Characterisation of a dipolar chromophore with third-harmonic generation applications in the near-IRElectronic supplementary information (ESI) available: DSC and TGA data for 1 and 2PA spectra for 2 and 3, and calculated dispersions of for 1. CCDC reference number 851132 (1). For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c2jm15599k

• Main Authors: Getmanenko, Yulia A, Hales, Joel M, Balu, Mihaela, Fu, Jie, Zojer, Egbert, Kwon, Ohyun, Mendez, Jeffrey, Thayumanavan, S, Walker, Gregory, Zhang, Qing, Bunge, Scott D, Brdas, Jean-Luc, Hagan, David J, Van Stryland, Eric W, Barlow, Stephen, Marder, Seth R
• Format: Journal Article
• Language: English
• Published: 14.02.2012
• ISSN: 0959-9428; 1364-5501
• DOI: 10.1039/c2jm15599k

E -2-Tricyanovinyl-3- n -hexyl-5-[4-{bis(4- n -butylphenyl)amino}-2-methoxystyryl]-thiophene, 1 , has previously been used to demonstrate applications relying on frequency tripling of 1.55 m light. Here we report the synthesis and chemical characterisation of 1 , along with quantum-chemical calculations and additional experimental investigations of its third-order nonlinear properties that give more insight into its frequency tripling properties. Although 1 can be processed into amorphous films, crystals can also be grown by slow evaporation of solutions; the crystal structure determined by X-ray diffraction shows evidence of significant contributions from zwitterionic resonance forms to the ground-state structure, and reveals centrosymmetric packing exhibiting and CHN&z.tbd;C interactions. Both solutions and films of 1 exhibit near-infrared two-photon absorption into the low-lying one-photon-allowed state with a peak two-photon cross-section of ca. 290 GM (measured using the white-light continuum method with a pump wavelength of 1800 nm) at a transition energy equivalent to degenerate two-photon absorption at ca. 1360 nm; two related chromophores are also found to show comparable near-IR two-photon cross-sections. Closed-aperture Z-scan measurements and quantum-chemical calculations indicate that the nonlinear refractive index and third-harmonic generation properties of 1 are strongly dependent on frequency in the telecommunications range, due the aforementioned two-photon resonance. The third-order nonlinear optical properties of a dipolar chromophore are the subject of a joint theoretical and experimental investigation.