Bis(4-nitroanilines) in interactions through a π-conjugated bridge: conformational effects and potential molecular switches. (18th September 2017)

• Record Type: Journal Article
• Authors: Guerrero, Tomás; Santillan, Rosa; García-Ortega, Héctor; Morales-Saavedra, Omar G.; Farfán, Norberto; Lacroix, Pascal G.
• Is Part Of: New journal of chemistry. Volume 41:Number 20(2017)
• Page Start: 11881
• Page End: 11890
• Publication Date: 2017-09-18
• Subjects: Chemistry -- Periodicals; Chimie -- Périodiques; 540
• DOI: 10.1039/c7nj02622f
• Languages: English
• ISSNs: 1144-0546

Abstract

Abstract : DFT computation suggests that two dipolar chromophores in rotation around an organic bridge could be aligned by an electric field. Abstract : Two molecules, 2, 2′-(1, 4-phenylenebis(ethyne-2, 1-diyl))bis(4-nitroaniline) (PNA ) and 2, 2′-(1, 4-phenylene-bis(ethyne-2, 1-diyl))bis( N, N -diethyl-4-nitroaniline) (PDNA ), built up from two p -nitroaniline " push–pull " nonlinear optical (NLO) chromophores slightly conjugated through a 1, 4-phenylenebis(ethyne-2, 1-diyl) bridge have been synthesized and fully characterized. The crystal structure ofPNA reveals that the ground (off) state conformation corresponds to the centrosymmetric anti-conformer in which the molecular hyperpolarizability ( β ) is equal to zero. A computational investigation reveals that, once submitted to an intense electric field ( E ), the two p -nitroaniline subunits are gradually aligned in the direction of the field with the appearance of a metastable (on) state ( β ≠ 0, when E = 0), stabilized by conjugation. A loop of hysteresis is observed during the on ⇋ off cycles leading to a form of molecular bistability. The NLO response ofPNA has been investigated at different field intensities by the electric-field induced second-harmonic (EFISH) technique to provide experimental evidence for this behavior.