Document Detail

Solvent and substituent effects on aggregation constants of perylene bisimide π-stacks - a linear free energy relationship analysis.
MedLine Citation:
PMID:  22391667     Owner:  NLM     Status:  Publisher    
A series of six perylene bisimides (PBIs) with hydrophilic and hydrophobic side chains at the imide nitrogens were applied for a comparative study of the solvent and structural effects on the aggregation behaviour of this class of dyes. A comparison of the binding constants in tetrachloromethane at room temperature revealed the highest binding constant of about 10(5) M(-1) for a PBI bearing 3,4,5-tridodecyloxyphenyl substituents at the imide nitrogens, followed by 3,4,5-tridodecylphenyl and alkyl-substituted PBIs, whereas no aggregation could be observed in the accessible concentration range for PBIs equipped with bulky 2,6-diisopropylphenyl substituents at the imide nitrogens. The aggregation behaviour of three properly soluble compounds was investigated in 17 different solvents covering a broad polarity range from nonpolar n-hexane to highly polar DMSO and water. Linear free energy relationships (LFER) revealed a biphasic behaviour between Gibbs free energies of aggregation and common empirical solvent polarity scales indicating particularly strong π-π stacking interactions in nonpolar aliphatic and polar alcoholic solvents whilst the weakest binding is observed in dichloromethane and chloroform. Accordingly, PBI aggregation is dominated by electrostatic interactions in nonpolar solvents and by solvophobic interactions in protic solvents. In water, the aggregation constant is increased far beyond LFER expectations pointing at a pronounced hydrophobic effect.
Zhijian Chen; Benjamin Fimmel; Frank Würthner
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Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2012-3-5
Journal Detail:
Title:  Organic & biomolecular chemistry     Volume:  -     ISSN:  1477-0539     ISO Abbreviation:  -     Publication Date:  2012 Mar 
Date Detail:
Created Date:  2012-3-6     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  101154995     Medline TA:  Org Biomol Chem     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
Universität Würzburg, Institut für Organische Chemie and Center for Nanosystems Chemistry, Am Hubland, 97074 Würzburg, Germany.
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