The Electron Transfer Process in Mixed Valence Compounds with a Low‐lying Energy Bridge in Different Oxidation States

Abstract

Mixed‐valence compounds with the iso‐cyanidometal‐ligand bridge in different oxidation states are used as models for the investigation of the electron‐transfer process. We synthesized a series of trimetallic isocyanidometal‐bridged compounds with [Fe–CN–Ru–NC–Fe]n+ (n=2–4), in which the one‐electron oxidation product (N3+) and two‐electron oxidation product (N4+) compounds possess an isocyanidometal bridge whose energy is, respectively lower and slightly higher than the terminal metal centers energies. For the N3+ compounds, the bridge state (FeII–RuIII–FeII) and mixed‐valence states (FeIII–RuII–FeII or FeII–RuII–FeIII) could be simultaneously observed on the IR timescale. For the N4+ compounds, as the donor becomes stronger the electron transfer bridge excited state (FeIII–RuII–FeIII) becomes more and more stable, and even becomes ground state due to the strong electronic coupling between Fe and Ru.

Effect of potential difference between the central and terminal metals on the electron communication in an Fe–Ru–Fe cyanidometal-bridged mixed valence system

“…27 Cp 1 (dppe)Fe (NCCH 3 )I, Cp 3 (dppe)Fe(NCCH 3 )PF 6 and Cp 4 (dppe)Fe(NCCH 3 ) PF 6 were prepared according to our previous work. 12 All other reagents were available commercially and used without further purification.…”

“…Recently, we have reported a work about adjusting the energy levels of R by changing the methyl substituents of the ligand to facilitate the study of the electron transfer processes of MV compounds with a low-lying B. 12 We found that the methyl substituents significantly affected the electron coupling between the two redox centers, and the MV compounds transitioned from being localized to delocalized.…”

Influence of Changing the Remote Substituents on Charge Transfer Properties of Cyanide‐Bridged Trinuclear Fe−Ru−Fe Complexes

“…These bands can be assigned as the Ru II →Fe III MMCT transition. By comparing the fitting peaks of 1[PF 6 ] 3 , 2[PF 6 ] 3 , 3[PF 6 ] 3 , 1[PF 6 ] 4 , 2[PF 6 ] 4 and 3[PF 6 ] 4 , it can be seen that as the electron donating ability of the remote substituents of the cyanidometal bridging auxiliary ligand increases from tertbutyl, methoxy and then to dimethylamino, the coupling of terminal metal and bridge metal centers become stronger, the energy barrier for hopping electron transfer process becomes lower, making the energy of the MMCT transition decreases [5a] …”

“…Mixedvalence complexes consisted of redox sites are also a classic experimental model for studying electron transfer. [5] A large number of mixed valence compounds with redox sites and electron transfer properties between the sites have been synthesized. [6] Meanwhile, cyanide is often used as a bridging ligand for the synthesis of mixed-valence metal compounds due to its good electron-mediating properties.…”

Diabatic States of Molecules

“…Electronic spectroscopy is usually discussed in terms of the Born–Oppenheimer adiabatic approximation, but simulating molecular dynamical processes involving electronically excited states almost always requires one to go beyond the adiabatic approximation. − In fact, diabatic states provide archetypical interpretations of charge transfer and many kinds of molecular collisions, ,− they provide a framework for modeling curve crossing and conical intersections, and they provide a useful computational basis for many kinds of dynamics calculation. The present Feature Article discusses the pros and cons of simulations with adiabatic and diabatic representations, with the emphasis on the definition, calculation, and usefulness of diabatic states.…”