title: Design, synthesis, and structural and spectroscopic studies of push-pull two-photon absorbing chromophores with acceptor groups of varying strength.
abstract: A new series of unsymmetrical diphenylaminofluorene-based chromophores with various strong π-electron acceptors were synthesized and fully characterized. The systematic alteration of the structural design facilitated the investigation of effects such as molecular symmetry and strength of electron-donating and/or -withdrawing termini have on optical nonlinearity. In order to determine the electronic and geometrical properties of the novel compounds, a thorough investigation was carried out by a combination of linear and nonlinear spectroscopic techniques, single-crystal X-ray diffraction, and quantum chemical calculations. Finally, on the basis of two-photon absorption (2PA) cross sections, the general trend for π-electron accepting ability, i.e., ability to accept charge transfer from diphenylamine was: 2-pyran-4-ylidene malononitrile (pyranone) > dicyanovinyl > bis(dicyanomethylidene)indane >1-(thiophen-2-yl)propenone > dicyanoethylenyl >3-(thiophen-2-yl)propenone. An analogue with the 2-pyran-4-ylidene malononitrile acceptor group exhibited a nearly 3-fold enhancement of the 2PA cross section (1650 GM at 840 nm), relative to other members of the series.
authors.affiliation: Department of Chemistry, University of Central Florida, Orlando, Florida 32816-2366, USA.
authors.forename: Alma R
authors.initials: AR
authors.lastname: Morales
authors.forename: Andrew
authors.initials: A
authors.lastname: Frazer
authors.forename: Adam W
authors.initials: AW
authors.lastname: Woodward
authors.forename: Hyo-Yang
authors.initials: HY
authors.lastname: Ahn-White
authors.forename: Alexandr
authors.initials: A
authors.lastname: Fonari
authors.forename: Paul
authors.initials: P
authors.lastname: Tongwa
authors.forename: Tatiana
authors.initials: T
authors.lastname: Timofeeva
authors.forename: Kevin D
authors.initials: KD
authors.lastname: Belfield
mesh_terms: D000042:Absorption; D018360:Crystallography, X-Ray; D009570:Nitriles / Q000138:chemical synthesis* / Q000737:chemistry*; D017785:Photons; D011714:Pyrans / Q000138:chemical synthesis* / Q000737:chemistry*; D011789:Quantum Theory; D013050:Spectrometry, Fluorescence; D014961:X-Ray Diffraction
chemical_list: D009570:Nitriles; D011714:Pyrans