Trans/cis‐Isomerization of Fluorene‐Bridged Azo Chromophore with Significant Two‐Photon Absorbability at Near‐Infrared Wavelength. Issue 12 (7th October 2014)

• Record Type: Journal Article
• Authors: Chu, Chih‐Chien; Chang, Ya‐Chi; Tsai, Bo‐Kai; Lin, Tzu‐Chau; Lin, Ja‐Hon; Hsiao, Vincent K. S.
• Is Part Of: Chemistry, an Asian journal. Volume 9:Issue 12(2014:Dec.)
• Page Start: 3390
• Page End: 3396
• Publication Date: 2014-10-07
• Subjects: Chemistry -- Periodicals; 540.5
• DOI: 10.1002/asia.201402896
• Languages: English
• ISSNs: 1861-4728

Abstract

<abstract abstract-type="main" xml:lang="en"> <title>Abstract</title> <p>Azo‐containing materials have been proven to possess second‐order nonlinear optical (NLO) properties, but their third‐order NLO properties, which involves two‐photon absorption (2PA), has rarely been reported. In this study, we demonstrate a significant 2PA behavior of the novel azo chromophore incorporated with bilateral diphenylaminofluorenes (DPAFs) as a π framework. The electron‐donating DPAF moieties cause a redshifted π–π* absorption band centered at 470 nm, thus allowing efficient blue‐light‐induced <italic>trans</italic>‐to‐<italic>cis</italic> photoisomerization with a rate constant of 2.04×10⁻¹ min⁻¹ at the photostationary state (PSS). The open‐aperture <italic>Z</italic>‐scan technique that adopted a femtosecond (fs) pulse laser as excitation source shows an appreciably higher 2PA cross‐section for the fluorene‐derived azo chromophore than that for common azobenzene dyes at near‐infrared wavelength (<italic>λ</italic>_ex=800 nm). Furthermore, the fs 2PA response is quite uniform regardless of the molecular geometry. On the basis of the computational modeling, the intramolecular charge‐transfer (ICT) process from peripheral diphenylamines to the central azo group through a fluorene π bridge is crucial to this remarkable 2PA behavior.</p> </abstract>