Heptametallic,Octupolar Nonlinear Optical Chromophores with Six Ferrocenyl Substituents |
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| Authors: | Dr Benjamin J Coe Dr Simon P Foxon Dr Madeleine Helliwell Dr Daniela Rusanova Dr Bruce S Brunschwig Prof?Dr Koen Clays Griet Depotter Dr Marcin Nyk Prof?Dr Marek Samoc Dominika Wawrzynczyk Prof?Dr Javier Garín Dr Jesús Orduna |
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| Institution: | 1. School of Chemistry, University of Manchester, Oxford Road, Manchester M13 9PL (UK), Fax: (+44)?161‐275‐4598;2. Molecular Materials Research Center, Beckman Institute, MC 139‐74, California Institute of Technology, 1200 East California Boulevard, Pasadena, California 91125 (USA);3. Department of Chemistry, University of Leuven, Celestijnenlaan 200D, 3001 Leuven (Belgium);4. Institute of Physical and Theoretical Chemistry, Wroc?aw University of Technology, Wybrze?e Wyspiańskiego 27, 50‐370 Wroc?aw (Poland);5. Departamento de Química Orgánica, ICMA, Universidad de Zaragoza‐CSIC, E‐50009 Zaragoza (Spain) |
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| Abstract: | New complexes with six ferrocenyl (Fc) groups connected to ZnII or CdII 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(FeII)→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 FeIII/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 β0 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 σ2 of up to 5400 GM in one case. DFT calculations reproduce the π‐conjugation dependence of β0, 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. |
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| Keywords: | chromophores coordination compounds density functional calculations ferrocenyl derivatives nonlinear optics |
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