Experimental and Theoretical Insights into the Optical Properties and Intermolecular Interactions in Push-Pull Bromide Salts.

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 (?_max) 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 ?_max 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/? and ????? 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.

SUBMITTER: Venkatesan P 

PROVIDER: S-EPMC6470380 | biostudies-literature | 2019 Apr

REPOSITORIES: biostudies-literature