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Substituent interference on supramolecular assembly in urea gelators: synthesis, structure prediction and NMR

Substituent interference on supramolecular assembly in urea gelators: synthesis, structure prediction and NMR
Substituent interference on supramolecular assembly in urea gelators: synthesis, structure prediction and NMR
Eighteen N-aryl-N?-alkyl urea gelators were synthesised in order to understand the effect of head substituents on gelation performance. Minimum gelation concentration values obtained from gel formation studies were used to rank the compounds and revealed the remarkable performance of 4-methoxyphenyl urea gelator 15 in comparison to 4-nitrophenyl analogue 14, which could not be simply ascribed to substituent effects on the hydrogen bonding capabilities of the urea protons. Crystal structure prediction calculations indicated alternative low energy hydrogen bonding arrangements between the nitro group and urea protons in gelator 14, which were supported experimentally by NMR spectroscopy. As a consequence, it was possible to relate the observed differences to interference of the head substituents with the urea tape motif, disrupting the order of supramolecular packing. The combination of unbiased structure prediction calculations with NMR is proposed as a powerful approach to investigate the supramolecular arrangement in gel fibres and help understand the relationships between molecular structure and gel formation.
1744-683X
4034-4043
Piana, Francesca
26f205ad-2e31-498e-96e2-e42f48c1df80
Case, David H.
5697af1e-06b6-4e46-83eb-185cec9699ec
Ramalhete, Susana M.
64cee88c-52b8-4dad-aaef-7c35c22401bf
Pileio, Giuseppe
13f78e66-0707-4438-b9c9-6dbd3eb7d4e8
Facciotti, Marco
4c7dc014-3d52-4fdb-98f2-867f81b3447b
Day, Graeme M.
e3be79ba-ad12-4461-b735-74d5c4355636
Khimyak, Yaroslav Z.
7705dc0f-42a7-4a0b-aa57-f95ff886454d
Angulo, Jesús
60b3e732-fbb6-46e6-8fea-6088c3c73171
Brown, Richard C.D.
21ce697a-7c3a-480e-919f-429a3d8550f5
Gale, Philip A.
c840b7e9-6847-4843-91af-fa0f8563d943
Piana, Francesca
26f205ad-2e31-498e-96e2-e42f48c1df80
Case, David H.
5697af1e-06b6-4e46-83eb-185cec9699ec
Ramalhete, Susana M.
64cee88c-52b8-4dad-aaef-7c35c22401bf
Pileio, Giuseppe
13f78e66-0707-4438-b9c9-6dbd3eb7d4e8
Facciotti, Marco
4c7dc014-3d52-4fdb-98f2-867f81b3447b
Day, Graeme M.
e3be79ba-ad12-4461-b735-74d5c4355636
Khimyak, Yaroslav Z.
7705dc0f-42a7-4a0b-aa57-f95ff886454d
Angulo, Jesús
60b3e732-fbb6-46e6-8fea-6088c3c73171
Brown, Richard C.D.
21ce697a-7c3a-480e-919f-429a3d8550f5
Gale, Philip A.
c840b7e9-6847-4843-91af-fa0f8563d943

Piana, Francesca, Case, David H., Ramalhete, Susana M., Pileio, Giuseppe, Facciotti, Marco, Day, Graeme M., Khimyak, Yaroslav Z., Angulo, Jesús, Brown, Richard C.D. and Gale, Philip A. (2016) Substituent interference on supramolecular assembly in urea gelators: synthesis, structure prediction and NMR. Soft Matter, 12, 4034-4043. (doi:10.1039/c6sm00607h).

Record type: Article

Abstract

Eighteen N-aryl-N?-alkyl urea gelators were synthesised in order to understand the effect of head substituents on gelation performance. Minimum gelation concentration values obtained from gel formation studies were used to rank the compounds and revealed the remarkable performance of 4-methoxyphenyl urea gelator 15 in comparison to 4-nitrophenyl analogue 14, which could not be simply ascribed to substituent effects on the hydrogen bonding capabilities of the urea protons. Crystal structure prediction calculations indicated alternative low energy hydrogen bonding arrangements between the nitro group and urea protons in gelator 14, which were supported experimentally by NMR spectroscopy. As a consequence, it was possible to relate the observed differences to interference of the head substituents with the urea tape motif, disrupting the order of supramolecular packing. The combination of unbiased structure prediction calculations with NMR is proposed as a powerful approach to investigate the supramolecular arrangement in gel fibres and help understand the relationships between molecular structure and gel formation.

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Accepted/In Press date: 16 March 2016
e-pub ahead of print date: 29 March 2016
Organisations: Organic Chemistry: SCF

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Local EPrints ID: 390634
URI: http://eprints.soton.ac.uk/id/eprint/390634
ISSN: 1744-683X
PURE UUID: 484d676c-fefa-41e8-b60b-725fda8f3617
ORCID for Giuseppe Pileio: ORCID iD orcid.org/0000-0001-9223-3896
ORCID for Graeme M. Day: ORCID iD orcid.org/0000-0001-8396-2771
ORCID for Richard C.D. Brown: ORCID iD orcid.org/0000-0003-0156-7087
ORCID for Philip A. Gale: ORCID iD orcid.org/0000-0001-9751-4910

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Date deposited: 06 Apr 2016 08:42
Last modified: 10 Jan 2022 05:15

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Contributors

Author: Francesca Piana
Author: David H. Case
Author: Susana M. Ramalhete
Author: Giuseppe Pileio ORCID iD
Author: Marco Facciotti
Author: Graeme M. Day ORCID iD
Author: Yaroslav Z. Khimyak
Author: Jesús Angulo
Author: Philip A. Gale ORCID iD

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