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Title: Supramolecular behaviour of some heterocyclic cored pincers
Author: Gomm, John Reginald
ISNI:       0000 0001 3503 4225
Awarding Body: University of Southampton
Current Institution: University of Southampton
Date of Award: 2002
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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.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Crystal engineering