Zinc Dialkylhydroxybenzoates with Unusual Structures: First Example of a Discrete Three‐Blade Paddle‐Wheel and a Solvent Engulfed Coordination Polymer

Abstract

Sterically encumbered 4‐hydroxy‐3,5‐diisopropylbenzoic acid (H2diphba), bearing a carboxylic acid, a phenol and two iso‐propyl substituents, has been investigated for the first time as a ligand and supramolecular synthon to isolate eight Zn(II) complexes, [Zn2(Hdiphba)3(OAc)(L)] (L=DMF(1) or pyz (2)), [Zn(Hdiphba)2(2,2′‐bpy)] (3), [Zn(Hdiphba)2(1,10‐phen)] (4), [Zn(Hdiphba)2(pz)2] (5) and [Zn2(Hdiphba)2(μ2‐dmpz)2(Hdmpz)2] (6), [Zn(Hdiphba)2(4,4′‐bpy)]n⋅4nCH3OH (7.4nCH3OH), [Zn2(Hdiphba)4(4,4′‐azobpy)(H2O)2] (8⋅H2diphba), which have been structurally characterized. Compounds 1 and 2 are rare examples of symmetrically bridged triple‐blade molecular tricarboxylate paddle‐wheels which self‐assemble into hexameric units. Compounds 3, 4 and 5 are mononuclear complexes, bearing two exposed phenolic –OH groups self‐assembled into 2‐D arrays via both hydrogen bonding and π‐π stacking interactions. Compound 6 is a rare example of bis‐pyrazolate bridged dinuclear Zn(II) complex with two pyrazole N−H and two phenolic ‐OH groups on the molecular periphery to form hydrogen bonds. The use of 4,4’‐bpy leading to a zig‐zag 1‐D polymer 7 composed of [Zn(Hdiphba)2(4,4’‐bpy)]n chains, positioned 10.77 Å apart. The 1‐D channels of 7 are occupied by hydrogen bonded methanol with a rare (CH3OH)4 cluster as the repeating unit. Compound 8 is a discrete bimetallic complex, isolated with a free H2diphba ligand. The photoluminescence spectra of 1–8 exhibit ligand centered emission at around 325 nm.

Structural Features of 1,3,4-Thiadiazole-Derived Ligands and Their Zn(II) and Cu(II) Complexes Which Demonstrate Synergistic Antibacterial Effects with Kanamycin

“…These findings were consistent with widely reported fact that thiadiazole-derived ligands may demonstrate versatile coordination modes which strongly depend on the presence of additional substituents [8,[22][23][24]. This diversity is particularly high in case of the coordination to Cu(II) and Zn(II) ions, which are well-known for their ability to adopt a wide variety of coordination modes [25,26].…”

Rare Supramolecular Assemblies of a Dicopper(II)‐tetracarboxylate Stabilized by (Methanol)6, Dimethyl Sulfoxide and 4,4′‐Azobipyridyl Bridges

“…It should be noted that only a few examples of Cu(II) paddle‐wheel complexes are reported in which axial and equatorial positions serve as the point of extension through intermolecular interaction ,. We are particularly interested in investigating systems of dinuclear Cu(II)‐carboxylates of structurally bifunctional ligand, 4‐hydroxy‐3,5‐diisopropyl benzoic acid (H 2 diphba, Scheme ) . H 2 diphba contains two functional groups, ‐COOH and –OH, placed diagonally opposite to each other on the benzene ring.…”

“…Further, the cavities formed in the extended networks can encapsulate potentially important solvent clathrates/guest molecules. By using H 2 diphba, we have earlier shown that Zn(II)‐Hdiphba complex encapsulates methanol tetramer which is a prominent species in methanol vapour ,…”