Effective Singlet Oxygen Sensitizers Based on the Phenazine Skeleton as Efficient Light Absorbers in Dye Photoinitiating Systems for Radical Polymerization of Acrylates.

A series of dyes based on the phenazine skeleton were synthesized. They differed in the number of conjugated double bonds, the arrangement of aromatic rings (linear and/or angular system), as well as the number and position of nitrogen atoms in the molecule. These compounds were investigated as potential singlet oxygen sensitizers and visible light absorbers in dye photoinitiating systems for radical polymerization.

New type of bonding formed from an overlap between pi aromatic and pi C=O molecular orbitals stabilizes the coexistence in one molecule of the ionic and neutral meso-ionic forms of imidazopyridine.

New bis(imidazo)pyridine dye has been synthesized and tested as a potential photoinitaitor for free-radical polymerization induced with the visible emission of an argon ion laser. The X-ray analysis based on data collected at 170 and 130 K, as well as density functional theory (DFT) calculations, revealed the presence of two different forms of imidazopyridine rings within the same molecule. These two forms of the same moiety had not only different geometries but different electronic structures as well.

Relationship between structure and photoinitiating abilities of selected bromide salts of 2-oxo-2,3-dihydro-1H-imidazo[1,2-a]pyridine (IMP): influence of the solvent and the substitution in benzaldehyde on the course of its reaction with IMP.

2-Oxo-2,3-dihydro-1H-imidazo[1,2-a]pyridinium bromide and its C3-substituted derivatives have been synthesized and structurally characterized by X-ray crystallography and quantum chemical calculations. Their potential as photoinitiators for free-radical polymerization has been investigated experimentally and compared with theoretical results. It has been established that the course of the reaction that introduces the substituted benzylidene group to the imidazole ring is different in the protic and dipolar aprotic solvents, and also depends on the character of the substituent, as the energy change in the reaction favours either R1R2C=CHR3 or R1R2CH-CH(OCH3)R3 formation.