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

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. Reaction of sterically encumbered 4‐hydroxy‐3,5‐diisopropylbenzoic acid (H2diphba) with zinc acetate affords eight complexes self‐assembled into supramolecules which have been structurally characterized. Two of the complexes are discrete three‐blade paddle‐wheels, complex with 4,4′‐bpy is a zig‐zag 1‐D polymer which crystallizes with tetra methanol cluster, (CH3OH)4.