A new, efficient method for the isolation of (2R,3S)-isocitric acid (ICA) from its fermentation solution was developed. It is noteworthy that this method is based on selective adsorption directly from the fermentation solution on activated carbon, followed by the release of both ICA and citric acid by means of elution with methanol and their final separation by known methods. Thereby, several disadvantages were overcome: Electrodialysis is no longer necessary to remove cations such as Na + from the fermentation solution. Also, several hitherto accompanying dyestuffs were not observed with this method. Furthermore, removal of water by distillation is expendable. Eventually, the new crude product is of a quality that also avoids the use of a tedious slide vane rotary vacuum pump distillation of the trimethyl esters of both acids, which hitherto was the basis for the separation of ICA. In summary, the new method distinctly spares energy as well as time.
The chemisorption of magnetically bistable transition metal complexes on planar surfaces has recently attracted increased scientific interest due to its potential application in various fields, including molecular spintronics. In this work, the synthesis of mixed-ligand complexes of the type [NiII
2L(L’)](ClO4), where L represents a 24-membered macrocyclic hexaazadithiophenolate ligand and L’ is a ω-mercapto-carboxylato ligand (L’ = HS(CH2)5CO2
− (6), HS(CH2)10CO2
− (7), or HS(C6H4)2CO2
− (8)), and their ability to adsorb on gold surfaces is reported. Besides elemental analysis, IR spectroscopy, electrospray ionization mass spectrometry (ESIMS), UV–vis spectroscopy, and X-ray crystallography (for 6 and 7), the compounds were also studied by temperature-dependent magnetic susceptibility measurements (for 7 and 8) and (broken symmetry) density functional theory (DFT) calculations. An S = 2 ground state is demonstrated by temperature-dependent susceptibility and magnetization measurements, achieved by ferromagnetic coupling between the spins of the Ni(II) ions in 7 (J = +22.3 cm−1) and 8 (J = +20.8 cm−1; H = −2JS1S2). The reactivity of complexes 6–8 is reminiscent of that of pure thiolato ligands, which readily chemisorb on Au surfaces as verified by contact angle, atomic force microscopy (AFM) and spectroscopic ellipsometry measurements. The large [Ni2L] tail groups, however, prevent the packing and self-assembly of the hydrocarbon chains. The smaller film thickness of 7 is attributed to the specific coordination mode of the coligand. Results of preliminary transport measurements utilizing rolled-up devices are also reported.
Metal-organic frameworks, a class of porous polymeric materials, are presenting a development on the interface between molecular coordination chemistry and materials science and are becoming one of the hottest research topics in chemistry. Two new metal-organic frameworks, [M' 2 {Co 3 (ACTBA) 2 }] n (1; M' = monocation) and [(NH 2 Et 2 ) 2 {Cd 3 (ACTBA) 2 }] n (2) (H 4 ACTBA = 2,6,9,10-tetrakis(p-carboxyphenyl)anthracene), composed of trinuclear Co or Cd moieties connected by anthracene tetracarboxylate ligands are presented here, which are highly stable on removal of solvent inside the pores. The synthesis, X-ray structure analysis, NMR spectroscopy (for 2), chemical and thermal stability, and magnetic properties (for 1) are discussed.
Temperature-sensitive crystalline phases, pertaining to discrete clusters of binary and ternary Co(II,III):iminodipropanol:(N,N′-aromatic binder) systems, were prepared. The rich structural speciation of such systems in alcoholic media and their unique structural, magnetic, and spectroscopic profiles have been demonstrated. The need to understand the chemical reactivity of such complex ternary Co(II)-(1,1′-iminodi-2-propanol) systems, in the presence of N,N′-aromatic chelators 2,2′-bipyridine and 1,10-phenanthroline and aromatic binder 4,4′-bipyridine in methanol, led to the synthetic development of well-defined hybrid metal-organic materials with discrete spectroscopic, structural, electrochemical, and magnetic prop-[a]
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