Dipolar second-order nonlinear optical chromophores containing ferrocene, octamethylferrocene, and ruthenocene donors and strong π-acceptors: crystal structures and comparison of ;r-donor strengths

Tiffany L. Kinnibrugh, Seyhan Salman, Yulia A. Getmanenko, Veaceslav Coropceanu, William W. Porter, Tatiana V. Timofeeva, Adam J. Matzger, Jean Luc Brédas, Seth R. Marder, Stephen Barlow

Research output: Contribution to journalArticlepeer-review

38 Scopus citations

Abstract

Crystal structures have been determined for six dipolar polyene chromophores with metaiiocenyi ferrocenyl (Fc), octamethylferroeenyl (Fc ), or ruthenocenyl (Rc)-donors and strong heterocyclic acceptors based on l,3-diethyl-2-thiobarbituric acid or 3-dicyanomethylidene-2,3- dihydrobenzothiophene-l,l-dioxide. In each case, crystals were found to belong to centrosymmetric space groups. For one example, polymer-induced heteronucleation revealed the existence of two additional forms, which were inactive in second-harmonic generation, suggesting that they were also centrosymmetric. The bond-length alternations between the formally double and single bonds of the polyene bridges are reduced compared to simple polyenes, indicating significant contribution from charge-separated resonance structures, although the metallocenes are not significantly distorted toward the [(η 6-fulvene)(η 5-eyelopentadienyl)metal(II)] + extreme. DFT geometries are in excellent agreement with those determined crystallographically; while the π-donor strengths of the three metaiiocenyi groups are insufficiently different to result in detectable differences in the crystallographic bond-length alternations, the DFT geometries, as well as DFT calculations of partial charges for atoms, suggest that π-donor strength decreases in the order Fc ≫ Fc > Rc. NMR, IR, and electrochemical evidence also suggests that octamethylferroeenyl is the stronger TT-donor, exhibiting similar π-donor strength to a p-(dialkylamino)phenyl group, while ferrocenyl and ruthenocenyl show very similar π-donor strengths to one another in chromophores of this type.

Original languageEnglish (US)
Pages (from-to)1350-1357
Number of pages8
JournalOrganometallics
Volume28
Issue number5
DOIs
StatePublished - Mar 9 2009
Externally publishedYes

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Organic Chemistry
  • Inorganic Chemistry

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