Symmetrical and asymmetrical (multi)branched truxene compounds: Structure and photophysical properties

A series of symmetrical and asymmetrical (multi)branched truxene derivatives have been synthesized by incorporating different π-conjugated functional groups to truxene. Linear absorption and single- and two-photon excited fluorescence properties of the obtained compounds were examined. The spectral data combining the results of theoretical calculation and the X-ray crystal structures demonstrate that the intramolecular charge transfer of the C3-symmetric truxene-core compounds keep independence of every branch and shifts site-to-site upon excitation. The asymmetric molecule SN behaves the intramolecular excitation transfer between more than two energy levels, which maybe different from the symmetric ones. Meanwhile, the C3-symmetric octupolar conformation and the C(sp2) = C(sp2) π-linker are effective structural pattern for two-photon absorption compounds.

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► Several symmetrical and asymmetrical truxene derivatives have been synthesized.
► Their photophysical properties and the X-ray crystal structures were explored.
► The results indicated that the symmetric dyes behaved a site-to-site charge shift.
► However, the asymmetrical dye was different from the symmetrical ones.