The effect of polyaromatic hydrocarbons on the spectral and photophysical properties of diaryl-pyrrole derivatives: an experimental and theoretical study

Abstract

A new class of diaryl-pyrrole derivatives of the polyaromatic hydrocarbons (PAH) benzene, naphthalene, anthracene and pyrene were synthesized in a multicomponent reaction under microwave irradiation and studied in solution at room (293 K) and low (77 K) temperature. The study includes a complete spectroscopic evaluation (singlet-singlet and triplet-triplet absorption, fluorescence and phosphorescence spectra) as well as photophysical evaluation (fluorescence, phosphorescence and triplet lifetimes together with fluorescence and triplet occupation and singlet oxygen sensitization quantum yields). From the above evaluation, a complete set of deactivation rate constants (kF, kIC and kISC) could be obtained. The study was further complemented with TDDFT calculations. It is shown that, with the exception of the anthracene derivative, the diaryl-pyrrole moiety strongly influences the spectral and photophysical properties of the PAH and that with the exception of the benzene derivative, the excited state internal conversion deactivation channel of the diaryl-pyrrole derivatives is higher than that of the PAH counterparts.

A novel non-fluorescent excited state intramolecular proton transfer phenomenon induced by intramolecular hydrogen bonds: an experimental and theoretical investigation

“…The occurrence of a cross between S 1 and T 2 is at approximately 1.5 Å to 1.6 Å, which corresponds to the coordinate of the S 1 keto* state, i.e., the ISC process occurs between the S 1 and T 2 states. Therefore, combined with the non-fluorescent excitation to the S 1 state, we concluded that the relaxation pathway of HP after ESIPT is the ISC process from the S 1 keto* to the T 2 state 29 30 31 . Comparing with the results of Weller’s 28 , we can find that both HP and MS have two stable equilibrium geometries after Frank-Condon transition to the S 1 state.…”

Supramolecular Anchoring of Octahedral Molybdenum Clusters onto Graphene and Their Synergies in Photocatalytic Water Reduction

“…Deactivation of the pyrene-group triplet state by the cluster core was confirmed by monitoring the decrease of the pyrene-group triplet state (420 nm) with the sequential addition of small volumes of a stock solution of Cs 2 Mo to a solution of PyBr (see Figure S15 for temporal profiles). We propose two possible reaction paths in the ET mechanism within the Py 2 Mo complex, by taking the energy positioning of cluster orbitals, calculated from the absorption and redox data of [Mo 6 I i 8 (OCOC 2 F 5 ) a 6 ] 2– (see section IV for details about calculations) and the pyrene orbitals. ,− In both paths, the increase of the cluster unit phosphorescence at 675 nm could be attributed to a combination of ET and intersystem crossing (ISC) processes, ensuring that the energy migrates from the pyrene group and the {Mo 6 I i 8 } 4+ -cluster-core-localized singlet excited states to the 3 MMCT state of the cluster unit. Upon excitation in the UV region, regarding the first mechanism proposed (blue line, Scheme ), the pyrene group S 1 excited state transfers the absorbed energy to the molybdenum cluster S 1 excited state, and the remaining energy is lost by fluorescence relaxation.…”

Dehydrative Substitution Reaction in Water for the Preparation of Unsymmetrically Substituted Triarylmethanes: Synthesis, Aggregation‐Enhanced Emission, and Mechanofluorochromism

“…Triarylmethane scaffold belongs to the category of polyaromatic hydrocarbons (PAH) which possess high intrinsic chemical and thermal stabilities as well as interesting photophysical properties in the solution state. [43,[66][67][68][69] However, the strong π-π interactions existing between the electron-rich aromatic rings of the PAHs are held responsible for the emission quenching in the aggregated or solid states. Solid-state emission is a much appealing property with remarkable applications in optoelectronics, biosensors, imaging, etc.…”