The optical and electrochemical properties of novel double-decker cerium bis-tetra-15-crown-5-phthalocyaninate [ Ce ( R 4 Pc 2−)2]0 (R4Pc2− = [4,5,4',5',4",5",4'",5'"-tetrakis-(1,4,7,10,13-pentaoxapentadecamethylene)-phthalocyaninate-anion]) Langmuir-Blodgett and cast films were investigated. The particular feature of cerium ion in complex with tetra-15-crown-5-phthalocyanine is the stability of oxidation state +4 unlike other lanthanide metal centers. Cyclic voltammetry curves exhibited three stable redox states in the Langmuir-Blodgett and cast films. Redox processes in Langmuir-Blodgett films are reversible and reproducible at multiple scan procedures. The mechanisms of redox transformations in Langmuir-Blodgett films are suggested. We demonstrated that the well-defined structure of Langmuir-Blodgett film is essential for fast electron transfer within the planar system, in which the charge is delocalized along the conjugated assembly of uniformly ordered stacks of discotic crown-phthalocyaninate. Fast charge relaxation was observed in highly ordered Langmuir-Blodgett film whereas the electrochemically written redox states remained unchanged in unordered cast film. The combination of electrochemistry with surface plasmon resonance spectroscopy allowed us to demonstrate that stepwise change of potential in the range 200-850 mV induced the respective optical response, which can be observed as the change in resonance angle value. High-speed response and reversibility of the switching process between stable states may be utilized as the basis for switchable optoelectronic devices. Electrochemical multistability of cerium crown-phthalocyaninate provided a basis for developing a simple strategy to fabricate nanoelectromechanical systems with high efficiency and fast response. Our approach relies on the modulation of the distance between decks in a complex stack via redox-controlled change of metal center size that results in change of linear dimensions of the stacks. The reported results are valuable, not only because of their potential applications, for instance, in OFET and MEMS fabrication, but also from a fundamental point of view since they illustrate the interplay between the orientation of stacks bearing discotic aromatic molecules and charge transfer within such a planar assembly.

The spectral, electrochemical, and optical properties of Langmuir-Blodgett films (LBFs) and cast films from a solution of new double decker cerium bis[tetra (15 crown 5) phthalocyaninate] (Ce(R 4 Pc) 2 ) are studied. Based on analysis of compression isotherms and quantum chemical calculations, schemes of the organization of Ce(R 4 Pc) 2 molecules at different states of its monolayers are proposed. Cor relation dependences are determined in order to relate the optical and electrochemical characteristics of monolayers and LBFs of sandwich type lanthanide phthalocyaninates to the ionic radii of their metal centers. The valent state of Ce ions in a monolayer forming complex is determined, and a sequence of redox trans formations occurring in LBF uppon appliance of a potential is proposed, one of the transformations being associated with the Ce 3+ /Ce 4+ redox transition. Orientation induced intramolecular electron transfer is revealed in the planar supramolecular system. It is shown that, during the formation of a monolayer from a Ce(R 4 Pc) 2 solution, a tetravalent metal center passes to a trivalent state. Monolayer compression to a high surface pressure reverts the complex to the electronic state typical of the solution. The reversible transforma tions observed upon the monolayer compression result from intramolecular electron transfer from the 4f orbital of Ce to the phthalocyanine ring and backwards. The high operation rate and the reversibility of switching between the stable states, which are determined by means of the surface plasmon resonance tech nique, upon a stepwise change in the electrode potential within the range of 200-850 mV may underlie the development of optoelectronic systems. With a large number of molecules in a stacking aggregate, changes in the distance between the decks of the complex that occur with changes in the oxidation level of the metal cen ter can substantially modulate the sizes of molecular ensembles. A supramolecular device capable of perform ing mechanical work can be developed based on this effect.

The behaviors of monolayers of novolac and diglycidyl ether of bisphenol A type epoxy oligomers on the surface of water were studied. Using a surface balance technique and FT-IR spectroscopy, it was found that the time evolution of surface pressure and surface area of the monolayers is controlled by the chemcial reactions of these oligomers with water and carbon dioxide. The specific reactivity of epoxy oligomers in a one-layer organized system at the air-water interface (in bulk similar reactions may proceed only under severe conditions) is enabled by the increased concentration and the mobility of protons in a thin layer of water adjacent to the monolayer and by the basicity of the epoxy groups of the oligomers. Surface reactions of epoxy oligomers are shown to be topochemical in nature; the kinetics of these reactions may be described by the Avrami-Erofeev equation. The magnitudes of the parameters of this equation which were determined for the monolayers of each of the oligomers lead to the conclusion that, generally, the dynamics of epoxy oligomer monolayers is controlled by chemical transformations in and rearrangement of the surface layer.

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