A series of diverse binuclear and mononuclear cyclometalated palladium(ii) complexes of different structure was investigated by electrochemical techniques combined with density functional theory (DFT) calculations. The studies including cyclic and differential pulse voltammetry, X-ray structure analysis and quantum chemical calculations revealed a regularity of the complexes oxidation potential on the metal-metal distance in the complexes: the larger Pd-Pd distance, the higher oxidation potentials. The reduction potentials feature unusually high negative values while no correlation depending on the structure could be observed. These results are in a good agreement with the electron density distribution in the complexes. Additionally, ESR data obtained for the complexes upon oxidation is reported.

Quantum chemical modeling in combination with vibrational and electronic absorption spectroscopy has delivered detailed information about supramolecular organization of azochromophore 4-amino-4′-nitroazobenzene (DO3), its solutions, and blends with poly(methyl methacrylate) (PMMA) polymer of various concentrations. It is shown that the neat chromophore contains both antistacked forms and hydrogen bonded associations of the "head-to-tail" type, while separate DO3 molecules dominate in diluted solutions of DO3 in chloroform. In PMMA/DO3 films with low concentrations of the chromophore, DO3 is mainly Hbonded to CO moieties of PMMA matrix, while in the blends with high concentrations of DO3 molecules, the latter form hydrogen bonds both with PMMA and with each other. Infrared, Raman, and UV−vis spectroscopic markers of isolated DO3 molecules and various modes of their supramolecular associations are revealed.

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Here, the synthesis, characterization, and photovoltaic properties of four new donor-acceptor copolymers are reported. These copolymers are based on 4,4-difl uoro-cyclopenta[2,1-b:3,4-b′] dithiophene as an acceptor unit and various donor moieties: 4,4-dialkyl derivatives of 4H-cyclopenta[2,1-b:3,4-b′]dithiophene and its silicon analog, dithieno[3,2-b:2′,3′-d]-silol. These copolymers have an almost identical bandgap of 1.7 eV and have a HOMO energy level that varies from −5.34 to −5.73 eV. DSC and X-ray diffraction (XRD) investigations reveal that linear octyl substituents promote the formation of ordered layered structures, while branched 2-ethylhexyl substituents lead to amorphous materials. Polymer solar cells based on these copolymers as donor and PC 61 BM as acceptor components yield a power conversion effi ciency of 2.4%.

Structure and nonlinear optical properties of small clusters formed of organic chromophores through H-bonding are studied by the example of dimer and trimer of p-nitroaniline (PNA). The analysis of the electron charge density pattern in the bonding region in terms of "Atoms in Molecules" approach is performed, and the values of electron charge density, Laplacian of electron density at critical points, etc. are determined. Topological analysis has given evidence of the existence of three-center interaction of one amino group hydrogen with oxygens of nitro group of the neighboring PNA, resulting in two H-bond formation. Solvent effect on the static (hyper)polarizability of the clusters is studied by the example of PNA dimer in acetone in the framework of conventional Polarizable Continuum Model as well as supermolecule and semicontinuum approaches. The essential increase of the cluster hyperpolarizability in comparison with that of a single chromophore is obtained. The account of specific interaction with the solvent molecule is shown to result in moderate or significant enhancement of ␤ ʈ depending on the structure of the formed cluster.