Stabilization of the Monovalent Nickel Complex with 1, 4, 8, 11-Tetraazacyclotetradecane in Aqueous Solutions by N- and C-Methylation. An Electrochemical and Pulse Radiolysis Study

Nusrallah Jubran, Gregory Ginzburg, Haim Cohen, Yaacov Koresh, Dan Meyerstein

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Abstract

The divalent nickel complexes with 1, 4, 8, 11-tetraazacyclotetradecane (L1), 1, 4, 8, 11-tetramethyl-l, 4, 8, 11-tetraazacyclotetradecane (L2), meso-5, 7, 7, 12, 14, 14-hexamethyl-l, 4, 8, 11-tetraazacyclotetradecane (L3), and l, 4, 5, 7, 7, 8, 11, 12, 14, 14-decamethyl-l, 4, 8, 11-tetraazacyclotetradecane (L4) were reduced by reactions with eaq-and CO2-and by electrochemical reactions in aqueous solutions. The redox potentials of the NiLi2+/NiLi+couples are -1.58, -1.15, -1.42, and -0.98 V vs. SCE for i = 1, 2, 3, and 4, respectively. The UV absorption bands of NiL, +are attributed to CTTS transitions. The kinetics of reduction of Co(NH3)63+, Ru(NH3)63+, O2, and N2O by NiLi+are reported and discussed. The self-exchange rates of reaction between NiLi+and NiLi2+were calculated by using the Marcus cross relation. The EPR spectra of NiL2+and NiL4+are reported. The complexation of NiLi2+by OH-was studied. The results are discussed in detail. NiL2+and NiL4+are suggested as new, powerful, easily attainable single-electron-reducing agents that can be used over a wide pH range in aqueous solutions.

Original languageEnglish
Pages (from-to)251-258
Number of pages8
JournalInorganic Chemistry
Volume24
Issue number3
DOIs
StatePublished - 1 Jan 1985

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