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Wechselwirkungen in Kristallen. 110. Mitteilung . Die Dimorphic von (2‐Pyridyl)(2‐pyrimidyl)amin
Author(s) -
Bock Hans,
Schödel Holger,
Näther Christian,
Butenschön Frauke
Publication year - 1997
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/hlca.19970800222
Subject(s) - chemistry , amine gas treating , crystallography , monoclinic crystal system , melting point , crystallization , differential thermal analysis , stereochemistry , crystal structure , diffraction , organic chemistry , physics , optics
Interactions in Crystals: The Dimorphism of (2‐Pyridyl)(2‐pyrimidyl)amine Preceding structural studies of 2‐aminopyridine derivatives prove that they form polymorphic H ‐pair‐bonded dimmers, and, therefore, (2‐pyrimidyl)amine has been crystallized under different conditions. Two different monoclinic modifications are characterized by their crystal structures of the same space group P 2 1 / c : form I exhibits the well known herringbone motif and form II the sandwich‐herringbone one. Both modifications contain almost identical planar, H‐pair‐bridged molecular dimmers. Crystals of form I are readily obtained from any solvent, whereas those of form II result either on fast evaporation of a Et 2 O solution or by resolidification of the melt. Differential thermal analysis (DTA) and crystallization experiments at different temperatures prove, for both modifications, no transitions in the temperature range between −25° and the melting point at 152° and, therefore the system should be monotropic. The structural and thermodynamic aspects of the (2‐pyridyl)(2‐pyrimidyl)amine dimorphism are discussed in comparison to those of the trimorphism observed for di(2‐pyridyl)amine.