Towards a Better Understanding of the Magnetic Interactions withinm-Phenyleneα-Nitronyl Imino Nitroxide Based Biradicals
摘要:
An extensive investigation of the magnetic properties of three series of biradicals (bis-nitronyl nitroxides diNN-R, bis-imino nitroxides diIN-R and mixed INNN-R. where R is either hydrogen, a triple bond or trimethylsilylacetylenic group) has been carried out to give clear values of the intramolecular interactions through the m-phenylene coupling unit with alpha -nitronyl nitroxides (NN) or alpha -imino nitroxides (IN). An EPR study of the molecules in the isolated state is validated by ab initio calculations, which show the respective influence of spin polarisation and molecular conformation on the singlet-triplet gaps. All these results indicate that the triplet state is the ground state for such biradicals. except when the imidazolyl cycles are orthogonal to the phenyl ring. The magnetic properties of the biradicals in the solid state can be rationalised by examination of the short contacts produced between the ONC-NO and ONCN groups. EPR studies on single crystals of the H-substituted series have confirmed the presence of a structural distortion for diNN-H whereas diIN-H and INNN-H do not exhibit such a peculiarity. The magnetic behav lour of diIN-H is described well by a four-spins model, with a strong intermolecular antiferromagnetic interaction of -90 K, whereas in the case of the two other compounds. a supplementary contact involves more complex interactions between the dimers. The compound diNN-tmsa exhibits a ferromagnetic intermolecular interaction of +11 K within the dimers, and this could be attributed to the relative disposition of the imidazolyl rings. Compound diNN-tr reveals a chain-like behaviour, whereas diIN-tr shows a predominant antiferromagnetic interaction within the dimers. The values for the intramolecular interactions in the solid state are in good agreement with those found for the isolated molecules.
Diverse Proton-Conducting Nanotubes via a Tandem Macrocyclization and Assembly Strategy
作者:Michael J. Strauss、Manping Jia、Austin M. Evans、Ioannina Castano、Rebecca L. Li、Xavier Aguilar-Enriquez、Emily K. Roesner、Jeremy L. Swartz、Anton D. Chavez、Alan E. Enciso、J. Fraser Stoddart、Marco Rolandi、William R. Dichtel
DOI:10.1021/jacs.1c02789
日期:2021.6.2
with various aromatic dialdehydes yields chemically distinct pentagonal [5 + 5], hexagonal [3 + 3], and diamond-shaped [2 + 2] macrocycles depending on the substitution pattern of the aromatic dialdehyde monomer. Atomic force microscopy and in solvo X-ray diffraction demonstrate that protonation of the macrocycles under the mild conditions used for their synthesis drives assembly into high-aspect ratio
Nine mostly novel aromatic Schiff bases containing from two-to-four terminal ethynyl groups and one or two methanimine groups per one molecule are reported. The spectral and density functional theory characteristics and the extent of conjugation are discussed in connection with the structure and architecture of the prepared compounds. The applicability of compounds as buildingblocks for conjugated
Synthesis of nitronyl- and imino-nitroxide-triradicals interconnected by phenyl ethynyl spacer
作者:Laure Catala、Philippe Turek、Jacques Le Moigne、André De Cian、Nathalie Kyritsakas
DOI:10.1016/s0040-4039(99)02218-2
日期:2000.2
The design and synthesis, as well as solid state and ESR characterisation of three new triradicals based on phenyl ethynyl backbone bearing nitronyl-nitroxide and imino-nitroxide groups, are reported. The synthesis of these compounds was based on palladium-coupling reactions between alkynyl and bromo derivatives. An ESR study showed magnetic interactions between the radicals through the phenyl ethynyl-coupling
An extensive investigation of the magnetic properties of three series of biradicals (bis-nitronyl nitroxides diNN-R, bis-imino nitroxides diIN-R and mixed INNN-R. where R is either hydrogen, a triple bond or trimethylsilylacetylenic group) has been carried out to give clear values of the intramolecular interactions through the m-phenylene coupling unit with alpha -nitronyl nitroxides (NN) or alpha -imino nitroxides (IN). An EPR study of the molecules in the isolated state is validated by ab initio calculations, which show the respective influence of spin polarisation and molecular conformation on the singlet-triplet gaps. All these results indicate that the triplet state is the ground state for such biradicals. except when the imidazolyl cycles are orthogonal to the phenyl ring. The magnetic properties of the biradicals in the solid state can be rationalised by examination of the short contacts produced between the ONC-NO and ONCN groups. EPR studies on single crystals of the H-substituted series have confirmed the presence of a structural distortion for diNN-H whereas diIN-H and INNN-H do not exhibit such a peculiarity. The magnetic behav lour of diIN-H is described well by a four-spins model, with a strong intermolecular antiferromagnetic interaction of -90 K, whereas in the case of the two other compounds. a supplementary contact involves more complex interactions between the dimers. The compound diNN-tmsa exhibits a ferromagnetic intermolecular interaction of +11 K within the dimers, and this could be attributed to the relative disposition of the imidazolyl rings. Compound diNN-tr reveals a chain-like behaviour, whereas diIN-tr shows a predominant antiferromagnetic interaction within the dimers. The values for the intramolecular interactions in the solid state are in good agreement with those found for the isolated molecules.