From Flexible to Constrained Tris(tetraamine) Ligands: Synthesis, Acid–Base Properties, and Structural Effect on the Coordination Process with Nucleotides

Abstract

International audienceThis work presents the synthesis and characterization of L2 and L3, which formed with the previously described ligand L1 a family of three tris(tetraamine) ligands based on a mesitylenyl spacer. The trimeric ligands differ from one to the other by the nature of their tetraamine moieties: triethylenetetraamine (L1), cyclen (L2), and constrained cyclen (L3). The impact of the rigidification of the structure from L1 to L3 on the acid–base properties is investigated, and the behavior of the ligands towards triphosphate (TriP), adenosine monophosphate (AMP), adenosine diphosphate (ADP), and adenosine triphosphate (ATP) anion receptors is explored by potentiometric investigations. To characterize and understand the driving forces implicated in the supramolecular assemblies, results are supported by 1H and 31P NMR measurements performed over a wide pH range. ATP appears as the most complexed anion and particular attention is given to comparison with its inorganic triphosphate analogue to highlight the contribution of π-stacking interactions. Results unambiguously show the various coordination scheme induced by the structure of the ligands

Anion receptor chemistry: highlights from 2010

“…9). 47 For example, the affinity towards triphosphate at pH 6 was found to decrease from 68 4 69 4 70 whereas at pH 3 the stability constants increase in the order is 70o68o69.…”

“…The determination of the protonation and stability constants of triphosphate with a series of tripodal tris(tetraamine) ligands described by Tripier and co-workers illustrates this strikingly. 47 The protonation constants were investigated by potentiometric titrations in aqueous solution at 25 1C and summarised in Table 8. The calculated species distribution diagrams (Fig.…”

trans-Methylpyridine cyclen versus cross-bridged trans-methylpyridine cyclen. Synthesis, acid–base and metal complexation studies (metal = Co2+, Cu2+, and Zn2+)

“…Selective syntheses also gave access to more rigid compounds, currently named constrained-or reinforcedmacrocycles, by binding two opposite nitrogen atoms by an alkyl bridge, such as ethylene or propylene chains. [14][15][16][17][18][19][20][21][22][23] These crossbridged ligands may adopt conformations where all four nitrogen lone pairs point inside of the cavity upon metal complexation. Moreover, the short bridging chain induces further rigidity in the ligand and forces the nitrogen lone pairs into a cis-folded geometry which promotes distorted coordination modes, such as tetrahedral, pseudo-octahedral, distorted trigonal-bipyramidal or distorted square pyramidal.…”

Selective Binding of Glyphosate by a Ditopic Cyclic–Open‐Chain Polyazaligand in Aqueous Solution

“…In this way, dimeric and trimeric ligands based on cyclic or linear tetraamines linked by aromatic spacers proved to be attractive and selective hosts for these anions. [22][23][24][25][26][27][28][29] Recently, a series of mixed ligands composed of a cyclam unit and an acyclic amino moiety linked by a pyridine spacer presented high complexation constants with the anions mentioned above. In some cases, the nitrogen atom of the pyridine linker provided an additional anchor point for the anionic guest due to the formation of a hydrogen bond, which enhanced the overall stability of the complex.…”