A study of hydrogen transfer photochromism

Robinson, M.T., 1988. A study of hydrogen transfer photochromism. PhD, Nottingham Trent University.

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2-(2',4'-dinitrobenzyl)pyridine 27 is a white crystalline compound which on exposure to 'sun-light' turns deep-blue. If this blue form is now stored in the dark overnight, the colour fades to produce the original white compound.

The aim of this work has been to synthesise compounds with structures related to 27 in order to investigate the requirements for hydrogen-transfer photochromism.

In the attempt to extend the colour range possible in this system, the 4'-nitro-group was selectively reduced to amine and converted to a range of azo-phenol and azo-amine derivatives. The colours of these products varied from tan through orange-yellow to red, but none was found to be photochromic in the solid state.

N-Salicylidene-[3-nitro-4-(a-picolyl)] aniline 142, a molecule possessing two potentially photochromic centres, was synthesised and its properties investigated.

Picolyllithium, picolylcopper and the novel reagent lithium dipicolylcuprate were synthesised and their reactions with a range of halides studied. Although in reaction with benzyl bromide there was a sharp increase in yield of 1-(2'-pyridyl)-2-phenylethane 153 in the order picolyllithium<picolylcopper<lithium dipicolylcuprate, it was found that all three reagents failed to bring about simple nucleophilic substitution of halide in reaction with 2-nitro-4-trifluoromethylchlorobenzene 146.

2-(2'-Nitro-4'-trifluoromethylbenzyl)pyridine 124 was obtained via a Grignard addition to 2-pyridinecarboxaldehyde 160, and found to be devoid of photochromic properties - unexpectedly. The reasons for this are examined.

Attempts to prepare 2,4-dinitrobenzylpyrazine 181 were unsuccessful. The anticipated absence of photochromicity in solid 3-(2',4'-dinitrobenzyl)pyridine 184 was confirmed.

The synthesis of 2,4-dinitrophenylacetaldehyde 200, surprisingly a novel compound, was achieved by reaction of 2,4-dinitrotoluene with dimethylformamidedimethylacetal. The aldehyde was condensed with a number of aromatic amines and the photochromicity and imine enamine equilibria of the products examined.

Item Type: Thesis
Creators: Robinson, M.T.
Date: 1988
ISBN: 9781369324341
Rights: This copy of the thesis has been supplied on condition that anyone who consults it is understood to recognise that its copyright rests with its author and that no quotation from the thesis and no information derived from it may be published without the author's prior written consent.
Divisions: Schools > School of Science and Technology
Record created by: Linda Sullivan
Date Added: 12 Nov 2020 10:40
Last Modified: 11 Oct 2023 10:26
URI: https://irep.ntu.ac.uk/id/eprint/41627

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