Visible Luminescence of Dimethylaminobenzylidene-1,3-indandione Compounds Excited by Ultrashort Infrared Light Pulses

Abstract

The origin of the nonlinear anti-Stokes luminescence effect in dimethylaminobenzylidene-1,3-indandione (DMABI) crystals and vacuum-evaporated films, i.e., the luminescence in the visible spectral region created by the infrared excitation, was investigated by means of the luminescence excitation stimulated by two excitation pulses separated in time and by means of ultrafast pump−probe spectroscopy. In contrast to the earlier proposed luminescence excitation model based on the low-energy exciton annihilation, the luminescence state was found to be excited via two-photon absorption through the virtual and real (characterized by 1 ps lifetime) intermediate states. Second harmonic generation and the pulse duration effect on the nonlinear luminescence are discussed. The exciton−exciton annihilation on a luminescent state manifold was observed at high excitation intensities.

Studies of Langmuir and Langmuir–Blodgett films of NLO-active amphiphilic 1,3-indanedione derivatives

“…The results were in agreement with the results obtained for vacuum deposited films of related compounds, DMABI. 13,14 The fluorescence spectra do not change in shape with increase of the number of layers, indicating that intermolecular interactions within the layers are dominant compared to interactions between layers, in line with the p-stacking discussed above.…”

“…Compounds 2a-2d were synthesized according to the general procedure. 7 Their structures and purity was confirmed by 1 H and 13 C NMR spectra, HRMS and elemental analyses. Full synthetic details will be given elsewhere.…”

Free and Self-Trapped Charge-Transfer Excitons in Crystals of Dipolar Molecules ofN,N-Dimethylaminobenzylidene 1,3-Indandione

“…Two kinds of intermediate states, i.e. virtual and real states, have been discovered in the DMABI crystal as being responsible for the two-photon absorption , which may be prescribed to higher vibrational levels of the electronic ground state of the DMABI molecule.…”

“…virtual and real states, have been discovered in the DMABI crystal as being responsible for the two-photon absorption. 18 Although the 1.174-eV photon energy seems to be in an almost transparent spectral region of the DMABI crystal, more careful absorption measurements show weak absorption bands in the IR spectral range (from 0.8 to 1.5 eV) shown in Figure 5, which may be prescribed to higher vibrational levels of the electronic ground state of the DMABI molecule. The mean lifetime of this intermediate real state was estimated to be about 1 ps, 18 which is a typical value for excited vibrational states of large molecules.…”

Langmuir and Langmuir−Blodgett Films of NLO Active 2-(p-N-Alkyl-N-methylamino)benzylidene-1,3-indandioneπ/A Curves, UV−Vis Spectra, and SHG Behavior

“…This compound is a simple prototype of a newly developed family of materials consisting of compounds derived from a 1,3-indandione-2-ylidene moiety as an acceptor (A) and a p -dimethylaminophenyl moiety as a donor (D). Recently, the photophysical properties of its N , N -dimethylamino analogue ( 1b ) in the solid state (crystals and thin films) have been studied. The 1,3-indandione moiety can also serve in the second role of a hydrophilic headgroup of an amphiphile.…”