ORIGINAL PAPER Emission Wavelength Changes www.crt-journal.org Preferential Orientation of Crystals and its Influence on the Emission Wavelength of Acrylonitrile Derivatives Treated with Polar Solvents Maria Judith Percino,* Margarita Cer´ on, Enrique P´ erez-Guti´ errez, Venkatesan Perumal, Maxime A. Siegler, Thamotharan Subbiah, Paulina Ceballos, Paola Gordillo-Guerra, Jos´ e Bonilla-Cruz, Francisco Enrique Longoria, and Tania Lara Photoluminescence properties in solid state and its relationship with structural features of prop-2-enenitrile derivatives containing any of functional groups 4-halogenphenyl, phenyl, 4-dimethylamino, or 4-diphenylamino are investigated. The compounds show change in color from yellow to orange after treatment with dimethyl sulfoxide or dimethyl formamide. Nevertheless, the single-crystal X-ray diffraction for both, the original yellow and the treated orange crystals, does not display any major structural differences. The optical properties are related to the crystal packing and intermolecular interactions such as edge-to-face through the vertices of aromatic rings. The last is supported by the behavior of the presence of functional group. The absorption spectrum in solution for all compounds shows two absorption bands with wavelength of maximum absorption around 390–430 nm and at 290–300 nm. Regardless of the crystal type, the maximum emission in solution was between 450–570 nm. In solid state, yellow crystals exhibit an emission in the 500–530 nm range and in the 580–630 nm range for orange crystals. Results suggest that optical properties are strongly dependent on morphology and habit. Powder X-ray characterization shows a preferential orientation for orange crystals. All compounds are characterized by common spectroscopy techniques, fluorescence, atomic force microscopy and X-ray diffraction. 1. Introduction Organic fluorescent nanocrystals have potential applications in the fields of biological sensing and imaging, [1,2] organic optoelectronics, [3,4] security printers, [5,6] and nanophotonic Dr. M. J. Percino, Dr. M. Cer´ on, Dr. E. P´ erez-Guti´ errez, Dr. V. Perumal, P. Ceballos,Dr. P. Gordillo-Guerra Unidad de Polimeros y Electronica Organica Instituto de Ciencias Benemerita Universidad Autonoma de Puebla Val3-Ecocampus Valsequillo, Independencia O2 Sur 50, San Pedro Zacachimalpa, Publa, C.P. 72960, Mexico E-mail: judith.percino@correo.buap.mx The ORCID identification number(s) for the author(s) of this article can be found under https://doi.org/10.1002/crat.201800156 DOI: 10.1002/crat.201800156 devices, [7,8] including solid-state lasers. For applications as dyes, it is required that they not exhibit aggregation-caused quenching (ACQ), because numerous or- ganic dyes are strongly fluorescent in di- lute solution, but often do not exhibit strong emission in the solid state. [9,10] This behavior is generally attributed to intermolecular interactions that provide non-radiative decay routes. Also, it has been reported that plane-to- plane stacking of a fluorophore hinders favorable intermolecular coupling of the transition dipole moments, which is the most common cause for the loss of emis- sion in the solid state. Recently Ghod- bane et al. [11,12] reported that halogenated 2-phenyl-benzoxazole derivatives showed photoluminescence in solution, as well as in the powders and crystals. They re- ported the fluorescence quantum yield for a series of compounds substituted with halogens atoms, which progres- sively decreased with the increase in the size of the halogen atom, that is, by the heavy atom effect. The photoluminescence properties in the solid-state are higher for compounds with Cl > F > Br, with the I atom in the compound quenching the fluorescence. [13–15] With respect to the question of stimuli-luminescent re- sponse for solid materials, various studies have shown that changes can be induced in the luminescence properties of these Dr. M. A. Siegler Department of Chemistry Johns Hopkins University New Chemistry Building, 3400 N. Charles St. Baltimore, MD 21218, USA Dr. T. Subbiah Biomolecular Crystallography Laboratory Department of Bioinformatics School of Chemical and Biotechnology SASTRA Deemed University Thanjavur 613401, India Dr. J. Bonilla-Cruz,Dr. F. E. Longoria, Dr. T.Lara Centro de Investigaci´ on en Materiales Avanzados S.C. Av. Alianza Norte 22, Autopista Monterrey-Aeropuerto Km 10, PIIT, Apodaca-Nuevo Le´ on, M´ exico, C.P. 66600 Cryst. Res. Technol. 2019, 1800156 C  2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim 1800156 (1 of 17)