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Two Different Emissions of (2Z)‑2-(4-Bromophenyl)-3-[4-(dimethylamino)phenyl]prop-2-enenitrile Due to Crystal Habit and Size: Synthesis, Optical, and Supramolecular Characterization

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journal contribution
posted on 21.02.2017, 00:00 by Judith Percino, Margarita Cerón, Perumal Venkatesan, Paulina Ceballos, Alejandro Bañuelos, Oscar Rodríguez, Maxime A. Siegler, Fernando Robles, Víctor M. Chapela, Guillermo Soriano-Moro, Enrique Pérez-Gutiérrez, José Bonilla-Cruz, Subbiah Thamotharan
Optical and X-ray diffraction characterizations of crystals I and II of (2Z)-2-(4-bromophenyl)-3-[4-(dimethylamino)­phenyl]­prop-2-enenitrile (Z-4-BrPhDMAPhACN) are reported. I and II belong to the same monoclinic space group and have nearly identical unit-cell dimensions [I: a = 11.0169(2); b = 6.02041(11); c = 21.8541(4); (β) 98.4082(18). II: a = 11.0475(6); b = 6.0273(3); c = 21.8533(11); (β) 98.315(5)]. Crystals I and II were formed under different conditions and have different crystal habits and colors: crystals I are yellow blocks, whereas crystals II are small, orange needles. I and II show absorption maxima (λabs) in solution at 404 nm and emission (λem) maxima at 501 nm (I) and at 502 nm (II). However, their emission maxima are different in the solid state: I shows an emission at 512 nm and a shoulder at 534 nm, whereas II exhibits a λem maximum at 582 nm. The differences in solid-state photoluminescence were attributed to variations in the crystal morphology and to the crystal habit and size. Both I and II were characterized by nuclear magnetic resonance, mass spectrometry, infrared spectroscopy, UV–vis spectroscopy, fluorescence, cyclic voltammetry, single-crystal and powder X-ray diffraction, differential scanning calorimetry, scanning electron microscopy, and density functional theory calculations.