Fluorescence and photostability studies of anthracene‐9‐carboxylic acid in different media

Abstract

Electronic absorption and fluorescence spectra of anthracene-9-carboxylic acid (ANCA) were studied in different homogeneous solvents, binary protic/aprotic solvent mixtures and in heterogeneous solutions of the cationic cetyltrimethyl ammonium bromide (CTAB) micelle. Different chemical species of ANCA were identified spectroscopically in different media. The results are discussed on the basis of a mechanism that involves two equilibria: acid-base equilibrium and monomer-dimer equilibrium. These equilibria were found to be very sensitive to the nature of the medium and the concentration of ANCA.Moreover, while it is photostable in most solvents studied, the ANCA was found to be photolabile in aqueous media of different pHs. The acid-base catalyzed photodegradation rate was studied by following up absorption and/or fluorescence intensities as a function of illumination dose. The determined rate of the photochemical degradation of ANCA depends on the nature of the medium. The first order degradation rate constant is remarkably enhanced in heterogeneous medium of CTAB. As expected, the determined activation energy is low (∼3.2 kJ.mol-1). This result favors photooxidation process. Anthraquinone was the main photodegradation product obtainedvia9,9′-dicarboxylic head-to-head dimer of anthracene that was identified by GC-Mass technique.

The polarity sensitivity factor of some fluorescent probe molecules used for studying supramolecular systems and other heterogeneous environments

“…[61][62][63][64][65] This is a highly complex molecule in aqueous solution, as it not only establishes an acid-base equilibrium, but it has also been shown in the literature that significant dimerization occurs, with the dimer having significantly different fluorescence properties than the monomer. [61][62][63] Photodimerization has also been shown to occur. 64 Ten of the probes studied showed the more common fluorescence polarity sensitivity of exhibiting increased intensity upon decrease in polarity (PSF > 1).…”

Morphology‐Dependent Luminescence and Optical Waveguide Property in Large‐Size Organic Charge Transfer Cocrystals with Anisotropic Spatial Distribution of Transition Dipole Moment

“…As shown in Figure J, Raman vibration wavenumber of the CN (at 2238 cm −1 ) in cocrystal is lower than that in 9AC. The 9AC single crystal gives lighter blue emission (425–625 nm, Figure S5, Supporting Information and Figure K), which is assigned to the hydrogen‐bonded dimer of 9AC . The fluorescent emission bands of 9AC‐TCNB cocrystals display significant redshifts (500–800 nm) relative to the 9AC crystal.…”

Metal Organic Framework Micro/Nanopillars of Cu(BTC)·3H2O and Zn(ADC)·DMSO

“…The peak in the solution is from the ADC monomer. The emission profiles observed in the powder are attributed to the excimer of ADC, which is common for solid state of polyaromatic hydrocarbons [ 30 , 31 , 32 ]. This 46 nm red-shift from solution to the powder state is attributed to J-aggregation of the anthracene molecules due to π–π stacking [ 31 ].…”