Anion-dependent dimerization of a guanidiniocarbonyl pyrrole cation in DMSO.
With spherical counteranions such as chloride or hexafluorophosphate, the glycine-derived guanidiniocarbonyl pyrrole cation 1 self-assembles into discrete dimers in DMSO, as can be seen by NMR and ESI mass spectral analysis. According to concentration- and temperature-dependent NMR studies, the dimerization is endothermic and therefore entropy driven. Molecular modeling suggests that the dimers are held together by hydrogen bonding in combination with pi-pi interactions. In the presence of picrate anions, dimerization of cation 1 does not occur, probably due to the formation of pi-stacked ion pairs.
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Institut für Organische Chemie, Universität zu Köln, Greinstrasse 4, 50939 Köln, Germany. carsten.schmuch@uni-koeln.de
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D000465:Algorithms; D001665:Binding Sites; D019281:Dimerization; D004121:Dimethyl Sulfoxide / Q000737:chemistry*; D005998:Glycine / Q000737:chemistry; D019791:Guanidine / Q000031:analogs & derivatives* / Q000737:chemistry; D006860:Hydrogen Bonding; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D015394:Molecular Structure; D011758:Pyrroles / Q000737:chemistry*; D021241:Spectrometry, Mass, Electrospray Ionization; D013329:Structure-Activity Relationship; D013816:Thermodynamics
D011758:Pyrroles; D019791:Guanidine; D005998:Glycine; D004121:Dimethyl Sulfoxide