Monolayers and Langmuir-Blodgett films of doxylstearic acids. Spreading isotherms and ESR study

Abstract

The spreading isotherms of monomolecular films of stearic acid nitroxides with a five-membered paramagnetic unit in different positions of the hydrocarbon chain were studied at 293 K. The presence of the substituent rendered more expanded monolayers, whose properties depend on the distance between the NO and COOH groups. Langmuir-Blodgett films of these nitroxides were deposited on quartz plates. The ESR spectra of both collapsed monolayers and oriented multilayers indicated a more opened structure with higher chain flexibility with respect to pure, bulk compounds. The dipole-dipole effects and the spin-exchange interactions were determined to mainly depend on the ring position along the hydrocarbon chain.

Structural Modifications of DMPC Vesicles upon Interaction with Poly(amidoamine) Dendrimers Studied by CW-Electron Paramagnetic Resonance and Electron Spin−Echo Techniques

“…The main axis of rotation may change from the usual Z axis, corresponding to the direction of the p orbital containing the unpaired electron (which also corresponds to the bilayer axis), to the X axis, which lays on the N−O bond direction. (b) The principal components of the g tensor (for the Zeeman coupling between the electron spin and the magnetic field) were assumed to be equivalent to those found for n DXSA embedded in Langmuir−Blodgett films: g xx = 2.0088, g yy = 2.0061, and g zz = 2.0027; the hyperfine A tensor components (for the coupling between the unpaired electron spin and the nuclear nitrogen spin), A ii , are obtained from the fitting between the experimental and the computed pattern and provide a measure of the environmental polarity (the accuracy of A ii , as obtained from spectral computation, is 2%). A decrease in 〈 A 〉 = ( A xx + A yy + A zz )/3 reflects a decrease in the polarity of the radical environment, such as nitroxides inserted in the lipid bilayer.…”

Langmuir−Blodgett Films of Known Layered Solids: Preparation and Structural Properties of Octadecylphosphonate Bilayers with Divalent Metals and Characterization of a Magnetic Langmuir−Blodgett Film

“…Magnetic studies of LB films are mostly limited to EPR determination of the orientation of organic radicals or metal complexes in transferred films. While evidence for magnetic exchange between molecular species in LB films has been observed in some instances, [57][58][59][60] there are no examples of magnetically ordered molecular films. The most extensive investigations of magnetism in LB films have focused on manganese stearate.…”

Chemisorption of nitronyl–nitroxide radicals on gold surface: an assessment of morphology, exchange interaction and decoherence time

“…Langmuir-Blodgett and SAM). 9,13,23 However, to date, only a few of papers have tacked the adsorption of the pure organic radicals at the computational level. 24 The interest toward nitronyl-nitroxide radicals (Nit) germinated from the observation of long-range magnetic order at low temperature in bulk phases 25 and from the possibility of using them as building blocks of more complex magnetic structures such us Single-Chain Magnets.…”