Long-wavelength absorbing fluorescent polymethine dyes derived from the 6-(N,N-diethylamino)-1,2,3,4-tetrahydroxanthylium system

Add time:09/08/2019    Source:sciencedirect.com

Several new dyes derivatives of the “rhodamine-like” 6-(N,N-diethylamino)-1,2,3,4-tetrahydroxanthylium heterocyclic system displaying absorption within the near-infrared were synthesized. The photochemical behaviour of these molecules was evaluated in dichloromethane, regarding their ground state absorption properties, fluorescence emission quantum yields and fluorescence lifetimes determinations. The singlet oxygen quantum yields of the new dyes were also obtained. The absorption and luminescence spectral data showed that the behaviour of these dyes is strongly dependant on the nature of the (hetero)aromatic substituent introduced in the 1,2,3,4-tetrahydroxanthylium scaffold. The performed quantum-chemical calculations indicated that those (hetero)aromatic terminal substituents are practically planar and hence are conjugated with the chromophoric system of the 1,2,3,4-tetrahydroxanthylium framework. Such elongation of total π-system is accompanied by regular delocalization of the frontier MOs and decreasing of the first electron transition energy manifested itself by bathochromic effect in dyes absorption.

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