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Supramolecular behaviour of some heterocyclic cored pincers

Supramolecular behaviour of some heterocyclic cored pincers
Supramolecular behaviour of some heterocyclic cored pincers

The solid-state behaviour of pincer shaped molecules with a heterocycle at the hinge and amide- or ester-linked aromatic arms are investigated. A number of core units have been investigated including pyridine-2,6-dicarboxylic acid, benzene-1,3-dicorboxylic acid, thiophene-2,5-dicarboxylic acid, pyridine-2,6-dicarboxylic acid N-oxide, furan-2,5-dicarboxylic acid and pyrrole-2,5-dicarboxylic acid. Furan-2,5- and pyrrole-2,5-dicarboamides have proved more difficult to synthesise.

The conformational behaviours of various core units were calculated using computational modelling and are compared with X-ray crystallographic results. The solid-state structures of amide-linked pincers are governed primarily by the formation of strong hydrogen bonds between both of the amide protons and one amide carbonyl, though in a few cases a different proton-acceptor (Npyridine or ArOMe) binds to the amide protons. The two environments of the carbonyl groups (bound and unbound) are clearly visible in the solid-state IR spectra.

Abstraction of the amide hydrogens with a base forms a dianionic ligand and bis (methyl-(2-pyridyl)) pyridine-2,6-dicarboxamide forms complexes with nickel (II) and copper (II).

The solid-state structures of the ester-linked pincers often contain supramolecular tapes that are held together by two weak C-H...O bonds between neighbouring hinge units (H...O distance 2.4-2,8Å). Pyridine-cored ester-linked pincers seem to have an additional, central C-H...N bond (H...N distance 2.4-2.7 Å), but this may be simply an artefact of the system's geometry. Solid-state IR identifies one carbonyl environment for esters that form symmetrical supramolecular tapes and two for esters that deviate from ideal tape formation.

University of Southampton
Gomm, John Reginald
Gomm, John Reginald

Gomm, John Reginald (2002) Supramolecular behaviour of some heterocyclic cored pincers. University of Southampton, Doctoral Thesis.

Record type: Thesis (Doctoral)

Abstract

The solid-state behaviour of pincer shaped molecules with a heterocycle at the hinge and amide- or ester-linked aromatic arms are investigated. A number of core units have been investigated including pyridine-2,6-dicarboxylic acid, benzene-1,3-dicorboxylic acid, thiophene-2,5-dicarboxylic acid, pyridine-2,6-dicarboxylic acid N-oxide, furan-2,5-dicarboxylic acid and pyrrole-2,5-dicarboxylic acid. Furan-2,5- and pyrrole-2,5-dicarboamides have proved more difficult to synthesise.

The conformational behaviours of various core units were calculated using computational modelling and are compared with X-ray crystallographic results. The solid-state structures of amide-linked pincers are governed primarily by the formation of strong hydrogen bonds between both of the amide protons and one amide carbonyl, though in a few cases a different proton-acceptor (Npyridine or ArOMe) binds to the amide protons. The two environments of the carbonyl groups (bound and unbound) are clearly visible in the solid-state IR spectra.

Abstraction of the amide hydrogens with a base forms a dianionic ligand and bis (methyl-(2-pyridyl)) pyridine-2,6-dicarboxamide forms complexes with nickel (II) and copper (II).

The solid-state structures of the ester-linked pincers often contain supramolecular tapes that are held together by two weak C-H...O bonds between neighbouring hinge units (H...O distance 2.4-2,8Å). Pyridine-cored ester-linked pincers seem to have an additional, central C-H...N bond (H...N distance 2.4-2.7 Å), but this may be simply an artefact of the system's geometry. Solid-state IR identifies one carbonyl environment for esters that form symmetrical supramolecular tapes and two for esters that deviate from ideal tape formation.

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Published date: 2002

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Local EPrints ID: 464761
URI: http://eprints.soton.ac.uk/id/eprint/464761
PURE UUID: 0fe47e29-7ddf-45e1-97cf-7ae63e9252de

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Date deposited: 05 Jul 2022 00:00
Last modified: 05 Jul 2022 03:05

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Author: John Reginald Gomm

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