weighted agreement factors of R ¼ 0.0698, wR ¼ 0.1649 for
1
2
3
171 reflections with I > 2sI and R ¼ 0.1165, wR ¼ 0.1888 for
1
2
all data (see Table 1). Simulated morphology, calculated from
the structural data with the geometric method published by
24
Bravais, Friedel, Donnay and Harker (BFDH), was deter-
mined, thanks to the Material Studio molecular modelling
33
software.
For 2,3-dichlorophenylacetic acid, the final cycle of full-matrix
2
least-square refinement on F was based on 1774 observed
reflections and 110 variable parameters and converged with
unweighted and weighted agreement factors of R1 ¼ 0.0476,
wR ¼ 0.1334 for 1523 reflections with I > 2sI and R ¼ 0.0537,
2
1
wR ¼ 0.1334 for all data (see Table 3).
2
Conclusion
Fig. 19 Principle of the AS3PC. Two consecutive temperature cycles are
represented: the enantiomeric excess at T engenders a preferential
secondary nucleation and crystal growth during the cooling ramp. At T
B
2+
B )
An unexpected hybrid salt–cocrystal between the dibase (H
2
F
,
ꢀ
and four monoacids (2AH and 2A ) has been characterized. It
crystallizes as a stable conglomerate. The stoichiometry of this
compound emphasizes the importance of enlarging the ‘‘classic’’
stoichiometries when screening conglomerates.
the suspension is filtered and the crop obtained is pure enantiomer,
whereas the solution is enriched in the counter-enantiomer (solid parts
and liquid parts of the system are depicted in dark and in light colours,
respectively).
The resolutions in methanol and in THF reveal that the
entrainment effect, at its best, persists up to 22% e.e.final in the
counter-enantiomer for a global concentration of 13% in meth-
anol. Furthermore these results prove that the non-chiral
protonated acid subslices do not induce any loss in the chiral
selectivity of the self-assembling process (i.e. the stereoselective
crystallization). The morphology of crystals and the high
performance of AS3PC suggest that the crystal growth proceeds
During these first tests, the aD of the mother liquor was
measured by off-line polarimetry. The filtration time was deter-
mined according to the monitoring of the a
D
of the mother
liquor.
2+
Single crystal X-ray structural determination
by direct incorporation of building units composed of H B ,
2
ꢀ
2
A , 2AH or reconstruction of some surfaces of the crystal might
0
A suitable single crystal of the title compound, (trans-N,N -
occur.
dibenzyldiaminocyclohexane) (2,3-dichlorophenylacetic acid) ,
1
4
was obtained by slow evaporation of a saturated solution in
methanol at room temperature. A single crystal of 2,3-dichlor-
ophenylacetic acid was obtained by slow evaporation of a satu-
rated solution in dichloromethane at room temperature.
Acknowledgements
We are grateful for financial support to the European collabo-
rative project: ‘‘IntEnant’’ FP7-NMP2-SL-2008-214219.
The crystal structures were determined by single crystal
diffraction on a SMART APEX diffractometer (with MoKa1
ꢂ
radiation: l ¼ 0.71073 A). The structures were solved by direct
3
0
Notes and references
methods (SHEL-XS ). Anisotropic displacement parameters
3
1
were refined for all non-hydrogen atoms using SHEL-XL
1 T. E. Beesley and R. P. W. Scott, Chiral Chromatography, J., Wiley,
Chichester, England, New York, 1998.
32
available with the WinGX package. All hydrogen atoms were
included in the models in calculated positions and were refined as
contained to bonding atoms.
2
3
4
5
R. A. Sheldon, Chirotechnology: Industrial Synthesis of Optical Active
Compounds, Marcel Dekker, New York, 1993.
J. Jacques, A. Collet and S. H. Wilen, Enantiomers, Racemates and
Resolutions, Krieger, Malabar, Fla, 1994.
D. Kozma, CRC Handbook of Optical Resolutions via Diastereomeric
Salt Formation, CRC Press, Hoboken, 2001.
P. Newman, Optical Resolutions Procedures for Chemical Compounds,
Optical Resolution Information Center, Manhattan College,
Riverdale, NY, 1978.
0
For (trans-N,N -dibenzyldiaminocyclohexane) (2,3-dichloro-
1
4
phenylacetic acid) , the final cycle of full-matrix least-square
2
refinement on F was based on 5300 observed reflections and 318
variable parameters and converged with unweighted and
6
K. Harata, Chem. Rev., 1998, 98, 1803–1828.
Table 9 AS3PC parameters
7 L. Addadi, J. Van Mil and M. Lahav, J. Am. Chem. Soc., 1981, 103,
249–1251.
8 N. Doki, M. Yokota, S. Sasaki and N. Kubota, Cryst. Growth Des.,
004, 4, 1359–1363.
1
Solvent
2
Methanol
THF
9 C. Viedma, J. Cryst. Growth, 2004, 261, 118–121.
0 W. L. Noorduin, E. Vlieg, R. M. Kellogg and B. Kaptein, Angew.
Chem., Int. Ed., 2009, 48, 9600–9606.
11 G. Coquerel, in Novel Optical Resolution Technologies, Springer,
Heidelberg, 2007, pp. 1–51.
12 G. Coquerel, M.-N. Petit and R. Bouaziz, PCT Pat., WO 95/08522,
1
ꢂ
T
T
B
/ C
/ C
40
25
40
30
ꢂ
F
ꢂ
ꢀ1
Cooling rate/ C min
ꢂ
ꢀ0.29
ꢀ0.20
Solubility at 40 C (% mass)
11.6
27.7
1
995.
1
10 | CrystEngComm, 2012, 14, 103–111
This journal is ª The Royal Society of Chemistry 2012