifications have been studied over a wide temperature range. The luminescence spectral properties have been discussed by means of the self-trapped exciton model. The crystal phase transition in both α and β modifications resulting in the deeply-trapped excitonic state formation has been observed at low temperatures, below 60 K.© (2003) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

The temperature dependencies of the intensities of the HCl stretching bands of the hydrogen chloride complexes with acetylene and ethylene have been used to obtain estimates of the dissociation enthalpies of the two complexes. Quantum chemical calculations on the Hartree Fock and DFT/B3LYP levels of theory have been combined with experimental data to give estimates of the intensities of the HCl stretching vibration in the two complexes.

N,N-dimethylaminobenzylidene 1,3-indandione (DMABI) was considered. The formation of charge transfer excitonstates in the absorption and luminescence spectra by increase of the thicknesses of DMABI films was observed. Theevidence of a strong exciton-phonon interaction and its effects on the exciton absorption and luminescence spectra wasdiscovered. The coexistence of free and self-trapped excitons at elevated temperatures was found in DMABI films. Thedynamics of both shallow short-lived and deeply trapped long-lived self-trapped exciton states in various films andcrystal of DMABI was discussed.Keywords: molecular crystals, N,N-dimethylaminobenzylidene 1 ,3 -indandione, spectroscopy, luminescence,self-trapped excitons, charge transfer1. INTRODUCTIONThe dipole moment of the electronic transition is the main parameter determining the excitonic feature of thespectrum of molecular crystals. The presence of steady-state dipole moments in the ground and excited molecularstates creates the interaction with other molecules of the surrounding. By means of the exciton theory, the latter causesan essential increase of the displacement gy'2 in comparison with the classical crystals and, moreover, strongelectron-phonon or electron-vibrational modes interaction cannot be treated perturbatively anymore. The dispersiveinteraction is responsible for absorption band shifts depending to the polarity of solvents or by modifying the crystalstructure, while strong electron-phonon interactions can create a distinct Stokes-shift of the fluorescence band. Due tothose interactions the spectral properties of polar systems become very sensitive to the structural changes, differenciesin temperature and excitation conditions, and these systems can express optically non-linear behaviour in somespectral regions.3 Therefore, new possibilities of their application to non-linear optics and molecular electronics are

The origin of the excited states in polar molecular compounds of N,N‐dimethylaminebenzylidene 1,3‐indandione (DMABI) has been investigated. The spectral, kinetic and polarization properties of the of self‐trapped exciton luminescence were discussed with special glance to the crystal structure of DMABI. The build up of DMABI crystal of α‐modification predetermines increased intermolecular interaction between donor and acceptor fragments of neighboring DMABI molecules. The intermolecular charge transfer transition was found to take place simultaneously with considerable intramolecular charge redistribution because of chemically bonded donor and acceptor fragments within polar DMABI molecule. A week, narrow luminescence line was observed in resonant with the lowest absorption band and was attributed to the free exciton radiative recombination. By increasing the excitation intensity the onset of non‐linear bimolecular annihilation of excitons was observed.

A set of novel hole-transporting materials (HTMs) based on pi-extension through carbazole units was designed and synthesized via a facile synthetic procedure. The impact of isomeric structural linking on their optical, thermal, electrophysical, and photovoltaic properties was thoroughly investigated by combining the experimental and simulation methods. Ionization energies of HTMs were measured and found to be suitable for a triple-cation perovskite active layer ensuring efficient hole injection. New materials were successfully applied in perovskite solar cells, which yielded a promising efficiency of up to almost 18% under standard 100 mW cm(-2) global AM1.5G illumination and showed a better stability tendency outperforming that of 2,2',7,7'-tetrakis-(N,N-di-p-methoxyphenylamine)-9,9'-spirobifluorene. This work provides guidance for the molecular design strategy of effective holeconducting materials for perovskite photovoltaics and similar electronic devices.

In this paper we consider the spectral properties of exciton transitions of N,N-dimethylaminobenzylidene 1,3-indandione (DMABI) films and crystals, which are typical examples of polar molecular compounds. A large dipole moment in the electronic ground state and the considerable change (up to 12 D) of this value by excitation of a free DMABI molecule induce strong polarization of the surroundings, which causes the remarkable self-trapping effects in the crystal. The exciton−phonon coupling value g = 1.87 is estimated for the crystal. Charge-transfer (CT) exciton formation is observed in the absorption and luminescence spectra by analyzing the spectral behavior at various thicknesses of DMABI films. The CT excitons created along molecular stacks dominate in the spectra of the DMABI crystals. Coexistence of free and self-trapped CT excitons is discovered at elevated temperatures. The exciton band parameters are estimated, and the adiabatic energy potential energy for two self-trapped excitons is suggested. R...

This paper considers the origin of the excited states and spectroscopic features of polar molecular compounds of N,N-dimethylaminobenzylidene 1,3-indandione (DMABI). Evidence of a strong exciton-phonon interaction and its effects on the exciton absorption and luminescence spectra was discovered. The spectral features were related to the crystal structure and were ascribed to self-trapped charge transfer excitons. A weak, narrow luminescence line was also observed in resonance with the lowest absorption band and was attributed to free exciton radiative recombination.

Most patients with hepatocellular carcinoma are inoperable and hepatoma cells are resistant to conventional chemotherapies. So, it is important to develop novel therapies. Treatment of mouse hepatoma MH-22A cells by vitamins C and K3 at the ratio of 100:1 greatly enhanced their cytotoxicity. When cells were subjected to vitamin C at 200 μM or K3 at 2 μM separately, viability was more than 90%. However, when vitamins C and K3 were combined at these concentrations, less than 10% of cells survived.To elucidate the mechanism of this synergy, theoretical quantum-chemical analysis of the dynamics of intermolecular electron transfer (IET) processes within the complexes containing C and K3 was carried out. Optimization of the ground state complex geometry was provided by means of GAUSSIAN03 package. Simulation of the IET was done using NUVOLA package, in the framework of molecular orbitals. Rate of IET was calculated using Fermi Golden rule.Two concurrent pathways of a plausible mechanism of the synergistic action of vitamins C and K3 were analyzed: increasing of acidity in the near surrounding of complex significantly affects redox-cycling and creating the most stable [C2K] complex stabilizes acidity at a high level.Out of the complexes of vitamin K3 with five different forms of vitamin C, the most stable one was the complex with de-hydro-ascorbic acid [C2K], and the second one - with ascorbic acid [C1K]. The spectra of IET represent the different nature of complexes. There are several possibilities for electron transfer in the less stable [C1K] complex, while for the most stable [C2K] complex; the number of resonant states significantly decreases. This confirms that the creation of complex [C1K] escalates increasing of acidity.