AN ELECTRON-SPIN-RESONANCE (ESR) AND SIMULTANEOUS ELECTROCHEMICAL AND ELECTRON-SPIN-RESONANCE (SEESR) SPECTROSCOPIC STUDY OF MOTION, STABILITY AND POTENTIAL CONTROLLED RELEASE OF RADICAL GUESTS FROM THE BETA-CYCLODEXTRIN INCLUSION POLYMER

The influence of molecular inclusion and separation of radical guests inside the amorphous beta-cyclodextrin host polymer (beta-CDP) matrices on the motion and stability as well as controlled potential release of radicals was studied by electron spin resonance spectroscopy (ESR) and simultaneous electrochemistry and electron spin resonance (SEESR) spectroscopy. A pronounced restriction of rotational motion was observed for the included stable protonated form of the 4-amino-2,2,6,6-tetramethylpiperidine-1-oxyl (4-amino-TEMPO) free radical and a partial restriction of motion of the N,N,N',N'-tetramethyl-1,4-phenylenediamine (TMPD.+) radical (generated ex situ by controlled potential electrolysis), while virtually no restriction was found in the case of the methyl (MV.+) and heptyl viologen (HV.+) monocation radicals as well as of the 2-nitrotoluene anion radical (2NT.-). The MV.+, HV.+ and 2NT.- unstable radicals were electrochemically generated inside the beta-CDP film coat at a Pt flag electrode. The rate of the open-circuit decay of the included unstable radicals was markedly decreased as compared with their decay at the bare electrode. It was also found that the extent of inclusion of alkyl viologens was governed by their ionic charge, i.e. the higher the charge of the ion the weaker its inclusion.