Isabelle Roth

A solvatochromic dye for probing significantly the dipolarity/polarizability of HBD (hydrogen bond donating) environments

The solvatochromism of the novel dye 4-tert-butyl-2-(dicyanomethylene)-5-[4-(diethylamino)benzylidene]-Δ3-thiazoline (1) has been investigated in 26 solvents of different polarity. 1 exhibits a positive solvatochromism, its solvent-induced bathochromic UV/Vis absorption band shift ranges from n-hexane (λmax = 566 nm) to dimethyl sulfoxide (λmax = 640 nm). The molar absorption energy of the solvatochromic band shift of 1 can be well correlated with Kamlet–Tafts and Catalans solvent polarity scales. 1 is mainly sensitive to the solvents dipolarity/polarizability (π* of SPPN term) rather than of its HBD (hydrogen-bond donating) or HBA (hydrogen-bond accepting) property. It is emphasized that the UV/Vis absorption band maximum of 1 in the strong HBD solvents acetic acid, 2,2,2-trifluoroethanol and 1,1,1,3,3,3-hexafluoropropan-2-ol fit well in the LSE (linear solvation energy) relationship with Kamlet and Tafts π* and Catalans SPPN scale, respectively, which makes this dye important as a dipolarity/polarizability indicator for various solid acids.

Solvatochromism and acidochromism of azobenzene-functionalized poly(vinyl amines)

Nucleophilic substitution of fluoroaromatics with poly(vinyl amine) (PVAm) is a suitable method for producing various azobenzene-functionalized PVAms. The solubility of the fluoroaromatic reagents in water was mediated by complexation with 2,6-O-dimethyl-β-cyclodextrin (DMCD). The degree of functionalization has been determined using model compounds as reference system. The solvatochromic properties of the polymers and the model compounds have been studied and interpreted using the well-established linear solvation energy relationships (LSER) of Kamlet–Taft and Catalan. The most dominant effect on the solvatochromic behavior is caused by interactions with solvents of a different dipolarity/polarizability. Also the basicity of the solvents is assumed to play an important role in the solvatochromism of the azobenzene-functionalized PVAms which shows the influence of the polymer chains. Furthermore, the UV/vis absorption spectra show a bathochromic shift with increasing acid strength of the medium. The impact of the PVAm backbone on the color of the chromophore bonded is highlighted.

Nucleophilic Substitution of 4-Fluoronitrobenzene with Polyvinylamine in Water Mediated by Cyclodextrins

Polyvinylamine (PVAm) can be readily functionalized by means of a nucleophilic substitution reaction with 4-fluoro-substituted aromatic compounds having a substituent with negative mesomeric effect in ortho and/or para position. PVAm is soluble in water only in which aromatic fluoro compounds are usually sparingly soluble. However, the solubility of aromatic compounds in water can be mediated in particular by cyclodextrin derivatives. This first report on the nucleophilic substitution reaction of 4-fluoronitrobenzene with PVAm provides an elegant method towards the preparation of chromophoric water-soluble polymers by means of a one-pot procedure.