The present study reports the synthesis and structural, photophysical and electrochemical properties of five new Schiff bases containing hydantoin rings. The compounds were synthesized via condensation reactions between 3-amino-5,5′-dimethylhydantoin and five different aromatic aldehydes. All compounds were characterized using different spectroscopic and electrochemical tools as well as single crystal X-ray diffraction analysis. The photochromic and molecular switching behaviours of the switchable –CHN– groups of Schiff bases were investigated by real time UV-vis spectroscopy in DMF under long wavelength UV light at λ = 365 nm for 90 min (mostly E → Z) and dark relaxation at room temperature for 60 min (mostly Z → E) in the spectral region of 250 nm to 600 nm at equal concentrations. The electrochemical properties of the compounds were investigated on a glassy platinum electrode (Pt-) in DMF using the cyclic voltammetric (CV) technique before and after UV irradiation. The effects of functional groups on the reduction potential of the Schiff bases are discussed. Electrochemical studies showed that the reduction of –CHN groups is mostly quasi-reversible, with adsorption-controlled processes for (E)-3-((2-hydroxybenzylidene)amino)-5,5′-dimethylimidazolidine-2,4-dione (SB2) and (E)-3-((4-(dimethylamino)benzylidene)amino)-5,5′-dimethylimidazolidine-2,4-dione (SB4) and intermediate processes for the remaining compounds.

Here we report on the synthesis and characterization of three new N-modified analogues of hemorphin-4 with rhodamine B. Modified with chloroacetyl, chloride cotton fabric has been dyed and color coordinates of the obtained textile materials were determined. Antiviral and virucidal activities of both the peptide-rhodamine B compounds and the dyed textile material were studied. Basic physicochemical properties (acid-base behavior, solvent influence, kinetics) related to the elucidation of structural activity of the new modified peptides based on their steric open/closed ring effect were studied. The obtained results lead to the conclusion that in protic solvent with change in pH of the environment, direct control over the dyeing of textiles can be achieved. Both the new hybrid peptide compounds and the modification of functionalized textile materials with these bioactive hemorphins showed virucidal activity against the human respiratory syncytial virus (HRSV-S2) and human adenovirus serotype 5 (HAdV-5) for different time intervals (30 and 60 min) and the most active compound was Rh-3.