Trimorphism of N-(3-pyridyl)-benzamideElectronic supplementary information available: X-ray powder pattern, DSC curves and thermomicroscopic images of different samples. This material is available free of charge via the internet at http://pubs.acs.org. CCDC 989630-989634. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c4ce00495g
Three polymorphic modifications of N -(3-pyridyl)-benzamide (form I , monoclinic, space group P 2 1 / c , Z = 4, form II , monoclinic, space group P 2 1 , Z = 4 and form III , monoclinic, space group C 2/ c , Z = 8) were obtained and characterized by single crystal X-ray diffraction. In all forms si...
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Main Authors | , , , , |
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Format | Journal Article |
Language | English |
Published |
02.06.2014
|
Online Access | Get full text |
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Summary: | Three polymorphic modifications of
N
-(3-pyridyl)-benzamide (form
I
, monoclinic, space group
P
2
1
/
c
,
Z
= 4, form
II
, monoclinic, space group
P
2
1
,
Z
= 4 and form
III
, monoclinic, space group
C
2/
c
,
Z
= 8) were obtained and characterized by single crystal X-ray diffraction. In all forms significant differences in the torsion of the phenyl rings and the arrangement of the molecules in the crystal are observed. Quantum chemical calculations of the conformational barriers reveal only small differences and indicate that the conformation of form
III
is energetically favoured but this form does not represent the minimum energy conformation. In the crystal structures of all forms the molecules are connected
via
intermolecular N-H N (form
I
) and N-H O (form
II
and
III
) hydrogen bonds into chains. Solvent mediated conversion and DSC experiments indicate that form
I
represents the thermodynamically stable form between −20 °C and its melting point. Solidification of the melt or sublimation leads directly to form
I
or to an amorphous material that transforms into form
I
on crystallization. Form
II
and form
III
cannot be obtained as phase-pure materials. Mixtures of form
I
and
II
with form
II
as the minor component can be obtained sometimes by crystallization under kinetic control. Upon heating these mixtures, form
II
transforms into form
I
in an endothermic reaction, which indicates that both modifications are enantiotropically related with form
II
being stable at lower temperatures. Thermomicroscopic investigations on selected single crystals of form
III
show a polymorphic transition presumably to form
I
because melting is observed at exactly the same temperature as measured for
I
.
Three polymorphic modifications of
N
-(3-pyridyl)-benzamide were structurally characterized and investigated for their transition behavior and thermodynamic relations. |
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Bibliography: | For ESI and crystallographic data in CIF or other electronic format see DOI 10.1039/c4ce00495g the internet at http://pubs.acs.org. CCDC 989630-989634 Electronic supplementary information available: X-ray powder pattern, DSC curves and thermomicroscopic images of different samples. This material is available free of charge via |
ISSN: | 1466-8033 |
DOI: | 10.1039/c4ce00495g |