Summary.
N-(2′-Hydroxy-4′-N,N-dimethylaminobenzylidene)-4-nitroaniline [HDBN] has been used as a model for investigating intra- and intermolecular D–A (donor–acceptor) interactions in various environments by means of UV/Vis spectroscopy. UV/Vis spectra of HDBN have been measured in various solvents, ethanolic solutions of different pH, adsorbed on silica, and in the solid state. A bathochromic shift of νmax is observed with increasing the dipolarity/polarizability and HBD (hydrogen bond donor) capacity of the solvent, which is described by means of a multiple LSE (linear solvation energy) relationship in terms of the empirical Kamlet-Taft solvent polarity parameters. The adsorption of HDBN on Aerosil® 300-silica particles in non-HBA (hydrogen bond acceptor) solvents is explained in the same sense. Mobile protons and sol–gel entrapping cause a hypsochromic shift due to protonation of the lone electron pair of the 4′-N,N-dimethylamino group. Hydroxide ions attack the 2′-hydroxy group which causes a bathochromic shift. A strong intramolecular hydrogen bond between the 2′-hydroxyl hydrogen and the imine nitrogen atom is present in the solid-state structure causing an unprecedented bathochromic shift.
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Corresponding author. E-mail: stefan.spange@chemie.tu-chemnitz.de
Received July 8, 2002; accepted (revised) September 30, 2002
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El-Sayed, M., Müller, H., Rheinwald , G. et al. UV/Vis Spectroscopic Properties of N-(2′-Hydroxy-4′-N,N-dimethyl-aminobenzylidene)-4-nitroaniline in Various Solvents and Solid Environments. Monatshefte für Chemie 134, 361–370 (2003). https://doi.org/10.1007/s00706-002-0550-3
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DOI: https://doi.org/10.1007/s00706-002-0550-3