The majority of dyes belong to the chromophoric class known as donor-acceptor systems, the essential structural feature of such systems being the presence of one or more electron donating groups conjugated to one or more electron withdrawing groups vi...
The majority of dyes belong to the chromophoric class known as donor-acceptor systems, the essential structural feature of such systems being the presence of one or more electron donating groups conjugated to one or more electron withdrawing groups via an unsaturated bridge. Visible light absorption is then associated with the migration of electron density from the donor region of the molecule to the acceptor region. H-Chromophores is a special type of donor-acceptor system, and can be regarded as made up of two cross-conjugated donor-acceptor systems sharing a common conjugating bridge. Several new H-chromophore systems were synthesised with a view to examining there colour properties, pH sensitivity and redox behaviour. This could be reversed by air-oxidised, suggesting that these chromophores could be useful as colour formers.