Exploratory studies into 3d/4f cluster formation with fully bridge-substituted calix[4]arenes

Abstract

Supporting information (additional figures to support discussion and crystallographic information files, CIFs) can can be accessed at https://doi.org/……. Exploratory studies into 3d/4f cluster formation with fully bridgesubstituted calix[4]arenes Calix[4]arenes are extremely versatile ligands that are capable of supporting the formation of a wide variety of polymetallic clusters of paramagnetic metal ions. One can exert influence over cluster formation through alteration of the calix[4]arene framework and subsequent 'expansion' of the lower-rim polyphenolic binding site. The present contribution investigates cluster formation with calix[4]arenes substituted at all four methylene bridge positions with furan moieties. Two known cluster types have been isolated with this ligand, the structures of which lend insight into factors that may ultimately preclude the formation of mixed-metal species.

Site-Specific Metal Chelation Facilitates the Unveiling of Hidden Coordination Sites in an FeII/FeIII-Seamed Pyrogallol[4]arene Nanocapsule

“…[1][2][3][4][5][6][7][8] These inorganic-organic hybrids are typically formed by the metal-directed assembly of suitably functionalized organic ligands, [9][10][11][12][13][14][15][16][17] and recent years have witnessed the synthesis of such species with paramagnetic metal ions; this is a popular strategy due to the inherent potential for one to control or influence the resulting magnetic properties of a system. 9,[18][19][20][21][22][23][24] Our efforts to synthesize such supramolecular hybrids primarily utilize C-alkylpyrogallol [4]arenes (PgCn, where n is the number of carbon atoms in pendant alkyl chains) as organic ligands. Having upper-rim phenolic groups and an associated bowl conformation, coordination to appropriate metal ions can, under appropriate conditions, drive PgCns to form a diverse range of metal-PgCn assembly types.…”

“…The design of metal–organic supramolecular structures with well-defined shapes and dimensions continues to attract intense interest, a primary reason being their ability to mimic biologically active sites. − These inorganic–organic hybrids are typically formed by the metal-directed assembly of suitably functionalized organic ligands, − and recent years have witnessed the synthesis of such species with paramagnetic metal ions; this is a popular strategy due to the inherent potential for one to control or influence the resulting magnetic properties of a system. ,− Our efforts to synthesize such supramolecular hybrids primarily utilize C -alkylpyrogallol­[4]­arenes (PgC n , where n is the number of carbon atoms in pendant alkyl chains) as organic ligands. Having upper-rim phenolic groups and an associated bowl conformation, coordination to appropriate metal ions can, under appropriate conditions, drive PgC n s to form a diverse range of metal–PgC n assembly types. ,− We are specifically interested in MONCs that typically exist in two general forms, termed hexamers (Figure a) and dimers hereafter. ,− These hexamers and dimers are nanoscale capsules containing either 6 or 2 PgC n units, and are formed through coordination to 24 or 8 divalent metal ions, respectively.…”

Enantiomerization Barrier of all‐cis C‐Me‐tetrahydroxy p‐tert‐butylcalix[4]arene and Atropisomeric Equilibrium of its Tetraacetoxy Derivatives

“…A iodocyclohexane/DMF mixture was introduced by Wang, Duan and co‐workers, as a reagent for the demethylation of aryl methyl ethers. This reagent was successfully used by the groups of Fantini and Dalgarno for the exhaustive demethylation of methylene‐substituted calixarene methyl ether derivatives.…”

C–Me Bond Formation at All Methylene Bridges of the Calix[4]arene Scaffold

“…Calix[4]­arenes with functionalized bridges have been prepared via cyclocondensation of suitable precursors or via direct modification of the methylene groups of a preformed calix scaffold. Using the second approach, calix[4]­arenes with all bridges monofunctionalized with a variety of substituents have been obtained via reaction of the bromocalixarenes derivatives (e.g., 1a , 1b ) with nucleophiles under S N 1 reactions conditions . Using this route, in a few cases, C–C bond formation has been achieved by a reaction with electron-rich aromatic groups (e.g., 2-methylfuran) .…”

“…Using the second approach, calix[4]­arenes with all bridges monofunctionalized with a variety of substituents have been obtained via reaction of the bromocalixarenes derivatives (e.g., 1a , 1b ) with nucleophiles under S N 1 reactions conditions . Using this route, in a few cases, C–C bond formation has been achieved by a reaction with electron-rich aromatic groups (e.g., 2-methylfuran) . Methyl groups (or more generally, simple alkyl groups) could not be incorporated by this route since both Grignard and organolithium reagents (which could serve as C-nucleophiles in the reaction with the carbocation intermediates) are incompatible with the acidic ionizing solvent used in the reaction (2,2,2-trifluoroethanol or hexafluoro isopropanol).…”