TY - JOUR

T1 - Aggregation-Caused quenching or Aggregation-Induced (Enhanced) Emission? The Decisive role of aggregation in solvents and their mixtures

AU - Fan, Haiyan

AU - Nurtay, Lazzat

AU - Safronov, Nikita E.

AU - Slepukhin, Pavel A.

AU - Belskaya, Nataliya P.

AU - Benassi, Enrico

N1 - HF thanks Nazarbayev University Faculty-Development Competitive Research Grants Programme with grants ID 11022021FD2928. The XRD analyses were carried out using equipment of the Center for Joint Use \u201CSpectroscopy and Analysis of Organic Compounds\u201D at the Postovsky Institute of Organic Synthesis of the Russian Academy of Sciences (Ural Branch) according scientific theme 124020200072-0. Computational resources were kindly provided by Shabyt HPCC at Nazarbayev University. The authors thank the facilities and technicians in Core facilities at Nazarbayev University.

PY - 2025/9/1

Y1 - 2025/9/1

N2 - An enhancement in the fluorescence quantum yield (FQY) of DMSO solutions of two carboxamide-based fluorophores — viz. 2-(4-methoxyphenyl)-5-amino-2H-1,2,3-triazole-4-carboxamide with piperidine (BSN1) and methylamino groups (BSN2) at the fifth position — upon the addition of water has been previously reported in the literature. Although the FQYs of BSN1 and BSN2 exhibited different trends as a function of water content, the dilution effect was attributed to the aggregation-induced enhanced emission (AIEE) phenomenon. However, either BSN1 or BSN2, in their solid phases, do not show fluorescence, suggesting the presence of aggregation-caused quenching (ACQ). Building on the molecular-level insights into the DMSO-water binary system from the prior study, the current work aims to clarify the origin of the AIEE phenomenon by investigating the intermolecular interactions between fluorophore molecules and between the fluorophores and the solvent. Vibrational spectroscopy and quantum mechanical calculations revealed that hydrogen bonds were formed between two dye molecules, between a dye molecule and a DMSO trimer, and among the dye molecule, DMSO trimer, and water. These interactions induced segregation, as evidenced by scanning electron microscopy (SEM) images, leading to an increase in FQY. Nevertheless, due to subtle structural differences between the two dyes, the morphological changes with varying water content exhibited different trends for BSN1 and BSN2, as reflected in UV–Visible spectroscopy and SEM. This work demonstrates that the increase in FQY upon adding water is not a monolithic characteristic of AIEE.

AB - An enhancement in the fluorescence quantum yield (FQY) of DMSO solutions of two carboxamide-based fluorophores — viz. 2-(4-methoxyphenyl)-5-amino-2H-1,2,3-triazole-4-carboxamide with piperidine (BSN1) and methylamino groups (BSN2) at the fifth position — upon the addition of water has been previously reported in the literature. Although the FQYs of BSN1 and BSN2 exhibited different trends as a function of water content, the dilution effect was attributed to the aggregation-induced enhanced emission (AIEE) phenomenon. However, either BSN1 or BSN2, in their solid phases, do not show fluorescence, suggesting the presence of aggregation-caused quenching (ACQ). Building on the molecular-level insights into the DMSO-water binary system from the prior study, the current work aims to clarify the origin of the AIEE phenomenon by investigating the intermolecular interactions between fluorophore molecules and between the fluorophores and the solvent. Vibrational spectroscopy and quantum mechanical calculations revealed that hydrogen bonds were formed between two dye molecules, between a dye molecule and a DMSO trimer, and among the dye molecule, DMSO trimer, and water. These interactions induced segregation, as evidenced by scanning electron microscopy (SEM) images, leading to an increase in FQY. Nevertheless, due to subtle structural differences between the two dyes, the morphological changes with varying water content exhibited different trends for BSN1 and BSN2, as reflected in UV–Visible spectroscopy and SEM. This work demonstrates that the increase in FQY upon adding water is not a monolithic characteristic of AIEE.

KW - Aggregation Induced Enhanced Emission (AIEE)

KW - Carboxamide-based fluorophores

KW - DMSO-water binary mixture

KW - Intermolecular interactions

KW - Solvent effects

UR - https://www.mendeley.com/catalogue/2233f624-ddee-38b0-bac2-e0d727f402b7/

UR - https://www.scopus.com/record/display.uri?eid=2-s2.0-105007225479&origin=inward&txGid=f5b9a696b603414d3c492f1dad7a63c7

U2 - 10.1016/j.molliq.2025.127901

DO - 10.1016/j.molliq.2025.127901

M3 - Article

VL - 433

JO - Journal of Molecular Liquids

JF - Journal of Molecular Liquids

SN - 0167-7322

M1 - 127901

ER -