Using Langmuir and Langmuir-Blodgett techniques molecular films of chlorinated perylene derivatives, namely tetra-n-butyl-1,6,7,12-tetrachloroperylene-3,4,9,10-tetracarboxylate (PCn for n = 1, 5, 9) have been studied. The Langmuir films of pure compounds and mixed with liquid crystalline 4-octyl-4′-cyanobiphenyl (8CB) were characterized by surface pressure-mean molecular area isotherms. An additive rule reveals miscibility of all the dyes with 8CB but shows different types of intermolecular interaction forces. The pure and mixed Langmuir films were transferred onto quartz plates and characterized spectroscopically. Absorption and fluorescence spectra were recorded for the samples in form of diluted chloroform solution, the dye with 8CB mixtures in monomolecular Langmuir-Blodgett films and in liquid crystal cells. Different tendency to aggregation of the dye with short and long alkyl chains was observed. It is shown that the dye molecule stacking and aggregation of the chlorinated perylene dyes depend on the dye concentration and are related to the torsion of the perylene core.
To study the influence of structural features of phthalocyanine (Pc) derivatives on their physico-chemical properties in bulk and thin films, 23 new phthalocyanines with different quantity and ratio of donor (alkyloxy-groups, in fragment “A”) and acceptor (Cl-, in fragment “B”) substituents in one molecule of the A3B, ABAB and AABB types with varied length of alkyloxy-substituents and their metal complexes were designed and synthesized. A comparative analysis of spectral, mesomorphic and photoelectric properties of these mix-substituted phthalocyanines of a “push–pull” type was performed. It was shown that non-peripheral substitution by alkyloxy-fragments in hetero-substituted Pcs (similar to homo-substituted Pc) leads to red-shifting of the Q-band into near-IR region. The intensity of photoluminescence, position of peaks and their splitting are strongly connected with chemical structure of Pcs and the type of solvent. In contrast to non-mesogenic octyloxy-Pc (A4) having alkyloxy-substituents in non-peripheral positions, 22 of 23 synthesized compounds possess columnar mesomorphism. The change of donor–acceptor ratio can influence the type of mesophase. A new approach to the creation of materials for optoelectronics is proposed and implemented, which includes design of compounds possessing vitrification from mesophase with maintenance of a columnar order, absorption in the near IR-region of the spectrum and good performance electrophysical characteristics simultaneously.