organic compounds
Acta Crystallographica Section C
Crystal Structure
Communications
internal angles at the C atoms. In polymorph (II), the hetero-
cyclic ring is slightly puckered. The ring-puckering parameters
(Cremer & Pople, 1975) for the atom sequence N1ÐC2Ð
N3ÐC4ÐN3iÐC2i [symmetry code: (i) 1 x, y, 12 z] of ꢁ =
90.0 (7)ꢀ and ' = 270.0 (6)ꢀ indicate a twist-boat ring confor-
mation (Boeyens, 1978), although the puckering amplitude Q
ISSN 0108-2701
Ê
Orthorhombic and monoclinic poly-
morphs of 1,3,5-triphenylperhydro-
1,3,5-triazine-2,4,6-trione at 120 K:
chains and sheets formed by
is fairly small, at 0.104 (2) A. The conformations de®ned by
the phenyl rings (Figs. 1 and 2, and Tables 1 and 3) are very
similar.
CÐHÁ Á Áp(arene) hydrogen bonds
M. Baby Mariyatra,a Krishnaswamy Panchanatheswaran,a
John N. Lowb³ and Christopher Glidewellc*
aDepartment of Chemistry, Bharathidasan University, Tiruchirappalli, Tamil Nadu
620 024, India, bDepartment of Chemistry, University of Aberdeen, Meston Walk,
Old Aberdeen AB24 3UE, Scotland, and cSchool of Chemistry, University of St
Andrews, Fife KY16 9ST, Scotland
In the crystal structure of (I), there are no CÐHÁ Á ÁO or CÐ
HÁ Á ÁN hydrogen bonds and no aromatic ꢀ±ꢀ stacking inter-
actions. However, the molecules are linked into chains by a
single CÐHÁ Á Áꢀ(arene) interaction (Table 2). Aromatic atom
Correspondence e-mail: cg@st-andrews.ac.uk
Received 13 July 2004
Accepted 15 July 2004
Online 21 August 2004
C14 in the molecule at (x, y, z) acts as hydrogen-bond donor to
1
4
phenyl ring C31±C36 in the molecule at (54 x, y
,
34 + z),
while atom C14 at (45 x, y 41, 34 + z) in turn acts as donor to
The title compound, C21H15N3O3, crystallizes in two poly-
morphic forms. In the orthorhombic polymorph, (I), in space
group Fdd2 with Z0 = 1, the molecules lie in general positions,
while in the monoclinic polymorph, (II), in space group C2/c
1
2
the C31±C36 ring at (x, y
,
32 + z), so producing a chain
running parallel to the [013] direction and generated by the d-
5
glide plane at x = (Fig. 3). There are no direction-speci®c
interactions between adjacent chains.
8
1
with Z0 = , the molecules lie across twofold rotation axes. In
2
The original report (Usanmaz, 1979) on the monoclinic
phase, (II), did not identify any direction-speci®c interactions
between the molecules. However, the intermolecular interac-
each polymorph, the molecules are linked by a single CÐHÁ Á Á
ꢀ(arene) hydrogen bond, forming chains in polymorph (I) and
sheets in (II).
Comment
We report here the molecular and supramolecular structures
at 120 K of two polymorphic forms of 1,3,5-triphenyl-1,3,5-
perhydrotriazine-2,4,6-trione, the cyclic trimer of phenyl
isocyanate, PhNCO. The orthorhombic polymorph, (I) (Fig. 1),
crystallizes in space group Fdd2 with Z0 = 1, and the mono-
clinic polymorph, (II) (Fig. 2), crystallizes in space group C2/c,
1
with Z0 = . The molecules in (II) lie across twofold rotation
2
axes, with the reference molecule lying across the axis along
(12, y, 14). The structure of (II) was reported from ambient-
temperature data some years ago (Usanmaz, 1979) and it is
clear from the cell dimensions and space group that this earlier
structure was of the same phase as (II), thus suggesting that
the monoclinic phase does not undergo any temperature-
dependent change, at least within the range 120±300 K.
The bond lengths and angles in (I) and (II) (Tables 1 and 3)
are very similar, and the distances show evidence of strong
bond ®xation. Within the heterocyclic rings, the internal bond
angles at the N atoms are consistently some 10ꢀ larger than the
Figure 1
The molecule in the orthorhombic polymorph, (I), showing the atom-
labelling scheme. Displacement ellipsoids are drawn at the 30%
probability level and H atoms are shown as small spheres of arbitrary
radii.
³ Postal address: Department of Electrical Engineering and Physics,
University of Dundee, Dundee DD1 4HN, Scotland.
o682 # 2004 International Union of Crystallography
DOI: 10.1107/S0108270104017342
Acta Cryst. (2004). C60, o682±o685