Dipolar and V-shaped structures incorporating methylenepyran and diazine fragments

Thirteen novel dipolar and V-shaped chromophores with pyranylidene electron-donating part, diazine electron-withdrawing part and various π-linkers were synthesized. The extent of intramolecular charge transfer, structure-property relationships and optical properties were further investigated by UV/Vis absorption, electrochemistry, and DFT calculations.     

Methylenepyran based dipolar and quadrupolar dyes: synthesis,electrochemical and photochemical properties

This paper presents the synthesis of a series of push–pull and quadrupolar π-conjugated structures incorporating pro-aromatic methylenepyran electron-donor groups and various electron-attracting groups. Some of the methylenepyran derivatives were oxidized by I₂ to give, after reduction by Na₂S₂O₃, bismethylenepyran compounds via successive steps.