Two-dimensional Arrays of Amphiphilic Zn2+ -cyclens for Guided Molecular Recognition at Interfaces

The sterically guided molecular recognition of nucleobases, phosphates, adenosine, and uridine nucleotides on Langmuir monolayers and Langmuir-Blodgett monolayers of amphiphilic mono- or bis(Zn2+-cyclen)s assembled on thiolated surfaces was investigated. The stepwise selective binding of metal ions, uracil, or phosphate by dicetyl cyclen monolayers with variously tuned structures at the air/water interface was corroborated by the measurements of the corresponding LB films deposited onto quartz crystals. Two types of recognition surfaces were fabricated from Zn2+-dicetyl cyclen. The surface covered with a complex preformed in the Langmuir monolayer was capable both of imide and of phosphate binding. The similar complex formed directly in an LB film on thiolated gold was inactive with respect to imide. The surface plasmon resonance measurements evidenced the stepwise assembly of complementary nucleotides on SAM/LB templates through consecutive phosphate-Zn2+-cyclen coordination. Base pairing between nucleotides resulted in a formation of A-U bilayers comprising two complementary monolayers. Finally, we report on SAM/LB patterns designed for divalent molecular recognition of uridine phosphate by amphiphilic bis(Zn2+-cyclen)

Orientation-Induced Redox Isomerism in Planar Supramolecular Systems

In this work, a previously undescribed 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). It was established that intramolecular electron transfer (IET) from the electronic system of phthalocyanine to the 4f-orbital of cerium atom occurs upon spreading of a (Ce[(15C5)4Pc]2) chloroform solution onto the air?water interface (3D -> 2D IET). This process is related to the transformation of Ce4+ cation in the solution to Ce3+ in the monolayer. It was also found that reversible Ce3+ Ce4+ IETs occur upon compression (π1 -> π2) and expansion (π2 -> π1) of monolayer (2Dπ1 2Dπ2 IET, π-surface pressure). The mechanism of genuine redox isomerism was confirmed by the results of in situ UV?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