Synthesis, x-ray diffraction, differential scanning calorimetry, and magnetic susceptibility studies of a series of binuclear ruthenium(II) carboxylates giving liquid-crystalline phases

Abstract

A wide series of diruthenium(II,II) tetracarboxylates of general formula Ru2(RCOO)4 was prepared; the carboxylate substituents include linear alkyl chains (R = C4H9 to C19H39), unsaturated chains (R = CH2=CH(CH2)8~, (CH3)2C=CHCH2CH2CH(CH3)CH2-) as well as a fluorinated chain (R = C7F15-). An adduct obtained by pyrazine intercalation was also characterized (R = CnH23-). The mesomorphic behavior of these compounds was investigated by differential scanning calorimetry and X-ray diffraction. A thermotropic columnar mesophase was observed above ca. 100 °C for all complexes except the perfluoro compound and the pyrazine adduct. Unsaturation in the peripheral alkyl chains strongly depresses the transition temperature to the liquid-crystalline phase. The magnetic susceptibility of three members of the series was measured in the range 6-400 K. A rigorous analytical expression of the magnetic susceptibility vs temperature was derived from the ( *)* 12( *)2 electronic configuration for the ground state of a diruthenium(II,II) core, by applying a spin-orbit Hamiltonian, and the data were successfully analyzed on this basis.

Tuning the Magnetic Moment of [Ru2(DPhF)3(O2CMe)L]+ Complexes (DPhF=N,N′‐Diphenylformamidinate): A Theoretical Explanation of the Axial Ligand Influence

“…In addition, a moderate or important interdimer magnetic interaction, depending on the structure of the complex, has been observed in Ru 2 5 + compounds. Also a moderate interdimer magnetic interaction in the molecular Ru 2 4 + complexes has been observed although a stronger magnetic interaction in some polymeric species [10,11] …”

Electronic Structure of Ru2(II,II) Oxypyridinates: Synthetic, Structural, and Theoretical Insights into Axial Ligand Binding

“…In comparison, the Ru 2 4+ tetra-acetate and tetrabenzoate complexes show similar magnetic behavior, with g values of 2.08 and 2.1 and zero-field splitting parameters of +351 and +309 K, respectively, 90 while g = 2.00 and D/k B = +375 K were found for the one-dimensional system [Ru 2 (O 2 CCF 3 ) 4 -(C 16 H 16 )]. 91 Similarly, Ru 2 4+ complexes with aliphatic carboxylates display g values from 2.05 to 2.12 and D/k B values ranging from +389 to +452 K. 92 However, a small (and suspect 93 ) g value of 1.64 was found for 4,0-Ru 2 (fhp) 4 (thf), a fluorine analogue of the studied molecules, with a comparable D/k B value of +378 K. 44 Most of the other treatments of the magnetic data of Ru 2 4+ compounds fix the g value to 2.00. In this way, a series of Ru 2 (O 2 CAr) 4 compounds, where Ar = fluorine-substituted phenyl, exhibited D/k B values ranging from +333 to +449 K; 10 the one-dimensional compound [Ru 2 (O 2 CCF 3 ) 4 (Phz)] gave D/k B = +399 K, 12 and the trifluoroactete and perfluorobenzoate (2,2,6,6-tetramethylpiperidin-1-yl)oxidanyl adducts revealed D/k B = +338 and +350 K, respectively.…”

USAXS studies of monosaccharide gels. I. Dependence of the glucofuranose-based gel structure on the gelator concentration

“…Many low-molecular-weight gels were characterized in the molecular range using spectroscopic methods, such as FT-IR, EPR and NMR, which indicated formation of intermolecular hydrogen bonds [2,3]. However, the structure of these gels on a larger length scale is not sufficiently documented yet.…”

“…However, the structure of these gels on a larger length scale is not sufficiently documented yet. SEM images of the outcoming gels often displayed fibril-like structure [2][3][4][5], but in those studies dry samples were used, and the process of drying can influence the subtle structure of the weak monosaccharide gels. Nevertheless, in one case a set of peaks generated by a parallel set of fibrils was detected on a SAXS curve [6,7].…”