Self-assembly and recognition properties of a tetraanionic macrocyclic boronate ester in aqueous medium. Issue 38 (30th March 2015)

• Record Type: Journal Article
• Authors: Martínez-Aguirre, Mayte A.; del Campo, Jorge M.; Escalante-Tovar, Sigfrido; Yatsimirsky, Anatoly K.
• Is Part Of: RSC advances. Volume 5:Issue 38(2015)
• Page Start: 30075
• Page End: 30083
• Publication Date: 2015-03-30
• Subjects: Chemistry -- Periodicals; 540.5
• DOI: 10.1039/c5ra03291a
• Languages: English
• ISSNs: 2046-2069

Abstract

Abstract : A tetraanionic [2 + 2] boronate ester macrocycle is self-assembled in water containing 0–5% vol DMSO and binds efficiently various cationic guests including R4 N + cations, choline, acetylcholine, 1-methylnicotinamide and an alkaloid berberine. Abstract : A tetraanionic [2 + 2] boronate ester macrocycle is self-assembled from a dicatechol 3, 3, 3′, 3′-tetramethyl-1, 1′-spirobiindane-5, 5′, 6, 6′-tetraol and 1, 4-benzenediboronic acid in the presence of 2 equivalents of NaOH in water containing 0–5% vol DMSO. No templating by potential guest molecules is required for the self-assembly with close to quantitative yield of the macrocycle. The macrocycle is stable and binds efficiently various cationic guests at pH 9. For alkali and R4 N + cations the association constants K A are growing in the order Cs + < Me ≪ Et ≪ n -Pr with K A = 180 M −1 for Cs + and >10 5 M −1 for Pr4 N + The inclusion of R4 N + cations is confirmed by 1D and 2D 1 H NMR and is further characterized by quantum mechanical calculations. The macrocycle binds efficiently some biologically important cationic guests (choline, acetylcholine, 1-methylnicotinamide) and discriminates Arg-OMe over Lys-OMe. It forms a highly fluorescent complex with an isoquinoline alkaloid berberine, which can be used for optical sensing of tetraalkylammonium guests by a displacement or ternary complex formation mechanism. These results extend previously limited to solid state or non-aqueous media applications of self-assembled boronate ester hosts for molecular recognition to practically more important aqueous solutions.