vortrag, erice, 2004 polymorphism and pigments ii martin u. schmidt, frankfurt am main presentation...

Vortrag, Erice, 2004

Polymorphism and Pigments II

Martin U. Schmidt, Frankfurt am Main

Presentation given in Erice, 2004

Quinacridone (Pigment Violet 19)

N

N

O

HO

H

diluted solution

N

N

O

HO

H

phase phase

Isolated molecule Crystal

phase

used for laquers, paints...

Colour of quinacridone

N

N

O

HO

H

N

N

O

HO

H

N

N

O

HO

H

MoleculeCrystal

N

N

O

HO

H

Weak conjugation between benzene rings

=> yellow

N

N

O

HO

H

H

ON

N

O

H

Colour shift from yellow to red because of:

1) Enhanced conjugation in the molecule=> Smaller HOMO-LUMO distances => Absorption bands shift from blue to green => Resulting colour shifts from yellow to red

2) Interaction of transition dipole moments (excitons)

Crystal structures of and quinacridone

phase phase

[E.F. Paulus et al., ECM-12, Moskow, 1989]

Polymorphism and crystal engineering

Polymorphism

Problems

"Polymorphism problem"

Using the advantages

"Crystal Engineering"

Properties depending on the polymorphic form

Selection of polymorphic form (and properties) using solid solutions

-Phase -Phase

NH

O

O

NH

H

H

NH

O

O

NH

Cl

NH

O

O

NH

H

O

NH

N

O

O

N

H

H

O

N

H

N

O

O

NH

H

N

O

O

N

Cl

H

H

Selection of polymorphic form (and properties) using solid solutions

-Phase -Phase

NH

O

O

NH

H

H

NH

O

O

NH

Cl

NH

O

O

NH

H

O

NH

N

O

O

N

H

H

O

N

H

N

O

O

NH

H

N

O

O

N

Cl

H

H

Cl

Cl

Selection of polymorphic form (and properties) using solid solutions

Pigment Red 207

(commercial)

Cl

Cl

Polymorphs of Pigment Orange 36

phase phase

N

Cl N

O

O

H

N

O

O

N

H

NH

NH

O

Pigment Orange 36 (Azo pigment)

Novoperm® Orange HL

SynthesisSolvent

(no use)

solvents

150°C, 2h

Polymorphs of Pigment Orange 72

with stirring

without stirring

phase(stable, but no use)

phase(stable, commercial)

phase(metastable)

Synthesis in water

N

H

N

O

CH3

O

N

H

N

N

O

H

H

N

N

H

CH3

O

N

O

ClCl

H

N

N

H

H

OPigment Orange 72

(a diaryl azo pigment)

How many polymorphic forms are known?

Number of known polymorphic forms

un

kno

wn

Nu

mb

er

of

pig

me

nts

Pigment Red 53

M2+

M2+ = Ca2+, Sr2+, Ba2+

Synthesis of Pigment Red 53:2

NNH

O

Cl

SO3

CH3

-

Ca2+

2

NH2

Cl

CH3

SO3HNaNO2

+ 2 HCl N+

N

Cl

CH3

SO3H

Cl-

NN

OH

Cl

SO3Na

CH3

+

OH

+ NaOH

+ CaCl2N

NH

O

Cl

SO3Na

CH3

+

Polymorphism of Pigment Red 53

Ba2+ salt, "Pigment Red 53:1"

- phase: bright red. Produced industrially (>> 10 000 tons / year) Used for printing inks (and plastics)

- phase: orange-red No longer commercially produced

Sr2+ salt, "Pigment Red 53:3"

- 6 polymorphic forms, orange - red

- Limited commercial use.

Compound invented 1902 [Deutsches Reichspatent Nr. 145908]

Ca2+ salt, "Pigment Red 53:2"

- Only 1 polymorphic form known until 1997. Then we started searching ...

Polymorphism of Pigment Red 53:2+ CaCl2

iso-butanole

(+ + Na salt)

(+ )

chlorobenzene

recryst. from DMAc / H2O

ethanole

1-butanole

aceto-phenone

(+)

(+)

DMSO

acetone

synthesis from K+ salt

glycole

glycolic acid butylester

NMF / H2O

Na+ salt

morpholene

DMSO

NMF / H2O

*

*

*

*

* Solvent containing

DMF

recryst. from

(Slurry)

M.U. Schmidt, H.J. Metz, EP 965616 (1999)M.U. Schmidt, H.J. Metz, EP 965617 (1999)M.U. Schmidt, EP 1010732 (1999)

(Na+ salt)

(K+ salt)

More than 200 experiments made

• All 15 phases are concomitant.

• All phases are stable from room temperatur to at least 250-300°C.

• Some phases transform on heating to 250-300°C.

• All reactions are kinetically controlled.

e.g. Slurry conversion experiments at about 100°C:

chlorobenzene / H2O

1-butanole

isobutanole / H2O

+ 2-ethylhexanole

=> Which is the thernodynamically stable phase at 100°C ??

Polymorphism of Pigment Red 53:2

Polymorphism of Pigment Red 53:2Practical Problems

• Most experiments give mixtures of phases.

• Some phases cannot be obtained in pure form (, , , )

• Several experiments could not be reproduced. E.g.

Exp. No. 99)Dissolution in

dimethylacetamide / H2OPrecipitation with H2O

Exp. No. 148)

Powder diagrams:

• Generally only 10-20 peaks.

• No diagram could be indexed reliably => electron diffraction (Ute Kolb)

Polymorphism of Pigment Red 53:2Practical Problems

• The synthesis is incomplete:

+ CaCl2Na+ salt(slurry)

Ca2+ salt(slurry)H2O, 90°C, 2h

=> Contamination with the Na+ salt

• Na+ content ? (AAS). => Admixture or solid solution Na+ / Ca2+?

• H2O content ? (Karl-Fischer titration). E.g. phase: 2H2O

• Solvent content ? (NMR) E.g. phase: pigment / solvent (glycolic acid butyl ester) = 1 / 7 => Solvent probably not in the crystal lattice, but on the surface But how to remove the solvent ??

Na+ salt(slurry)

+

Many questions still open.

Diaryl pigments

N

N

CH3

O

N

O

Cl

CH3 N

N

O

CH3

O

N

Cl

CH3

H

H

H

H

R

R

R1

R2

R1

R2

R1 = R2 = H: Pigment Yellow 12 3 polymorphs

R1 = R2 = CH3: Pigment Yellow 13 1 polymorph (... as far as I know)

R1 = CH3, R2 = H: Pigment Yellow 14 1 polymorph (... as far as I know)

No single crystals => Structure solved from X-ray powder data

Important yellow pigments

Sales > 200 Mio Euro per year

Pigment Yellow 14: Structure solution by lattice energy minimization using CRYSCA

10 15 20 25 30 35 2 / °

ExperimentalX-ray powder

diagram(Lab data)

50 000

40 000

30 000

20 000

10 000

0

Intensity / Counts

Lattice energy minimizations

(prediction of possible crystal structures)

by CRYSCA

Indexing• Unit cell• Possible space groups (P 1 or P 1, Z = 1)–

60 000

Pigment Yellow 14: Molecular geometry

N

N

CH3

O

N

O

Cl

CH3 N

N

O

CH3

O

N

Cl

CH3

H

H

H

H

R

R

5 intramolecular degrees of freedom

A, B, C: Force field parameters (C,H,B,N,O,F,Cl,Si,metals)

q: Atomic point charges

Eintramol.: Intramolecular energy, depending on the degrees of freedom,

e.g. for : 6-term cosine serie, fitted to ab initio calculations

Martin U. Schmidt, Ulli Englert: "Prediction of Crystal Structures", J. Chem. Soc., Dalton Trans. 1996, 2077-82.

• All space groups possible (even disorders etc.)

• User-selected intramolecular degrees of freedom (from the beginning)

• Lattice parameters either given or calculated by CRYSCA

CRYSCA: Prediction of possible crystal structures

Pigment Yellow 14: Structure solution by lattice energy minimization using CRYSCA

10 15 20 25 30 35 2 / °

ExperimentalX-ray powder

diagram(Lab data)

50 000

40 000

30 000

20 000

10 000

0

Intensity / Counts

Lattice energy minimizations

by CRYSCA (in P 1)• a, b, c, , , , fixed• Packing and 5 intramol. torsions optimized

Indexing• Unit cell• Possible space groups (P 1 or P 1, Z = 1)–

60 000

Pigment Yellow 14: Structure solution by lattice energy minimization using CRYSCA

10 15 20 25 30 35 2 / °

ExperimentalX-ray powder

diagram(Lab data)

Calculated Best minimum (P 1)

50 000

40 000

30 000

20 000

10 000

0

Intensity / Counts

Calculation of X-ray powder diagram

–

Indexing• Unit cell• Possible space groups (P 1 or P 1, Z = 1)–

60 000

Lattice energy minimizations

by CRYSCA (in P 1)• a, b, c, , , , fixed• Packing and 5 intramol. torsions optimized

Pigment Yellow 14: Synchrotron data and Rietveld refinement

Inte

nsi

tät

(Co

un

ts)

Dif

f.

experimentalcalculated

Rp = 8.53 %, Rwp = 12.87 %, RF2 =17.60%, 2 = 3.3

NSLS Brookhaven = 1.149 Å

Pigment Yellow 14

(R1 = CH3, R2 = H)

Pigment Yellow 12

(R1 = R2 = H)

Herringbone structure

Pigment Yellow 13

(R1 = R2 = CH3)

Pigment Yellow 12 / 13 / 14: Crystal structures

• Violet Pigment, high colour strength

• Insoluble in all solvents, even in: - DMSO or NMP at 200°C (detection limit about 10 g/l) - molten benzoic acid (about 200°C) - phthalic acid esters at 300°C

• Melting point > 400 °C (decomposition)

• Sublimation at 350°C, 10-3 mbar leads to poor crystallinity

• Bad powder diagrams

• No single crystals

• Nevertheless: 6 polymorphic forms!

Polymorphism: A really hard case

O

N

N

O

Cl

Cl

NH

NNH

NOO

CH3

CH3

Methyl-dioxazine

phase phase

Salt kneading with solvents

"dilution" withconc. CH3COOH

1) + dichlorobenzene

2) evaporation

phase phase

phase

Synthesis in conc. H2SO4/MnO2

NMP18h 200°

Methyl-dioxazine: Polymorphic forms

evaporation

phase

[P. Kempter, M.U. Schmidt, R. Born, European Patent, 2002]

CF3COOH

Protonated form

O

N

N

O

Cl

Cl

NH

NNH

NOO

CH3

CH3

• FWHM about 0.5° in 2• Crystallite size about 20 nm • Indexing not possible-Phase (metastabile)

Measuring conditions:• STOE STADI-P• capillary• transmission• primary Ge [111] monochromator • Cu-K1

• linear PSD

Crystal structure determination from a non-indexable powder diagram

O

N

N

O

Cl

Cl

NH

NNH

NOO

CH3

CH3

Can the crystal structure be determined from such a X-ray powder diagram?

Only method:

Lattice energy minimizations, using the molecular geometry

Methyl-dioxazine: Structure solution

P 1Z = 2

P 21

Z = 2P 21/cZ = 4

C 2/cZ = 8

P 212121

Z = 4P 1

Z = 1P 21/cZ = 2

P b c aZ = 4

––

5 10 15 20 25 30 2 / °

Lattice energy minimizations (CRYSCA)

Calculated possible crystal structures

Calculation of powder diagrams

Calculated structure(energy rank no. 5)

Intensity

Experimental X-ray powder diagram

(P 1, Z = 1)–

...

Methyl-dioxazine: Crystal structure

Cl

N

O

Density: = 1.71 g/cm3

Some remarks on the method

Crystal structures of organic and organometallic

compounds may be solved from X-ray powder data

by lattice energy minimizations

• even if the powder data are of low quality

• and even if indexing fails.

Limitations:• Compounds of unknown composition• Amorphous compounds• Less than 10-15 peaks in the X-ray powder diagram• Unexpected crystal symmetries (if indexing fails)• Unsuitable or missing force field parameters

Warning: It's not a black box method.

Coworkers (Hoechst / Clariant GmbH):• Dr. H. Kalkhof, F. Becker, T. Simon, H.-J. Remsperger

Coworkers (Frankfurt University):• J. Djanhan, Dr. L. Fink, E. Alig, Dr. D.W.M. Hofmann, C. Buchsbaum

X-ray powder diagrams:• Prof. E. F. Paulus, U. Conrad (former Hoechst AG)• Dr. M. Ermrich (X-ray lab, Reinheim)

Synchrotron measurements:• Prof. P.W. Stephens (NSLS Brookhaven)

Rietveld refinements:• Dr. R. E. Dinnebier (MPI Solid State Research, Stuttgart)

Electron diffraction:• Dr. U. Kolb, Univ. Mainz

Financial support:

Acknowledgements

Acknowledgements

Acknowledgements

and all the others

...