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Binding ability of Zn(ii) complexes of [9]aneN3-based receptors for selective recognition of glyphosate in aqueous media.

The synthesis, solution studies, photochemical properties and the X-ray structure of a chromone based fluorescent PdII complex are reported. The ligand contains two chromone units linked as side arms to an ethylenediamine moiety; in the PdII complex the metal ion preorganizes the two hydroxychromone units forming a rigid structure with a negatively charged pocket formed by four oxygen atoms that is able to interact with hard metal cations, such as ions, giving rise to stable bimetallic complexes. Upon interaction with LaIII and GdIII, in particular, the emission intensity at 423 nm increases by a factor of 2 and 8, respectively, while the other rare earth ions quench the fluorescence. Spectrofluorimetric studies on real matrices showed the possibility to use this system as a selective fluorescence probe to detect and trace the presence of Gadolinium in environmental water acting as an OFF–ON chemosensor, with a LOD of 0.4 ppm and a LOQ of 1.2 ppm.

A ligand comprised of a macrocyclic pyridinophane core having a pendant arm containing a secondary amine group linked through a methylene spacer to a pyridyl–oxadiazole–phenyl (PyPD) fluorescent system has been prepared (L). The crystal structures of [ZnL](ClO4)2 and [CuL](ClO4)2 show that M2+ is coordinated to all the nitrogen atoms of the macrocyclic core, the secondary amine of the pendant arm and the nitrogen atom of the pyridine group of the fluorescent moiety, the latter bond being clearly weaker than the one with the pyridine of the macrocycle. Solution studies showed the formation of a highly stable Cu2+ complex with 1 : 1 stoichiometry, whereas with Zn2+ least stable complexes were formed and, given the right conditions, a [Zn3L2]6+ species was also detected, but it was not possible to isolate this species in the solid state. Following Zn2+ coordination, a strong chelation-induced enhancement of fluorescence was observed, a behaviour that was not observed with any of the other metal cations tested.

International audience; Novel adducts of lithium hexafluoroacetylacetonato {Li(hfa)} with polyethers (monoglyme = {CH3OCH2CH2OCH3}, diglyme = {CH3O(CH2CH2O)2CH3}, triglyme = {CH3O(CH2CH2O)3CH3} and tetraglyme {CH3O(CH2CH2O)4CH3} have been synthesized through a single step reaction and characterized by FT-IR spectroscopy, 1H, and 13C NMR, single crystal X-ray diffraction studies along with thermal analysis.

The iminodiphosphine 2-(PPh(2))C(6)H(4)-1-CH=NC(6)H(4)-2-(PPh(2)) (P-N-P') is used for the preparation of the complexes [Pd(η(1)-CHR(1)-CH=CR(2)R(3))(P-N-P')]BF(4) [R(1) = R(2) = R(3) = H: (1); R(1) = R(2) = Ph, R(3) = H: (2); R(1) = R(3) = H, R(2) = Ph: (3); R(1) = H, R(2) = R(3) = Me: (4)]. The P-N-P' tridentate coordination and the η(1)-allyl bonding mode in the solid are confirmed by the X-ray structural analysis of 1. In solution, the complexes 1 and 2 undergo an η(1)-η(3)-η(1) rearrangement at 298 K interconverting the bonding site of the allyl group. A five-coordinate structure with the phosphine ligands in the axial position is proposed for the η(3)-allyl intermediate. For the dynamic process, a ΔG(≠) value of 53.8 kJ mol(-1) is obtained from (1)H NMR data of 2. In 3 and 4, the allyl ligand is rigidly bound to the metal through the less substituted terminus, in line with the higher free energy content of the corresponding isomers: [Pd(η(1)-CHPh-CH=CH(2))(P-N-P')](+) +48.78 kJ mol(-1); [Pd(η(1)-CMe(2)-CH[double bond, length as m-dash]CH(2))(P-N-P')](+) +69.35 kJ mol(-1). The complexes react with secondary amines in the presence of fumaronitrile at different rates yielding allylamines and the palladium(0) derivative [Pd(η(2)-fn)(P-N-P')] (5). On the basis of charge distribution on the allylic carbon atoms and of steric factors, the difference in rate and the regioselectivity in the amination of 1-3 are better rationalized by a mechanism with nucleophilic attack at the η(3)-intermediate rather than by an S(N)2 mechanism with nucleophilic attack at the Pd-CHR(1) carbon atom. The high regioselectivity in the reaction of 4 with piperidine implies an S(N)2' mechanism with nucleophilic attack at the CMe(2) allyl carbon. A dynamic process occurs also for the 18-electron complex 5 consisting in a dissociation-association equilibrium of the olefin.