RESUMEN
Phosphate ester bonds are widely present in nature (e. g. DNA/RNA) and can be extremely stable against hydrolysis without the help of catalysts. Previously, we showed how the combination of phosphoryl and calix[4]arene moieties in the same organic framework (LPO ) allows isolation of single lanthanide (Ln) metal ions as [LnIII (LPO )2 ](O3 SCF3 )3 . Here we report how by controlling the reaction conditions a new hydrolyzed phosphoryl-calix[4]arene ligand (H3 LHPO ) is formed as a result of LnIII -mediated P-OEt bond cleavage in three out of the eight possible sites in LPO . The chelating nature of H3 LHPO traps the LnIII species in the form of [LnIII (LHPO )((EtO)2 P(O)OH)]2 dimers (Ln=La, Dy, Tb, Gd), where the Dy derivative shows slow magnetization relaxation. The strategy presented herein could be extended to access a broader library of hydrolyzed platforms (Hx LHPO ; x=1-8) that may represent mimics of nuclease enzymes.
RESUMEN
Combination of phosphoryl and calix[4]arene moieties in the same organic framework (LPO) directs the formation of homoleptic double-decker complexes [LnIII(LPO)2](OTf)3 for Ln = Tb and Dy, with the latter displaying slow relaxation of the magnetisation.
RESUMEN
Intravascular (IV) catheters are essential devices in the hospital that are used to monitor a patient's blood and for administering drugs or nutrients. However, IV catheters are also prone to blood clotting at the point of insertion and infection by formation of robust bacterial biofilms on their surface. Nitric oxide (NO) is ideally suited to counteract both of these problems, due to its antimicrobial properties and its ability to inhibit platelet activation/aggregation. One way to equip catheters with NO releasing properties is by electrocatalytic nitrite reduction to NO by copper complexes in a multi-lumen configuration. In this work, we systematically investigate six closely related Cu(II) BMPA- and BEPA-carboxylate complexes (BMPA = bis-(2-methylpyridyl)amine); BEPA = bis-(2-ethylpyridyl)amine), using carboxylate groups of different chain lengths. The corresponding Cu(II) complexes were characterized using UV-Vis, EPR spectroscopy, and X-ray crystallography. Using detailed cyclic voltammetry (CV) and bulk electrocatalyic studies (with real-time NO quantification), in aqueous buffer, pH 7.4, we are able to derive clear reactivity relations between the ligand structures of the complexes, their Faradaic efficiencies for NO generation, their turnover frequencies (TOFs), and their redox potentials. Our results show that the complex [Cu(BEPA-Bu)](OAc) is the best catalyst with a high Faradaic efficiency over large nitrite concentration ranges and the expected best tolerance to oxygen levels. For this species, the more positive redox potential suppresses NO disproportionation, which is a major Achilles heel of the (faster) catalysts with the more negative reduction potentials.
RESUMEN
The new palladacyclopropa[60]fullerene complexes incorporating α-keto stabilized phosphorus ylides were synthesized in a three-component reaction of the unsymmetrical phosphorus ylides [Ph2P(CH2)nPPh2[double bond, length as m-dash]C(H)C(O)C6H4-m-R] (n = 1, R = Br, NO2, (Y(1), Y(2)); n = 2, R = Br, NO2, (Y(3), Y(4))), C60 and Pd(dba)2 (dba = dibenzylideneacetone). The obtained novel P,C-chelated [(η(2)-C60)Pd(κ(2)-Y(1))] (1) and [(η(2)-C60)Pd(κ(2)-Y(2))] (2) complexes and P,P-coordinated [(η(2)-C60)Pd(Y(3))2] (3) and [(η(2)-C60)Pd(Y(4))2] (4) complexes were characterized successfully by IR, UV-Vis, ESI-MS and NMR ((1)H, (13)C and (31)P) spectroscopic methods. Complexes 1-4 are rare examples of palladacyclopropa[60]fullerene complexes with phosphorus ylide ligands. Spectroscopic results revealed that none of possible side products including P,P-coordinated [(η(2)-C60)Pd(Y(1))2] and [(η(2)-C60)Pd(Y(2))2] complexes and also P,C-chelated [(η(2)-C60)Pd(κ(2)-Y(3))] and [(η(2)-C60)Pd(κ(2)-Y(4))] complexes are formed. The EDA analysis indicated that in all the above complexes the metal-ligand bonds are mostly electrostatic in nature.