Synthesis, Structure, and Solution Studies of Cyclohexantriol Complexes of Europium(III)

Abstract

cis,cis-1,3,5-Trihydroxycyclohexane (L(1)()) and cis,cis-1,2,3-trihydroxycyclohexane (L(2)()) have been considered as ligands for the complexation of europium(III) in organic solvents. Three complexes were prepared and characterized by X-ray diffraction analysis, microanalysis, electrospray mass spectrometry, and proton NMR. Depending on the europium(III)-to-ligand ratio, ML or ML(2) complexes were formed in organic solution. Complexes formed with ligand L(2)() are stable in methanol solution, while those obtained from L(1)() are stable only in nonprotic solvents. This difference is related to the amount of energy involved in the necessary chair-chair conversion prior to complexation of the europium(III) ion. In the solid state the coordination sphere including in each case two L(1)()or L(2 )()molecules( )()as tridentate ligands, is completed by a bidentate nitrate anion and one molecule of water in 1, [Eu(L(1))(2)(NO(3))(H(2)O)](NO(3))(2), two monodentate triflate anions and one molecule of water in 2, [Eu(L(1))(2)(OTf)(2)(H(2)O)](OTf), and a bidentate and a monodentate nitrate anion in 3, [Eu(L(2))(2)(NO(3))(2)](NO(3)). Many strong H bonds are present in the crystalline network with H.O distances between 1.77 and 2.301 Å. Proton NMR studies have shown that a moderate lowering of the temperature is sufficient to observe the different species present in solution, the proportions of which depend on the metal-to-ligand ratio. Conductometric studies have also provided indication about the number of coordinated anion in methanol and acetonitrile solutions.

Understanding the relative binding ability of hydroxyfullerene to divalent and trivalent metals

“…It should be noted, however, that in the crystallographically characterized [Ga(catecholate) 3 ] 3− anion, the cations (K + ) have significant interactions with the catecholate ligands which may cause some distortion as compared to the isolated coordination complex. 37 Given the distribution of hydroxyl groups around a fullerenol, it is possible that a similar coordination would be favourable for the fullerenol as observed for cis,cis-1,3,5-trihydroxycyclohexane. S4 and S5, see ESI †) and [M(catecholate) 3 ] 3− (M = Al, Ga, In; Fig.…”

Lipophilic Ligands Derived from 1,3,5-Triamino-1,3,5-trideoxy-cis-inositol (Taci) for Trivalent Lanthanide Complexation in Aqueous and Organic Solutions

“…For several years, we have been engaged in the studies of polyfunctional ligands based on cyclohexanic platforms for group f element selective complexation. [11,12] Among the ligands studied in our laboratory, 1,3,5-triamino-1,3,5-trideoxy-cis-inositol (taci) was found to be a model compound of great interest for this purpose. It is a rigid receptor with preorganized N-and Odonor atoms (Scheme 1), which offer different chelating calculated for Nd 3+ , Eu 3+ , and in some cases for Lu 3+ .…”

Crystal structure of all-cis-cyclohexane-1,2,3-triol, C6H12O3

“…In contrast to cis-inositol, where metal binding via a1,3,5-triaxial or a1,2,3-axial-equatorial-axial coordination mode is possible, only the 1,2,3-axial-equatorial-axial coordination mode is available in the title compound [3,4]. Moreover, one would expect that the chair conformation with one equatorial and two axial hydroxy groups, as required for metal binding, is of higher energy compared to the reversed form with one axial and two equatorial hydroxy groups.…”