Solvent and media effects on the photophysics of cranad-2 and cranad-58

[Display omitted] •CRANAD-2 and CRANAD-58 show intramolecular charge transfer phenomena, resulting in an increase of the dipole moment of the excited singlet sate.•The interaction of the first excited singlet state of CRANAD-2 and CRANAD-58 with polar solvents induces a redshift in the emission spectra and originates non-radiative deactivation pathways, leading to a significant reduction in fluorescence quantum yield.•In non-polar environments, the emission of CRANAD-2 and CRANAD-58 is notably enhanced, causing a blue shift in fluorescence maxima in non-polar media and microheterogeneous systems characterized by negatively or positively charged interphases, as well as non-charged interphases.•The practical utilization of these probes in “in vivo” experiments performed in cellular media may be constrained due to their fast association with charged or non-charged molecular microstructures.•Although CRANAD-2 and CRANAD-58 demonstrate promising potential for detecting Aβ species, their interaction with micro-organized systems within complicated biological environments could introduce complexities, thus potentially limiting their practical application in in vivo experiments. Alzheimer’s disease (AD) represents the most widespread form of age-related cognitive degeneration, characterized by long-term degenerative damage, cognitive dysfunction, and profound deficits in logical thinking, knowledge acquisition, and interpersonal communication. A principal biomarker of AD involves the emergence and aggregation of β-amyloid (Aβ). Cranad derivatives are fluorescent probes capable of detecting, quantifying, and imaging Aβ aggregates. In this work, the effect of solvent and microheterogeneous environments on the photophysical behavior of CRANAD-2 and CRANAD-58 was investigated employing a large solvent set and several microorganized systems. Both the absorption and fluorescence spectra exhibit a substantial solvatochromic effect, resulting in significant Stokes shifts. Application of linear solvation energy relationships to correlate the fluorescence spectra maxima and the Stokes shift with microscopic solvent parameters suggests significant intramolecular charge transfer during the excitation, as corroborated by the increased dipole moment in the excited state. Generally, fluorescence quantum yields determined for CRANAD-2 exceed those of CRANAD-58 in most solvents, with low values in polar solvents and bigger values in non-polar solvents. Introduction of CRANAD-2 and