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Mix and (Mis)match: further studies of the electronic structure and mixed-valence characteristics of 1,4-diethynylbenzene-bridged bimetallic complexes

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Abstract

The 1,4-diethynylbenzene motif is commonly employed as a bridging ligand in bimetallic molecular systems intended to show pronounced intramolecular electronic interactions, delocalized electronic structures and ‘wire-like’ properties between the metal fragments at the ligand termini. In contrast to these expectations, the donor–acceptor compounds [{Cp′(CO)xM′}(μ-C[triple bond, length as m-dash]CC6H4C[triple bond, length as m-dash]C){M(PP)Cp′}]n+ [n = 0, 1; M′(CO)xCp′ = Fe(CO)2Cp, W(CO)3Cp*; M(PP)Cp′ = Fe(dppe)Cp, Fe(dppe)Cp*, Ru(PPh3)2Cp, Ru(dppe)Cp, Ru(dppe)Cp*] display remarkably little bridge-mediated electronic interaction between the electron-rich {M(PP)Cp′} and electron-poor {M′(CO)xCp′} fragments in the ground state. However, a relatively high-energy (26 000–30 000 cm−1) M-to-M′ charge transfer can be identified. One-electron oxidation is largely localized on the {M(C[triple bond, length as m-dash]CR)(PP)Cp′} fragment and gives rise to a new charge transfer band with bridging-ligand-to-{M(PP)Cp′}+ (M′(CO)xCp′ = Fe(CO)2Cp) or M′-to-M(+) (M(CO)xCp′ = W(CO)3Cp*) character. The localized electronic ground state of these complexes is better revealed through analysis of the IR spectra, taking advantage of the well-resolved ν(C[triple bond, length as m-dash]C) and ν(CO) bands and IR spectroelectrochemical methods, than through the more classical analysis based on the concepts of Marcus–Hush theory and analysis of the putative IVCT electronic transition. The conclusions are supported by DFT calculations using the BLYP35 functional.

Graphical abstract: Mix and (Mis)match: further studies of the electronic structure and mixed-valence characteristics of 1,4-diethynylbenzene-bridged bimetallic complexes

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Supplementary files

Article information


Submitted
19 May 2020
Accepted
24 Jun 2020
First published
26 Jun 2020

Dalton Trans., 2020, Advance Article
Article type
Paper

Mix and (Mis)match: further studies of the electronic structure and mixed-valence characteristics of 1,4-diethynylbenzene-bridged bimetallic complexes

P. Safari, S. A. Moggach and P. J. Low, Dalton Trans., 2020, Advance Article , DOI: 10.1039/D0DT01794A

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