Fluorescence Quenching in J-Aggregates through the Formation of Unusual Metastable Dimers

Abstract

Molecular aggregation alters the optical properties of a system as fluorescence may be activated or quenched. This is usually described within the well-established framework of H- and J-aggregates. While H-aggregates show nonfluorescent blueshifted absorption bands with respect to the isolated monomer, J-aggregates are fluorescent displaying a redshifted peak. In this publication, we employ a combined approach of experiment and theory to study the complex aggregation features and photophysical properties of diaminodicyanoquinone derivatives, which show unusual and puzzling nonfluorescent redshifted absorption bands upon aggregation. Our theoretical analysis demonstrates that stable aggregates do not account for the experimental observations. Instead, we propose an unprecedented mechanism involving metastable dimeric species formed from stable dimers to generate nonfluorescent J-aggregates. These results represent a novel kind of aggregation-induced optical effect and may have broad implications for the photophysics of dye aggregates.

Enhancement of Fluorescence Emission Intensity in a Sulfonyl Hydrazide Derivative of tri(biphenyl‐4‐yl)amine via Solid‐state Grinding with Various Metal Salts: Combined Experimental and Computational Studies

“…The reason behind the almost no emission in the pristine TBA‐THZ may be the H‐aggregation or strong H‐bonding interactions contributed to the lower emission. However, in the literature, H‐aggregates with enhanced emission [50] and colloidal aggregates in J‐aggregates form showed quenching of emission [51] Diaminodicyanoquinone forms metastable J‐aggregate dimers in solution and showed quenching in emission intensity [52] . In the present case, the TBA‐THZ is in dimeric form, as shown in Figures S25a–e.…”

The Interplay of Weakly Coordinating Anions and the Mechanical Bond: A Systematic Study of the Explicit Influence of Counterions on the Properties of (Pseudo)rotaxanes

“…Energy decomposition analysis based on the fragment molecular orbital method (FMO-EDA) [ 37 , 38 ] can be used to obtain a qualitative idea of the inter-component interactions [ 61 ] in A1@TTFC8 and A1 @TTFC8 , thus, providing insight into the mechanical bonds. Stronger dispersion interactions upon rotaxane formation are almost fully counterbalanced by an increase in exchange interactions , while the electrostatic contribution remains virtually the same ( Table 3 ).…”

Synthesis and Characterization of Novel Thienothiadiazole-Based D−π–A−π–D Fluorophores as Potential NIR Imaging Agents

“…The excited-state lifetimes for the TTD-HexT-Cbz and TTD-T-Cbz nanoparticles were extended compared to the unencapsulated fluorophores. This is due to the stabilization of the excited-state species within an aggregated environment …”

“…This is due to the stabilization of the excited-state species within an aggregated environment. 60 DLS analysis of the encapsulated fluorophores indicates that the two fluorophores aggregate differently upon encapsulation (Supporting Information, Table S2). The TTD-T-Cbz nanoparticles gave larger average hydrodynamic radii than the TTD-HexT-Cbz nanoparticles.…”