SYNTHESIS AND CHARACTERIZATION OF 3-HEXYL MULTISUBSTITUTED ALPHA,OMEGA-DIFORMYL-ALPHA-OLIGOTHIOPHENES (N=3, 6, 8)

The synthesis and characterization of a series of thienylenic alpha,om ega-diformyl-alpha-oligothiophenes with 3, 6 and 8 residues is reporte d. The chemical structure was determined by H-1 NMR, FT-IR, mass and G PC analyses, while the electronic properties in the neutral state were studied by UV-Vis spectroscopy both in solution and in the solid stat e. In the UV-Vis spectra of thin films, the vibronic structure is obse rved. The pronounced red-shift of the absorption maximum, with respect to spectra of unsubstituted alpha-oligothiophenes, is indicative of a contribution of carbonyl pi-electrons to the overall delocalization v ia a mesomeric effect leading to a more planar structure. The solid st ate aggregation was investigated by XRD spectroscopy and optical micro scopy. We observed for the longest terms a smectic arrangement typical of liquid crystalline compounds and a tendency to self-assembling ont o hydrophilic substrates, forming angles ranging from 40-50 degrees wi th respect to the normal to the surface.