Pyridine replaces water molecules at the electrode surface the number of removed H2O molecules depends on the orientation of pyridine molecules with respect to the electrode surface. Īdsorption of pyridine, a rigid molecule able to attain various orientations with respect to the metal surface, evidently remains the most studied process of adsorption of organic molecules at the electrodes. It was shown that the rate of the reaction of Ps with iodine bound by pyridine in a comparatively stable complex was only half of the value expected on the basis of the theory of diffusion-controlled reactions, taking into account the changes due to complex formation in the diffusion coefficients. These assumptions were later proved directly, on the example of the formation of the pyridine-iodine charge-transfer complex. An account of the different types of molecular complexes formed with various polymers has been published. The poly(vinyl alcohol)-iodine charge transfer complexes have been the subject of many investigations " Water-soluble iodine complexes with ix)ly(l- vinyl-pyrrolidone) are commercially available as disinfecting agents PoIy(N-vinyl car-bazole) polyamides and poly(ethylene oxide) are also found to form molecular addition complexes with iodine and iodine compounds. It has been identified as being due to a promotion of the HOMO benzene n electron to a a LUMO orbital on iodine resulting in benzene iodine electron transfer. The characteristic 280 nm absorption band of the benzene-iodine system is distinct from any absorption features of neat iodine or benzene.
In solutions this system is the prototypical case of charge transfer as reported by Mulliken. This is the case with the bimolecular benzene iodine charge-transfer complex. ĭirect excitation of electron-transfer states may yield surprising results. Solvation of NI3 NH3 in diethylether in the presence of ammonium iodide yields the ether-soluble charge transfer complex NH3 I2. The equihbria (426) are reversible, and on the side of the ammonia-iodine charge transfer complex. At temperatures below 200 K, red NI3-5NH3 is obtained. The reaction proceeds via ammonia-iodine charge transfer complexes (I2 NH3 and I2 2NH3 are known), to iodamine, diiodamine, and to triiodamine. Īddition of I2 to liquid ammonia at temperatures below 240 K results in the precipitation of green NI3-3NH3. Ma and Wu have carried out SERS studies on pyridine-iodine charge-transfer complex on pc-Ag electrode.
Orientation principle in the benzene-iodine charge-transfer complex (a) S and P Oi (b) jS and = 0. Li-I 2 Li + I2 2 Lil 2.8 0.9 290 soHd electrolyte, 10+ year life welded constmction, used in most of heart pacers, iodine charge transfer complex Medtronic Catalyst WUson Greatbatch.
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