Watching crystals grow and transform

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1 Watching crystals grow and transform Elias Vlieg Radboud University, Institute for Molecules and Materials crystals transforming crystals solution-mediated solid-solid transition Institute for Molecules and Materials Chemical Storage, TU/e 27 November 2014

2 Crystals in different shapes and sizes Institute for Molecules and Materials 2

3 Why grow crystals? For fun(damental research) understand shape atomic to macroscopic scale To do crystallography determine the structure of the building blocks (e.g. protein crystallography) Industrial applications production and purification of materials with specific properties size morphology polymorph Institute for Molecules and Materials 3

4 Crystals for fun: art intermezzo Mondriaan anthraquinone on NaCl(100) template W.S. Graswinckel et al. Escher NaCl, W. Noorduin, W.S. Graswinckel et al. Institute for Molecules and Materials 4

5 Application: heat battery Proposed consortium TU/e, TNO, UT, TUD, RU, Save energy by heat storage using Thermochemical Materials (TCMs): crystals! MgSO 4 + 7H 2 O MgSO 4 7H 2 O + heat (~400 kj/mol!) solid-solid transition how does this take place? how often can you do this? Research proposal: no results from RU yet Different example of hydrate: rock salt Institute for Molecules and Materials 5

anti-caking agent below 0 ºC (road salt!

6 NaCl and NaCl.2H 2 O NaCl has lots of applications source of Cl 2 for chemical industry food road salt NaCl crystals tend to stick together need anti-caking agent below 0 ºC (road salt!) also formation of hydrate: problem with anti-caking agent Institute for Molecules and Materials 6

7 anti-caking and role of NaCl.2H 2 O NaCl surface hydrate layer hydrate layer grows on top of NaCl and hampers anticaking agent Arno Bode et al., to be published Institute for Molecules and Materials 7

Polymorphism & transformations polymorphism: same chemical compound, different crystal structures (possible) differences in A A A A A A A A A A A A A melting point A A A A A A solubility

8 Polymorphism & transformations polymorphism: same chemical compound, different crystal structures (possible) differences in A A A A A A A A A A A A A melting point A A A A A A solubility (bioavailability) A A A A A A A colour morphology etc. important for many industries, e.g. pharmaceuticals, dyes A A A A A A A A A A A A A A A A A A A A A A pseudo-polymorphism crystal structure containing the chemical compound, but including solvent (solvate or hydrate) Institute for Molecules and Materials 8

9 Polymorphic systems monotropic enantiotropic liquid liquid polymorph 1 free energy G polymorph 2 polymorph 1 free energy G polymorph 2 temperature T T m1 T m2 T t temperature T T m1 T m2 one polymorph stable up to melting point no transition temperature stable form temperature dependent transition temperature Institute for Molecules and Materials 9

10 Nucleation in polymorphic system solution growth by lowering temperature solubility solution + solid C 2 1 B A solution A: no crystals B: formation of crystal 1 depends on nucleation barrier C: formation of crystals 1 and/or 2 depends on nucleation barrier of each temperature Institute for Molecules and Materials 10

11 Ostwald rule of stages Ostwald (1897): at a phase transition not the most stable phase is formed, but the one with the smallest change in free energy Ostwald solution + solid 2 1 B: crystals 1 C: first metastable crystals 2, then crystals 1 solubility C B solution A this is a rule not a law many exceptions temperature Institute for Molecules and Materials 11

12 Steroid polymorphs P1; metastable P2 1 ; stable Institute for Molecules and Materials 12

13 In situ microscopy camera sample cells computer temperature controlled water bath experimental cell (top view) In situ set-up for growth and dissolution at well defined temperature and supersaturation Institute for Molecules and Materials 13

14 3D nucleation Follows Ostwald s rule metastable form nucleates Crystals are twinned: two mirror halves P1 Institute for Molecules and Materials 14

15 Polymorphic epitaxy Start with metastable crystal Reducing supersaturation stable form nucleates on (010) face stable C. Stoica et al., Int. J. Pharmaceutics 309 (2006) 16 Institute for Molecules and Materials 15

16 Why on {010} faces? Answer: structural similarity along {010}. Epitaxial polymorphic nucleation (010) (010) Institute for Molecules and Materials 16

17 Ostwald s rule epitaxial growth of P2 1 on P1 (010) dissolution of P1 solution-mediated transformation Institute for Molecules and Materials 17

18 Control over both polymorphs low supersaturation stable form grows, on (010) face metastable dissolves ethanol solution higher supersaturation concomitant polymorphism Institute for Molecules and Materials 18

19 DL-norleucine (NLE) 2-amino-hexanoic acid Non-natural Polymorph β (LT) α (RT) γ (HT) Space group C2/c P2 1 /c C2/c Crystal system Monoclinic Monoclinic Monoclinic Z / Z 8 / 1 4 / 1 8 / 1 α β: transition T not well-characterized, very variable α γ: 391 K (118 ºC) Institute for Molecules and Materials 19

20 DL-norleucine Phase transitions: α β: shift bilayers of half cell axis in b and c direction α γ: shift bilayers + conformational change molecules Coles et al., Cryst. Growth & Des., 9 (2009) Institute for Molecules and Materials 20

21 How do the transitions take place? Use many techniques DSC solid-state NMR X-ray diffraction optical microscopy Molecular Dynamics Institute for Molecules and Materials 21

22 Molecular Dynamics of α-β transition evidence for cooperative motion bilayers move independently J.A. van den Ende and H.M. Cuppen, 2014 Cryst. Growth Des, 14, Institute for Molecules and Materials 22

23 Conclusions crystals can transform in several ways solution-mediated solid-solid DL-norleucine α and β polymorphs very close in structure and energy worst choice for energy storage!s solid-solid transition transformation depends strongly on local conditions Congratulations with the new Darcy Center! Institute for Molecules and Materials 23

Thermodynamic stability and transformation of pharmaceutical polymorphs*

Pure Appl. Chem., Vol. 77, No. 3, pp. 581 591, 2005. DOI: 10.1351/pac200577030581 2005 IUPAC Thermodynamic stability and transformation of pharmaceutical polymorphs* Mitsutaka Kitamura Department of Mechanical