Heptametallic, Octupolar Nonlinear Optical Chromophores with Six Ferrocenyl Substituents. Issue 21 (27th March 2013)

• Record Type: Journal Article
• Authors: Coe, Benjamin J.; Foxon, Simon P.; Helliwell, Madeleine; Rusanova, Daniela; Brunschwig, Bruce S.; Clays, Koen; Depotter, Griet; Nyk, Marcin; Samoc, Marek; Wawrzynczyk, Dominika; Garín, Javier; Orduna, Jesús
• Is Part Of: Chemistry. Volume 19:Issue 21(2013)
• Page Start: 6613
• Page End: 6629
• Publication Date: 2013-03-27
• Subjects: Chemistry -- Periodicals; 540
• DOI: 10.1002/chem.201204453
• Languages: English
• ISSNs: 0947-6539

Abstract

<abstract abstract-type="main" xml:lang="en"> <title>Abstract</title> <p>New complexes with six ferrocenyl (Fc) groups connected to Zn^II or Cd^II tris(2, 2′‐bipyridyl) cores are described. A thorough characterisation of their BPh₄⁻ salts includes two single‐crystal X‐ray structures, highly unusual for such species with multiple, extended substituents. Intense, visible d(Fe^II)→π* metal‐to‐ligand charge‐transfer (MLCT) bands accompany the π→π* intraligand charge‐transfer absorptions in the near UV region. Each complex shows a single, fully reversible Fe^III/II wave when probed electrochemically. Molecular quadratic nonlinear optical (NLO) responses are determined by using hyper‐Rayleigh scattering and Stark spectroscopy. The latter gives static first hyperpolarisabilities <italic>β</italic>₀ reaching as high as approximately 10⁻²⁷ esu and generally increasing with π‐conjugation extension. Z‐scan cubic NLO measurements reveal high two‐photon absorption cross‐sections <italic>σ</italic>₂ of up to 5400 GM in one case. DFT calculations reproduce the π‐conjugation dependence of <italic>β</italic>₀, and TD‐DFT predicts three transitions close in energy contributing to the MLCT bands. The lowest energy transition has octupolar character, whereas the other two are degenerate and dipolar in nature.</p> </abstract>