Summary.
A crystal structure determination of the 9-acyl-dipyrrinone 9-butanoyl-2,3,7,8-tetramethyl-(10H)-dipyrrin-1-one indicates the presence of intermolecularly hydrogen-bonded dimers; however, in CHCl3 solution the pigment is monomeric as determined by vapor pressure osmometry measurements. Lacking an alkyl group at C(8), the 9-acyl-dipyrrinone exhibits only a weak tendency to form dimers in CHCl3 (K A ∼ 60 M −1) as determined by analysis of variable temperature 1H NMR data. In contrast, when the 9-acyl group is replaced by formyl or when the acyl group is fixed in a syn orientation to the pyrrole NH, the dipyrrinone is strongly prone to dimerization in CHCl3.
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Received August 22, 2000. Accepted September 5, 2000
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Huggins, M., Lightner, D. Hydrogen-Bonded Dimers in Dipyrrinones and Acyldipyrrinones. Monatshefte fuer Chemie 132, 203–221 (2001). https://doi.org/10.1007/s007060170131
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DOI: https://doi.org/10.1007/s007060170131