biostudies-literatureLapesova JEuropean Research CouncilMinisterstvo ?kolstv?, Ml?de?e a Telov?chovyGrantov? Agentura, Univerzita Karlova25077-25088https://www.ebi.ac.uk/biostudies/studies/S-EPMC12754792biostudies-literatureUnknown64(51)Azaphthalocyanines are fluorescent dyes and photosensitizers with promising applications in photodynamic therapy (PDT) and fluorescence sensing. However, achieving precise control over their photophysical behavior remains a major challenge. Here, we report a supramolecular approach to enhance fluorescence quenching via charge-transfer complex formation. An electron-deficient azaphthalocyanine derivative incorporating a naphthalene-2,6-diol moiety as a charge-transfer donor was synthesized, and its fluorescence response toward a tailored quencher was evaluated. A ferrocene-methylviologen conjugate that simultaneously functions as a quencher and an acceptor in charge-transfer complexes was designed and synthesized for this purpose. Compared to ferrocenemethanol and methylviologen alone, the conjugate quencher exhibited an enhanced quenching efficiency in acetonitrile. The quenching followed a nonlinear Stern-Volmer dependence, indicating both static and dynamic quenching mechanisms, with the former one being more efficient with <i>K</i>_S = 241 M^-1 due to directed charge-transfer complex formation between methylviologen and the naphthalene-2,6-diol moiety serving as a staple. These findings demonstrate that complexation can enhance the fluorescence quenching of AzaPc derivatives and suggest a general approach for designing responsive photosensitizers in smart PDT systems or molecular sensing.Inorganic chemistryEnhanced Quenching in an Azaphthalocyanine-Ferrocene Supramolecular Dyad upon Charge-Transfer Complex Formation.PMC12754792170223101041554LL2318CZ.02.01.01/00/22_008/0004607Slanina TLudvikova LDemuth JZimcik PNovakova VLapesova JfalseEnhanced Quenching in an Azaphthalocyanine-Ferrocene Supramolecular Dyad upon Charge-Transfer Complex Formation.Azaphthalocyanines are fluorescent dyes and photosensitizers with promising applications in photodynamic therapy (PDT) and fluorescence sensing. However, achieving precise control over their photophysical behavior remains a major challenge. Here, we report a supramolecular approach to enhance fluorescence quenching via charge-transfer complex formation. An electron-deficient azaphthalocyanine derivative incorporating a naphthalene-2,6-diol moiety as a charge-transfer donor was synthesized, and its fluorescence response toward a tailored quencher was evaluated. A ferrocene-methylviologen conjugate that simultaneously functions as a quencher and an acceptor in charge-transfer complexes was designed and synthesized for this purpose. Compared to ferrocenemethanol and methylviologen alone, the conjugate quencher exhibited an enhanced quenching efficiency in acetonitrile. The quenching followed a nonlinear Stern-Volmer dependence, indicating both static and dynamic quenching mechanisms, with the former one being more efficient with <i>K</i>_S = 241 M^-1 due to directed charge-transfer complex formation between methylviologen and the naphthalene-2,6-diol moiety serving as a staple. These findings demonstrate that complexation can enhance the fluorescence quenching of AzaPc derivatives and suggest a general approach for designing responsive photosensitizers in smart PDT systems or molecular sensing.2025-01-01T00:00:00Z2025 Dec2026-06-06T08:25:25.11Z2026-05-27T03:11:51.973ZS-EPMC127547924139269310.1021/acs.inorgchem.5c03733