Oxoanion binding to a cyclic pseudopeptide containing 1,4-disubstituted 1,2,3-triazole moieties

Abstract

A macrocyclic pseudopeptide 3 is described featuring three amide groups and three 1,4-disubstituted 1,2,3-triazole units along the ring. This pseudopeptide was designed such that the amide NH groups and the triazole CH groups converge toward the cavity, thus creating an environment well suited for anion recognition. Conformational studies in solution combined with X-ray crystallography confirmed this preorganisation. Solubility of 3 restricted binding studies to organic media such as 5 vol% DMSO/acetone or DMSO/water mixtures with a water content up to 5 vol%. These binding studies demonstrated that 3 binds to a variety of inorganic anions in DMSO/acetone including chloride, nitrate, sulfate, and dihydrogenphosphate anions. In the more competitive DMSO/water mixtures, only affinity to the more strongly coordinating oxoanions is retained. Quantitative binding studies showed that dihydrogen phosphate complexation in DMSO/water involves the dimer of the HPO anion. By contrast, sulfate and hydrogenpyrophosphate complexation involves a stepwise process comprising formation of a 1 : 1 complex followed by a 2 : 1 complex in which two molecules of 3 (R) bind to a single anion (A). While the second binding equilibrium is associated with a much smaller stability constant in comparison with the first one in the case of sulfate complexation, the two binding constants are of similar magnitude in the case of the hydrogenpyrophosphate anion. Formation of the 2 : 1 complex was attributed to the fact that the cavity size and rigidity of 3 prevents saturation of all hydrogen acceptor sites on the anionic guests.

Protonation and Anion Binding Properties of Aromatic Bis‐Urea Derivatives—Comprehending the Proton Transfer

“…This characteristic, owing its existence to interanionic hydrogen bonds, has been recognized in several examples during the last decade, including complex of an analog of 1 H 2 comprising a cyclohexane linker . However, the thermodynamics of the effect was thoroughly explored only recently, which led to exploitation of the attractive interaction between dihydrogen phosphates to afford interesting self‐assembled systems with advantageous properties . In this context, our results present a valuable contribution, providing an insight into the spatial arrangement of the donor moieties required for optimal interaction between the two DHP units.…”

“…[12] However,t he thermodynamics of the effect was thoroughly explored only recently, [39] which led to exploitation of the attractive interaction between dihydrogen phosphates to afford interesting self-assembled systemsw ith advantageous properties. [44][45][46] In this context, our results present av aluablec ontribution, providing an insight into the spatial arrangemento ft he donor moieties required for optimal interaction between the two DHP units. It is our strong belief that hydrogen bonds between phosphate moieties could be exploited as avaluable interaction, affording exciting new supramolecular systemsint he future.…”

“…In the fitting procedures, the protonation constants and characteristic spectra of the deprotonated forms of receptors were kept fixed at the values determined by 1 HNMR titrations and spectrophotometric titrations with DBU respectively.A cid-base processes of acetic and phosphoric acid in DMSO (protonation, homoassociation, and dimerization) were accounted for and their equilibrium constants were kept fixed at the values recently reported by us:l ogK H (AcOH) = 12.82, logK(AcOH·AcO À ) = 2. 45 [39] Spectrophotometric titrations regarding other studied anions were performed by adding solutions of TEACl, TBANO 3 ,a nd TBAClO 4 (c % 7 10 À3 mol dm À3 )t or eceptor solutions (c % 3.0 10 À3 mol dm À3 , V 0 = 2.32 mL) in DMSO at 25 8C until the n(salt)/n(receptor) molar ratio was around 100. 1 HNMR titrations of the investigated receptors with TBAOAc and TBAH 2 PO 4 were conducted by recording spectral changes of solutions of receptors (c % 6.0 10 À4 mol dm À3 , V 0 = 0.525 mL) upon stepwise addition of as olution of TBAOAc (c % 1.0 10 À2 mol dm À3 ) or TBAH 2 PO 4 (c % 1.0 10 À2 mol dm À3 ).…”

Synthesis, Secondary Structure, and Anion Binding of Acyclic Carbohydrate‐Derived Oligo(amide‐triazole)s

“…[11] The groups of Flood, [12,13] Craig, [14] Hecht, [15] Beer, [16] Schubert, [17] and Kubik [18][19][20][21] have significantly contributed to the study of 1,2,3-triazoles as anion receptors. [11] The groups of Flood, [12,13] Craig, [14] Hecht, [15] Beer, [16] Schubert, [17] and Kubik [18][19][20][21] have significantly contributed to the study of 1,2,3-triazoles as anion receptors.…”

“…donors. [11] The groups of Flood, [12,13] Craig, [14] Hecht, [15] Beer, [16] Schubert, [17] and Kubik [18][19][20][21] have significantly contributed to the study of 1,2,3-triazoles as anion receptors. Oligo and polytriazoles can adopt a U-turn conformation either mediated by metal cations or anions, or by dipole-dipole interactions.…”