Metal–Metal Electronic Coupling in syn and anti Stereoisomers of Mixed‐Valent (FeCp)₂‐, (RhL₂)₂‐, and (FeCp)(RhL₂)‐as‐Indacenediide Ions

Abstract

The extent of metal-metal electronic coupling was quantified for a series of syn and anti stereoisomers of (FeCp)(2)-, (RhL(2))(2)- and (FeCp)(RhL(2))- (L(2)=1,5-cyclooctadiene (cod), L=CO) as-indacenediide mixed-valent ions by spectroelectrochemical and DFT studies. The effect of the syn/anti orientation of the metal units with respect to the planar aromatic ligand indicates that electron transfer occurs through the bridge rather than through space. The nature of the metal was found to be crucial: while homobimetallic diiron species are localised valence-trapped ions (Class II), the dirhodium analogues are almost delocalised mixed-valent ions (borderline and Class III). Finally, despite their redox asymmetry, even in the heterobimetallic iron-rhodium as-indacenediide complexes, strong metal-metal coupling is present. In fact, oxidation of the iron centre is accompanied by electron transfer from rhodium to iron and formation of a reactive 17-electron rhodium site. syn and anti Fe-Rh as-indacenediide complexes are rare examples of heterobimetallic systems which can be classified as borderline Class II/Class III species.

Charge‐Transfer Interactions in Tris‐Donor–Tris‐Acceptor Hexaarylbenzene Redox Chromophores

“…[Bu 4 N][BA C H T U N G T R E N N U N G (C 6 F 5 ) 4 ] was prepared according to a literature procedure [35] from Li[BA C H T U N G T R E N N U N G (C 6 F 5 ) 4 ] [36] and recovered by recrystallization in n-hexane/ CH 2 Cl 2 after use.…”

Electronically Strongly Coupled Divinylheterocyclic‐Bridged Diruthenium Complexes

“…[40] This view is also in accord with the high overall absorptivities and the rathers harpa bsorptions with full-width-at-half-maximum( FWHM)v alues Dṽ 1/2 of smaller than 2000cm À1 and the lack of ab and shift on changings olvent polarity. [95,96] Within the framework of the un-derlyingH ush formalism, the electronic coupling strength H ab , which is am easureo ft he energetic splitting between the two adiabatic states, assumes values ranging from 4800t o 6100 cm À1 (H ab = ṽ max /2). [95,97,98] We note that an increasei nH ab is here paralleled by an increase in the redox splitting DE8', which is an intuitively satisfying result.…”

Density functional theory studies on the structures and electronic communication of meso-ferrocenylporphyrins: Long range orbital coupling via porphyrin core

“…The LACVP(d) basis set [34,35], which is a combination of the 6-31G(d) basis set for C/H/N with the LanL2DZ effective core basis set for Fe, was chosen. The B3LYP functional method with LACVP(d) basis set is proved suitable for geometry optimizations of porphyrins [17][18][19][20] and ferrocenyl-containing systems [28,29]. The Berny algorithm using redundant internal coordinates [36] was employed in energy minimization and the default cutoffs were used throughout.…”

“…This, however, has not yet been confirmed from the point of theoretical investigation because of the lack of theoretical calculations in this regard. On the other hand, density functional theory (DFT) and time dependant density functional theory (TD-DFT) methods have proved suitable for the calculation of the energy-minimized structures, electronic distribution, molecular orbitals, electron transfer, and electronic absorption spectra of a series of porphyrin and phthalocyanine derivatives [17][18][19][20][21][22][23] as well as ferrocene derivatives [24][25][26][27][28][29]. As a consequence, towards understanding the long range electronic coupling between ferrocenyl groups connected via porphyrin framework, theoretical studies over multi-component compounds composed of porphyrin and ferrocenyl units appear interesting.…”