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Titolo:
Bis(amino acid) oxalyl amides as ambidextrous gelators of water and organic solvents: Supramolecular gels with temperature dependent assembly/dissolution equilibrium
Autore:
Makarevic, J; Jokic, M; Peric, B; Tomisic, V; Kojic-Prodic, B; Zinic, M;
Indirizzi:
Rudjer Boskovic Inst, Lab Chem Crystallog & Biocrystallog, Zagreb 10002, Croatia Rudjer Boskovic Inst Zagreb Croatia 10002 stallog, Zagreb 10002, Croatia Rudjer Boskovic Inst, Lab Supramol & Nucleoside Chem, Zagreb 10002, Croatia Rudjer Boskovic Inst Zagreb Croatia 10002 de Chem, Zagreb 10002, Croatia Univ Zagreb, Fac Sci, Phys Chem Lab, Zagreb 41000, Croatia Univ Zagreb Zagreb Croatia 41000 i, Phys Chem Lab, Zagreb 41000, Croatia
Titolo Testata:
CHEMISTRY-A EUROPEAN JOURNAL
fascicolo: 15, volume: 7, anno: 2001,
pagine: 3328 - 3341
SICI:
0947-6539(20010803)7:15<3328:BAOAAA>2.0.ZU;2-6
Fonte:
ISI
Lingua:
ENG
Soggetto:
GELATION ABILITY; SOLID-STATE; PHASE-TRANSITION; GELLING AGENT; ORGANOGELS; DESIGN; AGGREGATION; ASSEMBLIES; MOLECULES; LIQUIDS;
Keywords:
amino acids; amides; gels; NMR spectroscopy; supramolecular chemistry;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Physical, Chemical & Earth Sciences
Citazioni:
53
Recensione:
Indirizzi per estratti:
Indirizzo: Kojic-Prodic, B Rudjer Boskovic Inst, Lab Chem Crystallog & Biocrystallog,POB 180, Zagreb10002, Croatia Rudjer Boskovic Inst POB 180 Zagreb Croatia10002 Croatia
Citazione:
J. Makarevic et al., "Bis(amino acid) oxalyl amides as ambidextrous gelators of water and organic solvents: Supramolecular gels with temperature dependent assembly/dissolution equilibrium", CHEM-EUR J, 7(15), 2001, pp. 3328-3341

Abstract

Bis(LeuOH) (1a), bis(ValOH) (2a) and bis(PhgOH) (5a) (Phg denotes (R)-phenviglycine) oxalyl amides are efficient low molecular weight organic gelators of various organic solvents and their mixtures as well as water, water/DMSO, and water/DMF mixtures. The organisational motifs in aqueous gels are dominated primarily by lipophilic interactions while those in organic solvents are formed by intermolecular hydrogen bonding. Most of the gels are thermoreversible and stable for many months. However, 2a forms unstable gels with organic solvents which upon ageing transform into variety of crystallineshapes. For some 1a/alcohol gets, a linear correlation between alcohol dielectric constants (epsilon) and gel melting temperatures (T-g) was found. The H-1 NMR and FTIR spectroscopic investigations of selected gels reveal the existence of temperature dependent network assembly/dissolution equilibrium. In the H-1 NMR spectra of gels only the molecules dissolved in entrapped solvent could be observed. By using an internal standard. the concentration of dissolved gelator molecules could be determined. In FTIR spectra, thebands corresponding to network assembled and dissolved gelator molecules are simultaneously present. This enabled determination of the K-gel values by using both methods. From the plots of ln K-gel versus 1/T, the DeltaH(gel) values of selected gels have been determined (-DeltaH(gel) 10-36 kJ mol(-1) range) and found to be strongly solvent dependent. The DeltaH(gel) values determined by H-1 NMR and FTIR spectroscopy are in excellent agreement. Crystal structures of 2a and rac-5a show the presence of organisational motifs and intermolecular interactions in agreement with those in get fibres elucidated by spectroscopic methods.

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Documento generato il 04/04/20 alle ore 07:44:41