Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Crystal Structures of N-Aryl-N′-4-Nitrophenyl Ureas: Molecular Conformation and Weak Interactions Direct the Strong Hydrogen Bond Synthon
University of Hyderabad, School of Chemistry.
University of Hyderabad, School of Chemistry.
University of Hyderabad, School of Chemistry.
Show others and affiliations
2007 (English)In: Crystal Growth & Design, ISSN 1528-7483, E-ISSN 1528-7505, Vol. 7, no 12, p. 2675-2690Article in journal (Refereed) Published
Abstract [en]

Hydrogen bond competition was studied in 21 X-ray crystal structures of N-X-phenyl-N′-p-nitrophenyl urea compounds (X = H, F, Cl, Br, I, CN, C≡CH, CONH2, COCH3, OH, Me). These structures are classified into two families depending on the hydrogen bond pattern: urea tape structures contain the well-known α-network assembled via N-HO hydrogen bonds; however, in nonurea tape structures the N-H donors hydrogen bond with NO2 groups or solvent O acceptor atoms. Surprisingly, the urea CO hardly accepts strong H bonds in nonurea type structures sustained by ureanitro and ureasolvent synthons. The carbonyl group accepts intra- and intermolecular C-HO interactions. The molecular conformation and H bonding motifs are different in the two categories of structures: the phenyl rings are twisted out of the urea plane in the tape motif, but they are coplanar in the nonurea category. Even though hydrogen bond synthon energy and urea carbonyl acceptor strength favor the N-HO tape structure, the dominant pattern in electron-withdrawing aryl urea crystal structures is the ureanitro/ureasolvent synthon and persistence of intramolecular C-HO interactions. Remarkably, the presence of functional groups that can promote specific C-IO or C-HO interactions with the interfering NO2 group, for example, when X = I, C≡CH, NMe2, and Me, steers crystallization toward the N-HO urea tape structure, and now the diaryl urea molecule adopts the metastable, twisted conformation. Molecular conformer energy calculations and difference nuclear Overhauser enhancement NMR experiments show that the planar, trans-trans-N,N′-diphenyl urea conformation is more stable than the N-Ph twisted rotamer. However, the urea CO is a better hydrogen bond acceptor in the twisted conformer compared to the planar one, based on electrostatic surface potential (ESP) charges. These diaryl ureas together with previously reported crystal structures provide a global structural model to understand how functional groups, molecular conformation, hydrogen bonding, and crystal packing are closely related and influence each other in subtle yet definitive ways. Our strategy simultaneously exploits weak, soft intermolecular interactions and strong, hard hydrogen bonds [supramolecular hard and soft acid-base (HSAB) principle] in the crystal engineering of multifunctional molecules.

Place, publisher, year, edition, pages
2007. Vol. 7, no 12, p. 2675-2690
Identifiers
URN: urn:nbn:se:ltu:diva-7257DOI: 10.1021/cg070155jLocal ID: 599c9b50-07ba-11dd-97e0-000ea68e967bOAI: oai:DiVA.org:ltu-7257DiVA, id: diva2:980146
Note
Upprättat; 2007; 20080411 (andbra)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2017-11-24Bibliographically approved

Open Access in DiVA

No full text in DiVA

Other links

Publisher's full text

Authority records BETA

George, Sumod

Search in DiVA

By author/editor
George, Sumod
In the same journal
Crystal Growth & Design

Search outside of DiVA

GoogleGoogle Scholar

doi
urn-nbn

Altmetric score

doi
urn-nbn
Total: 40 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf