Oxime-Bridged Mn₆ Clusters Inserted in One-Dimensional Coordination Polymer

Abstract

The reaction of MnCl 2 •4H 2 O with salicylaldoxime (H 2 salox) and the sodium salt of 1,3-bis(carboxypropyl)tetramethyldisiloxane (H 2 L) in a 1:1:1 molar ratio led to the self-assembly of {[Mn 6 O 2 (salox) 6 (H 2 salox)(H 2 O) 3 (μ-L)]H 2 salox• 1.2H 2 O} n , a 1D coordination polymer consisting of hexamanganese(III) salicylaldoximate cluster as secondary building unit (SBU) and tetramethyldisiloxane-based dicarboxylate linker, namely, 1,3-bis(carboxypropyl)tetramethyldisiloxane. The structure of the compound was established by single crystal X-ray diffraction. The Mn(III) clusters consist of two staggered μ 3 -oxo-bridged Mn 3 triangles held together by the oxygen atoms of the oxime groups. Because of Jahn−Teller distortion, the Mn−O distances reach 2.5 Å for the oxygen atoms located above and below the triangles mean planes. The compound showed a glass transition peak at around 14 °C in the differential scanning calorimetry (DSC) curve. The magnetic susceptibility data were fitted with a set of three intracluster antiferromagnetic exchange interaction coupling constants: J 1 = −0.65 cm −1 , J 2 = −1.5 cm −1 , and J 3 = −0.9 cm −1 . The ac magnetic susceptibility measurements in the 2−5 K temperature range reveal a frequencydependent behavior indicative of a slow relaxation of magnetization at low temperature. The coexistence of the lypophilic 1,3-bis(propyl)tetramethyldisiloxane moieties and hydrophilic polar SBUs confers to the structure an amphiphilic character. Dynamic light scattering (DLS), small-angle X-ray scattering (SAXS), and transmission (TEM) and scanning (SEM) electron microscopies demonstrate that in dimethylformamide (DMF) the coordination polymer organizes as micelles, whereas in chloroform it tends to form inverse micelles and vesicles.

Hydrophobic, amorphous metal–organic network readily prepared by complexing the aluminum ion with a siloxane spaced dicarboxylic acid in aqueous medium

“…The SiOSi bond angle has the value of 156.2 (1)°. It falls in the range observed for a variety of supramolecular and coordination compounds containing 1,3‐bis(carboxypropyl)tetramethyldisiloxane units as free molecule and coordinated mono‐ or bi‐nodal ligand published by our group. It is to mention also that both cis ‐ and trans ‐oide conformations have been observed for these compounds depending on the coordination geometry of the SBUs and H‐bonding configuration.…”

“…The particularity of this ditopic ligand lies in the containment of the tetramethyldisiloxane moiety with high flexibility conferred by the siloxane linkage and hydrophobicity conferred by the methyl groups (known as the most hydrophobic organic groups) attached to the silicon atoms. 1,3‐Bis(carboxypropyl)tetramethyldisiloxane was prepared according to the procedure previously reported by us since 1999 although, meanwhile, the compound has become commercially available at Gelest, Inc., Morrisville, PA. We have previously used this acid in the preparation of complexes of metals, most of which are crystalline and structurally characterized, but the acid as such, although crystalline having a melting point around 50 °C, has never been isolated alone as crystals suitable for crystallographic analysis. In the context of the study presented in this manuscript, when crystallization of the network was attempted by the addition of formic acid as a framework modulator, according to Wißmann et al ., the disiloxanic acid liberated from the salt form by the stronger formic acid unexpectedly separated itself in the form of crystals perfectly suited for single crystal X‐ray diffraction analysis.…”

“…While Davies et al . synthesized and used as ligands hexa(4‐carboxyphenyl)disiloxane molecules, we tried to use a longer and more flexible dicarboxylic acid, 1,3‐bis(carboxypropyl)tetramethyldisiloxane, as a ligand for metals or for the construction of more complex structures …”

Syntheses and crystal structures of the one-dimensional coordination polymers formed by [Ni(cyclam)]2+ cations and 1,3-bis(3-carboxypropyl)tetramethyldisiloxane anions in different degrees of deprotonation

“…Two of them are co-crystals of the acid with organic bases derived from pyridine [refcodes NERTOV (Vlad et al, 2013a) and VIPZUR (Racles et al, 2013)]. Other complexes represent one-or two-dimensional coordination polymers formed by Cu II (YIGXOD; Vlad et al, 2013b), Co II (NERTIP; Vlad et al, 2013a), Zn II [NERTUB (Vlad et al, 2013a), GIWSAI (Vlad et al, 2014) and GAPKOA (Zaltariov et al, 2016)]. Except for the last complex, in which the secondary building unit is a hexametal oxocluster bridged by salicylaldoxime ligands, all of the other compounds contain additional heterocyclic co-ligands.…”

From Amorphous Silicones to Si-Containing Highly Ordered Polymers: Some Romanian Contributions in the Field

“…Carboxylic ligands containing silicon in the substrate (a) and organic co-ligands (b) used; 1D coordination polymer based on: diphenylsilane-spaced dicarboxylate (H2L1 ligand) coordinated to the NiL [131] (c), tetramethyl-Figure 9. Carboxylic ligands containing silicon in the substrate (a) and organic co-ligands (b) used; 1D coordination polymer based on: diphenylsilane-spaced dicarboxylate (H 2 L 1 ligand) coordinated to the NiL[131] (c), tetramethyldisiloxane-spaced dicarboxylate (H 2 CX ligand) coordinated to the NiL preformed complex[130] (d) and to oxime-bridged Mn 6+ cluster[55] (e); Covalent 2D coordination polymers looking like nano-sheets consisting of: dimanganese coordinated by H 2 CX and 4,4'-azopyridine[56] (f); trinuclear (g) and pentanuclear (h) manganese coordinated with H 2 L 1[127].…”