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Biomedical subjects

Arie van der Lee

Publications and source records attributed to Arie van der Lee.

8 recordsLinked to original sources
PubMed2006

Synthesis, structural characterization, and properties of aluminum (III) meso-tetraphenylporphyrin complexes axially bonded to phosphinate anions.

Aluminum (III) meso-tetraphenylporphyrins axially bonded to phosphinate anions have been synthesized and characterized by NMR and UV-visible spectroscopy, single-crystal X-ray diffraction, and FAB+ mass spectrometry. According to the solvent and the size of the anion, these compounds are able to self-assemble in two different manners.

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PubMed2006

Columnar self-assembled ureido crown ethers: an example of ion-channel organization in lipid bilayers.

The self-assembly of ureido crown-ether derivatives has been examined in homogeneous solution, in the solid state, and in planar bilayer membranes. The self-assembly is driven by head-to-tail hydrogen bonding between the urea functional groups. Dimers and higher oligomers are formed in CDCl3 solution as assessed by the change in the ureido NH chemical shift as a function of concentration. Single-crystal X-ray diffraction shows that an antiparallel association of the ureas produces columnar channels composed of face-to-face crown ethers. Powder X-ray diffraction studies also show the presence of a minor phase based upon a parallel urea association leading to an alternative columnar arrangement of the crown ethers. In bilayer membranes at low concentration of ureido crown ether added, membrane disruption is observed together with rare single-channel openings, but at higher concentration, a rich array of interconverting channel conductance states is observed. The channel results are interpreted as arising from discreet stacks of ureido crown ethers where the transport of cations would occur via the macrocycles, admixed with larger pores formed by association of the crown ether headgroups around a central large pore.

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PubMed2005

Silver(I) coordination polymers containing heteroditopic ureidopyridine ligands: the role of ligand isomerism, hydrogen bonding, and stacking interactions.

New silver (I) coordination polymers has been successfully designed and synthesized using heteroditopic ureidopyridine ligands 1 and 2 via a combination of coordinations bonds, hydrogen bonding, and pi-pi stacking interactions. This study shows an example of the orientation of the pyridine nitrogen relative to the urea moiety (4-substituted, 1, or 3-substituted, 2), used to control the packing of resulting crystalline coordination polymers. The ureidopyridine ligands present some flexibility because of the conformational rotation around the central urea moiety. The co-complexation of the silver(I) cation by two pyridine moieties and of the PF(6)(-) counteranion by the urea moiety results in the formation of discrete [1(2)Ag](+)PF(6)(-), (3) and [2(2)Ag](+)PF(6)(-), (4) complexes presenting restricted rotation around the central urea functionality. The geometrical information contained in the structures of ligands 1 and 2 and the heteroditopic complexation of silver hexafluorophosphate are fully exploited in an independent manner resulting in the emergence of quasi-rigidly preorganized linear and angular building blocks of 3 and 4, respectively. Additional pi-pi stacking contacts involving interactions between the pi-donor benzene and the pi-acceptor pyridine systems reinforce and direct the self-assembly of the above-described combined structural motifs in the solid state. Accordingly, linear and tubular arrays of pi-pi stacked architectures are generated in the solid state by synergistic and sequential metal ion complexation, hydrogen bonding, and pi-pi stacking interactions.

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PubMed2005

Redox-active pH-responsive molecules: ferrocenylphosphonic acid, ferrocenylmethylphosphonic acid and 1,1'-ferrocenylbisphosphonic acid. Structural determination of FcPO3Na2.5H2O.

The acidity constants of the reduced and oxidized species of ferrocenylphosphonic acids FcPO3H2, FcCH2PO3H2 and fc(PO3H2)2 (Fc = (eta5-C5H5)Fe(eta5-C5H4), fc = (eta5-C5H4)Fe(eta5-C5H4)) in water have been evaluated by potentiometric, 31P NMR, and electrochemical methods. The oxidized forms are more acidic than the reduced ones. The interaction between the redox centre and the charged oxygen atoms of the phosphonate group is shown to be electrostatic. The maximum oxidation shift DeltaE between the protonated and unprotonated species increases with the number of charges of the substrate and decreases with the increase of the distance between the ferrocenyl centre and the oxygen atoms of the phosphonate group. The structure of FcPO3Na2.5H2O is determined. The compound crystallizes in the monoclinic system. It is lamellar with an inorganic layer formed by tetramers Na4O14, the ferrocenyl groups occupying the interlamellar space.

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PubMed2004

Mixed 1D-2D inorganic polymeric zinc ferrocenylphosphonate: crystal structure and electrochemical study.

Needs for ferrocene immobilization on robust host structures are considerable since derivative materials may find applications in medical areas, optical devices, or catalysis. Synthesis of phosphonate functionalized ferrocene allowed its subsequent inorganic polymerization with a zinc salt. The crystallographic structure of the compound obtained, Zn(HO(3)PFc)(2).2H(2)O, shows a unique two-dimensional ferrocene arrangement anchored on a one-dimensional Zn-O-P-O-Zn backbone. The ferrocene packing in the title compound is very similar to the packing found in molecular ferrocene. The electroactivity of Zn(HO(3)PFc)(2).2H(2)O is thoroughly studied. It shows a reversible surface oxidation of ferrocene. Mössbauer spectroscopy for the oxidized compound shows an isomer shift of IS(2b) = 0.432 mm x s(-1) and a quadrupolar splitting of QS(2b) = 0.205 mm x s(-1), which is consistent with a stable S = 1/2 ferrocenium state. The magnetic susceptibility study, Mössbauer spectroscopy, and galvanostatic titration show that only the ferrocene moieties present at the surface of the crystallites are reversibly oxidized. This observation is reinforced by a complex impedance study showing mainly resistive behavior and conductivity measurements indicating weak, thermally assisted, conductivity. The general properties of this compound demonstrate that phosphonato functionalization may be a useful approach for all fields concerned by immobilization of ferrocene.

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PubMed2004

Ion-driven ATP pump by self-organized hybrid membrane materials.

We report new hybrid organic-inorganic materials, based on macrocyclic receptors 1-3 self-organized in tubular superstructures prepared by sol-gel process. Fourier transform infrared (FTIR) and NMR spectroscopic analyses demonstrate that the self-organization by hydrogen bonding of organogel superstructures of 2 and 3 were preserved in the hybrid materials throughout the sol-gel process. The molecular arrangement of heteroditopic receptors defines a particularly attractive functional transport device for both cation (tubular macrocycles) and anion (sandwich-urea) directional-diffusion transport mechanism in the hybrid membrane material. This system has been employed successfully to design a solid dense membrane, functioning as an ion-powered adenosine triphosphate (ATP(2)(-)) pump, and illustrates how a self-organized hybrid material performs interesting and potentially useful functions.

Adenosine Triphosphate↗
PubMed2003

Self-organized heteroditopic macrocyclic superstructures.

[structure: see text] The synthesis of heteroditopic macrocyclic ureido receptors and of their NaX complexes is described. NMR studies and determination of the crystal structure show the formation of self-organized dimeric or polymeric superstructures by a cooperative macrocyclic cation complexation, anion-hydrogen bonding, and pi-pi stacking interactions. Membrane transport experiments show a direct relation between the synergetic ion-pair recognition and the transport properties of these molecular information transfer devices.

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