A calix[5]arene-based heterotetratopic host for molecular recognition of long-chain, ion-paired alpha,omega-alkanediyldiammonium salts.
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Alkanes↗
Biomedical subjects
Melchiorre F Parisi
Publications and source records attributed to Melchiorre F Parisi.
Inclusion networks of a calix[5]arene-based exoditopic receptor and long-chain alkyldiammonium ions.
[structure: see text]. Tail-to-tail connection of two cone calix[5]arene moieties by a rigid p-xylyl spacer affords the new exoditopic receptor 3 featuring two pi-rich cavities (assembling cores) in a centrosymmetric divergent arrangement, as established by a single-crystal X-ray analysis. 1H NMR complexation studies of 3 with alkyldiammonium ions support the formation of discrete bis-endo-cavity complexes and/or capsular assemblies along a polymer chain (polycaps), according to the length of the connector.
Alkanes↗
Multipoint molecular recognition of amino acids and biogenic amines by ureidocalix[5]arene receptors.
[reaction: see text] p-tert-Butylcalix[5]arenes in a fixed cone conformation, endowed with a urea functionality at the upper rim, behave as remarkably efficient abiotic receptors of omega-amino acids and biogenic amines, which are bound with one end of the chain within the pi-basic cavity (primary recognition site) and the other grasped by the secondary hydrogen bonding donor/acceptor binding site.
Amino Acids↗
Calix[4]- and calix[5]arene-based multicavity macrocycles.
Synthesis and single-crystal X-ray structures of mixed triple and double calixarenes 6 and 7, obtained from the base-catalyzed condensation of calix[5]arene 1 with cone pertosylated calix[4]arene 2, are reported. VT-NMR studies on 7 are consistent with a molecular motion arising from the anti-gauche conformational interconversion of its ethylene linkages.
Journal Article↗
The Elusive beta-unsubstituted calix[5]pyrrole finally captured.
[reaction: see text] The meso-decamethyl-calix[5]pyrrole 2b was synthesized from the furan-based analogue 1b via the homologation of the furan rings to pyrrole, and its solid-state structure was determined by X-ray crystallography: surprisingly, the binding constant of 2b toward chloride is found to be lower than that of the tetrameric analogue 2a.
Journal Article↗
Calix[6]pyrrole and hybrid calix[n]furan[m]pyrroles (n+m=6): syntheses and host-guest chemistry.
Calix[6]pyrrole 2 and the "hybrid systems" calix[3]furan[3]pyrrole 12, calix[2]furan[4]pyrrole 13, and calix[1]furan[5]pyrrole 14, have been synthesized by increasing conversion of the furan units present in the readily accessible calix[6]furan 3 to pyrroles. The host-guest chemistry of these novel macrocycles towards a number of anions, including halogen ions, dihydrogen phosphate, hydrogen sulfate, nitrate, and cyanide has been investigated in solution by (1)H NMR titration techniques and/or phase transfer experiments. The solid-state structures of the free receptors 2, 12, and 13, the 1:1 complexes of calix[6]pyrrole 2 with chloride and bromide, and the 1:1 complex of 14 with chloride are also reported.
Binding Sites↗
Shape recognition of alkylammonium ions by 1,3-bridged calix[5]arene crown-6 ethers: endo- vs exo-cavity complexation.
A series of tri-O-substituted 1,3-bridged calix[5]arene crown-6 ethers bearing alkyl, arylalkyl, alkoxyalkyl, and alkoxycarbonylmethyl residues at the lower rim and either (t)()Bu or H substituents at the upper rim have been synthesized. (1)H NMR studies have shown that p-tert-butylcalix[5]crowns, irrespective of the size and nature of their lower rim pendant groups, adopt preorganized conelike conformations, whereas p-H-calix[5]crowns with bulky substituents preferentially exist in solution as partial cone conformers (C(1) symmetry). Calix[5]crown derivatives behave as mono- or ditopic receptors for isomeric butylammonium ions, forming endo-cavity (inside the calixarene cup) and/or exo-cavity (at the crown ether moiety) 1:1 complexes according to the shape of the guest. These two binding modes can be clearly distinguished and monitored by (1)H NMR titration experiments.
Journal Article↗
Effect of lipophylic salts on ise detection limit: application to calixarene-based highly efficient potassium-selective electrodes.
A new interpretative model for interpolation of potentiometric data from liquid membrane ion selective electrodes has been formulated; the model allows one to achieve information about partitioning equilibria establishing at the membrane-analysed solution interface of hydrophilic cations present in the membrane as counterions of exchanger lipophylic anions. The fundamental importance of such equilibria is related to their contribution to the detection limit of the electrodes. The soundness of the proposed model was positively verified by employing it in the characterization of new K(+)-selective electrodes based on a calixarenic ionophore. Although the validity of interpolation based on our model does not significantly differ from that obtained with the simpler model providing the inclusion of a constant parameter in the logarithmic argument of Nicolski-Eisenman's equation, the information obtained resulted to be analytically suitable for optimising the membrane composition and, as a consequence, the performance of the electrodes.
Calixarenes↗