The present report describes the first isolation of monomeric N-alkoxyarylaminyls and their chemical and magnetic properties. Reaction of the corresponding lithium amides of 2,4-diaryl-6-tert-butylanilines, 2,6-diaryl-4-tert-butylanilines, or 2,4,6-triarylanilines with tert-butyl peroxybenzoate in THF at -78 degrees C yielded quite persistent N-tert-butoxy-2,4-diaryl-6-tert-butylphenylaminyls (1), N-tert-butoxy-2,6-diaryl-4-tert-butylphenylaminyls (2), and N-tert-butoxy-2,4,6-triarylphenylaminyls (3), respectively, which were isolated in the monomeric form in 17-25% yields. All radicals prepared were oxygen insensitive and thermally very stable. X-ray crystallographic analyses were carried out for two radicals, and it was shown that the N and O atoms are coplanar with the anilino benzene ring. The ESR spectra of 1-3 gave a(N) = 0.984-1.05 and a(H) (anilino meta) = 0.158-0.170 mT (g = 2.0041-2.0043), indicating that the unpaired electron mainly resides on the nitrogen and anilino benzene ring. Magnetic susceptibility measurements for 1 and 3 showed that one radical revealed a weak ferromagnetic interaction and an analysis by the Curie-Weiss law gave 0.3 K as theta. The other radicals examined showed weak antiferromagnetic interactions and theta's were determined to be -0.3 to -1.5 K.
N-[(2-Benzothiazolyl)thio]- (1), N-[(2-benzoxazolyl)thio]- (2), and N-(2-pyrimidylthio)-2,4,6-trisubstituted-phenylaminyls (3) were generated by oxidation of the corresponding amines. Although 2 and 3 were not sufficiently persistent to be isolated, 1 was very persistent and could be isolated as radical crystals. The ESR spectra of nondeuterated and partially deuterated 1-3 radicals were measured, and the spin density distributions were estimated from the hyperfine coupling constants. Ab initio molecular orbital calculations were made for 1 to discuss the spin density distribution in more detail. Single-crystal X-ray crystallographic analysis was performed for one radical. Magnetic properties were measured for isolated four radicals with a SQUID. Two radicals showed ferromagnetic interaction, and analyses of chiT vs T plots with the one-dimensional regular Heisenberg model gave 2J/k(B) = 5.8 and 8.6 K. The remaining two radicals showed antiferromagnetic interaction. Analyses of the chiT vs T plots with the Curie-Weiss law or dimer model gave theta = -1.4 K and 2J/k(B) = -1370 K. The strong antiferromagnetic interaction could be explained in terms of the X-ray crystallographic results.
published as an Advance Article on the web 14th March 2001 N-(tert-Butoxy)-N-(2,4-diaryl-6-tert-butylphenyl)aminyls have been isolated; this is the first isolation of N-alkoxyaminyl radicals.
Key words crystal structure, isotope effect, Na 5 H 3 (SeO 4 ) 4 ·2H 2 O, Na 5 D 3 (SeO 4 ) 4 ·2D 2 O, X-ray, DSC.Differential scanning calorimetry (DSC) and X-ray diffraction measurements have been performed on pentasodium trihydrogen tetraselenate dihydrate Na 5 H 3 (SeO 4 ) 4 ·2H 2 O and deuterated Na 5 D 3 (SeO 4 ) 4 ·2D 2 O crystals. Any distinct anomaly around 428 K in the DSC curves for both crystals is suggested to be caused by a chemical reaction of thermal decomposition with hydrolysis at high temperature. The space group symmetry (triclinic P1) and the structure parameters are determined at room temperature. The hydrogen atom in the centrosymmetric O-H(D)-O hydrogen bond of both crystals is found to be equally distributed at two equivalent sites in the bond. The expansions of two O-H-O hydrogen bonds by the substitution of deuterium are observed to be 0.016(6) and 0.011(4) Å. The geometric isotope effect on hydrogen bonds is confirmed to be existed in Na 5 H 3 (SeO 4 ) 4 ·2H 2 O.
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