Pavlenko O. Physical properties and mechanisms of intermolecular interaction in π-conjugated nanosystems

The work deals with systematical study of the structure and properties of π-conjugated molecules with different topology without interaction between them, as well as in the complexes based on them and manifestations of the interaction in the condensed state. For linear π-conjugated molecules on the example of neutral polymethine squarain, merocyanine dyes and their bases in low-concentrated solutions, where the interaction between the molecules can be neglected, it is shown that the spectra of these molecules are sensitive to the type and location of heteroatoms, donor-acceptor functional groups in the π-branched electronic system. Quantum-mechanical analysis of charge distribution in one-dimensional π-electron systems at injection of 1-5 charge carriers, in particular for the elongated linear and broadened polymethine chains was performed and the formation of soliton-like waves was shown. The formation of dye-based films leads to shift of the absorption maximum compared to the spectra in solution, due to the aggregation of molecules, which depends on the charge distribution in their chromophores. The broadening of the absorption spectra of dyes in films in comparison with the spectra in solutions is the result of molecular interaction, namely the formation of aggregates of different types. The dye interacting with fullerenes in films and solutions causes the electronic structure rearrangement, which manifests itself in new spectral effects. Ability of fullerene to form stable - complexes with biologically active compounds - derivatives of 1,3-oxazole containing donor -acceptor substituents is considered basing on the spectral and quantum-chemical analysis. For antitumor solutions of doxorubicin as well as gemcitabine containing π-conjugated fragments with albumin, complexation is observed as a result of the addition of drug molecules to aromatic aminoacids. The calculated doxorubicin binding constants decrease under conjugation of the molecules with gold nanoparticles. The obtained results can be applied in the creation of active elements for bionanotechnology and nanoelectronics.