The complexes [M(oespz)Cl][M = MnIII or FeIII; oespz = 2,3,7,8,12,13,17,18-octakis(ethylsulfanyl)-5,10,15,20-tetraazaporphyrinate dianion] have been prepared and their structures determined. The isomorphous structures consist of stacked dimers. Monomers, within each dimer, are slipped and faced in trans fashion respect to the M–Cl bond. Weak interdimer interactions arise from Cl S contacts. Intradimer interactions are provided by relatively long M S and N (pyrrole) S contacts. Magnetic susceptibility measurements revealed that [Mn(oespz)Cl] is a high-spin (S= 2) complex with weak antiferromagnetic coupling between the MnIII. The toluene frozen-glass EPR spectrum of [Fe(oespz)Cl] seems to be consistent with a S= ground state, whereas the polycrystalline powder EPR spectrum at 4.2 K and magnetic susceptibility data are better rationalized in terms of a S=5//2 and ½ admixture. The crowding of the UV/VIS spectra of both complexes and the red shift of the Soret and Q bands of [Fe(oespz)Cl] are related to the effects of the peripheral ethylsulfanyl groups on the porphyrazinato ring. Both compounds show characteristic NIR absorptions. Voltammetric data are consistent with the tendency of the porphyrazinate ligand to stabilize the lower oxidation states of metals relative to phthalocyanines and porphyrins
We report on the use of a copper compound of 2,3,7,8,12,13,17,18-octakis(octylthio)-5,10,15,20-tetraazaporphyrin
for the fabrication of a spreading monolayer and Langmuir-Blodgett films. This compound, as a free ligand
or metal substituted, gives mesogenic material with a discotic, columnar structure. Its structural and magnetic
properties have been characterized by optical and ESR spectroscopies. The spreading monolayer was not
homogeneous and use of a typical film-forming amphiphile, such as stearic acid, was necessary for obtaining
stable, reproducible surface films, which were easily transferred onto quartz plates treated with dimethyldichlorosilane.
The properties of the film were also analyzed with both UV-vis and ESR spectroscopies. The
film did not show orientation order, and the discotic material maintained a columnar aggregate structure
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.
By surface tension and ellipsometric measurements, we studied how
2D crystallization of fatty alcohol
monolayers is influenced by the presence in the subphase of a short
chain carboxylic acid, whose surface
activity is dependent upon pH. The surface crystallization of the
alcohol monolayer was appreciably
perturbed for pH values smaller than the pK
a of
the acid, that is when the protonated form of the acid
was predominant in the bulk solution. On the contrary, for pH
values above the pK
a of the acid,
the
monolayer was not influenced by the presence of the acid in the
subphase. The effect was greatly dependent
on the acid concentration in the subphase, at a fixed pH. We also
studied the effect of the acid chain length
(C6−C10) on a decanol monolayer, the effect
of the alcohol chain length with octanoic acid in the
subphase,
and the effect of the lateral surface pressure of the
monolayer.
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