Design of molecular ferromagnets

A large variety of molecular ferromagnets have been synthesized since the discovery of the first organic ferromagnets, including pure organic compounds, organometallic charge-transfer complexes, metal complex-organic radical compounds, and transition metal complexes coupled to organic radicals. Besides, there are many reports on the observation of ferromagnetism in polymers and organic matrix composites. Molecular ferromagnets have great potential in different areas of technology such as low frequency magnetic shielding, magnetic imaging, magneto-optics and information storage. We provide a brief review on the current strategies for the design of molecular (organic) ferromagnets. This includes exploiting the inherent advantages of molecular systems, such as the ability to fine-tune the properties at the molecular level, and to control dimensionality, supramolecular structuring and hierarchy of spin interactions etc. for carrying out structural modifications and chemical functionalisations of stable open-shell molecules in order to generate supramolecular structures in which the natural prediction for antiparallel spin alignment (antiferromagnetism) is avoided.     

Fluorophilic properties of (perfluorooctyl)ethyldimethylsilyl substituted and tetramethyl(perfluoroalkyl) substituted cyclopentadienes and their Ti(IV), Rh(III), and Rh(I) complexes

Fluorous partition coefficients in perfluorohexane/toluene system for 37 fluorinated silylcyclopentadienes, titanium(IV) complexes derived from them, perfluoroalkyl substituted tetramethylcyclopentadienes, and their Rh(III) and Rh(I) complexes were determined. Specific fluorophilicity and fluorousness according to Kiss and Rábai were calculated for each compound with the help of molecular volume computed with the Gaussian program. The results show relative unimportance of fluorine content parameter for fluorophilicity as shown by a rhodium(I) complex being fluorophilic at fluorine content as low as 46.3%. As expected, fluorophilicity increased with the fluorous ponytail length and ponytail number in series of similar compounds, whereas polar M-Cl bonds were decreasing it. Fluorophilicities of tetramethyl(perfluoroalkyl)cyclopentadiene tautomers varied considerably despite only small differences in molecular volume being found. Most of the compounds were prepared previously, several new silylcyclopentadienes and titanium(IV) silylcyclopentadienyl complexes are reported here for completion.     

Complexes of transition metals bonded to silica via β-diketonate groups — synthesis, structure, and catalytic activity

Transition metal complexes bonded to silica via silanes with β-diketonate groups can be used as packings for complexation gas chromatography or as immobilized homogenous metal complex catalysts. On basis of elemental analysis and the determination of surface area, possible structures of the complexes formed on the silica surface have been proposed. The possibility of using the immobilized complexes as catalysts has been indicated. Especially nickel complexes were taken into consideration. These immobilized complexes were used previously as packings for complexation gas chromatography.     

Reactions of 2-chlorobutane with polynuclear bimetallic aluminum and cobalt chloride complexes: low-temperature synthesis and structure of adducts

Co-condensation of aluminum and cobalt chlorides and 2-chlorobutane leads to the formation of triple complexes. Density functional method PBE was used for the quantum chemical calculations of structures and harmonic vibration frequencies. The structures of associates were established by the comparison of experimental and theoretical IR spectra. Introduction of cobalt chloride into the system 2-chlorobutane-aluminum chloride leads to the formation of a triple molecular associate, in which coordination of the organic substrate with the bimetallic complex is accomplished through the transition metal atom. The triple complex is stable in the temperature range 80–240 K and in contrast to the binary complex of butyl chloride with aluminum halide is not capable of self-ionization to form sec-butyl cation.