1

Supporting Information

Pressure inverse solubility and polymorphism of edible γ-cyclodextrin-based metal-organic

frameworkEwa Patyk-Kaźmierczak,a Mark R. Warren,b David R. Allan,b Andrzej Katrusiaka

a Department of Materials Chemistry, Faculty of Chemistry, Umultowska 89b, 61-614 Poznań Poland; b Diamond Light Source, Harwell Science and Innovation Campus, Didcot, Oxon

OX11 0DE, UK

Experimentalγ-Cyclodextrin (γ-CD) and potassium hydroxide (KOH) both from Sigma-Aldrich were mixed in

a 1:8 molar ratio and dissolved in distilled water. The flask with this solution was sealed in a

container filled with methanol (in other experiments with isopropanol) and large transparent

cube-like crystals were obtained by the vapour diffusion method. The γ-CD-MOF-1 crystals

consist of γ-cyclodextrin molecules coordinating potassium cations, their charge being

balanced by hydroxide anions, also present in the crystal structure.11 The pores in their

structures are easily-accessible allowing the adsorption of solvent molecules used in the

crystallization process, i.e. water and methanol, which can also be present in the crystal.

In order to measure the diffraction at ambient pressure a γ-CD-MOF-1 single crystal

coated with a small amount of the mother liquor (methanol:water or isopropanol:water) or

methanol was inserted into a quartz capillary 0.5 or 1 mm in diameter, then sealed with wax.

The X-ray diffraction data for these sample crystals were measured at 295 K with

synchrotron radiation, and at 270, 280, 290, 300, 310 K with MoKα radiation. The crystal in

isopropanol:water mother liquor was measured at 295, 270, 245, 220 and 195 K, while that

in pure methanol was measured at 200, 250 and 295 K, both with MoKα radiation. For high-

pressure experiments a modified Merrill-Bassett diamond-anvil cell20 was used. Crystals of

γ-CD-MOF-1 were placed in the 0.2-0.5 mm wide hole in 0.2-0.3 mm thick tungsten gasket,

along with a small ruby sphere or chips and submerged in the mother liquid. After sealing

Electronic Supplementary Material (ESI) for Physical Chemistry Chemical Physics.This journal is © the Owner Societies 2017

2

the DAC, the pressure was increased to 0.1, 0.16 and 0.26 GPa and sample crystals were

dissolved by heating the DAC with hot-air gun, and then recrystallized by slowly cooling the

DAC (Figure 1). The single crystal grown at 0.1 GPa was compressed to 0.57, 0.99 and 1.76

GPa, and at each of these pressure points studied by X-ray diffraction. Two other sample

crystals were measured at 0.16, 0.25, 0.33, 0.41, 0.49 GPa, and at 0.26, 0.86, 1.36 GPa,

respectively. Beyond these pressure limits the sample crystals dissolved hampering X-ray

diffraction experiments at high pressure. The microscope observation of the pressure

induced dissolution of the crystal was continued to over 2.0 GPa. The attempt to recrystallize

the sample by further compression resulted in obtaining ice VI only. The pressure-induced

dissolution of γ-CD-MOF-1-α was also studied for the crystal grown in the DAC (Figure S1) at

0.12 GPa. Its cubic symmetry of space group I432 was confirmed with X-ray diffraction

experiment. The gradual compression of the sample crystal eventually led to its complete

dissolution at 2.1 GPa. Pressure was increased in steps and stabilised for approximately 30

minutes (Figure S3). Compression above 3 GPa resulted in crystallization of the solvent and

therefore pressure needed to be lowered to 2.1 GPa in order to enable solvent molecules to

further dissolve the γ-CD-MOF-1-α crystal. On decreasing the pressure small cube-like

crystals appeared at 0.53 GPa.

Single-crystal X-ray diffraction on γ-CD-MOF-1 revealed, apart from the known cubic

form (hereafter labelled as phase α), a new trigonal form of space group R32 (labelled as

phase β). Their crystallographic data are listed in Tables S1 and S2 in Supporting Information,

and summarised in Table 1. Pressure inside the DAC was measured by the ruby fluorescence

method21 with a Photon Control Inc. spectrometer affording an 0.02GPa accuracy. The

crystal structures of γ-CD-MOF-1 have been deposited with the Cambridge Crystallographic

Data Centre (CCDC1488039-1488055; 1488057-1488060; 1488073-148878) and with Crystal

Open Database. Copies of the data can be obtained, free of charge, by filling online the

application form at https://summary.ccdc.cam.ac.uk/structure-summary-form and from

http://www.crystallography.net/cod/, respectively.

3

Figure S1. Dissolving γ-CD-MOF-1-α powder (a-e) and the single crystal grow (f-j) from water:methanol mixture inside the DAC: (a) few crystals at 0.12 GPa/295 K, (b) 398 K; (c) 411 K; (c,d) polycrystalline mass at 414 and 424 K; (e) small crystal seed by the left edge of the gasket; (f-i) crystal growth at 403, 392, 382, and 351 K; (h) the single crystal at 295 K and 0.18 GPa. A small ruby sphere lies by the left edge of the chamber.

Figure S2. Dissolving γ-CD-MOF-1-α powder (a-c) and the single crystal grow (d-h) from water:methanol mixture inside the DAC: (a) polycrystalline mass at 0.16 GPa/295 K and (b) 405 K; (c) and small crystal seed by the left edge of the gasket; (d-g) crystal growth at 345, 327, 317 and 314 K; the (h) single crystal at 295 K and 0.16 GPa. A small ruby sphere lies by the left edge of the chamber.

4

Figure S3. Pressure dissolution of γ-CD-MOF-1-α crystal (a-i) and few single crystals grown on lowering the pressure to 0.53 GPa (j) from water:methanol mixture inside the DAC: (a) single crystal at 0.19 GPa/295 K; (b-i) crystal dissolving at 0.39, 0.67, 1.50, 2.09, 3.17, 3.45, 2.15 and 2.10 GPa; (j) single crystals at 295 K and 0.53 GPa. A small ruby chip lies by the left edge of the chamber. In part (g) crystallization of solvent around the gasket can be observed.

The compression of γ-CD-MOF-1 crystals grown at ambient conditions and then

loaded into the DAC were measured in fluorinert at 0.03 and 0.41 GPa, in methanol at

0.01 GPa (10 MPa) and in ethanol at 0.19 GP. In all these experiments the diffraction was

very weak, or even hardly detectable, giving no satisfactory crystallographic information. The

weak diffraction of γ-CD-MOF-1-α grown at ambient conditions and compressed in various

hydrostatic fluids has been associated with defects in the fragile framework. The poor

diffraction of γ-CD-MOF-1-α measured at ambient conditions in the open air could be caused

by the decomposition of the crystals removed from the mother liquor. The solvent

molecules leaving the pores affect the structure. The compression, in a hydrostatic medium,

either of small or large molecules, destabilises of the framework, too, which lowers the

quality of the crystal and its diffraction.

In order to obtain more meaningful data, the measurements at 0.1 MPa and between

0.16 and 0.49 GPa were performed with synchrotron radiation (λ=0.6889 Å) using a 4-circle

Newport diffractometer equipped with a Pilatus 300K detector at I19 beamline of the

Diamond Light Source. The GDA software was used for collecting data and converting them

for the CrysAlisPro software, used for determining the UB-matrix, absorption corrections and

data reduction. The synchrotron radiation gradually destroyed the sample (Figure 3), which

affected the data sets at 0.41 and 0.49 GPa and precision of refinements. The remaining

high-pressure measurements were performed with MoKα graphite monochromated

5

radiation and a 4-circle KUMA diffractometer. High and low-temperature measurements

were performed with a 4-circle Xcalibur diffractometer equipped in an EOS CCD detector and

a gaseous-nitrogen open-flow Oxford Cryosystems attachment. Program CrysAlisPro was

used for the data collections, UB-matrix determination, absorption corrections and data

reductions.

The crystal structures were solved by direct methods with program Shelxs22 or by

intrinsic phasing with Shelxt22 and refined by least-squares with program Shelxl.22 Hydrogen

atoms were located, where possible, of the molecular geometry with Uiso equal to 1.2 Ueq for

C-carriers and 1.5 Ueq for O-carriers. The O-H and C-H bonds length were fixed to the

distances of 0.82 Å for oxygen atoms, and 0.98 or 0.97 Å for tertiary and secondary carbon

atoms, respectively. Due to the low resolution of data at 0.26 and 1.76 GPa only the unit-cell

parameters were reliably determined.

Low and high-temperature measurements performed with MoKα radiation were

aimed at obtaining the temperature dependence of unit-cell parameters and volume only,

and due to the low resolution of collected data no structure refinement was performed for

the crystals measured in methanol and methanol:water mother liquor. The data set

collected for the crystal in isopropanol:water mixture were sufficient for the crystal structure

solution and refinement. The difference in the diffracting properties of crystals plausibly originates

from the local differences in the crystal structure distorted due to differently packed and interacting

small molecules of methanol.

The recrystallization of γ-CD-MOF-1 at the pressure slightly elevated to approximately

few MPa yielded the crystals mixed of cubic and trigonal phases (Figure S4). The

recrystallization of the mixed crystal at 0.25 GPa resulted in the cubic crystals of space group

I432, consistent with the symmetry of all γ-CD-MOF-1-α crystals obtained under high

pressure and those measured at ambient pressure and varied temperature with MoKα

radiation, as well as the literature data.11 Two sample crystals, one crystallized by methanol

vapour diffusion and studied at 295 K/0.1 MPa with synchrotron radiation, and the other

crystallized by the isopropanol vapour diffusion and measured with MoKα radiation were of

trigonal R32 symmetry similar to the one reported for γ-CD-MOF-1 crystal with benzoate

ions included in the γ-CD channels.11 The phase β sample crystal sealed in a capillary at the

presence of isopropanol:water mixture, when studied at 295 K/0.1 MPa again after 12 days,

has shown cubic symmetry of phase α. Only after lowering the temperature to 245 K crystal

underwent the transformation to hexagonal phase β.

6

Figures

Figure S4. Ewald sphere of γ-CD-MOF-1 crystal (shown in the middle) of mixed trigonal and cubic phases with cubic (a) and trigonal (b) unit cells marked.

Figure S5. Schematic (a) representation of γ-CD-MOF-1-α crystal structure (b) with γ-cyclodextrin rings and potassium ions marked in green and purple respectively, shown along direction [100].

7

Figure S6. Pressure dependence of K—O coordination bonds in γ-CD-MOF-1-α and β crystals involving the oxygen atoms of glucose units in γ-cyclodextrin. Four such bonds to oxygen atoms O2, O3, O5 and O6 are marked in blue, purple, red and green respectively. For the γ-CD-MOF-1-β an average length of corresponding coordination bonds have been plotted. The lengths within γ-CD-MOF-1-α are marked as diamonds with navy blue edges. The inset shows the maltose unit of γ-cyclodextrin ring with its coordination bonds to potassium ions, with the oxygen atoms labelled in colours corresponding to those of the plots.

Figure S7. Pressure dependence of unit-cell volume and parameters in γ-CD-MOF-1 crystals. Parameters for trigonal form are marked in greed, while for cubic in blue and red for data collected at 93 K/0.1 MPa and 295 K/high-pressure, respectively. Data collected with synchrotron radiation are marked with empty symbols and those collected with MoKα radiation with full symbols.

8

Figure S8.Temperature dependence of unit-cell volume (a) and parameters (b) of γ-CD-MOF-1-α and β. Different data sets are marked with solid, dashed and dotted lines according to the legend included in the figure. Lines are for guiding the eye only.

9

Figure S9. Pressure (red) and temperature (blue and greed) dependence of rhombohedral unit-cell volume of γ-CD-MOF-1-α and β. Data collected with synchrotron radiation are marked with opened symbols. Different data sets are marked with solid, dashed and dotted lines according to the legend included in the figure. Lines are for guiding the eye only.

10

Figure S10. Pressure (red) and temperature (blue and greed) dependence of rhombohedral (b) unit-cell parameter a and (b) α angle of γ-CD-MOF-1-α and β. Data collected with synchrotron radiation are marked with opened symbols. Different data sets are marked with solid, dashed and dotted lines according to the legend included in the figure. Lines are for guiding the eye only. Horizontal purple dashed line represents value of the α angle in rhombohedral lattice derived from cubic I Bravais lattice.

11

Figure S11. Pressure (red) and temperature (blue) dependence of solvent accessible voids volume in γ-CD-MOF-1 crystals. The percentage contribution (a) and actual volume per molecule in Å3 (b). Pressure points of form α of γ-CD-MOF-1 are marked as circles, while of β by diamonds. Open and full symbols mark data collected with synchrotron and MoKα radiation, respectively. Data collected at 295 K and 0.1 MPa for phase β are marked in green. Solvent accessible volume was calculated with program Mercury31 for the probe radius and grid spacing of 1.2 and 0.2 Å, respectively, and for structures with H-atoms excluded for preserving the consistency of the data.

12

Figure S12. Conversion of cubic I Bravais lattice (pink) to trigonal P (blue) and rhombohedral (green) lattices. 0,0,0 and ½, ½, ½, Nodes are marked in black and red, respectively.

13

TablesTable S1. High and low-temperature crystallographic and experimental data for γ-CD-MOF-1-α and β crystal structures.

Phase α Phase α Phase β Phase β Phase β Phase βPressure (GPa) 0.0001 0.0001 0.0001 0.0001 0.0001 0.0001

Temperature (K) 295.01(10) 269.99(10) 244.98(10) 219.98(10) 194.98(10) 295(2)Formula weight 1409.33 1409.33 1409.33 1409.33 1409.33 1409.33

Crystal colour Colourless Colourless Colourless Colourless Colourless ColourlessProtecting liquid iPrOH:H2O iPrOH:H2O iPrOH:H2O iPrOH:H2O iPrOH:H2O MeOH:H2O

Crystal size (mm) 0.50x0.48x0.47 0.50x0.48x0.47 0.50x0.48x0.47 0.50x0.48x0.47 0.50x0.48x0.47 0.50x0.40x0.40Crystal system Cubic Cubic Trigonal Trigonal Trigonal Trigonal

Space group I432 I432 R32 R32 R32 R32Unit cell dimensions (Å)

a 31.2093(7) 31.2093(16) 43.260(16) 43.643(13) 43.367(6) 43.6764(14)c 28.104(16) 28.059(13) 28.090(5) 28.1864(9)

Volume (Å3) 30399(1) 30399(3) 45547(30) 46284(20) 45752(12) 46565(3)Z 12 12 18 18 18 18

Dx (g cm-3) 0.924 0.924 0.925 0.910 0.920 0.904Radiation source MoKα MoKα MoKα MoKα MoKα Synchrotron

Wavelength λ (Å) 0.71073 0.71073 0.71073 0.71073 0.71073 0.6889Absorption coefficient (mm-1) 0.161 0.161 0.161 0.158 0.160 0.146

F(000) (e) 8928 8928 13392 13392 13392 133922θ max (o) 27.38 27.38 27.36 27.40 27.47 30.74

Min./Max. indices hkl

-20/20-20/20-20/20

-20/20-20/20-20/19

-28/28-28/28-18/18

-28/28-28/28-18/18

-28/28-28/28-18/18

-33/33-33/33-21/21

Reflections collected/unique 19855/725 20814/766 21233/3104 21248/3100 21398/3106 40108/4856Rint 0.0938 0.1616 0.2076 0.1632 0.1558 0.0850

Observed reflections (I>4σI) 663 694 2197 2440 2537 4856Data/parameters 725/93 766/93 3104/340 3100/330 3106/340 4856/810

Goodness of fit on F2 1.092 1.086 0.995 1.181 1.283 1.946Final R1 indices (I>4σI) 0.0485 0.0594 0.0812 0.0740 0.1122 0.1354

R1/wR2 indices (all data) 0.0522/0.1326 0.0652/0.1534 0.1079/0.2034 0.0949/0.1618 0.1291/0.2938 0.1379/0.3798Δσmax, Δσmin (eÅ-3) 0.141, -0.118 0.141, -0.138 0.169, -0.192 0.176, -0.193 0.345, -0.301 0.549, -0.395

Weighting schemea: x; y 0.0863, 47.2516 0.0986, 25.3536 0.0963, 0 0.0558, 0 0.1621, 0 0.2, 0Extinction coefficient − − − − − −

Absorption corrections sample crystal sample crystal sample crystal sample crystal sample crystal sample crystalSample transmission min/max 0.65/ 1.00 0.42/ 1.00 0.14/ 1.00 0.31/ 1.00 0.24/ 1.00 0.25/ 1.00

aw = 1/(σ2(Fo2)+x2P2+yP), where P=(Max(Fo2, 0)+2Fc2)/3

14

Table S2. Continuation.

Phase α Phase α Phase α Phase αPressure (GPa) 0.0001 0.0001 0.0001 0.0001

Temperature (K) 299.5(8) 289.4(9) 279.3(10) 269.4(9)Formula weight 1409.33 1409.33 1409.33 1409.33

Crystal colour Colourless Colourless Colourless ColourlessProtecting liquid MeOH:H2O MeOH:H2O MeOH:H2O MeOH:H2O

Crystal size (mm) 0.19x0.13x0.11 0.19x0.13x0.11 0.19x0.13x0.11 0.19x0.13x0.11Crystal system Cubic Cubic Cubic Cubic

Space group I432 I432 I432 I432Unit cell dimensions (Å)

a 31.327(9) 31.42(2) 31.383(13) 31.415(13)c

Volume (Å3) 30745(16) 31029(30) 30910(20) 31003(20)Z 12 12 12 12

Dx (g cm-3) 0.913 0.905 0.908 0.906Radiation source MoKα MoKα MoKα MoKα

Wavelength λ (Å) 0.71073 0.71073 0.71073 0.71073Absorption coefficient (mm-1) 0.158 0.157 0.157 0.157

F(000) (e) 8928 8928 8928 90962θ max (o) 20.40 16.14 13.51 11.61

Min./Max. indices hkl

-15/15-15/15-15/15

-12/12-12/12-12/12

-10/10-10/10-10/10

-8/8-8/8-8/8

Reflections collected 7665 3362 1865 1090Rint 0.2795 0.2803 0.1429 0.1082

Absorption corrections Not enough coverage in data - absorption correction could not be applied

Table S3. Continuation.

Phase α Phase α Phase αPressure (GPa) 0.0001 0.0001 0.0001

Temperature (K) 295.00(14) 249.9(2) 199.90(14)Formula weight 1409.33 1409.33 1409.33

Crystal colour Colourless Colourless ColourlessProtecting liquid MeOH MeOH MeOH

Crystal size (mm) 0.16x0.11x0.10 0.16x0.11x0.10 0.16x0.11x0.10Crystal system Cubic Cubic Cubic

Space group I432 I432 I432Unit cell dimensions (Å)

a 31.255(9) 31.247(12) 31.255(9)c

Volume (Å3) 30531(16) 30508(36) 30531(15)Z 12 12 12

Dx (g cm-3) 0.920 0.921 0.920Radiation source MoKα MoKα MoKα

Wavelength λ (Å) 0.71073 0.71073 0.71073Absorption coefficient (mm-1) 0.162 0.163 0.160

F(000) (e) 8928 8928 89282θ max (o) 16.22 16.22 13.57

Min./Max. indices hkl

-12/12-12/12-12/12

-12/12-12/12-12/12

-10/10-10/10-10/10

Reflections collected/unique 3788/167 3798/167 1660/93Rint 0.2507 0.2630 0.2139

Observed reflections (I>4σI) 134 132 78Absorption corrections Not enough coverage in data - absorption correction could not be

applied

15

Table S2. High-pressure crystallographic and experimental data for γ-CD-MOF-1-α crystal structures in 0.16-1.76 GPa pressure range. Due to the poor quality of data collected at 0.26 and 1.76 GPa inhibiting the structure solution, information included in the table are limited.

aw = 1/(σ2(Fo2)+x2P2+yP), where P=(Max(Fo2, 0)+2Fc2)/3

Phase α Phase α Phase α Phase α Phase α Phase α Phase α Phase α Phase α Phase α Phase αPressure (GPa) 0.16(2) 0.25(2) 0.26(2) 0.33(2) 0.41(2) 0.49(2) 0.57(2) 0.86(2) 0.99(2) 1.36(2) 1.76(2)

Temperature (K) 295(2) 295(2) 295(2) 295(2) 295(2) 295(2) 295(2) 295(2) 295(2) 295(2) 295(2)Formula weight 1409.33 1409.33 1409.33 1409.33 1409.33 1409.33 1409.33 1409.33 1409.33 1409.33 1409.33

Crystal colour Colourless Colourless Colourless Colourless Colourless Colourless Colourless Colourless Colourless Colourless ColourlessCrystal size (mm) 0.15x0.14x0.05 0.15x0.14x0.05 0.18x0.17x0.10 0.15x0.14x0.04 0.14x0.13x0.03 0.14x0.13x0.01 0.17x0.16x0.10 0.18x0.17x0.10 0.17x0.16x0.10 0.16x0.15x0.10 0.15x0.14x0.08

Crystal system Cubic Cubic Cubic Cubic Cubic Cubic Cubic Cubic Cubic Cubic CubicSpace group I432 I432 I432 I432 I432 I432 I432 I432 I432 I432 I432

Unit cell dimensions (Å; o) a = 31.3469(11) 31.3031(11) 31.17(2) 31.2695(18) 31.238(2) 31.223(3) 31.179(11) 30.988(3) 30.968(6) 30.898(3) 30.56(3)

Volume (Å3) 30802(3) 30673(2) 30273(70) 30575(3) 30481(4) 30438(5) 30309(18) 29758(6) 29699(11) 29499(5) 28529(78)Z 12 12 12 12 12 12 12 12 12 12 12

Dx (g cm-3) 0.912 0.915 0.928 0.918 0.921 0.922 0.926 0.944 0.945 0.952 0.984Wavelength MoKα, λ (Å) 0.6889 0.6889 0.71073 0.6889 0.6889 0.6889 0.71073 0.71073 0.71073 0.71073 0.71073

Absorption coefficient (mm-

1)0.149 0.145 0.157 0.148 0.146 0.149 0.161 0.164 0.164 0.165 0.171

F(000) (e) 8928 8928 8928 8928 8928 8928 8928 8928 8928 8928 89282θ max (o) 22.00 26.50 20.52 26.54 26.50 26.52 20.42 20.38 20.40 20.44 20.40

Min./Max. indices h k l

-17/17-17/17-8/8

-20/20-20/20-9/9

-7/7-15/15

-20/20-9/9

-20/20

-20/20-9/9

-20/20

-20/20-9/9

-20/20

-15/15-15/15-7/7

-15/15-15/15-7/7

-15/15-15/15-7/7

-15/15-15/15-7/7

-15/15-15/15-8/9

Reflections collected/unique 4484/351 4737/594 9708/315 5461/601 2510/558 2461/524 3862/283 9256/299 7547/264 9046/283 8391/284Rint 0.1007 0.0810 0.8770 0.0542 0.0543 0.2693 0.3847 0.1133 0.2967 0.1072 0.6092

Observed reflections (I>4σ(I))

326 466 163 384 288 173 254 297 260 275 251

Data/parameters 351/79 594 /75 315/− 601/77 558/76 524/73 283/76 299/75 264/75 283/75 284/−Goodness of fit on F2 1.130 1.189 − 1.035 0.960 0.940 0.944 1.126 1.174 1.283 −

Final R1 indices (I>4σ(I)) 0.0745 0.0955 − 0.0814 0.0922 0.0670 0.0640 0.0863 0.0865 0.0907 −R1/wR2 indices (all data) 0.0794/0.2092 0.1071/0.2807 − 0.1019, /0.2317 0.1248/0.2494 0.2266/0.2693 0.0699/0.1406 0.0863/0.2187 0.0869/0.2326 0.0924/0.2350 −

Δσmax, Δσmin (eÅ-3) 0.119, -0.128 0.208, -0.169 − 0.133, -0.123 0.126, -0.109 0.112, -0.124 0.056, -0.048 0.115, -0.145 0.107, -0.092 0.162, -0.183 −Weighting schemea: x; y 0.1818; 0 0.2; 0 − 0.1543;0 0.1624; 0 0.1518; 0 0; 0 0.1319, 337.37 0.2; 0 0.2; 0 −

Extinction coefficient − − − − − − − − − − −Absorption corrections sample crystal sample crystal sample crystal sample crystal sample crystal sample crystal −- sample crystal sample crystal sample crystal −

Sample transmission min/max

0.56/1.00 0.761.00 0.27/1.00 0.55/1.00 0.88/1.00 0.75/1.00 −- 0.20/1.00 0.68/1.00 0.33/1.00 −