Tetracene Dimer

Abstract

It is shown that tetracene dimerizes. The association equilibrium constant K=2.2×10−4 exp(7.2/RT) for 283°≥T≥168°K. The absorption and emission spectra of the dimer are compared with those of the monomer and of crystalline tetracene. The dimer and the crystal spectra are similar.

On dimers and complexes of tetracene and the Kasha's molecular excitonic model

“…of Ref. ), or simply by activating a kinetic process from a certain temperature as shown in our laboratory, as it is the case for the trans ‐stilbene dimerization process …”

“…Figure (b) shows the spectra recorded at different times once the temperature of 223 K is reached, t = 0, 45 and 90 min. As can be seen, the three spectra can be regarded as identical; therefore, no modification is detected, which may indicate that the chromophore has not evolved into a new equilibrium as proposed by Katul and Zahlan …”

“…Above the latter temperatures, the spectra are unchanged (Figs and (a)). This evidence allows us to reconsider the proposal by Katul and Zahlan that the tetracene molecule undergoes a process towards equilibrium as the temperature lowers down. Those processes are characterized by an equilibrium constant, which can be estimated from the respective monomer and dimer band absorptions involved.…”

“…A year later, Zahlan and Kazzaz analyzed the dependence of fluorescence with temperature of a crystalline sample of tetracene and concluded that the fluorescence that had been assigned to the dimeric structure of tetracene changes significantly on going from 89 to 4 K. In 1972, however, Fournie et al . ascribed to tetracene microcrystals the spectral behaviour reported by Katul and Zahlan corresponding to tetracene dimers. Furthermore, Fournie et al .…”

“…Theoretical efforts to analyse the structure of the dimers formed by these polyacenes have been made both theoretically as spectroscopically and have focused mainly on anthracene and tetracene . Information on the spectral behaviour of tetracene as essential for the design of electronic devices is insufficient, and therefore, it needs to be further studied.…”