Abstract

Synthesis and UV/Vis spectroscopic properties of the negathe @(30) values of 1 and the G(30) values of 2 for both aprotic tively solvatochromic, relative to 1 homomorphic, thiobetaine and protic solvents, despite of the fact that sulfur is usually dye 2 are described. The new thiobetaine 2 exhibits an even known to act as worse hydrogen-bond acceptor than oxygen. larger negative solvatochromism and thermochromism than Possible reasons for this extraordinary behaviour of 2 are disthe standard betaine dye 1, which has been used to establish cussed. In contrast to 2, the sulfo-substituted betaine dye 4 an empirical scale of solvent polarity, the so-called ET (30) does not exhibit any solvatochromism. scale. Surprisingly, there exists a linear correlation between Beim Losungsmittelwechsel Diphenylether -+ Wasser wird die Iangstwellige, intramolekulare Charge-Transfer-(CT-)UV/Vis-Absorptionsbande des intramolekular ionoiden Pyridinium-N-phenolat-Farbstoffs 1 um 357 nm (von 810 nach 453 nm) hypsochrom verschoben, begleitet von einer entsprechenden, mit dem Auge verfolgbaren Farbanderung der Losungen von 1. Diese auoergewohnlich groBe, im sichtbaren Wellenlangenbereich liegende, negative Solvatochromie macht 1 zu einem idealen empirischen Indikator der Losungsmittelpolaritat 3,4), der vielfaltige Anwendungen in der Korrelationsanalyse losungsmittelabhangiger Prozesse (Reaktionen und Absorptionen) gefunden hat 3,5). Die als quantitative, empirische Parameter der Losungsmittelpolaritat eingefuhrten und nach Gleichung (1) berechneten molaren Anregungsenergien ET(30) (Transition Energies in kcal . mol-') von l6) sind fur uber 300 Losungsmittel 3,4) und zahlreiche binare Los~ngsmittelgemische~~~) bekannt. Ursache der drastischen negativen Solvatochromie von 1 ist die mit zunehmender Losungsmittelpolaritat (d. h. mit zunehmendem Solvatationsvermogen des Losungsmittels) auftretende energetische Stabilisierung des dipolaren Elektronengrundzustandes von 1 relativ zum weniger dipolaren CT-Anregungszustand (pG > pA) durch differenzierende Solvatation beider Zustande. AuDer den nichtspezifischen zwischenmolekularen Wechselwirkungskraften zwischen gelostem Farbstoff und Losungsmittel wird die Solvatochromie von 1 in H-Briicken-Donor-(HBD-)Losungsmitteln vor allem durch die spezifische H-Briicken-Wechselwirkung zwischen Phenolat-Sauerstoffatom und protischem Losungsmittel entsprechend Gleichung (2) (X = 0) verursacht. ET(30)/(kcal .mol-') = h .c. t. N A --28591 2.8591. 1 0 -3~l c m -' =-A~,~, +ROH [ / . k (

X-ray photoelectron spectroscopy (XPS) was used to detect the bonding between a silica particle surface and attached silanes. In addition to the commonly recorded Si 2p spectrum, the Si 1 s level is also accessible when monochromatic Ag Lalpha X-rays are applied. Furthermore, the spectrum of the Si 1 s level shows a fine structure. After spectrum deconvolution, we assigned the fitted spectral peaks to Si-C bonds of the silanes and to the Si-O bonds of the silica network. The recorded Si 1 s spectra were deconvoluted into peaks originating from Si-C bonds and the Si-O-Si silica network. To check the results of spectrum deconvolution, several differently functionalized silanes containing stoichiometric amounts of heteroatoms were applied for silica surface modification. We conclude that spectra deconvolution of the Si 1 s signal is an appropriate means for quantification of surface attached silane molecules.

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Syntheses and negative solvatochromism of three new ‘fluorophilic’ fluorine‐ and perfluoroalkyl‐substituted pyridinium N‐phenolate betaine dyes 3–5 are described in order to obtain new zwitterionic dyes which should be less basic and better soluble in perfluorinated solvents than the solvatochromic standard betaine dyes 1 and 2, used to establish an empirical scale of solvent polarity, called the E T (30) or $E_{T}^{N}$ scale. The new betaine dyes 3–5 were designed to allow an extension of the existing E T (30) scale to new solvents. Copyright © 2001 John Wiley & Sons, Ltd.

We present electrochemical and spectroelectrochemical data for the bipolar azo compound N,N'-diphenyl-N,N'-bis[4-(phenylazo)phenyl]-4,4'diaminobiphenyl (AZOPD) demonstrating reversible bipolar redox behaviour with a bandgap of 2.1 eV. The reduced species formed upon two-electron transfer can be described as bis(radical anion) as was confirmed by comparison with a reference compound with only one azo chromophore. Hole and electron transport behaviour in amorphous films was demonstrated by the fabrication of organic field-effect transistors using gold and magnesium contacts, respectively. The transistors are sensitive to light due to E-Z photoisomerization.

The crystal structure and the surface of alumina layers on silicon wafers were investigated by means of GIWAXS, WAXS, and AFM. Self‐assembled monolayers of ω‐substituted long‐chain alkylphosphonic acids were deposited on alumina and the layer thickness and homogeneity were determined by ellipsometry revealing a dependency of thickness and homogeneity on the nature of the substituent. During the adsorption process surface etching by the phosphonic acid was observed causing an increase in surface roughness.Furthermore, ex post functional group conversions were carried out yielding surface bound azides and rhodanides.