Intramolecular Optical Electron Transfer in Mixed-Valent Dinuclear Iron−Ruthenium Complexes Featuring a 1,4-Diethynylaryl Spacer

Abstract

The ground-state electronic structure and the lowest-lying excited states of the cationic mixed-valent dinuclear complexes [(η2-dppe)(η5-C5Me5)Fe[CC-1,4-(C6H4)CC]Ru(η2-dppe)2(X)][PF6] (X = Cl, 2; X = CC(4-C6H4NO2), 5) are discussed, with particular emphasis on the photoinduced intramolecular electron transfer between the ruthenium and iron centers. The location and intensities of the low-lying absorptions exhibited in the near-infrared (near-IR) range by these heterodinuclear mixed-valent (MV) complexes correlate with predictions based on the Hush model, strongly suggesting that they correspond to intervalence charge-transfer (IVCT) bands.

Electron‐Rich Iron/Ruthenium Arylalkynyl Complexes for Third‐Order Nonlinear Optics: Redox‐Switching between Three States

“…[8] As previously discussed, the first oxidation at À0.23 V and the second oxidation at 0.42 V correspond to the oxidation of the Fe II and Ru II centers, respectively. The Fe III /Fe II redox potentials suggest that replacement of the chloro ligand at Ru II by the phenylethynyl and eventually the 4-nitrophenylethynyl ligand is apparently not "sensed" by the Fe II center.…”

“…More recently, with 2 + and the extended analogue 3-NO 2 + (Scheme 2), we demonstrated that strong electronic coupling exists in these Fe III / Ru II heterobinuclear compounds, which are new examples of nonsymmetrical mixedvalent (MV) complexes. [8] In this contribution, we report the synthesis and characterization of a new analogue (3-H) of these compounds as well as an extended hexanuclear Fe/Ru complex (4) containing three such units assembled in a C 3v fashion around a central phenyl core; the latter is a logical extension to previous studies designed to enhance the magnitude of the thirdorder NLO response (Scheme 2). We also disclose our complete results concerning the linear and nonlinear optical properties of these four redox families of heteropolynuclear compounds.…”

“…The extended compound 4 was obtained by a similar synthetic protocol to that previously used to synthesize 2, [8] that is, by reaction of the known Ru II trinuclear complex 1 a [11] with a five-fold excess of the organoiron complex 5 (Scheme 4). [12] The complex was purified by extraction and successive washings with n-pentane.…”

“…Isolation and characterization of the mono-oxidized state of 3-H: In a similar manner to that previously described for 2- [8] the mono-oxidized compound 3-H-A C H T U N G T R E N N U N G [PF 6 ] was isolated by using the corresponding ferrocenium salt as an oxidant (Scheme 5). As expected, 3-HA C H T U N G T R E N N U N G [PF 6 ] exhibits a similar cyclic voltammogram to that of its neutral parent 3-H, but infrared spectroscopy clearly reveals its mono-oxidized structure.…”

[Fp*Fc][PF6]: A remarkable non-symmetric dinuclear cation in a very stable mixed-valent state

“…Due to its insensitivity to substituent effects in 1a-c, the less intense transition detected near 380 nm is attributed to the (forbidden) LF transition at the origin of the photo-ejection of one carbonyl ligand (when 2 or 1a-c are employed as photocatalysts), [1,23] while that at somewhat higher energy, near 350 nm, probably corresponds to an (allowed) dFe  *CO Following a classic approach, [37] we have therefore deconvoluted this IVCT band (A) into its Gaussian components (Figure 2b) and used eqs 3-4, 3 based on Hush theory for unsymmetrical class-II MV complexes, to derive the electronic coupling (see Supporting Information section for details). [15,3 In these equations, max, ῡmax and ῡ1/2 are the extinction coefficient, the energy of the maximum and the halfwidth of the IVCT band, respectively, while G 0 is the energy difference between the MV isomers (A and B).…”