Electrolyte effects on the intervalence transition within discrete binuclear cyano-bridged complexes. An estimation of activation free energy from static, optical and electrochemical data

• Published in: Inorganica Chimica Acta 2006, Vol.359 (1), p.149-158
• Main Authors: Pérez-Tejeda, P., López-Pérez, G., Prado-Gotor, R., Sánchez, F., González-Arjona, D., López-López, M., Bozoglián, F., González, G., Martínez, M.
• Format: Article
• Language: English
• Subjects: Cyano-bridged complexes; Ion-pairing; Marcus–Hush; Static data
• ISSN: 0020-1693; 1873-3255
• DOI: 10.1016/j.ica.2005.09.011

Structure and UV-spectrum of the trans-[L 14Co III(μ-CN)Fe II(CN) 5] − complex. The picture shows experimental (symbols) and simulated (solid lines) data of the characteristic bands for the chromophores Co III and Fe II. The metal to metal charge transfer (MMCT) band is also shown (dashed line). The connection between optical and thermal electron transfer processes allow the estimation of the activation free energy. A study of the metal-to-metal charge-transfer (MMCT) transition within the binuclear cyano-bridged complexes cis-[L 13Co III(μ-NC)Fe II(CN) 5] − (L 13 = 12-methyl-1,4,7,10-tetraazacyclotridecan-12-amine), trans-[L 14Co III(μ-NC)Fe II(CN) 5] − (L 14 = 6-methyl-1,4,8,11-tetraazacyclotetradecan-6-amine) and trans-[L 15Co III(μ-NC)Fe II(CN) 5] − (L 15 = 10-methyl-1,4,8,12-tetraazacyclopentadecan-10-amine) has been carried out in electrolyte solutions at varying concentrations. Using these data, as well as the reaction free energies obtained from electrochemical measurements, the reorganisation and activation free energies for the forward and reverse thermal electron-transfer processes have been estimated. The changes of these parameters with the electrolyte concentration, as well as those of the energy of the maximum MMCT band and the reaction free energy, are mainly due to ion-pairing effects.