MMCT energy change in cyanidometal-bridged trinuclear complexes by changing the ligand electron donating ability?

New Journal of Chemistry Pub Date: 2023-03-14 DOI: 10.1039/D2NJ06104J

Abstract

To investigate the effect of metal-to-metal charge transfer (MMCT) in the complexes of cyanidometal-bridges, we synthesized and fully characterized a series of trimetallic cyanidometal-bridged compounds with the formula trans-[CpMexFe–NC–Ru(L)4–CN–FeCpMex][PF6]2, N2+[PF6]2 (L = i-PrPy, N = 1, x = 0; N = 2, x = 1; N = 3, x = 3; N = 4, x = 4; N = 5, x = 5), and their one-electron and two-electron oxidized products N3+[PF6]3 and N4+[PF6]4. Electrochemical measurements show the presence of electronic interactions between the two terminal Fe units. As methyl substituents on the Cp ligands increase, the change trend of the MMCT energy from the remote terminal FeII to FeIII in complexes N3+ is not obvious, which may be due to the increase in the electron-donating ability of the Cp ligands on both the terminals, electron-donating FeII and electron-accepting FeIII ions, while the MMCT energy from the neighboring RuII to the terminal FeIII in complexes N4+ decreases, strongly supported by the TDDFT calculations. All the mixed-valence compounds N3+ and N4+ belong to Class II systems.

Graphical abstract: MMCT energy change in cyanidometal-bridged trinuclear complexes by changing the ligand electron donating ability
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