Chalcogenopyrylium dyes

Fig. 2 Reductive elimination of halogens from chalcogenopyrylium dyes 6-11 containing tellurium(IV) dihalide groups. 

Fig. 27 Two-electron reductions of cationic chalcogenopyrylium dyes with tellurium(IV) atoms in the 7r-framework.

In a spectral UV-VIS study of a series of chalcogenopyrylium dyes it has been shown that the aromaticity of the heterocycles decreases with the size of the chalcogen, whereas the bathochromic effect increases from the oxygen to tellurium [7], The aromaticity index based on data from experimentally determined bond lengths, which yield statistically evaluated bond orders, has been proposed and applied to neutral and ionic five-membered selenaheterocycles. A reasonable parallel also exists between the aromaticity index and resonance energies [37],... 

Seleno- and telluro-containing chalcogenopyrylium dyes can be promising, as singlet-oxygen-producing photosensitizers, in photodynamic therapy (Section V). 

Recently, a new class of ultra sensitive, NIR RRMs—2-thienyl-substituted chalcogenopyrylium dye—was synthesized (Harmsen et al. 2015b). The 2-thienyl... 

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