Synthesis and Detailed Photophysical Studies of Pyrene-Based Molecules Substituted with Extended Chains

Abstract

Applications of conjugated organic compounds in the field of electronics and optoelectronics and of pyrene derivatives as fluorescent probes are well established. The synthesis of the novel pyrene-based 2,11-di-tert-butyl-6,7,15,16-tetrakis(alkoxy/alkythio)quinoxaline[2',3':9,10]phenanthro[4,5-abc]phenazine, TQPP-[t-Bu](2)-[XR](4) (X = O, S; R = C(n)H(2n+1)), is reported along with an in-depth spectroscopic characterization and evaluation of their photophysical properties. Despite their larger core size, the reported TQPP materials showed similar fluorescence behavior to that of pyrene itself, with no significant shift in their fluorescence peak. The fluorescence spectra showed peaks corresponding to the monomer and to the excimer. Even though these TQPP compounds showed poor solubility in various solvents, their solvatochromism could be investigated in different solvents ranging from polar solvents such as methanol to nonpolar solvents such as cyclohexane; Stokes shifts, fluorescence lifetimes, fluorescence quantum yields, as well as radiative and nonradiative rate constants are determined for four of these TQPP materials in various solvents. Quantum yields were found to be low for these TQPP compounds in solvents such as tetrahydrofuran (THF), whereas they were relatively higher in cyclohexane and dioxane. Monomer to excimer intensity ratio versus gross solvent scale (E(T)30) and orientation polarizabilty (Delta f) were correlated. Although TQPP-[t-Bu](2)-[XR](4) displayed similar fluorescent emission and excitation behavior as that of pyrene, a relatively smaller lifetime was observed for these compounds compared to that of pyrene.

Synchronous fluorescence spectroscopic study of solvatochromic curcumin dye

“…The Lippert-Mataga equation [29][30][31][32] shows that the solvent dependence of the Stokes' shift for a compound depends on the change in the dipole moment of the fluorescence moiety upon excitation, the dielectric constant, and the refractive index of the solvents being used [29][30][31][32][33][34][35]:…”

Fluorescence Lifetime Measurements and Biological Imaging

“…The excimer forming pyrene (Fig. 11) and its derivatives have been used extensively in fluorescence steady-state and dynamic imaging 191-193. The importance of pyrene in steady-state imaging lies in its large spectral shift from the monomer (400 nm) to the excimer (485 nm) state.…”

Unique role of ionic liquid [bmin][BF4] during curcumin–surfactant association and micellization of cationic, anionic and non-ionic surfactant solutions

“…A red shift was also observed after the cmc for CTAB. The Stokes' shift of curcumin in various concentrations of CTAB, SDS and TX100 was determined as the difference between absorption and emission maxima obtained from the corrected spectra on the wavenumber scale [41,42]. The plot of Stokes' shift versus surfactant concentration offered three different kinds of change, respectively, for cationic (CTAB), anionic (SDS) and neutral (TX100) surfactant solutions.…”