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Nick Bampos

Publications and source records attributed to Nick Bampos.

7 recordsLinked to original sources
PubMed2003

Synthesis and characterization of carboxylate complexes of Sn(IV) porphyrin monomers and oligomers.

Most of the porphyrin-recognition chemistry we have investigated previously has centred on kinetically labile metal-ligand interactions, such as Z-N and Ru-N. Our interest in the broader scope of molecular recognition required a metal with the ability to specifically recognise non-nitrogen-based ligands, with a significantly different binding interaction to distinguish it from nitrogen-based analogues. In this report we describe interactions of Sn(IV) porphyrins that bind oxygen-based ligands and for which the Sn(IV)bond;O bond is in slow exchange on the NMR timescale. A series of carboxylate complexes is employed to highlight the structural/geometric features of porphyrin monomers and cyclic oligomers. Where more than one porphyrin unit is present in a molecular scaffold, we report the effect of carboxylate binding on the complex when the two porphyrins contain different metals (typically Sn(IV) and Zn(II)). The unexpected spectroscopic and structural properties of the Sn(2)(9-anthroic acid)porphyrin dimer are also reported.

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PubMed2003

A self-assembling polymer-bound rotaxane under thermodynamic control.

The thermodynamically controlled self-assembly of a neutral donor-acceptor rotaxane, stoppered via porphyrin coordination and bound to polystyrene beads is described, and the dynamic equilibrium between solid and solution phases has been examined by HR MAS nmr spectroscopy.

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PubMed1998

High Catalytic Activity of Chiral Amino Alcohol Ligands Anchored to Polystyrene Resins.

Enantiomerically pure (2S,3S)-2,3-epoxy-3-phenylpropanol (3) has been anchored to Merrifield resins with different degrees of cross-linking and functionalization. The resulting epoxy-functionalized resins 4 have been submitted to completely regioselective (C-3 attack) and stereospecific ring-opening with secondary amines [piperidine (a), N-methylpiperazine (b), and cis-2,6-dimethylpiperidine (c)] in the presence of lithium perchlorate to afford (2R,3R)-3-(dialkylamino)-2-hydroxy-3-phenylpropoxy resin ethers 5a-c. The progress of these two processes has been monitored by (13)C gel-phase NMR spectroscopy. Polymer-supported amino alcohols 5a-c have been evaluated as catalytic ligands in the enantioselective addition of diethylzinc to benzaldehyde, best results being obtained with the cis-2,6-dimethylpiperidine containing ligand 5c. Analogously, (2R,3R)-3-(cis-2,6-dimethylpiperidino)-3-phenyl-1,2-propanediol (11) has been anchored to a 2-chlorotrityl chloride resin (Barlos resin) in dichloromethane in the presence of diisopropylethylamine, and the anchoring process has been also monitored by (13)C gel-phase NMR spectroscopy. The resulting resin 12 has subsequently been used as a chiral ligand in the catalytic addition at 0 degrees C of diethylzinc to a family of fourteen representative aromatic and aliphatic aldehydes 8a-n, to afford the corresponding (S)-1-substituted 1-propanols 10a-n with a mean enantiomeric excess of 92%.

Journal Article↗
PubMed1997

Stepwise Approach to Bimetalic Porphyrin Hosts: Spatially Enforced Coordination of a Nickel(II) Porphyrin.

The synthesis of the Zn(3) 1,1,2-trimer Zn(3)()3 and the NiZn(2) 1,1,2-trimer NiZn(2)()3 by a stepwise convergent route is described. A large affinity for Py(3)()T by both cyclic 1,1,2-trimers, Zn(3)()3 or NiZn(2)()3, with respect to the linear trimers, provides a thermodynamic driving force for the templated cyclization of the new host molecules, which were fully characterized by NMR spectroscopy (COSY and NOESY). The binding properties of several pyridine-containing bidentate and tridentate ligands have been investigated in order to probe the shape and the size of the cavity of the host molecule. Both Py(2)()Pr and Py(2)()Py bind very strongly to Zn(3)()3 and NiZn(2)()3 (ligand affinities in CH(2)Cl(2) at 25 degrees C, >10(8) M(-)(1)), while the tridentate ligand Py(3)()T binds to both Zn(3)()3 and NiZn(2)()3 with a very high binding constant (ligand affinities in CH(2)Cl(2) at 25 degrees C, >10(9) M(-)(1)). This unexpected result for NiZn(2)()3 suggests that the cavity-enforced effective molarity of the third pyridyl of Py(3)()T at the Ni site is high enough to form the first example of a stable 1:1 Ni(II)-pyridyl complex. The resulting Ni(II) paramagnetic complex has been characterized by NMR; the temperature dependence deviates slightly from ideal Curie behavior.

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