COLLABORATION IN BASIC SCIENCE AND ENGINEERING (COBASE)

Quintus Fernando hosted Laila Mosina of Russia for two weeks in April 1999. The particular interest of this group was in studying the exchange interactions of binuclear copper (II) chelates of amide-based cyclophanes and the subsequent correlation of exchange interactions with the structure of these complexes. During her visit to the U.S., Mosina was able to perform measurements to determine the dependence of the EPR spectra intensities on temperature for three binuclear Cu(II) complexes: Cu2(bis-edtapdn), Cu2(bis-edtanap) and Cu2(bis-edtabpe) in a temperature range from 4 to 77K. A manuscript that describes and discusses all of their experimental findings is in the last stage of preparation and is to be submitted to Applied Magnetic Resonance. The visit by Mosina was very successful in several respects. First, the binuclear nature of the investigated copper(II) chelates has been confirmed by EPR and ESE measurements. Second it was shown that all these compounds have weak exchange interaction (compared with operational X-band frequency), and third, the magnitude of these interactions has been determined and shown to be dependent on the nature of bridging group. Fernando feels that the next steps in this research are threefold. They should consist of (1) correlation of the structure of the investigated compounds with the determined values of the exchange interaction, (2) complete simulations of EPR spectra that include evaluated values of the exchange interaction and the hyperfine interaction, and (3) additional pulsed ESEEM and ELDOR experiments to obtain more detailed information on the mutual arrangement of Cu centers in binuclear complexes relative to each other. Fernando and Mosina think that these objectives will lead to a proposal that would be appropriate for submission to NSF.