Influence of the Sign of Solvatochromism of Merocyanines on their Photoelectric Properties in Polymer Films

Holographic Recording Media Based on Systems with Intramolecular and Intermolecular Charge Transfer

“…We studied holographic recording media based on poly( N -epoxypropylcarbazole) (PEPK) films doped with organic compounds of the three aforementioned types: (1) PEPK + 1 mol % 2,4,7-trinitro-9-fluorenone (TNF) acceptor; (2) PEPK + 1 mol % ICTC (compounds 1 and 2), in which the carbazole donor group is covalently linked by the polymethylene spacer bridge to the polynitro-9-phenylmethylidenefluorenone acceptor unit; and (3) PEPK + 1 mol % ICTC (compounds 3, 4 [6], 5 [7]), in which the donor group D (isomeric 1,3-and 1,2-dithiols and 3 H-indolinylidene, respectively) and the acceptor group A (tetranitro-9-fluorene and dicyano group) are in conjugation with one another and, hence, their electronic structure is mesomeric between the main resonance structures (3a-3c; 4a-4c; 5a, 5b). The structural formulas of PEPK and TNF molecules and compounds 1-5 are presented below: Compounds 1 (9-[4-(3-carbazol-9-yl-2-hydroxypropyloxy)benzylidene]-2,5,7-trinitro-4-methoxyfluorene) and 2 (9-[4-(3-carbazol-9-yl-2-hydroxypropyloxy)benzylidene]-2,4,5,7-tetranitro-4-methoxyfluorene) were prepared by condensation of 9-(3-p -formylphenoxy-2-hydroxypropyl)carbazole with corresponding nitrofluorenes in dimethylformamide followed by their precipitation with 2-propanol, isolation, and treatment with the same solvent upon heating.…”

“…The charge transfer can occur by three main ways: intermolecularly to form the adduct (D…A) between the donor (D) and the acceptor (A) called charge transfer complex (CTC) [2], intramolecularly upon covalent linking of D and A by a spacer groups of atoms [2,5,6], and intramolecularly over the system of π conjugated bonds provided that conjugation between D and A exists [7,8]. The latter two types of compound are briefly named intramolecular charge transfer compounds (ICTC) [5].…”