Self-association of an indole based guanidinium-carboxylate-zwitterion: formation of stable dimers in solution and the solid state

• Carolin Rether,
• Wilhelm Sicking,
• Roland Boese and
• Carsten Schmuck

Beilstein J. Org. Chem. 2010, 6, No. 3, doi:10.3762/bjoc.6.3

• UV spectral changes was performed using the Specfit/32 software program from Spectrum Software Associates. However, the pKa of the guanidinium group in 2 also obtained from a UV-pH-titration is significantly larger with pKa = 10.6 ± 0.1. Hence, the lower acidity of the NHs in 2 is a second important