No abstract

www.rsc.org/ ab Ruthenium(II) tetra-15-crown-5-phthalocyaninate with axially coordinated molecules of pyrazine [(15C5)4Pc]Ru (pyz)2 (1) was synthesized from carbonyl complex [(15C5)4Pc]Ru(CO)(MeOH) (2),and the structure of the solvate complex (1)·6CHCl3 was revealed by the single crystal X-ray diffraction method. Analysis of crystal packing shows the essential role of weak intermolecular interactions, such as CH…π, CH…N, CH…O and CH…Cl, in the formation of stable assemblies and their organization within the crystals. The interplay between the intramolecular axial coordinated pyrazine contacts and weak intermolecular interactions of solvate molecules with crown-ether fragments provides the basis for rationalizing the observed self-assembling of molecules in solutions of tetrachloroethane and polymeric composites with polyvinylcarbazole. The self-assembling was investigated by means of UV-Vis spectroscopy, dynamic light scattering measurements, AFM and TEM techniques. The formation of nanoparticles of complex (1) from a tetrachloroethane solution after three cycles of heating to 70°C/cooling to 5°C and 2-days storage was proved. Thin films (7 µm) of polymeric composites with polyvinylcarbazole prepared from solution containing nanoparticles exhibit nonlinear optical response measured by the Z-scan technique with application of femtosecond (1030 nm) and nanosecond (1064 nm) pulse lasers.The measured third-order susceptibility (χ (3) ) of the polyvinylcarbazole composite with 4 wt% of complex (1) is equal to 1.94×10 -10 esu, while the same composite prepared without the above-described special treatment has zero susceptibility.This result proves the essential role of self-assembling in further development of nonlinear optical materials.

The spectral and electrochemical properties of Langmuir-Blodgett (LB) films of homoleptic double decker cerium bis [tetra 15 crown 5] phthalocyaninate Ce [R 4 Pc] 2 and its heteroleptic analog [Pc]Ce[R 4 Pc] were studied. It was shown that during formation of Langmuir monolayers upon contact of both complexes solutions with water subphase the metal center with valent state IV in the solution transforms into one with the valent state III in the monolayer. Upon cyclic compression expansion of these monolayers, orientation induced reversible intramolecular transfers of electron from 4f orbital of cerium ion to the phth alocyanine macrocycle (compression) and in reverse direction (expansion) occur in a planar supramolecular system. Scheme of reversible electrochemical transformations occurring in ultrathin films of double decker cerium crown phthalocyaninates, one of which is associated with the Ce +3 /Ce +4 redox transition of metal center of the complex, was proposed and substantiated using the results of spectro electrochemical investi gations. It was shown that one of these transformations is associated with the Ce +3 /Ce +4 redox transition of metal center of the complex and upon change of metal center oxidation state its size changes, and, conse quently, the distance between the decks of the complex also changes. This change in the distance can lead to a substantial (13-15%) modulation of the linear size of molecular assemblies with a large number of mole cules in stack. On the basis of this effect the supramolecular device that can perform mechanical work can be developed. Using surface plasmon resonance technique we have demonstrated that a step change in electrode potential in region of 200-1000 mV induces a corresponding optical response reflected in a step change of the resonance angle. High operation speed and reversibility of switching between stable states can serve as a basis for development of optoelectronic switching systems.

No abstract