Electrochemically Controlled Multistability of Ultrathin Films of Double-Decker Lanthanides Phthalocyanines

Molecular-scale systems that exhibit intramolecular electron transfer (IET) induced by various external stimuli occupy a special place among the systems whose behaviour is determined by charge transfer processes. Such redox-isomeric materials are indeed promising for applications in the development of nanoscale information storage devices. Complexes in which both metal and ligand are redox-active are target objects for the study of redox isomerism phenomenon (reversible intramolecular metal−ligand electron transfer). From this standpoint, tetrapyrrole complexes of metals with variable oxidation states are one of the most promising compounds. Lanthanides phthalocyaninates proved to be very promising objects for the development of “molecular switches” and memory devices.

Herein, we report on the electrochemical properties of Langmuir-Blodgett films of series of lanthanides complexes with bis-tetra-15-crown-5-phthalocyanines^1,2. A previously unknown phenomenon of orientation-induced redox isomerism in a Langmuir monolayer is revealed in the case of cerium bis-[tetra-(15-crown-5)-phthalocyaninate] – (Ce[(15C5)₄Pc]₂)^3,4 (Fig.1). The mechanism of genuine redox isomerism was confirmed by the results of in-situUV-Vis spectral measurements performed on monolayers and Langmuir-Blodgett films, AFM, and XPS studies of Langmuir-Blodgett films transferred at different surface pressures. The understanding of this reversible IET mechanism is especially important due to possible applications of such redox-isomeric systems in the development of nanoscale multibit information storage devices.

1.         Selector, S. L.; Arslanov, V. V.; Gorbunova, Y. G.; Raitman, O. A.; Sheinina, L. S.; Birin, K. P.; Tsivadze, A. Y. Journal of Porphyrins and Phthalocyanines 2008, 12, 1154.

2.         Selector, S. L.; Shokurov, A. V; Arslanov, V. V; Gorbunova, Y. G.; Raitman, O. A.; Isakova, A. A.; Birin, K. P.; Tsivadze, A. Y. Rus. J. of Electrochemistry 2012, 48, 218.

3.         Selektor, S. L.; Shokurov, A. V.; Raitman, O. A.; Sheinina, L. S.; Arslanov, V. V.; Birin, K. P.; Gorbunova, Y. G.; Tsivadze, A. Y. Colloid J. 2012, 74, 334.

4.         Selektor, S.L.; Shokurov, A.V.; Arslanov, V.V.; Gorbunova, Y.G.; Birin, K.P.; Raitman, O.A.; Morote, F.; Cohen-Bouhacina, T.; Grauby-Heywang, Ch.; Tsivadze, A.Yu. J. Phys. Chem. C.,    2014, 118, 4250.