Novel symmetrical and unsymmetrical squaraine dyes were synthesized by condensation of  electron-rich 3,5-dihydroxyanilines and 3-ethylbenzothiazoles with squaric acid, producing symmetrical 2,4-bis[4-(N,N-dialkylamino)-2,6-dihydroxy-phenyl]squaraine derivatives and unsymmetrical (Z)-4-(4-(4-(decyloxycarbonyl)pipeidinium-1-ylidene)-2,6-dihydroxycyclohexa-2,5-dienylidene-2-((3-ethylbenzo[d]thiazol-2(3H)-ylidene)methyl)squaraine analogs. Comprehensive photophysical characterization by UV-vis absorption, steady-state fluorescence emission, fluorescence quantum yields, fluorescence lifetimes, and two-photon absorption (2PA) spectra are reported. Studies of photophysical properties as well as aggregation behavior in solutions of varying polarity and the stability of those aggregates upon perturbation of the solution environment with nucleophilic and/or host guest-assembly substrates, along with comparative studies of how branching affects self-assembly were conducted. In this work select symmetrical and unsymmetrical squaraines have demonstrated the possibility of forming H- and/or J-aggregates in solution. A possible application for these dyes is their use as lipophilic probes for two-photon fluorescence microscopy (2PFM) imaging of cell membranes.

Photophysical characterization and aggregation properties of symmetrical and unsymmetrical donor-acceptor-donor squaraine derivatives

245th National Meeting (2013)

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