Experimental and Theoretical Insights into the Optical Properties and Intermolecular Interactions in Push-Pull Bromide Salts |
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Authors: | Dr. Perumal Venkatesan Dr. Margarita Cerón Dr. Enrique Pérez-Gutiérrez Armando E. Castillo Dr. Subbiah Thamotharan Fernando Robles Dr. Maxime A. Siegler Prof. M. Judith Percino |
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Affiliation: | 1. Unidad de Polímeros y Electrónica Orgánica, Instituto de Ciencias, Benemérita Universidad Autónoma de Puebla, Val3-Ecocampus Valsequillo, Independencia O2 Sur 50, San Pedro Zacachimalpa, Pue, México;2. Biomolecular Crystallography Laboratory, Department of Bioinfor- matics, School of Chemical and Biotechnology, SASTRA Deemed University, Thanjavur, 613 401 India;3. Laboratorio Nacional del Sureste de México, BUAP, Blvd., Valsequillo S/N esquina Blvd. Municipio Libre, C.P., 72500 Puebla, México;4. Department of Chemistry, Johns Hopkins University, New Chemistry Building, 3400N., Charles St. Baltimore, MD, 21218 USA |
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Abstract: | Experimental and theoretical insights into the nature of intermolecular interactions and their effect on optical properties of 1-allyl-4-(1-cyano-2-(4-dialkylaminophenyl)vinyl)pyridin-1-ium bromide salts ( I and II ) are reported. A comparison of optical properties in solution and in the solid-state of the salts ( I and II ) with their precursors ( Ia and IIa ) is made. The experimental absorption maxima (λmax) in CHCl3 is at 528 nm for I and at 542 nm for II , and a strong bathochromic shift of ∼110 nm is observed for salts I and II compared with their precursors. The absorption bands in solid-state at ∼627 nm for I and at ∼615 nm for II that are assigned to charge transfer (CT) effect. The optical properties and single crystal structural features of I and II are explored by experimental and computational tools. The calculated λmax and the CT are in good agreement with the experimental results. The intermolecular interactions existing in the crystal structures and their energies are quantified for various dimers by PIXEL, QTAIM and DFT approaches. Three types of interactions, (i) the cation⋅⋅⋅cation interactions, (ii) cation⋅⋅⋅anion interactions and (iii) anion⋅⋅⋅anion interactions are observed. The cationic moiety is mainly destabilized by C−H⋅⋅⋅N/π and π⋅⋅⋅π interactions whereas the cation and anion moiety is predominantly stabilized by strong C−H⋅⋅⋅Br− interactions in both structures. The existence of charge transfer between cation and anion moieties in these structures is established through NBO analysis. |
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Keywords: | bromide salts quaternary salts optical properties intermolecular interactions DFT calculation |
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