Tridentate aromatic receptors L1–L4 containing the 2,6-bis(benzimidazol-2-yl)pyridine chelating unit are designed to exhibit thermotropic calamitic liquid-crystalline phases; the mesomorphic behaviour is essentially retained in the complex [LuL2(NO3)3].
The present disclosure provides nitroxyl donating pharmaceutical compositions comprising N-substituted hydroxylamine derivatives. The compositions are highly efficacious in treating cardiovascular diseases (e.g., heart failure), have a suitable toxicological profile, and are sufficiently stable for intravenous or oral administration.
The present disclosure provides nitroxyl donating pharmaceutical compositions comprising N-substituted hydroxylamine derivatives. The compositions are highly efficacious in treating cardiovascular diseases (e.g., heart failure), have a suitable toxicological profile, and are sufficiently stable for intravenous or oral administration.
Allosteric Effects in Binuclear Homo- and Heterometallic Triple-Stranded Lanthanide Podates
作者:Patrick E. Ryan、Gabriel Canard、Sylvain Koeller、Bernard Bocquet、Claude Piguet
DOI:10.1021/ic301631n
日期:2012.9.17
This work illustrates a simple approach for deciphering and exploiting the various free energy contributions to the global complexation process leading to the binuclear triple-stranded podates [Ln(2)(L9)](6+) (Ln is a trivalent lanthanide). Despite the larger microscopic affinities exhibited by the binding sites for small Ln(3+), the stability constants measured for [Ln(2)(L9)](6+) decrease along the lanthanide series; a phenomenon which can be ascribed to the severe enthalpic penalty accompanying the intramolecular cyclization around small Ln(III), combined with increasing anticooperative allosteric interligand interactions. Altogether, the microscopic thermodynamic characteristics predict beta(La,Lu,L9)(1,1,1)/beta(Lu,La,L9)(1,1,1) = 145 for the ratio of the formation constants of the target heterobimetallic [LaLu(L9)](6+) and [LuLa(L9)](6+) microspecies, a value in line with the quantitative preparation (>90%) of [LaLu(L9)](6+) at millimolar concentrations. Preliminary NMR titrations indeed confirm the rare thermodynamic programming of a pure heterometallic f-f' complex.
Effective Concentration as a Tool for Quantitatively Addressing Preorganization in Multicomponent Assemblies: Application to the Selective Complexation of Lanthanide Cations
The beneficial entropic effect, which may be expected from the connection of three tridentate binding units to a strain-free covalent tripod for complexing nine-coordinate cations (Mz(+) = Ca2+, La3+, Eu3+, Lu3+), is quantitatively analyzed by using a simple thermodynamic additive model. The switch from pure intermolecular binding processes, characterizing the formation of the triple-helical complexes [M(L2)(3)](z+), to a combination of inter- and intramolecular complexation events in [M(L8)](z+) shows that the ideal structural fit observed in [M(L8)](z+) indeed masks large energetic constraints. This limitation is evidenced by the faint effective concentrations, c(eff), which control the intramolecular ring-closing reactions operating in [M(L8)](z+). This predominence of the thermodynamic approach over the usual structural analysis agrees with the hierarchical relationships linking energetics and structures. Its simple estimation by using a single microscopic parameter, c(eff), opens novel perspectives for the molecular tuning of specific receptors for the recognition of large cations, a crucial point for the programming of heterometallic f-f complexes under thermodynamic control.