Electronically-coupled MM quadruply-bonded complexes of molybdenum and tungsten

Malcolm H. Chisholm, Nathan J. Patmore

Research output: Contribution to journalArticle

13 Citations (Scopus)

Abstract

The reaction of M 2(O 2CBu t) 4 (M = Mo, W) with a dicarboxylic acid in toluene yields compounds of general formula [M 2]-O 2C-X-CO 2-[M 2] ([M 2] = M 2(O 2CBu t) 3; X = conjugated spacer). The M 2 units are electronically coupled via interactions between the M 2 δ and dicarboxylate π* orbitals, and the magnitude of this coupling is revealed by electronic structure calculations and spectroscopic data. These compounds show intense metal to ligand charge transfer (MLCT) absorptions in the visible region of the electronic spectrum that are temperature and solvent dependent. Evidence of electronic coupling is seen in their cyclic voltammograms, which show two successive one-electron oxidations. The extent of electronic coupling in the mixed valence radical cations [M 2]-O 2C-X-CO 2-[M 2] +, generated by oxidation with one equivalent of AgPF 6 or FeCp 2PF 6, is evaluated by EPR and UV-vis-NIR spectroscopic data, and delocalized behavior is observed in compounds with W 2 units separated by up to 13.6 Å. The simplicity of the frontier M 2 orbital interactions with the bridge π orbitals provides a convenient system with which to study electron transfer in mixed valence systems, as compared to the extensively studied, but more complicated, dinuclear t 2g 6/t 2g 5 mixed valence compounds. Oligomeric and polymeric compounds incorporating M 2 units have also been synthesized, having general formula [M 2(O 2CR) 2(O 2C-Thio-CO 2)] n (Thio = n-hexyl substituted ter- and quinque-thiophenes). They can be deposited as thin films by spin coating, and show photoluminescence and electroluminescence. These metallo-polythiophenes show potential for application in electronic materials.

Original languageEnglish
Pages (from-to)308-320
Number of pages13
JournalChemical Record
Volume5
Issue number5
DOIs
Publication statusPublished - 12 Oct 2005
Externally publishedYes

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