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CHEMISTRY
ISSN: 2053-2296

Polymorphism and phase transformation in the di­methyl sulfoxide solvate of 2,3,5,6-tetra­fluoro-1,4-di­iodo­benzene

aDepartment of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, England
*Correspondence e-mail: adb29@cam.ac.uk

Edited by A. L. Spek, Utrecht University, The Netherlands (Received 13 April 2020; accepted 24 April 2020; online 30 April 2020)

A new polymorph (form II) is reported for the 1:1 dimethyl sulfoxide solvate of 2,3,5,6-tetra­fluoro-1,4-di­iodo­benzene (TFDIB·DMSO or C6F4I2·C2H6SO). The structure is similar to that of a previously reported polymorph (form I) [Britton (2003[Britton, D. (2003). Acta Cryst. E59, o1332-o1333.]). Acta Cryst. E59, o1332–o1333], containing layers of TFDIB mol­ecules with DMSO mol­ecules between, accepting I⋯O halogen bonds from two TFDIB mol­ecules. Re-examination of form I over the temperature range 300–120 K shows that it undergoes a phase transformation around 220 K, where the DMSO mol­ecules undergo re-orientation and become ordered. The unit cell expands by ca 0.5 Å along the c axis and contracts by ca 1.0 Å along the a axis, and the space-group symmetry is reduced from Pnma to P212121. Refinement of form I against data collected at 220 K captures the (average) structure of the crystal prior to the phase transformation, with the DMSO mol­ecules showing four distinct disorder com­ponents, corresponding to an overlay of the 297 and 120 K structures. Assessment of the inter­molecular inter­action energies using the PIXEL method indicates that the various orientations of the DMSO mol­ecules have very similar total inter­action energies with the molecules of the TFDIB framework. The phase transformation is driven by inter­actions between DMSO mol­ecules, whereby re-orientation at lower temperature yields significantly closer and more stabilizing inter­actions between neighbouring DMSO mol­ecules, which lock in an ordered arrangement along the shortened a axis.

1. Introduction

The mol­ecule 2,3,5,6-tetra­fluoro-1,4-di­iodo­benzene (TFDIB) is a common halogen-bond donor (Metrangolo & Resnati, 2001[Metrangolo, P. & Resnati, G. (2001). Chem. Eur. J. 7, 2511-2519.]; Cavallo et al., 2016[Cavallo, G., Metrangolo, P., Milani, R., Pilati, T., Priimagi, A., Resnati, G. & Terraneo, G. (2016). Chem. Rev. 116, 2478-2601.]). The work described in this article originated from a cocrystal screening, where TFDIB was combined with a series of potential halogen-bond acceptors in dimethyl sulfoxide (DMSO) solution. Crystals of TFDIB·DMSO (see Scheme) were quite commonly obtained from these experiments, some of which were found to be different from a previously reported crystal structure at 297 K [Britton, 2003[Britton, D. (2003). Acta Cryst. E59, o1332-o1333.]; Cambridge Structural Database (CSD; Groom et al., 2016[Groom, C. R., Bruno, I. J., Lightfoot, M. P. & Ward, S. C. (2016). Acta Cryst. B72, 171-179.]) refcode IKIFOX]. We refer to the previously reported structure (IKIFOX) as form I and the newly obtained polymorph as form II. The structures are similar and we suspected at first that form II might have arisen from a phase transformation on cooling of form I in the N2 cryostream during single-crystal data collection. We therefore obtained crystals of form I and measured them at various temperatures. We did not find any transformation of form I to form II, but instead observed re-orientation of the DMSO mol­ecules in form I to give a further new structure measured at 120 K. We describe herein the various crystal structures of TFDIB·DMSO and the application of dispersion-corrected DFT and PIXEL calculations (Gavezzotti, 2002[Gavezzotti, A. (2002). J. Phys. Chem. B, 106, 4145-4154.], 2003[Gavezzotti, A. (2003). J. Phys. Chem. B, 107, 2344-2353.], 2011[Gavezzotti, A. (2011). New J. Chem. 35, 1360-1389.]) to examine the DMSO re-orientation on cooling of form I.

[Scheme 1]

2. Experimental

2.1. Synthesis and crystallization

Crystals of forms I and II were produced during a sequence of attempted cocrystallization experiments. TFDIB and an anti­cipated coformer were dissolved in DMSO, and crystals were produced by vapour diffusion of water into the solution under ambient conditions. Form I (CSD refcode IKIFOX; Britton, 2003[Britton, D. (2003). Acta Cryst. E59, o1332-o1333.]) was obtained frequently, while crystals of form II were obtained specifically from a 2:3 mixture of TFDIB and melamine (C3H6N6). The structure of form II was measured at 180 K, whereby the crystals were plunged directly from ambient conditions into a cold N2 stream. Similar treatment of form I resulted in cracking and the loss of single crystallinity. Analysis of form I was therefore made by placing the crystal initially into the N2 stream at room temperature, followed by slow cooling as described in §3.2[link].

2.2. Refinement

Crystal data, data collection and structure refinement details are summarized in Table 1[link]. Determination of the structure of form II at 180 K was straightforward. The DMSO mol­ecule in the asymmetric unit is situated with its inter­nal mirror plane on the crystallographic mirror plane at x,[1 \over 4],z in the space group Pnma (Fig. 1[link]). The S atom is split into two atomic sites within the mirror plane, with refined site occupancies of 0.424 (5) and 0.576 (5).

Table 1
Experimental details

For all structures: C6F4I2·C2H6OS, Mr = 479.99, Z = 4. Experiments were carried out with Mo Kα radiation using a Nonius KappaCCD diffractometer. Absorption was corrected for by multi-scan methods (SORTAV; Blessing, 1995[Blessing, R. H. (1995). Acta Cryst. A51, 33-38.]). H-atom parameters were constrained.

  Form II Form I (120 K) Form I (220 K)
Crystal data
Crystal system, space group Orthorhombic, Pnma Orthorhombic, P212121 Orthorhombic, Pnma
Temperature (K) 180 120 220
a, b, c (Å) 12.8308 (6), 21.3307 (12), 4.6463 (2) 10.6731 (2), 18.0023 (5), 6.5470 (2) 11.6799 (4), 18.2664 (8), 6.0984 (2)
V3) 1271.65 (11) 1257.94 (5) 1301.09 (8)
μ (mm−1) 5.14 5.19 5.02
Crystal size (mm) 0.14 × 0.14 × 0.14 0.12 × 0.10 × 0.10 0.12 × 0.10 × 0.10
 
Data collection
Tmin, Tmax 0.411, 0.464 0.475, 0.599 0.541, 0.611
No. of measured, independent and observed [I > 2σ(I)] reflections 7999, 1463, 952 11512, 2834, 2141 8062, 1520, 948
Rint 0.049 0.089 0.057
(sin θ/λ)max−1) 0.649 0.649 0.650
 
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.033, 0.086, 1.01 0.043, 0.078, 0.99 0.038, 0.082, 1.06
No. of reflections 1463 2834 1520
No. of parameters 83 148 112
No. of restraints 0 0 71
Δρmax, Δρmin (e Å−3) 1.01, −1.27 0.91, −1.18 0.62, −0.69
Absolute structure Refined as an inversion twin.
Absolute structure parameter 0.19 (5)
Computer programs: COLLECT (Nonius, 1998[Nonius (1998). COLLECT. Nonius BV, Delft, The Netherlands.]), HKL SCALEPACK (Otwinowski & Minor, 1997[Otwinowski, Z. & Minor, W. (1997). Methods in Enzymology, Vol. 276, Macromolecular Crystallography, Part A, edited by C. W. Carter Jr & R. M. Sweet, pp. 307-326. New York: Academic Press.]), HKL DENZO (Otwinowski & Minor, 1997[Otwinowski, Z. & Minor, W. (1997). Methods in Enzymology, Vol. 276, Macromolecular Crystallography, Part A, edited by C. W. Carter Jr & R. M. Sweet, pp. 307-326. New York: Academic Press.]), SHELXT (Sheldrick, 2015a[Sheldrick, G. M. (2015a). Acta Cryst. C71, 3-8.]), SHELXL2018 (Sheldrick, 2015b[Sheldrick, G. M. (2015b). Acta Cryst. A71, 3-8.]) and Mercury (Macrae et al., 2020[Macrae, C. F., Sovago, I., Cottrell, S. J., Galek, P. T. A., McCabe, P., Pidcock, E., Platings, M., Shields, G. P., Stevens, J. S., Towler, M. & Wood, P. A. (2020). J. Appl. Cryst. 53, 226-235.]).
[Figure 1]
Figure 1
The mol­ecular structure of form II at 180 K, with displacement ellipsoids at the 50% probability level for non-H atoms. The site-occupancy factors for atoms S1 and S1A are 0.424 (5) and 0.576 (5), respectively. Only the major com­ponent is shown as connected. [Symmetry codes: (i) −x + 1, −y + 1, −z; (ii) x, −y + [{3\over 2}], z.]

For form I at 120 K, the space group is clearly P212121, with the DMSO mol­ecule ordered on a general equivalent position and with no significant residual electron density in the vicinity of the mol­ecule (Fig. 2[link]). The structure was refined as an inversion twin with the Flack parameter converging to 0.19 (5). The applied unit-cell setting and origin (placing the 21 screw axes at x,[1 \over 2],[1 \over 2]; 0,y,0; [1 \over 2],0,z) are nonstandard for the space group P212121 [Hall symbol: P 2ac 2n], but chosen to maintain the relationship with the form I structure at 297 K (IKIFOX) in its standard setting of Pnma.

[Figure 2]
Figure 2
The mol­ecular structure of form I at 120 K, with displacement ellipsoids at the 50% probability level for non-H atoms.

For the refinement of form I after cooling to 220 K, the DMSO mol­ecule was modelled in four orientations (Fig. 3[link]). Two orientations are similar to those in form II, with the inter­nal mirror plane of the DMSO mol­ecule coincident with the mirror plane at x,[1 \over 4],z in the space group Pnma, and with the S atom split into two atomic sites with refined site occupancies of 0.356 (3) and 0.191 (3). A further orientation is defined with the S atom out of the mirror plane with a refined site occupancy of 0.226 (2), giving two further orientations of the DMSO mol­ecule. The site occupancies of the three refined com­ponents were tightly restrained to sum to unity (using SUMP in SHELXL; Sheldrick, 2015b[Sheldrick, G. M. (2015b). Acta Cryst. A71, 3-8.]) and restraints were applied to all S—O, S—C and C⋯C distances. All non-H atoms were refined with anisotropic displacement parameters, restrained to resemble isotropic behaviour (ISOR in SHELXL). An extinction coefficient was refined. In all struc­tures, the H atoms of the DMSO mol­ecule were placed in idealized positions, with Uiso(H) = 1.5Ueq(C). The methyl groups were not permitted to rotate around their local three­fold axes, since this prevented convergence of the refinement. The structure and refinement details are presented in Table 1[link].

[Figure 3]
Figure 3
The mol­ecular structure of form I at 220 K, with displacement ellipsoids at the 50% probability level. H atoms have been omitted from the disordered DMSO mol­ecule for clarity, and only the major com­ponent is shown as connected. The site-occupancy factors for the DMSO com­ponents containing atom S1, S1A and S1B are 0.356 (3), 0.191 (3) and 0.226 (2), respectively. [Symmetry codes: (i) −x + 1, −y + 1, −z − 1; (ii) x, −y + [{3\over 2}], z.]

2.3. Computational details

The crystal structures were energy-minimized with dispersion-corrected density functional theory (DFT-D) using the CASTEP module (Clark et al., 2005[Clark, S. J., Segall, M. D., Pickard, C. J., Hasnip, P. J., Probert, M. J., Refson, K. & Payne, M. C. (2005). Z. Kristallogr. 220, 567-570.]) in Materials Studio (Accelrys, 2011[Accelrys (2011). Materials Studio. Accelrys Software Inc., San Diego, CA, USA.]). The PBE functional (Perdew et al., 1996[Perdew, J. P., Burke, K. & Ernzerhof, M. (1996). Phys. Rev. Lett. 77, 3865-3868.]) was applied with a plane-wave cut-off energy of 520 eV, in combination with the Grimme semi-empirical dispersion correction (Grimme, 2006[Grimme, S. (2006). J. Comput. Chem. 27, 1787-1799.]). The structures in the space group Pnma were reduced to the space group P212121 to allow the definition of com­plete mol­ecules, so all optimizations were carried out in P212121. The unit-cell parameters were constrained to the experimental values. For the disordered structures, models were built containing the various individual DMSO com­ponents and optimized separately. The DFT-D-optimized structures were used as input for the PIXEL module of the CSP package (Gavezzotti, 2002[Gavezzotti, A. (2002). J. Phys. Chem. B, 106, 4145-4154.], 2003[Gavezzotti, A. (2003). J. Phys. Chem. B, 107, 2344-2353.], 2011[Gavezzotti, A. (2011). New J. Chem. 35, 1360-1389.]) to examine the energies of the pairwise inter­molecular inter­actions. The calculated inter­action energies are estimated to have accuracy within the range ca ±3 kJ mol−1.

3. Results and discussion

3.1. Structure of form II

Both form I and form II adopt structures with a layered arrangement of TFDIB mol­ecules in the (020) planes (Fig. 4[link]). The DMSO mol­ecules occupy sites between these layers. The difference between forms I and II reveals some flexibility in the structure of the TFDIB layers within the crystalline state. Taking one layer and looking side-on to the mol­ecules [projecting onto the (110) planes], form II shows an approximately perpendicular arrangement of mol­ecules, while form I shows a smaller angle between the mol­ecular planes (Fig. 5[link]). This difference is reflected in the unit-cell parameters (Table 1[link]), particularly in the substanti­ally shorter c axis for form II. The sites occupied by the DMSO mol­ecules between the TFDIB layers in form II are substanti­ally similar to those in form I, as described in §3.2[link]. The DMSO mol­ecules lie on the crystallographic mirror planes at x,[1 \over 4],z and x,[3 \over 4],z, accepting I⋯O halogen bonds from two TFDIB mol­ecules either side of the mirror plane [I1⋯O1 = 2.847 (2) Å]. Disorder is present in the manner described for form I at 297 K (§3.2[link]), with the DMSO mol­ecules adopting orientations A and B with refined site occupancies of 0.576 (5) and 0.424 (5), respectively.

[Figure 4]
Figure 4
The form I and II structures, viewed along the c axis, showing layers of TFDIB mol­ecules in the (020) planes. The arrangement of TFDIB mol­ecules in form I is closely com­parable at 297 and 120 K (the 120 K structure is shown).
[Figure 5]
Figure 5
A single layer of TFDIB mol­ecules, looking side-on to the mol­ecules [projecting approximately onto the (110) planes]. Form I shows a smaller angle between the mol­ecular planes and has a longer c axis. The arrangement of TFDIB mol­ecules in form I is closely com­parable at both 297 and 120 K (the 120 K structure is shown).

3.2. Temperature-dependent structure of form I

The previously-reported structure of form I at 297 K (Britton, 2003[Britton, D. (2003). Acta Cryst. E59, o1332-o1333.]; CSD refcode IKIFOX) exhibits two orientations of the DMSO mol­ecules (labelled A and B), as illustrated in Fig. 6[link]. We obtained an identical disorder model in our own refinements at 300 K (not reported). Each DMSO mol­ecule lies on a mirror plane in a pocket between eight TFDIB mol­ecules. The position of the O atom is approximately consistent in both orientations, acting as an acceptor for I⋯O halogen bonds from two TFDIB mol­ecules (I⋯O ≃ 2.80–2.90 Å). In orientation A, the S—CH3 bond vectors point approximately perpendicular to the planes of two TFDIB mol­ecules. In orientation B, the S—CH3 bonds lie closer to parallel to the TFDIB planes (Fig. 6[link]). Thus, the DMSO mol­ecules are `anchored' by the I⋯O halogen bonds, but the S—CH3 bond vectors can point either perpendicular or parallel to the neighbouring TFDIB rings. In the structure reported by Britton (2003[Britton, D. (2003). Acta Cryst. E59, o1332-o1333.]), the refined site occupancies for A and B were 0.620 (17) and 0.380 (17), respectively.

[Figure 6]
Figure 6
Two orientations (A and B) of the DMSO mol­ecule in the form I structure at 297 K (Britton, 2003[Britton, D. (2003). Acta Cryst. E59, o1332-o1333.]). The mol­ecules occupy a site between eight TFDIB mol­ecules. The arrows indicate the directions of the S—CH3 bond vectors, i.e. perpendicular (A) or parallel (B) to the planes of the two TFDIB mol­ecules at the top in the front plane.

On cooling of form I to 220 K, the unit cell and positions of the TFDIB mol­ecules remain com­parable to those at 297 K and both DMSO orientations A and B remain present. However, new peaks arise in the electron density corresponding to further orientations of the DMSO mol­ecules. At first it was difficult to unravel this disorder, but the situation became clear after the structure was determined at 120 K. The disorder at 220 K corresponds to four DMSO orientations, com­prising A, B and two new (symmetry-related) orientations described below for the 120 K structure. A significant feature of the form I structure at 220 K is that its unit-cell parameters and TFDIB positions remain com­parable to those at 297 K (Britton, 2003[Britton, D. (2003). Acta Cryst. E59, o1332-o1333.]). Thus, cooling of the structure from 297 to 220 K causes some re-orientation of the DMSO mol­ecules, but the crystal does not yet appear to have undergone any phase transformation.

After cooling the crystal slowly (ca 1 K min−1) to 120 K, the structure changes clearly from the 297 and 220 K structures. The unit cell expands by ca 0.5 Å along the c axis and contracts by ca 1.0 Å along the a axis. Looking side-on to the TFDIB mol­ecules in one layer shows only a very subtle change com­pared to the 297 K structure (Fig. 7[link]). However, the DMSO mol­ecules are ordered and the space-group symmetry is reduced to P212121. The DMSO orientation (labelled C, Fig. 8[link]) retains essentially the same O-atom position, anchored by the I⋯O halogen bonds [I1⋯O1i = 2.874 (7) Å and I4⋯O1ii = 2.871 (7) Å; symmetry codes: (i) x, y, z − 1; (ii) −x, y − [{1\over 2}], −z + 1]. Compared to orientations A and B (Fig. 6[link]), the mol­ecule rotates approximately around its S—O bond. One of the S—CH3 bond vectors retains a position com­parable to orientation A, with a `perpendicular' approach to the face of the neighbouring TFDIB mol­ecule. The other adopts a new position pointing approximately along the c axis, between TFDIB mol­ecules. Although the symmetry of the structure is clearly reduced to P212121, the TFDIB mol­ecules retain the effective mirror symmetry of the Pnma structure, so that two locally equivalent DMSO orientations can be envisaged, with the S—CH3 bond pointing towards the face of either TFDIB mol­ecule related by the local mirror symmetry (Fig. 8[link]). Neighbouring DMSO mol­ecules along the a axis alternate in this respect (visible in Fig. 4[link]), and the two additional com­ponents seen in the 220 K structure correspond to an overlay of these two orientations. It appears from the partial observation of orientation C at 220 K that some degree of DMSO reorientation can be tolerated within the `high-temperature' TFDIB framework in form I, but the DMSO re-orientation ultimately drives the phase transformation to the ordered `low-temperature' structure.

[Figure 7]
Figure 7
Overlay of a single layer of TFDIB mol­ecules [projecting approximately onto the (110) planes] in the form I structure at 297 K (red; Britton, 2003[Britton, D. (2003). Acta Cryst. E59, o1332-o1333.]) and 120 K (blue). The change in the unit-cell parameters is clear, but the positions of the TFDIB mol­ecules change only very slightly.
[Figure 8]
Figure 8
Orientation C for the DMSO mol­ecule in the form I structure at 120 K. The arrows indicate the directions of the S—CH3 bond vectors: one is equivalent to orientation A (Fig. 6[link]), while one is distinct, pointing between TFDIP mol­ecules. Due to the local mirror symmetry, two locally equivalent orientations are possible for the DMSO mol­ecule, pointing either to the left or to the right in the diagram; these orientations alternate for neighbouring mol­ecules along the c axis (Fig. 4[link]).

Additional temperature-dependent measurements were made to examine the unit-cell parameters in the region of the phase transformation. A crystal of form I was cooled from 300 to 200 K at a rate of ca 2 K min−1, with the unit cell determined at 10 K inter­vals. The unit-cell volume (Fig. 9[link]a) shows an approximately linear decrease over the range 300→230 K, but a clear change of gradient occurs between 230 and 220 K, suggesting that reorientation of the DMSO mol­ecules begins to take place significantly around this temperature. Clear discontinuities are evident for both the a and the c axes (Fig. 9[link]b) between the measurements made at 220 K (resembling the 297 K structure) and 210 (resembling the 120 K structure), suggesting that the reorientation is largely com­plete by 210 K. Hence, the disordered structure at 220 K captures the (average) structure of the crystal mid-transformation.

[Figure 9]
Figure 9
Variation in (a) the unit-cell volume (•) and (b) the a (□) and c (filled □) axis lengths over the temperature range 300→200 K for form I. Error bars (where visible) are drawn at ±(3 × s.u.). The clear discontinuities in the axis lengths correspond to the phase transformation from the `high-temperature' TFDIB framework to the `low-temperature' framework.

3.3. DFT-D and PIXEL calculations

To investigate the energetics of the associated inter­molecular inter­actions, models were constructed containing the various DMSO com­ponents and optimized using dispersion-corrected DFT calculations (DFT-D; see Experimental, §2[link]). The purpose of the DFT-D step is to produce a model with an optimized representation of the disordered solvent mol­ecules, where the geometry from the X-ray refinement is likely to be less well defined. The pairwise inter­actions in the optimized structures were analysed using the PIXEL approach (Gavezzotti, 2002[Gavezzotti, A. (2002). J. Phys. Chem. B, 106, 4145-4154.], 2003[Gavezzotti, A. (2003). J. Phys. Chem. B, 107, 2344-2353.], 2011[Gavezzotti, A. (2011). New J. Chem. 35, 1360-1389.]). The principal inter­est is the total inter­action energy between the DMSO mol­ecules and its neighbours for orientations A, B and C in the form I structure. In each structure, the pairwise inter­actions sorted by centroid–centroid distance show a clear set of eight DMSO–TFDIB inter­actions, as indicated in Figs. 6[link] and 8[link], with no other DMSO–TFDIB inter­actions having significant inter­action energy. Similarly, each structure shows a clear set of six significant DMSO–DMSO inter­actions, which are directly com­parable between the structures. Table 2[link] shows the sums of the total energies for these sets of inter­actions. It is evident that the total inter­action energy between DMSO and the TFDIB framework changes little between orientations A, B and C. Orientation B appears slightly favoured over orientation A in the form I structure at 297 K.1 For orientation C, however, the calculations give a clear indication: orientation C is favoured on account of significantly more stabilizing inter­actions between the DMSO mol­ecules. In particular, the inter­action between DMSO mol­ecules along the a axis (Fig. 4[link]) has a centroid–centroid distance ca 0.5 Å shorter than any other DMSO–DMSO inter­action and is particularly stabilizing (Etot = −17.3 kJ mol−1). It appears that this inter­action drives the ordering of the DMSO mol­ecules, resulting in the ca 1.0 Å contraction of the a axis and symmetry reduction to the space group P212121. The DMSO reorientation takes place within a TFDIB framework that is clearly flexible, as evidenced by the existence of the three closely-related framework structures reported herein, and with little consequence for the total energy of the DMSO–TFDIB inter­actions.

Table 2
Total inter­molecular inter­action energies (kJ mol−1) involving the DMSO mol­ecules in form I, calculated using the PIXEL method, applied to the DFT-D-optimized structures

Structure Disorder com­ponent Refinement temperature (K) a (Å) b (Å) c (Å) Etot DMSO–TFDIB Etot DMSO–DMSO
Form I A 297 11.819 18.418 6.075 −107.4 −25.0
Form I B 297 11.819 18.418 6.075 −112.0 −27.4
Form I C 120 10.673 18.002 6.547 −109.8 −44.6

4. Conclusion

The existence of TFDIB·DMSO form II and the variation of the form I structure as a function of temperature shows that the layered arrangement of TFDIB mol­ecules can exhibit significant flexibility in the crystalline state. This flexibility accommodates several orientations for the DMSO mol­ecules between the layers, with apparently little variation in the DMSO–TFDIB inter­action energies. The DMSO mol­ecules are consistently anchored by accepting I⋯O halogen bonds, but their orientation can vary relative to the TFDIB mol­ecules and relative to each other. The PIXEL calculations suggest no clear preference for orientations A or B in form I, consistent with the observed disorder in the structure at 297 K, but they show clearly why orientation C is preferred in the structure at 120 K. Optimization of the inter­actions between neighbouring DMSO mol­ecules locks in an ordered arrangement, which accounts for the observed changes in the unit-cell parameters and space group on cooling of form I below ca 220 K. The applied combination of temperature-dependent X-ray dif­fraction measurements and inter­molecular energy calculations provides a clear picture of the temperature-dependent phase transformation in this case

Supporting information


Computing details top

For all structures, data collection: COLLECT (Nonius, 1998); cell refinement: HKL SCALEPACK (Otwinowski & Minor, 1997); data reduction: HKL DENZO and SCALEPACK (Otwinowski & Minor, 1997); program(s) used to solve structure: SHELXT (Sheldrick, 2015a); program(s) used to refine structure: SHELXL2018 (Sheldrick, 2015b); molecular graphics: Mercury (Macrae et al., 2020); software used to prepare material for publication: SHELXL2018 (Sheldrick, 2015b).

2,3,5,6-Tetrafluoro-1,4-diiodobenzene dimethyl sulfoxide (Form_II) top
Crystal data top
C6F4I2·C2H6OSDx = 2.507 Mg m3
Mr = 479.99Mo Kα radiation, λ = 0.71073 Å
Orthorhombic, PnmaCell parameters from 21867 reflections
a = 12.8308 (6) Åθ = 1.0–27.5°
b = 21.3307 (12) ŵ = 5.14 mm1
c = 4.6463 (2) ÅT = 180 K
V = 1271.65 (11) Å3Block, colourless
Z = 40.14 × 0.14 × 0.14 mm
F(000) = 880
Data collection top
Nonius KappaCCD
diffractometer
952 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tubeRint = 0.049
ω and φ–scansθmax = 27.5°, θmin = 3.7°
Absorption correction: multi-scan
(SORTAV; Blessing, 1995)
h = 1616
Tmin = 0.411, Tmax = 0.464k = 2721
7999 measured reflectionsl = 66
1463 independent reflections
Refinement top
Refinement on F2Primary atom site location: dual
Least-squares matrix: fullSecondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.033Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.086H-atom parameters constrained
S = 1.01 w = 1/[σ2(Fo2) + (0.0432P)2]
where P = (Fo2 + 2Fc2)/3
1463 reflections(Δ/σ)max = 0.001
83 parametersΔρmax = 1.01 e Å3
0 restraintsΔρmin = 1.26 e Å3
Special details top

Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/UeqOcc. (<1)
I10.38600 (2)0.63930 (2)0.24280 (5)0.03540 (15)
F30.69292 (19)0.46774 (12)0.1884 (5)0.0431 (7)
F20.60539 (19)0.57331 (13)0.3762 (7)0.0494 (7)
C10.4543 (3)0.55611 (18)0.0978 (9)0.0299 (10)
C20.5514 (3)0.5373 (2)0.1889 (9)0.0337 (10)
C30.5972 (3)0.4832 (2)0.0928 (9)0.0341 (10)
S10.1684 (3)0.7500000.5001 (8)0.0401 (14)0.424 (5)
O10.2819 (4)0.7500000.4285 (11)0.0624 (15)0.424 (5)
C40.1438 (4)0.8137 (3)0.7210 (9)0.0539 (16)0.424 (5)
H4A0.0696190.8146060.7707850.081*0.424 (5)
H4B0.1854060.8100220.8970900.081*0.424 (5)
H4C0.1624950.8524170.6200540.081*0.424 (5)
S1A0.2350 (2)0.7500000.7040 (6)0.0357 (10)0.576 (5)
O1A0.2819 (4)0.7500000.4285 (11)0.0624 (15)0.576 (5)
C4A0.1438 (4)0.8137 (3)0.7210 (9)0.0539 (16)0.576 (5)
H4D0.1106040.8142850.9108760.081*0.576 (5)
H4E0.1805720.8533440.6891870.081*0.576 (5)
H4F0.0904870.8081530.5721220.081*0.576 (5)
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
I10.0367 (2)0.0246 (2)0.0449 (3)0.00355 (11)0.00368 (13)0.00443 (13)
F30.0317 (14)0.0379 (16)0.0597 (16)0.0061 (12)0.0097 (12)0.0088 (12)
F20.0490 (15)0.0381 (17)0.0610 (18)0.0041 (13)0.0148 (14)0.0193 (16)
C10.028 (2)0.022 (2)0.039 (3)0.0015 (19)0.005 (2)0.0002 (19)
C20.037 (2)0.027 (2)0.037 (3)0.004 (2)0.0025 (19)0.003 (2)
C30.031 (2)0.034 (3)0.038 (3)0.001 (2)0.002 (2)0.000 (2)
S10.053 (3)0.032 (2)0.035 (2)0.0000.006 (2)0.000
O10.067 (3)0.026 (3)0.094 (4)0.0000.045 (3)0.000
C40.050 (3)0.045 (4)0.066 (4)0.011 (3)0.011 (2)0.009 (3)
S1A0.0364 (17)0.0259 (16)0.045 (2)0.0000.0053 (13)0.000
O1A0.067 (3)0.026 (3)0.094 (4)0.0000.045 (3)0.000
C4A0.050 (3)0.045 (4)0.066 (4)0.011 (3)0.011 (2)0.009 (3)
Geometric parameters (Å, º) top
I1—C12.090 (4)S1—C41.731 (6)
I1—O12.847 (2)C4—H4A0.9800
F3—C31.347 (5)C4—H4B0.9800
F2—C21.351 (5)C4—H4C0.9800
C1—C21.376 (6)S1A—O1A1.414 (5)
C1—C3i1.386 (6)S1A—C4A1.794 (6)
C2—C31.371 (6)C4A—H4D0.9800
S1—O11.494 (6)C4A—H4E0.9800
S1—C4ii1.731 (6)C4A—H4F0.9800
C1—I1—O1176.73 (14)S1—C4—H4A109.5
C2—C1—C3i116.9 (4)S1—C4—H4B109.5
C2—C1—I1121.8 (3)H4A—C4—H4B109.5
C3i—C1—I1121.3 (3)S1—C4—H4C109.5
F2—C2—C3118.0 (4)H4A—C4—H4C109.5
F2—C2—C1119.8 (4)H4B—C4—H4C109.5
C3—C2—C1122.2 (4)O1A—S1A—C4A108.5 (2)
F3—C3—C2119.3 (4)S1A—C4A—H4D109.5
F3—C3—C1i119.8 (4)S1A—C4A—H4E109.5
C2—C3—C1i120.9 (4)H4D—C4A—H4E109.5
O1—S1—C4ii108.1 (3)S1A—C4A—H4F109.5
O1—S1—C4108.1 (3)H4D—C4A—H4F109.5
C4ii—S1—C4103.3 (4)H4E—C4A—H4F109.5
S1—O1—I1121.65 (11)
C3i—C1—C2—F2179.5 (4)C1—C2—C3—F3179.4 (4)
I1—C1—C2—F20.3 (6)F2—C2—C3—C1i179.5 (4)
C3i—C1—C2—C31.4 (7)C1—C2—C3—C1i1.5 (8)
I1—C1—C2—C3179.4 (3)C4ii—S1—O1—I147.4 (4)
F2—C2—C3—F30.3 (6)C4—S1—O1—I1158.6 (3)
Symmetry codes: (i) x+1, y+1, z; (ii) x, y+3/2, z.
2,3,5,6-Tetrafluoro-1,4-diiodobenzene dimethyl sulfoxide (Form_I_120K) top
Crystal data top
C6F4I2·C2H6OSDx = 2.534 Mg m3
Mr = 479.99Mo Kα radiation, λ = 0.71073 Å
Orthorhombic, P212121Cell parameters from 22578 reflections
a = 10.6731 (2) Åθ = 1.0–27.5°
b = 18.0023 (5) ŵ = 5.19 mm1
c = 6.5470 (2) ÅT = 120 K
V = 1257.94 (5) Å3Block, colourless
Z = 40.12 × 0.10 × 0.10 mm
F(000) = 880
Data collection top
Nonius KappaCCD
diffractometer
2141 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tubeRint = 0.089
ω and φ–scansθmax = 27.5°, θmin = 3.7°
Absorption correction: multi-scan
(SORTAV; Blessing, 1995)
h = 1313
Tmin = 0.475, Tmax = 0.599k = 2222
11512 measured reflectionsl = 88
2834 independent reflections
Refinement top
Refinement on F2Secondary atom site location: difference Fourier map
Least-squares matrix: fullHydrogen site location: inferred from neighbouring sites
R[F2 > 2σ(F2)] = 0.043H-atom parameters constrained
wR(F2) = 0.078 w = 1/[σ2(Fo2) + (0.0294P)2]
where P = (Fo2 + 2Fc2)/3
S = 0.99(Δ/σ)max < 0.001
2834 reflectionsΔρmax = 0.91 e Å3
148 parametersΔρmin = 1.17 e Å3
0 restraintsAbsolute structure: Refined as an inversion twin.
Primary atom site location: dualAbsolute structure parameter: 0.19 (5)
Special details top

Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.

Refinement. Refined as a 2-component inversion twin.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/Ueq
I10.16341 (6)0.65366 (4)0.30645 (10)0.0241 (2)
I40.11363 (6)0.38880 (4)0.33529 (10)0.0238 (2)
F20.0772 (5)0.5501 (3)0.3553 (8)0.0258 (15)
F30.1813 (6)0.4475 (4)0.1158 (8)0.0286 (16)
F50.1268 (5)0.4943 (3)0.3876 (9)0.0263 (16)
F60.2318 (5)0.5959 (3)0.1467 (8)0.0265 (15)
C10.0822 (10)0.5744 (6)0.1121 (15)0.023 (3)
C20.0242 (9)0.5361 (6)0.1730 (16)0.020 (2)
C30.0796 (10)0.4838 (7)0.0479 (17)0.025 (3)
C40.0315 (10)0.4683 (6)0.1451 (16)0.022 (3)
C50.0748 (10)0.5076 (6)0.2036 (16)0.021 (2)
C60.1290 (10)0.5591 (6)0.0776 (15)0.024 (3)
S10.3629 (3)0.79817 (17)0.3362 (4)0.0283 (7)
O10.2421 (7)0.7752 (4)0.4393 (10)0.027 (2)
C70.4693 (12)0.7225 (8)0.3733 (18)0.046 (4)
H7A0.4964850.7213030.5162690.068*
H7B0.5424620.7289830.2845660.068*
H7C0.4273060.6756580.3394130.068*
C80.3380 (12)0.7839 (7)0.0711 (16)0.036 (3)
H8A0.3050560.7337410.0487770.054*
H8B0.4174970.7895650.0020880.054*
H8C0.2776130.8205200.0203170.054*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
I10.0231 (4)0.0235 (4)0.0257 (4)0.0015 (3)0.0009 (3)0.0009 (3)
I40.0259 (4)0.0216 (4)0.0239 (3)0.0010 (3)0.0026 (3)0.0003 (3)
F20.026 (3)0.028 (4)0.024 (3)0.001 (3)0.006 (3)0.001 (3)
F30.025 (4)0.033 (4)0.028 (3)0.004 (3)0.003 (3)0.002 (3)
F50.024 (4)0.028 (4)0.027 (3)0.001 (3)0.001 (3)0.001 (3)
F60.024 (3)0.027 (4)0.028 (3)0.006 (3)0.002 (3)0.003 (3)
C10.025 (7)0.016 (6)0.027 (6)0.003 (5)0.006 (5)0.009 (5)
C20.014 (5)0.030 (7)0.017 (5)0.008 (5)0.002 (5)0.007 (6)
C30.020 (6)0.030 (8)0.025 (6)0.003 (6)0.004 (5)0.001 (5)
C40.024 (6)0.020 (7)0.021 (6)0.009 (5)0.002 (5)0.004 (5)
C50.020 (6)0.020 (6)0.023 (6)0.003 (5)0.000 (5)0.004 (5)
C60.022 (7)0.024 (7)0.026 (5)0.004 (6)0.009 (5)0.016 (5)
S10.0264 (17)0.0278 (17)0.0306 (14)0.0038 (13)0.0005 (14)0.0076 (14)
O10.027 (5)0.028 (5)0.026 (4)0.005 (4)0.009 (4)0.003 (4)
C70.042 (9)0.058 (11)0.037 (8)0.020 (7)0.006 (7)0.005 (7)
C80.033 (7)0.051 (10)0.024 (6)0.002 (7)0.002 (6)0.005 (6)
Geometric parameters (Å, º) top
I1—C12.099 (11)C4—C51.391 (15)
I1—O1i2.874 (7)C5—C61.369 (15)
I4—C42.090 (11)S1—O11.513 (8)
I4—O1ii2.871 (7)S1—C81.774 (11)
F2—C21.344 (11)S1—C71.791 (13)
F3—C31.343 (12)C7—H7A0.9800
F5—C51.348 (12)C7—H7B0.9800
F6—C61.359 (12)C7—H7C0.9800
C1—C61.367 (14)C8—H8A0.9800
C1—C21.387 (15)C8—H8B0.9800
C2—C31.381 (15)C8—H8C0.9800
C3—C41.392 (15)
C1—I1—O1i171.5 (3)F6—C6—C5118.1 (9)
C4—I4—O1ii174.0 (3)C1—C6—C5122.0 (10)
C6—C1—C2117.4 (11)O1—S1—C8105.6 (5)
C6—C1—I1122.5 (9)O1—S1—C7105.8 (6)
C2—C1—I1120.1 (8)C8—S1—C796.8 (6)
F2—C2—C3118.3 (9)S1—C7—H7A109.5
F2—C2—C1120.4 (10)S1—C7—H7B109.5
C3—C2—C1121.3 (10)H7A—C7—H7B109.5
F3—C3—C2118.8 (10)S1—C7—H7C109.5
F3—C3—C4120.1 (10)H7A—C7—H7C109.5
C2—C3—C4121.1 (11)H7B—C7—H7C109.5
C5—C4—C3116.7 (10)S1—C8—H8A109.5
C5—C4—I4121.8 (8)S1—C8—H8B109.5
C3—C4—I4121.5 (8)H8A—C8—H8B109.5
F5—C5—C6119.1 (9)S1—C8—H8C109.5
F5—C5—C4119.4 (9)H8A—C8—H8C109.5
C6—C5—C4121.5 (10)H8B—C8—H8C109.5
F6—C6—C1119.9 (10)
C6—C1—C2—F2178.1 (9)C3—C4—C5—F5179.0 (9)
I1—C1—C2—F20.9 (13)I4—C4—C5—F50.0 (13)
C6—C1—C2—C30.9 (16)C3—C4—C5—C60.3 (16)
I1—C1—C2—C3179.9 (9)I4—C4—C5—C6179.3 (8)
F2—C2—C3—F32.1 (16)C2—C1—C6—F6178.9 (9)
C1—C2—C3—F3178.9 (9)I1—C1—C6—F60.1 (14)
F2—C2—C3—C4178.1 (9)C2—C1—C6—C50.7 (16)
C1—C2—C3—C40.9 (17)I1—C1—C6—C5179.6 (8)
F3—C3—C4—C5179.3 (9)F5—C5—C6—F61.5 (15)
C2—C3—C4—C50.6 (16)C4—C5—C6—F6179.2 (9)
F3—C3—C4—I40.2 (15)F5—C5—C6—C1178.9 (9)
C2—C3—C4—I4179.6 (8)C4—C5—C6—C10.3 (17)
Symmetry codes: (i) x, y, z1; (ii) x, y1/2, z+1.
2,3,5,6-Tetrafluoro-1,4-diiodobenzene dimethyl sulfoxide (Form_I_220K) top
Crystal data top
C6F4I2·C2H6OSDx = 2.450 Mg m3
Mr = 479.99Mo Kα radiation, λ = 0.71073 Å
Orthorhombic, PnmaCell parameters from 4026 reflections
a = 11.6799 (4) Åθ = 1.0–27.5°
b = 18.2664 (8) ŵ = 5.02 mm1
c = 6.0984 (2) ÅT = 220 K
V = 1301.09 (8) Å3Block, colourless
Z = 40.12 × 0.10 × 0.10 mm
F(000) = 880
Data collection top
Nonius KappaCCD
diffractometer
948 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tubeRint = 0.057
ω and φ–scansθmax = 27.5°, θmin = 3.5°
Absorption correction: multi-scan
(SORTAV; Blessing, 1995)
h = 1515
Tmin = 0.541, Tmax = 0.611k = 2323
8062 measured reflectionsl = 77
1520 independent reflections
Refinement top
Refinement on F2Secondary atom site location: difference Fourier map
Least-squares matrix: fullHydrogen site location: mixed
R[F2 > 2σ(F2)] = 0.038H-atom parameters constrained
wR(F2) = 0.082 w = 1/[σ2(Fo2) + (0.0284P)2 + 1.1523P]
where P = (Fo2 + 2Fc2)/3
S = 1.06(Δ/σ)max = 0.001
1520 reflectionsΔρmax = 0.62 e Å3
112 parametersΔρmin = 0.68 e Å3
71 restraintsExtinction correction: (SHELXL2018; Sheldrick, 2015b)
Primary atom site location: dualExtinction coefficient: 0.0132 (6)
Special details top

Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/UeqOcc. (<1)
I10.64113 (3)0.63330 (2)0.19139 (6)0.0723 (2)
F20.4101 (3)0.54499 (18)0.1142 (4)0.0772 (9)
F30.2989 (3)0.44527 (19)0.3508 (5)0.0790 (9)
C10.5582 (4)0.5530 (3)0.3749 (8)0.0581 (13)
C20.4550 (4)0.5233 (3)0.3061 (7)0.0584 (13)
C30.3987 (4)0.4720 (3)0.4276 (8)0.0595 (13)
S10.3111 (5)0.7500000.2275 (10)0.0568 (15)0.356 (3)
O10.2370 (5)0.7500000.4298 (11)0.110 (2)0.356 (3)
C40.4068 (8)0.67661 (19)0.2756 (19)0.090 (4)0.356 (3)
H4A0.4800390.6873200.2077910.136*0.356 (3)
H4B0.3755830.6320420.2130790.136*0.356 (3)
H4C0.4172180.6702310.4322210.136*0.356 (3)
S1A0.3676 (8)0.7500000.4425 (19)0.067 (3)0.191 (3)
O1A0.2370 (5)0.7500000.4298 (11)0.110 (2)0.191 (3)
C4A0.4068 (8)0.67661 (19)0.2756 (19)0.090 (4)0.191 (3)
H4D0.3707040.6817970.1331780.136*0.191 (3)
H4E0.3821580.6311410.3428510.136*0.191 (3)
H4F0.4893310.6760740.2578850.136*0.191 (3)
S1B0.3538 (6)0.7203 (5)0.3374 (15)0.084 (2)0.2261 (16)
O1B0.2370 (5)0.7500000.4298 (11)0.110 (2)0.452 (3)
C4B0.334 (2)0.7500000.060 (2)0.137 (10)0.452 (3)
H4G0.2745090.7213100.0054200.205*0.2261 (16)
H4H0.3127490.8007300.0588200.205*0.2261 (16)
H4I0.4038490.7436300.0210900.205*0.2261 (16)
C5B0.463 (3)0.7845 (16)0.405 (5)0.157 (17)0.2261 (16)
H5A0.4880100.7773300.5537950.236*0.2261 (16)
H5B0.5268500.7765500.3077350.236*0.2261 (16)
H5C0.4357390.8336510.3876450.236*0.2261 (16)
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
I10.0789 (3)0.0640 (3)0.0739 (3)0.00229 (18)0.01656 (19)0.00687 (17)
F20.0743 (19)0.100 (3)0.0575 (16)0.0044 (18)0.0064 (15)0.0184 (16)
F30.0617 (18)0.106 (3)0.0691 (17)0.0177 (18)0.0025 (16)0.0027 (17)
C10.065 (3)0.055 (3)0.055 (3)0.008 (3)0.011 (2)0.003 (2)
C20.061 (3)0.063 (3)0.051 (3)0.008 (3)0.003 (3)0.002 (2)
C30.056 (3)0.067 (3)0.055 (3)0.003 (3)0.003 (3)0.006 (3)
S10.057 (3)0.070 (4)0.044 (3)0.0000.002 (3)0.000
O10.108 (4)0.088 (4)0.133 (5)0.0000.056 (4)0.000
C40.068 (6)0.080 (8)0.123 (8)0.015 (6)0.015 (6)0.018 (7)
S1A0.086 (7)0.058 (7)0.055 (6)0.0000.025 (5)0.000
O1A0.108 (4)0.088 (4)0.133 (5)0.0000.056 (4)0.000
C4A0.068 (6)0.080 (8)0.123 (8)0.015 (6)0.015 (6)0.018 (7)
S1B0.086 (5)0.076 (5)0.091 (6)0.013 (4)0.021 (4)0.009 (4)
O1B0.108 (4)0.088 (4)0.133 (5)0.0000.056 (4)0.000
C4B0.139 (12)0.140 (13)0.132 (12)0.0000.003 (9)0.000
C5B0.157 (19)0.16 (2)0.153 (19)0.006 (10)0.009 (10)0.001 (10)
Geometric parameters (Å, º) top
I1—C12.083 (5)C4A—H4E0.9700
I1—O1i2.888 (4)C4A—H4F0.9700
F2—C21.342 (5)S1B—S1Biii1.085 (18)
F3—C31.348 (6)S1B—C5Biii1.35 (2)
C1—C3ii1.384 (7)S1B—O1B1.573 (8)
C1—C21.387 (7)S1B—C5B1.785 (10)
C2—C31.363 (7)S1B—C4B1.789 (10)
S1—O11.508 (7)S1B—H4Hiii1.806 (11)
S1—C4iii1.770 (7)C4B—H4G0.9600
S1—C41.770 (7)C4B—H4H0.9600
S1—H4Giii1.573 (12)C4B—H4I0.9600
S1—H4Hiii1.385 (10)C4B—H4Giii0.9600
C4—H4A0.9700C4B—H4Hiii0.9600
C4—H4B0.9700C4B—H4Iiii0.9600
C4—H4C0.9700C5B—C5Biii1.26 (6)
S1A—O1A1.528 (9)C5B—H5A0.9600
S1A—C4A1.744 (8)C5B—H5B0.9601
S1A—C4Aiii1.744 (8)C5B—H5C0.9600
C4A—H4D0.9700
C1—I1—O1i175.05 (18)S1—C4—H4A109.5
C3ii—C1—C2116.7 (5)S1—C4—H4B109.5
C3ii—C1—I1122.1 (4)H4A—C4—H4B109.5
C2—C1—I1121.2 (4)S1—C4—H4C109.5
F2—C2—C3119.3 (5)H4A—C4—H4C109.5
F2—C2—C1119.1 (5)H4B—C4—H4C109.5
C3—C2—C1121.6 (5)O1A—S1A—C4A103.4 (5)
F3—C3—C2118.5 (4)S1A—C4A—H4D109.5
F3—C3—C1ii119.8 (5)S1A—C4A—H4E109.5
C2—C3—C1ii121.7 (5)H4D—C4A—H4E109.5
O1—S1—C4iii103.1 (5)S1A—C4A—H4F109.5
O1—S1—C4103.1 (5)H4D—C4A—H4F109.5
C4iii—S1—C498.5 (6)H4E—C4A—H4F109.5
C3ii—C1—C2—F2179.1 (4)F2—C2—C3—F30.5 (7)
I1—C1—C2—F22.3 (6)C1—C2—C3—F3179.8 (4)
C3ii—C1—C2—C30.2 (8)F2—C2—C3—C1ii179.1 (4)
I1—C1—C2—C3178.4 (4)C1—C2—C3—C1ii0.2 (8)
Symmetry codes: (i) x+1/2, y, z+1/2; (ii) x+1, y+1, z1; (iii) x, y+3/2, z.
Total intermolecular interaction energies involving the DMSO molecules in form I, calculated using the PIXEL method, applied to the DFT-D optimised structures top
StructureDisorder componentRefinement temperature (K)a (Å)b (Å)c (Å)Etot DMSO–TFDIBEtot DMSO–DMSO
Form IA297 K11.81918.4186.075-107.4-25.0
Form IB297 K11.81918.4186.075-112.0-27.4
Form IC120 K10.67318.0026.547-109.8-44.6
 

Footnotes

1The fact that this is not immediately consistent with the site occupancies reported by Britton (2003[Britton, D. (2003). Acta Cryst. E59, o1332-o1333.]) might be attributed to several factors: (i) the accuracy of the calculations; (ii) the calculations are static and do not consider entropic contributions that must become relevant at real temperatures; (iii) the DMSO orientations may be established during crystal growth, and not solely determined by their relative inter­action energies.

Acknowledgements

The cocrystallization study that led to this work was carried out by CLT under the supervision of Professor Stuart Clarke (Department of Chemistry, University of Cambridge).

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