Optical and Photophysical Properties of Indolocarbazole Derivatives

Abstract

We present a study of the optical and photophysical properties of five ladder indolo[3,2-b]carbazoles, namely, M1, M2, M3, M4, and M5. The ground-state optimized structures were obtained by B3LYP/6-31G* density functional theory (DFT) calculations, whereas the optimization (relaxation) of the first singlet excited electronic state (S1) was performed using the restricted configuration interaction (singles) (RCIS/6-31G*) approach. The excitation to the S1 state does not cause important changes in the geometrical parameters of the compounds, as corroborated by the small Stokes shifts. The excitation and emission energies have been obtained by employing the time-dependent density functional theory (TDDFT). For all the compounds, excitation to the S1 state is weakly allowed, whereas the S2 ← S0 electronic transition of each oligomer possesses a much larger oscillator strength. The absorption and fluorescence spectra of the compounds have been recorded in chloroform. A reasonable agreement is obtained between TDDFT vertical transition energies and the (0,0) absorption and fluorescence bands. On one hand, the pattern of the aliphatic side chains does not affect the absorption and fluorescence maxima of the compounds. On the other hand, the replacement of aliphatic chains by phenyl or thiophene rings induces hypsochromic shifts in the absorption and fluorescence spectra. Finally, the fluorescence quantum yield and lifetime of the compounds in chloroform have been obtained. From these data, the radiative and nonradiative rate constants of the deactivation of the S1 state have been determined.

Fluorescence quenching by charge carriers in indolo[3,2-b]carbazole-based polymer

“…7 ns. The decay time is more than two times longer than that of indolo [3,2-b]carbazole in chloroform [29]. The fluorescence decay of the PIC film is non-exponential.…”

Syntheses and properties of copolymers containing indolocarbazole moiety in the side chain

“…INC is known to show strong blue fluorescence under irradiation by ultraviolet (UV) light. In recent years, there have been some reports on the preparation and characterization of derivatives of INC. [16][17][18][19][20][21][22][23][24][25] In particular, Hu et al 21 have reported 1,7-dinaphtylindolo [3,2-b]carbazole, which showed excellent hole-transport properties in light-emitting diodes. Later, the first organic field-effect transistors using N-alkylated INC as an active layer was successfully fabricated.…”

Synthesis of Poly(2,7‐carbazole)s and Derivatives

“…This is especially true for the synthesis of polymers because of their low solubility, but for oligomers and small molecules the performances are quite similar [130]. These ladder-like molecules are even easier to study because it is much easier to grow single crystals, which help defining some structure-property relationships [129,133]. However, the main goal is to obtain highly performing polymers, where the monomers are quickly and easily synthesized with high overall yields.…”

“…Over the last years, only a few IC-based monomers have been used and they are generally 2,8-(59) or 3,9-dihaloindolo[3,2-b]carbazoles (60). However, numerous side chains have been added onto the nitrogen atoms to increase the solubility [125,131,132], to lower the short contact distance between separate molecules [127,128], or to completely change the thin film organization [129,130,133,134]. The first successful synthesis of IC-based polymers was reported in 2006 [125].…”