Si(100) surfaces were molecularly engineered by covalent linkage of a monolayer of two stilbene-based chromophores, either 1-cyano-1-phenyl-2-[4 0 -(10-undecenyloxy)phenyl]-ethylene or its chlorine derivative, 1-cyano-1-(4-Cl-phenyl)-2-[4 0 -(10-undecenyloxy)phenyl]-ethylene. The hybrid systems have been probed by monochromatized angle-resolved X-ray photoelectron spectroscopy (AR-XPS) and atomic force microscopy (AFM) measurements. Results indicated robust covalent linkage of stilbene molecules to the functionalized substrate surfaces. AFM lithography and contact angle (CA) analysis confirmed that the adopted molecular architectures proved to be well-suited for reversible cis-trans photoswitching promoted by UV irradiation in the solid state.

Starch enzymatic degradation caused by endogenous hydrolases is studied by in situ NMR spectroscopy on a set of hard and soft wheat flours. The results obtained by two different techniques (HR-MAS and (1)H NMR in solution) are analyzed in terms of a Michaelis-Menten kinetic phenomenological model taking into account the presence of endogenous enzymes and their eventual inactivation. The parameters resulting from the best fit of all experimental data to the kinetic model equations are submitted to a multivariate statistical analysis to assess the role of the oligosaccharides release in distinguishing between hard and soft wheats.

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Di-2-pyridyl sulphide has been prepared and its electric dipole moment measured a t 25 and 45" (3.50 D, in benzene solution). The 250 MHz variable temperature pulsed Fourier transform l H n.m.r. spectrum has been also measured and analysed. Results of theoretical energy calculations (CN D0/2 type) together with the experimental data have been interpreted in terms of molecular solute conformations. It has been found that the molecule prefers a twisted conformation in which the ring planes are rotated ca. 36" out of the CSC plane. A fast interconversion between the three conformers that correspond to the possible relative orientations of the pyridine rings in this structure was found to occur in the solution state.OUR current interest in the study of the relationship Now if the symmetry and typical linear structure of the between the conformational properties and the chelating U022+ systems is considered,1° it clearly appears that ability of sulphur compounds containing pyridine knowledge of the conformational properties of the chelatrings 1-5 has prompted us to examine the conformation ing molecule is a potentially useful tool for the prediction of di-2-pyridyl sulphide. This molecule has been shown of the stereochemistry of the co-ordination compounds. to be a complexing agent for transition metals6-8 and, Previous investigations of the conformation of the more recently, for uranyl In these complexes, di-similar diphenyl sulphide molecule have been reported. 2-pyridyl sulphide acts as a bidentate ligand, co-ordin-These used the EHMO approach l1 and experimental ation Occurring Only through the two nitrogen atoms'

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