Self‐Assembly of Triphenylboroxine and the Phenylboronic Ester of Pentaerythritol with Piperazine, trans‐1,4‐Diaminocyclohexane, and 4‐Aminopyridine

Abstract

AbstractThe dinuclear phenylboronic ester derived from pentaerythritol and trinuclear triphenylboroxine were combined with three diamine tectons, that is, 1,4‐diazacyclohexane (pz), trans‐1,4‐diaminocyclohexane (1,4‐chda), and 4‐aminopyridine (4‐apy), to generate supramolecular N→B bound assemblies and to enhance the knowledge concerning the factors governing the formation of such aggregates. From these reactions, three novel complexes of composition {(PhBO)3(pz)}n·nDMF (2), {[(PhBO)3]2(1,4‐chda)}·1,4‐chda (3), and {[(PhBO2)2(C5H8)][4‐apy]2}·CHCl3·1.25H2O (4) were achieved and characterized by elemental analysis, IR and NMR spectroscopy, and single‐crystal X‐ray diffraction analysis. Structural characterization in the solid state revealed that all three products exhibit N→B bonds but have different compositions concerning the B and N tectons to give a 1:1 adduct for 2, a 2:1 adduct for 3, and a 1:2 adduct for 4. In the solid state, compound 2 comprises a 1D coordination polymer, whereas compounds 3 and 4 have discrete molecular structures. Owing to the presence of N–H hydrogen‐bonding sites, in all cases overall 2D or 3D hydrogen‐bonding networks are formed. In solution, the N→B aggregates are mostly dissociated at room temperature, as shown by 11B NMR spectroscopy.