Effect of Intramolecular Twisting on the Fluorescence Spectra of Sterically Hindered Tetraphenylbutadienes

Abstract

Absorption and fluorescence spectra of trans-1,1,4-triphenylbutadiene, trans-1,1,4,4-tetraphenylbutadiene (TPB), and trans-1,1,4,4-tetraphenyl-2-methylbutadiene (TPMB) were measured in an isopentane-methylcyclohexane mixture at room temperature and in rigid glass at 77°K. Absorption maxima exhibit a polarization red shift while fluorescence maxima exhibit a large blue shift upon freezing the samples at 77°K. Thus the intense blue fluorescence of tetraphenyl-2-methylbutadiene appears as a weak yellow fluorescence as soon as the rigid glass begins to melt. In these sterically hindered molecules the equilibrium configuration in the excited state is different from that in the ground state, and an intramolecular twisting relaxation process occurs before emission in fluid media. In rigid media and in the crystal, the twisting relaxation is slowed down, and emission originates from a Frank–Condon state which lies at higher energies. Quantum yield and energy of fluorescence of sterically hindered molecules in general are expected to be viscosity sensitive.

VUV-Vis optical characterization of Tetraphenyl-butadiene films on glass and specular reflector substrates from room to liquid Argon temperature

“…The PL spectra of the 1% sample as a function of temperature are shown in Fig.14. A remarkable difference with pure TPB evaporated on glass or polymeric layers is that we do not observe the vibronic structures neither at room temperature nor at lower temperatures, and the emission 300 350 400 450 500 lineshape is hardly affected by temperature. This behavior closely resembles that of TPB in liquid solutions, where the randomness of the environment geometry around the TPB molecule induces the observed inhomogenous broadening of the vibronic structures, which merge in a single, unresolved band [15,16].…”

Characterization of protonated and deuterated tetra-phenyl butadiene film in a polystyrene matrix

“…It appears that the emission spectrum is affected by the environment in which the TPB molecules are placed. Similar effects have been observed in previous studies in the literature [31].…”

“…It appears that the emission spectrum is affected by the environment in which the TPB molecules are placed. Similar effects have been observed in previous studies in the literature [31]. For convenient comparison by the reader, we reproduce those previous fluorescence spectra here in Figure 2.…”

Thermoresponsive icy road sign by light scattering and enhanced fluorescence

“…The 'solid state' which triggers the fluorescence increase can be generated by low temperatures and/or high viscosities, in matrixes that are amorphous or crystalline. The effect of viscosity and temperature on the fluorescence quantum yield of TPE 50,51 and other molecules [52][53][54][55] was studied between 1967-1990. In more recent years the phenomenon was popularised by Tang and co-workers with the term aggregated-induced emission (AIE).…”