A Robust Open Framework Formed by Decavanadate Clusters and Copper(II) Complexes of Macrocyclic Polyamines: Permanent Microporosity and Catalytic Oxidation of Cycloalkanes

Abstract

The first decavanadate-based microporous hybrid, namely, [Cu(cyclam)][{Cu(cyclam)}2(V10O28)]·10H2O(1, cyclam = 1,4,8,11-tetraazacyclotetradecane) has been prepared by reaction of (VO3) -anions and {Cu(cyclam)} 2+ complexes in NaCl (aq) at pH 4.6-4.7, and characterized by elemental analyses, thermogravimetry, and X-ray diffraction techniques (powder, single-crystal). Compound 1 exhibits a POMOF-like supramolecular open-framework built up of covalent decavanadate/metalorganic layers with square-like voids, the stacking of which is aided by interlamellar cementing complexes and generates water-filled channels with approximate cross-sections of. 10.4 × 8.8 Å 2 . The framework is robust enough to remain virtually unaltered upon thermal evacuation of all water molecules of hydration, as demonstrated through single-crystal X-ray diffraction studies on the anhydrous phase 1a. This permanent microporosity renders interesting functionality to 1, such as selective adsorption of CO2 over N2 and remarkable activity as heterogeneous catalyst toward the H2O2-based oxidation of the highly-stable, tricyclic alkane adamantane.Porous crystalline materials such as metal organic frameworks (MOFs) have attracted great attention due to their wide range of relevant applications. 1 These materials are constructed by coordination of metal ions or metalcontaining units (nodes) to organic bridging ligands (linkers) to form open crystalline frameworks with permanent porosity. This feature qualifies them as suitable candidates for gas storage and separation, ion exchange, host-guest chemistry, magnetism, biomedicine and catalysis. 2 However, the synthesis of MOFs usually requires harsh conditions (e.g. high temperature or pressure, prolonged reaction times, harmful solvents, etc.), and removal of guest molecules from their cavities often leads to the collapse of the porous structure when flexible linkers are used. In this context, the incorporation of rigid and voluminous species such as metal clusters could increase the overall robustness

A Robust Framework Based on Polymeric Octamolybdate Anions and Copper(II) Complexes of Tetradentate N-donor Ligands

“…The TGA curve (Figure 2a In order to investigate thermally triggered structural transformations that 1 could undergo, variable temperature PXRD experiments were carried out. As mentioned before, two different behaviors have been observed in related hybrid compounds based on {Cu(cyclam)} 2+ units previously reported by some of us [28][29][30]. In the case of robust frameworks, they remained virtually unaltered upon thermal evacuation of guest solvent molecules, whereas dynamic structures undergo crystalline phase transitions promoted by the thermal stimulus.…”

Thermally‐Triggered Crystal Dynamics and Permanent Porosity in the First Heptatungstate‐Metalorganic Three‐Dimensional Hybrid Framework

“…All of the {Cu(cyclam)} 2 + complexes displayt he trans-III configuration in which the NÀHb onds of the two pairs of propylene-bridged N atoms point to opposite directions ( Figure S6). [9] Thisc ompound shows square-like grids, the stacking of whichi sc emented through extensive hydrogen-bonding established with square-planar complex cations that occupy interlamellar spaces, resulting in as upramolecular open-framework architecture. [28] The crystal packing of 1 consists of ac ovalent open-framework constructed by hybrid layers of W 7 units, each linked to four neighboring clusters through four bridging {Cu(cyclam)} 2 + complexes (Cu1B,C u1C, Cu1D, and Cu1E;C u ÀO POM = 2.348(6)-2.572(6) )i nt he crystallographic xz plane ( Figure 3).…”

“…5 )] with ar obust supramolecular framework that closely relatesw ith that of 1 and displays selectivea dsorption of CO 2 overN 2 (BET:2 05 m 2 g À1 ); [9] and 2) the 3D network (TBA) 2 [Cu(BBTZ) 2 (a-Mo 8 O 26 )] (BBTZ = 1,4bis(1,2,4-triazol-1-ylmethyl)-benzene, TBA = tetrabutylammonium), which exhibits the highest sorption capacity reported for aP OM-based hybrid (BET:7 73 m 2 g À1 )d ue to ac rystal packing in which the total solvent accessible void accountsfor as much as the half of the unit cell volume. 5 )] with ar obust supramolecular framework that closely relatesw ith that of 1 and displays selectivea dsorption of CO 2 overN 2 (BET:2 05 m 2 g À1 ); [9] and 2) the 3D network (TBA) 2 [Cu(BBTZ) 2 (a-Mo 8 O 26 )] (BBTZ = 1,4bis(1,2,4-triazol-1-ylmethyl)-benzene, TBA = tetrabutylammonium), which exhibits the highest sorption capacity reported for aP OM-based hybrid (BET:7 73 m 2 g À1 )d ue to ac rystal packing in which the total solvent accessible void accountsfor as much as the half of the unit cell volume.…”

“…Moderately acidic conditions (pH 4-6) afforded the [Cu(cyclam)][{Cu(cyclam)} 2 (V 10 O 28 )]·10 H 2 Os upramolecular POMOF-like material, the architecture of which remains virtually unaltered upon thermale vacuation of solvent molecules to lead to as ystem of microporous channels operative for the selective adsorption of CO 2 over N 2 . [9] In contrast, basic conditions (optimum pH 9) yielded the [{Cu(cyclam)}(VO 3 ) 2 ]·5H 2 O three-dimensional open-framework hybrid,t he porous structure of which collapses upon thermal dehydration and does not show any applicability in gas sorptiona saresult. [10] In both cases, the crystallinity was fully retained throughout the whole dehydration process, and this fact allowed us to unequivocally prove by single-crystal X-ray diffraction analyses the robustness of the decavanadate-baseda rchitecture, as well as the dynamic nature of the metavanadate-based structure, which undergoes as much as three sequential single-crystal-tosingle-crystal (SCSC)t ransitions involving rupture and formation of coordinative bonds.…”

A Versatile Polyoxovanadate in Diverse Cation Matrices: A Supramolecular Perspective

“…In a recent report, de Carvalho and co-workers have demonstrated that decavanadate can interact with G-actin (multifunctional proteins), activating a protein conformational change and thereby that induces oxidation of the cysteine core residues (Marques et al, 2017). Even though, a good number of reports of the decavanadate cluster anion on diverse aspects of its biological significance is available including its catalytic applications (Kwon et al, 1988; Villa et al, 2001; Derat et al, 2006; Conte and Floris, 2010; Mestiri et al, 2013; Martín-Caballero et al, 2016; Amini et al, 2017; Huang et al, 2018), there are only few reports on decavanadate-based inorganic compounds along with their structural characterizations, that have been used as models to understand the formation of decavanadate-based minerals in Nature. D. C. Crans and C. C. McLauchlan and their co-workers have recently published an excellent review article covering the mineral-aspects of decavanadate compounds (Crans et al, 2017).…”