Group 17 elements charge-transfer complexes

Safin, D.K. and Chmutova, G.A. (1985) Solvation effects in complexation reactions, n. Sol-vatochromism and the nature of absorption bands in the electronic spectra of charge-transfer complexes between iodine and Group VIA element-containing organic compounds. Zh. Ob-shch. Khim., 55, 2564-2572. 

Metalloporphyrins containing low valent main group elements show hyper-type UV-visible spectra and the corresponding higher valent complexes show normal spectra. Despite this, the phosphorus complexes [P(OEP)R2] show spectra with distinctly hyper character, with two extra Soret bands apparent. The extra Soret band in hyper complexes has been assigned to charge transfer from the low... 

The impact of nucleophilic and electrophilic groups of the active center on the substrate at the contact area in the enzyme-substrate complex (the effect of synchronous intramolecular catalysis). The polyfunctional catalysis involves a great many processes push-pull mechanisms, processes involving a relay charge transfer, as well as a general acid-base catalysis. Presumably, the enzyme in the initial state of the enzymatic reaction already contains structural elements of the transition state and in this case the reaction must be thermodynamically more advantageous. 

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