Crystal Engineering on Organic Pigments

<strong>Crystal</strong> <strong>Engineering</strong> 

on 

Organic Pigments 

by 

Martin U. Schmidt 

für Vorlesung Technische Chemie 

SS 2010

Pigments = Insoluble, coloured compounds 

Inorganic pigments: e.g. TiO 2 , Fe 2 O 3 , PbCrO 4 ... 

Organic pigments: e.g. 

N N 

H 

O 

R 

Pigments 

Azo pigment Heterocyclic pigment 

Properties like inorganic pigments (insoluble powders) 

Chemistry like dyestuffs 

H 

N 

O 

O 

N 

H

Applications: 

- Laquers & paints 

- Plastics 

- Printing inks 

- ... 

Organic pigments 

Fine dispersions 

(no dissolution) 

Properties depend on the crystal structures 

<strong>Crystal</strong> <strong>Engineering</strong>: 

<strong>Crystal</strong> 

structures are 

maintained 

Using structure - property relationships to 

synthesize materials with improved properties 

Required: Knowledge of the crystal structures 

(from experiments or predictions)

O 

R 

H 

N 

N 

Examples for <strong>Crystal</strong> <strong>Engineering</strong> 

N 

O 

H 

N 

O 

Colour 

Cl 

Cl 

O 

N 

Density 

O 

N 

H 

N 

N 

H 

R 

O 

R 

CH 3 

N 

H 2 

N 

N 

O 

H 

O 

O 

H 

N 

O 

Photostability 

CH 3 

CH 2 

O 

. 

H N 

Cl 

H O 

N N 

N 

O H 

N 

. 

.. 

.. 

Cl 

C 

H 3 

N 

H 

. 

O 

. 

- Colour strength (Extinction coeff.) 

- Price 

R

Example 1: Colours of quinacridones 

H 

Quinacridone 

(Pigment Violet 19) 

Used for cars, plastics, etc. 

Production: >> 1000 t / year 

Sales: > 100 Mio € / year 

N 

O 

O 

N 

H

Example 1: Colours of quinacridones 

(Pigment Violet 19) 

H 

N 

O 

O 

N 

H 

Molecule 

Diluted solution in 

DMSO at 185°C 

H 

N 

O 


O 

N 

H

H 

N 

O 

H 

N 

O 

Isolated molecule 

Weak conjugation 

of benzene rings 

=> yellow 

Colours of quinacridone 

O 

N 

H 

O 

N 

H

H 

N 

O 

H 

N 

O 

Isolated molecule 

Weak conjugation 

of benzene rings 

=> yellow 

Colours of quinacridone 

O 

N 

H 

O 

N 

H 

H 

N 

O 

H 

N 

O 

O 

N 

H 

O 

N 

H 


Reasons for the colour change: 

(1) Enhanced conjugation 

=> HOMO-LUMO distance smaller 

=> Absorption changes from violet to green-yellow 

=> Colour changes from yellow to red-violet 

(2) Interaction of transition dipole moments 

(Exciton coupling) 

N 

O 

H 

N 

O 

H 

H 

O 

N 

H 

O 

N 

[Calculation by P. Erk]

Polymorphs of quinacridone: 

A real chaos

Described 

polymorphs 


A real chaos

Described 

polymorphs 

� 


A real chaos

Described 

polymorphs 

� 

� 


A real chaos

Described 

polymorphs 

� 

� 

B I 


A real chaos

Described 

polymorphs 

� 

� 

B I 

� 


A real chaos

Described 

polymorphs 

� 

� 

B I 

� 

�' 


A real chaos

Described 

polymorphs 

� 

� 

B I 

� 

�' 

� I 


A real chaos

Described 

polymorphs 

� 

� 

B I 

� 

�' 

� I 

� II 


A real chaos

Described 

polymorphs 

� 

� 

B I 

� 

�' 

� I 

� II 

� �� 


A real chaos

Described 

polymorphs 

� 

� 

B I 

� 

�' 

� I 

� II 

� �� 

� IV 


A real chaos

Described 

polymorphs 

� 

� 

B I 

� 

�' 

� I 

� II 

� �� 

� IV 

several � 


A real chaos

Described 

polymorphs 

� 

� 

B I 

� 

�' 

� I 

� II 

� �� 

� IV 

several � 

� 


A real chaos

Described 

polymorphs 

� 

� 

B I 

� 

�' 

� I 

� II 

� �� 

� IV 

several � 

� 

� 


A real chaos

Described 

polymorphs 

� 

� 

B I 

� 

�' 

� I 

� II 

� �� 

� IV 

several � 

� 

� 

another � 


A real chaos

Described 

polymorphs 

� 

� 

B I 

� 

�' 

� I 

� II 

� �� 

� IV 

several � 

� 

� 

another � 

� 


A real chaos

Described 

polymorphs 

� 

� 

B I 

� 

�' 

� I 

� II 

� �� 

� IV 

several � 

� 

� 

another � 

� 


A real chaos 

Different X-ray powder diagrams

Described 

polymorphs 

� 

� 

B I 

� 

�' 

� I 

� II 

� �� 

� IV 

several � 

� 

� 

another � 

� 


A real chaos 

Different X-ray powder diagrams 

But powder diagrams depend on: 

- <strong>Crystal</strong> size and morphology 

- <strong>Crystal</strong> quality 

- Preferred orientation 

(Old measurements in reflection mode) 

- Impurities or byproducts, which are 

incorporated into the crystal lattice 

=> distortion of the lattice 

=> peak shifts 

- ...

Described 

polymorphs 

� 

� 

B I 

� 

�' 

� I 

� II 

� �� 

� IV 

several � 

� 

� 

another � 

� 


Real 

polymorphs 

A real chaos

Described 

polymorphs 

� 

� 

B I 

� 

�' 

� I 

� II 

� �� 

� IV 

several � 

� 

� 

another � 

� 


Real 

polymorphs 

� 

A real chaos

Described 

polymorphs 

� 

� 

B I 

� 

�' 

� I 

� II 

� �� 

� IV 

several � 

� 

� 

another � 

� 


Real 

polymorphs 

� 

� 

A real chaos

Described 

polymorphs 

� 

� 

B I 

� 

�' 

� I 

� II 

� �� 

� IV 

several � 

� 

� 

another � 

� 


Real 

polymorphs 

� 

� 

A real chaos

Described 

polymorphs 

� 

� 

B I 

� 

�' 

� I 

� II 

� �� 

� IV 

several � 

� 

� 

another � 

� 


Real 

polymorphs 

� 

� 

� 

A real chaos

Described 

polymorphs 

� 

� 

B I 

� 

�' 

� I 

� II 

� �� 

� IV 

several � 

� 

� 

another � 

� 


Real 

polymorphs 

� 

� 

� 

A real chaos

Described 

polymorphs 

� 

� 

B I 

� 

�' 

� I 

� II 

� �� 

� IV 

several � 

� 

� 

another � 

� 


Real 

polymorphs 

� 

� 

� 

��or � + �) 

A real chaos

Described 

polymorphs 

� 

� 

B I 

� 

�' 

� I 

� II 

� �� 

� IV 

several � 

� 

� 

another � 

� 


Real 

polymorphs 

� 

� 

� 

��or � + �) 

� 

A real chaos

Described 

polymorphs 

� 

� 

B I 

� 

�' 

� I 

� II 

� �� 

� IV 

several � 

� 

� 

another � 

� 


Real 

polymorphs 

� 

� 

� 

��or � + �) 

� 

� 

A real chaos

Described 

polymorphs 

� 

� 

B I 

� 

�' 

� I 

� II 

� �� 

� IV 

several � 

� 

� 

another � 

� 


Real 

polymorphs 

� 

� 

� 

��or � + �) 

� 

� 

� 

A real chaos

Described 

polymorphs 

� 

� 

B I 

� 

�' 

� I 

� II 

� �� 

� IV 

several � 

� 

� 

another � 

� 


Real 

polymorphs 

� 

� 

� 

��or � + �) 

� 

� 

� 

� + � + � 

A real chaos

Described 

polymorphs 

� 

� 

B I 

� 

�' 

� I 

� II 

� �� 

� IV 

several � 

� 

� 

another � 

� 


Real 

polymorphs 

� 

� 

� 

��or � + �) 

� 

� 

� 

� + � + � 

A real chaos

Described 

polymorphs 

� 

� 

B I 

� 

�' 

� I 

� II 

� �� 

� IV 

several � 

� 

� 

another � 

� 


Real 

polymorphs 

� 

� 

� 

��or � + �) 

� 

� 

� 

� + � + � 

A real chaos 

Only 3 polymorphs? 

�� , � , ��

Described 

polymorphs 

� 

� 

B I 

� 

�' 

� I 

� II 

� �� 

� IV 

several � 

� 

� 

another � 

� 


Real 

polymorphs 

� 

� 

� 

��or � + �) 

� 

� 

� 

� + � + � 

A real chaos 


�� , � , �� 

No!

Described 

polymorphs 

� 

� 

B I 

� 

�' 

� I 

� II 

� �� 

� IV 

several � 

� 

� 

another � 

� 


Real 

polymorphs 

� 

� 

� 

��or � + �) 

� 

� 

� 

� + � + � 

A real chaos 

2 different 

polymorphs 

� I 

� II 


�� , � , �� 

No!

Described 

polymorphs 

� 

� 

B I 

� 

�' 

� I 

� II 

� �� 

� IV 

several � 

� 

� 

another � 

� 


Real 

polymorphs 

� 

� 

� 

��or � + �) 

� 

� 

� 

� + � + � 

A real chaos 

2 different 

polymorphs 

� I 

� II 


�� , � , �� 

� I � II 

No!

Polymorphs of quinacridones 

� I 

� II 

� 

� 

� I 

� II 

� 

�

Quinacridone: Polymorphs 

NaOH 

Synthesis 

� I or � II 

phases 

Solvent 

� phase � phase

� phase 

Quinacridone: Synthesis 

NH 2 

+ H 2 O 

120-170°C 

O 

COOCH 3 

+ + 

H COOC 3 

O H N 2 

H 

N 

HOOC 

COOH 

NaOH Solvent 

N 

H 

O 

N 

H 

(HPO 3 ) n 

+ H2O H 

N 

O 

low 

temp. 

� I or � II phases 

+ small amounts of H 2 O 

120-170°C 

� phase

<strong>Crystal</strong> structures of quinacridone 

� phase � phase 

[Paulus, Leusen & Schmidt, CrystEngComm 9, 2007, 131]

<strong>Crystal</strong> <strong>Engineering</strong> of quinacridones 

H 

N 

O 

H 

N 

O 

H 

N 

O 

O 

N 

H 

O 

N 

H 

O 

N 

H 

H 

H 

H 


[Paulus, Leusen & Schmidt, CrystEngComm 9, 2007, 131] 

H 

N 

O 

H 

N 

O 

H 

N 

O 

N H 

N 

O 

O 

N 

H 

O 

N 

H 

O 

N 

H


H 

N 

O 

H 

N 

O 

H 

N 

O 

O 

N 

H 

O 

N 

H 

O 

N 

H 

H 

H 

H 

Cl 



H 

N 

O 

H 

N 

O 

H 

N 

O 

N H 

N 

O 

O 

N 

H 

O 

N 

H 

O 

N 

H 

Cl


H 

N 

O 

H 

N 

O 

H 

N 

O 

O 

N 

H 

O 

N 

H 

O 

N 

H 

H 

H 

H 

Cl 



Cl 

H 

N 

O 

H 

N 

O 

H 

N 

O 

N H 

N 

O 

O 

N 

H 

O 

N 

H 

O 

N 

H 

Cl


Cl 

O O H 

H 

N 

O 

O 

N 

H 

Pigment Red 207 

(commercial) 


Cl 

Cl

Polymorph screening 

without knowledge of the crystal structure 

CH 3 

Cl 

N N 

O 

O 

S 

H O 

O 

2 

Ca 2+ 

Until 1997: Only 1 polymorphic form 

No crystal structure 

Compound known since 1902 

[Deutsches Reichspatent Nr. 145908 

by Griesheim-Elektron (Frankfurt)] 

(Ba 2+ salt: used for 

newspaper printings ...) 

Then we started syntheses and crystallizations ...

Polymorphism of Pigment Red 53:2 

Na + salt 

+ CaCl 2 

�


Na + salt 

+ CaCl 2 

� 

DMSO 

DMSO solvate 

*


Na + salt 

� 

+ CaCl 2 

DMSO 

� 

DMSO 

DMSO solvate 

*


Na + salt 

� 

� 

+ CaCl 2 

Bright orange pigment 

e.g. for printing inks 

DMSO 

iso-butanole 

� 

DMSO 

DMSO solvate 

*


Na + salt 

� 

� 

� 



+ CaCl 2 

DMSO 

iso-butanole 

chlorobenzene 

� 

DMSO 

DMSO solvate 

*


Na + salt 

� 

� 

� (Na + salt) 



+ CaCl 2 

DMSO 

iso-butanole 

chlorobenzene 

� 

DMSO 

DMSO solvate 

*


Na + salt 

� 

� 

� 


+ CaCl 2 

DMSO 

iso-butanole 

chlorobenzene 

recryst. from 

DMAc / H 2 O 

� 

DMSO 

DMSO solvate 

*


Na + salt 

� 

� 

� 

� 


+ CaCl 2 

DMSO 

iso-butanole 

chlorobenzene 

recryst. from 

DMAc / H2O ethanole 

� 

DMSO 

DMSO solvate 

*


Na + salt 

� 

� 

� 

� 


� (+ � + Na salt) 

+ CaCl 2 

DMSO 

iso-butanole 

chlorobenzene 

recryst. from 


1-butanole 

� 

DMSO 

DMSO solvate 

*


Na + salt 

� 

� 

� 

� 


� (+ � + Na salt) 

+ CaCl 2 

DMSO 

iso-butanole 

chlorobenzene 

recryst. from 


��(+ �) 

1-butanole 

acetophenone 

� 

DMSO 

DMSO solvate 

*


Na + salt 

� 

� 

� 

� 


� (+ � + Na salt) 

+ CaCl 2 

DMSO 

iso-butanole 

chlorobenzene 

recryst. from 


��(+ �) 

1-butanole 


� 

DMSO 

morpholene 

DMSO solvate 

� 

*


Na + salt 

� 

� 

� 

� 


� (+ � + Na salt) 

+ CaCl 2 

DMSO 

iso-butanole 

chlorobenzene 

recryst. from 


��(+ �) 

1-butanole 


� 

DMSO 

morpholene 

DMSO solvate 

recryst. from 

NMF / H2O � 

* 

� (+�)


Na + salt 

� 

� 

� 

� 


� (+ � + Na salt) 

+ CaCl 2 

DMSO 

iso-butanole 

chlorobenzene 

recryst. from 


��(+ �) 

1-butanole 


� 

DMSO 

morpholene 

DMSO solvate 

recryst. from 

NMF / H2O acetone 

� 

* 

� (+�) 

� (+�)


Na + salt 

� 

� 

� 

� 


� (+ � + Na salt) 

+ CaCl 2 

DMSO 

iso-butanole 

chlorobenzene 

recryst. from 


��(+ �) 

1-butanole 


� 

DMSO 

morpholene 

DMSO solvate 

recryst. from 


synthesis 

from K + salt 

� 

* 

� (+�) 

� (+�) 

�


Na + salt 

� 

� 

� 

� 


� (+ � + Na salt) 

+ CaCl 2 

DMSO 

iso-butanole 

chlorobenzene 

recryst. from 


��(+ �) 

1-butanole 


� 

DMSO 

morpholene 

DMSO solvate 

recryst. from 


synthesis 

from K + salt 

� 

* 

� (+�) 

� (+�) 

� (K + salt)


Na + salt 

� 

� 

� 

� 


� (+ � + Na salt) 

+ CaCl 2 

DMSO 

iso-butanole 

chlorobenzene 

recryst. from 


��(+ �) 

1-butanole 


� 

DMSO 

morpholene 

DMSO solvate 

recryst. from 


synthesis 

from K + salt 

glycole 

� 

* 

� (+�) 

� (+�) 

� (K + salt) 

�


Na + salt 

� 

� 

� 

� 


� (+ � + Na salt) 

+ CaCl 2 

DMSO 

iso-butanole 

chlorobenzene 

recryst. from 


��(+ �) 

1-butanole 


� 

DMSO 

morpholene 

DMSO solvate 

recryst. from 


synthesis 

from K + salt 

glycole 

glycolic acid 

butylester 

� 

* 

� (+�) 

� (+�) 

� (K + salt) 

� 

�


Na + salt 

� 

� 

� 

� 


� (+ � + Na salt) 

+ CaCl 2 

DMSO 

iso-butanole 

chlorobenzene 

recryst. from 


��(+ �) 

1-butanole 


� 

DMSO 

morpholene 

DMSO solvate 

recryst. from 


synthesis 

from K + salt 

glycole 

glycolic acid 

butylester 

NMF / H2O (Susp.) 

� 

� 

* 

� (+�) 

� (+�) 

� (K + salt) 

� 

�

� 


Na + salt 

� 

� 

� 


� (+ � + Na salt) 

��(+ �) 

+ CaCl 2 

iso-butanole 

chlorobenzene 

recryst. from 

DMAc / H 2 O 

ethanole 

DMSO 

1-butanole 


� 

DMSO 

morpholene 

recryst. from 


synthesis 

from K + salt 

glycole 

glycolic acid 

butylester 


� 

� 

� 

* 

� (+�) 

� (+�) 

� 

� 

* 

� (K + salt) 

* 

* Solvent containing 

*

� 


Na + salt 

� 

� 

� 


� (+ � + Na salt) 

��(+ �) 

+ CaCl 2 

iso-butanole 

chlorobenzene 

recryst. from 

DMAc / H 2 O 

ethanole 

DMSO 

1-butanole 


M.U. Schmidt, H.-J. Metz, EP 965616 A1 (1999) 


M.U. Schmidt, EP 1010732 A1 (1999) 

� 

DMSO 

morpholene 

� 

recryst. from 


synthesis 

from K + salt 

glycole 

glycolic acid 

butylester 


� 

� 

* 

� (+�) 

� (+�) 

� 

� 

* 

� (K + salt) 

* 


*

� 


Na + salt 

� 

� 

� 


� (+ � + Na salt) 

��(+ �) 

+ CaCl 2 

iso-butanole 

chlorobenzene 

recryst. from 

DMAc / H 2 O 

ethanole 

DMSO 

1-butanole 


� 

DMSO 

morpholene 

� 

� 

acetone 

synthesis 

from K + salt 

glycole 

glycolic acid 

butylester 

NMF / H2O DMF 

recryst. from 


� 

� 

* 

� (+�) 

� (+�) 

� 

� 

* 

� (K + salt) 

* 




M.U. Schmidt, EP 1010732 A1 (1999) 15 (pseudo-) polymorphic phases 

*

Example 2: 

Weather fastness of Pigment Red 170 

N 

H 2 

Used for paints and laquers (e.g. cars) 

Production: >> 1000 t / year 

Sales: > 100 Mio € / year 

N 

N 

O 

H 

O 

O 

H 

N 

O 

CH 3 

CH 2

N 

H 2 

N 

N 


O 

H 

O 

O 

H 

N 

O 

CH 3 

CH 2 

Why ethoxy group? 

Ethoxy: 

Good properties

N 

H 2 

N 

N 


O 

H 

O 

O 

H 

N 

O 

CH 3 


Ethoxy: 

Good properties 

Methoxy: 

Solubility higher 

Properties worse

N 

H 2 

N 

N 


O 

H 

O 

O 

H 

N 

O 

CH 2 

CH 2 

CH 3 


Ethoxy: 


Methoxy: 


Properties worse 

Propoxy: 


Properties worse

N 

H 2 

N 

N 


O 

H 

O 

O 

H 

N 

O 

CH 2 

CH 2 

CH 3 


Ethoxy: 


Methoxy: 



Propoxy: 



Reason?

"Single" 

crystals

Extraction of reliable 

reflection intensities failed 

=> Structure solution failed

Extraction of reliable 

reflection intensities failed 

=> Structure solution failed 

Finally: Structure determined 

from X-ray powder data 

(easier + faster)

Determination of crystal structures from 

powder data by energy minimization 

X-ray powder 

diagram 

(Lab data) 

Synchrotron data 

(if sensible) 

Indexing 

if possible 

Lattice params. 

and possible 

space groups 

Comparison 

Structure model 

Rietveld 

refinement 

Molec. geometry and 

additional informations 

Prediction of crystal 

structures 

by global lattice 

energy minimization 

Calculation of X-ray 

powder diagrams 


structure

Lattice energy minimizations (CRYSCA) 

1 � 

6 C r 1 qi 

q � 

E � 

� 

ij 

j 

� �� 

� � � 

� A�rij 

�B 

�e 

� � � �E 

2 � 

4 

i j 0 r � 

� 

�� ij � 

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

q: Atomic charges 

E intramol. : Intramolecular energy, depending on the 

intramolecular degrees of freedom, 

intramol . 

e.g. for : 6-term cosine series 

� fitted to ab initio calculations 

[M.U. Schmidt, U. Englert, J. Chem. Soc., Dalton Trans. 1996, 2077-82]


Molecular 

geometry 

Global minimum 

<strong>Crystal</strong> symmetry 

Space group 

Site symmetry 

Start: 1000 - 100000 random crystal structures 

Random values for: Lattice parameters (if not known) 

Position of the molecules 

Orientation of the molecules 

Intramolecular degrees of freedom 

"Predicted 

crystal structure" 

Minimization of the lattice energy 

Simultaneous optimization of all parameters 

Additional informations, e.g. 

Lattice params. from indexing 

Electron diffraction data 

Spectroscopic data 

Other minima with low energies Local minima 

Other possible 

polymorphic forms 

with higher 

energies


P2 1 /n, Z = 4, a = 10.8222 Å, b = 24.169 Å, c = 8.3623 Å, � = 100.576° 

R wp = 7.7%, R p = 5.4%, red. � 2 = 8.0. 

[M. U. Schmidt, D.W.M. Hofmann, C. Buchsbaum, H. J. Metz, Angew. Chem. Int. Ed. 45 (2006), 1313-1317]


P2 1 /n, Z = 4, a = 10.8222 Å, b = 24.169 Å, c = 8.3623 Å, � = 100.576° 

R wp = 7.7%, R p = 5.4%, red. � 2 = 8.0. 

X 



P2 1 /n, Z = 4, a = 10.8222 Å, b = 24.169 Å, c = 8.3623 Å, � = 100.576° 

R wp = 7.7%, R p = 5.4%, red. � 2 = 8.0. 

X 

N 

H 2 

N 

N 

O 

H 

O 

O 

X 

H 

N 

O 

X = CH 3 , F, Cl, Br, ... 

(new compounds) 

[M. U. Schmidt, D.W.M. Hofmann, C. Buchsbaum, H. J. Metz, Angew. Chem. Int. Ed. 45 (2006), 1313-1317] 

CH 3 

CH 2

Pigment Red 170: 

New derivatives and solid solutions 

X = H 

(P.R.170) 

X = Cl 

Space "X" too 

small for Cl atom 

Other crystal 

structure formed 

Different colour 

Worse properties 

[M. U. Schmidt, A. Wacker, H. J. Metz: 

International Patent WO 2003099936 A1 (2003), 

International Patent WO 2005019346 A1 (2005), 

Solid solution: 

10% X = Cl 

90% X = H 

<strong>Crystal</strong> structure 

like P.R.170 

Colour like P.R.170 

Weather fastness 

improved 

Already in industrial 

development 


O 

Violet pigment 

Example 3: Methyl-dioxazine 

C 

H 3 

H 

N 

N 

N 

O 

Cl 

Cl 

O 

N 

N 

N 

H 

CH 3 

Insouble in all solvents, even in DMSO or NMP at 200°C 

(detection limit 10 -5 g/L), 

Melting point > 300°C (decomposition) 

6 polymorphic forms 

No single crystals 

No suitable powder diagrams 

Indexing failed (triclinic) 

O

O 

Violet pigment 

Example 3: Methyl-dioxazine 

C 

H 3 

H 

N 

N 

O 

=> Structure determination 

from unindexed powder data 

N 

Cl 

Cl 

O 

N 

N 

N 

H 

CH 3 

Insouble in all solvents, even in DMSO or NMP at 200°C 

(detection limit 10 -5 g/L), 

Melting point > 300°C (decomposition) 

6 polymorphic forms 

No single crystals 

No suitable powder diagrams 

Indexing failed (triclinic) 

O

Methyl-dioxazine: Structure solution 

– 

P 1 

Z = 2 

P 2 1 

Z = 2 

P 2 1 /c 

Z = 4 

C 2/c 

Z = 8 

P 2 1 2 1 2 1 

Z = 4 

... 

– 

P 1 

Z = 1 

P 2 1 /c 

Z = 2 

Pbca 

Z = 4


– 

P 1 

Z = 2 

P 2 1 

Z = 2 

P 2 1 /c 

Z = 4 

C 2/c 

Z = 8 

P 2 1 2 1 2 1 

Z = 4 

– 

P 1 

Z = 1 


... 

P 2 1 /c 

Z = 2 

Pbca 

Z = 4


– 

P 1 

Z = 2 

P 2 1 

Z = 2 

P 2 1 /c 

Z = 4 

C 2/c 

Z = 8 

P 2 1 2 1 2 1 

Z = 4 

– 

P 1 

Z = 1 


... 

Predicted crystal structures 

P 2 1 /c 

Z = 2 

Pbca 

Z = 4


– 

P 1 

Z = 2 

P 2 1 

Z = 2 

P 2 1 /c 

Z = 4 

C 2/c 

Z = 8 

P 2 1 2 1 2 1 

Z = 4 

– 

P 1 

Z = 1 


... 


Calculation of powder diagrams 

P 2 1 /c 

Z = 2 

Pbca 

Z = 4


– 

P 1 

Z = 2 

Intensity 

P 2 1 

Z = 2 

P 2 1 /c 

Z = 4 

C 2/c 

Z = 8 

P 2 1 2 1 2 1 

Z = 4 

– 

P 1 

Z = 1 



P 2 1 /c 

Z = 2 

5 10 15 20 25 30 2� / ° 

... 


Pbca 

Z = 4 

Calculated structure 

(energy rank no. 5) 

– 

(P 1, Z = 1)


– 

P 1 

Z = 2 

Intensity 

P 2 1 

Z = 2 

P 2 1 /c 

Z = 4 

C 2/c 

Z = 8 

P 2 1 2 1 2 1 

Z = 4 

– 

P 1 

Z = 1 



P 2 1 /c 

Z = 2 

5 10 15 20 25 30 2� / ° 

... 


Pbca 

Z = 4 

Experimental X-ray 

powder diagram 

Calculated structure 

(energy rank no. 5) 

– 

(P 1, Z = 1)


O 

N 

[M.U. Schmidt, R.E. Dinnebier, M. Ermrich, Acta Cryst. B 61, 37-45 (2005)] 

Cl 

– 

P 1, Z = 1 

a = 4.335 Å 

b = 8.419 Å 

c = 13.906 Å 

� = 106.9 º 

� = 92.9 º 

� = 95.1 º


X 

O 

N 


Cl 

– 

P 1, Z = 1 

a = 4.335 Å 

b = 8.419 Å 

c = 13.906 Å 

� = 106.9 º 

� = 92.9 º 

� = 95.1 º


O 

-CH 3 

N 


Cl 

– 

P 1, Z = 1 

a = 4.335 Å 

b = 8.419 Å 

c = 13.906 Å 

� = 106.9 º 

� = 92.9 º 

� = 95.1 º


O 

H 3 C- 

N 


Cl 

– 

P 1, Z = 1 

a = 4.335 Å 

b = 8.419 Å 

c = 13.906 Å 

� = 106.9 º 

� = 92.9 º 

� = 95.1 º


O 

-CH H3C- 3 

N 


Cl 

– 

P 1, Z = 1 

a = 4.335 Å 

b = 8.419 Å 

c = 13.906 Å 

� = 106.9 º 

� = 92.9 º 

� = 95.1 º


CH 3 

O 

H 3 C 

N 


Cl 

– 

P 1, Z = 1 

a = 4.335 Å 

b = 8.419 Å 

c = 13.906 Å 

� = 106.9 º 

� = 92.9 º 

� = 95.1 º


CH 3 

O 

H 3 C 

N 

Cl 

Ethyl: 

– 

P 1, Z = 1 

a = 5.190 Å 

b = 9.547 Å 

c = 11.743 Å 

� = 102.4 º 

� = 97.9 º 

� = 104.1 º 

R p = 9.7, 

R wp = 12.7, 

red. � 2 = 12.1

Methyl - ethyl compound 

O 

C 

H 3 

H 

N 

N 

N 

O 

Cl 

Cl 

O 

N 

CH CH 2 3 

N 

N 

H 

O

O 


C 

H 3 

H 

N 

N 

O 

C 

H 3 

H 

N 

N 

NH 2 

Cl 

O 

N 

O 

Cl 

Cl 

Cl 

O 

+ + 

Cl 

Cl N 

O 

N 

H 2 

CH CH 2 3 

N 

N 

H 

N 

N 

H 

CH 2 

O 

CH 3 

O

H 

N 

O 

N 

H3C N 

O 

O 

C 

H 3 

Cl 

Cl 


H 

N 

N 

25 % 

O 

O 

N 

C 

H 3 

H 

N 

N 

NH 2 

N 

N 

H 

Cl 

O 

N 

O 

Cl 

Cl 

Cl 

O 

+ + 

CH 3 

O 

Cl 

50 % 

Cl N 

O 

N 

H 2 

Solid solution 

O 

C 

H 3 

H 

N 

N 

CH 2 

CH CH 2 3 

N 

N 

H 

N 

N 

H 

CH 2 

O 

CH 3 

O 

N 

O 

Cl 

Cl 

25 % 

O 

N 

N 

N 

H 

CH 2 

O 

CH 3



(�� phase) 

N O 

Cl 

N N 

N 

H 

N 

Cl 

O 

H 

H C CH 3 2 

O O 

N 

CH3 Methyl compd 


N O 

Cl 

N N 

N 

H 

N 

Cl 

O 

H 

H C 3 

O O 

N 

CH3




N O 

Cl 

N N 

N 

H 

N 

Cl 

O 

H 

H C CH 3 2 

O O 

N 

CH3 Methyl compd 


N O 

Cl 

N N 

N 

H 

N 

Cl 

O 

H 

H C 3 

O O 

N 

CH3

<strong>Crystal</strong> structure of the solid solution 

Rietveld refinement (Synchrotron data): R p = 5.4, R wp = 8.0, R F2 = 17.3, � 2 = 11.7 

Better lattice energy 

Higher density (� = 1.75)

<strong>Crystal</strong> structure of the solid solution 

Rietveld refinement (Synchrotron data): R p = 5.4, R wp = 8.0, R F2 = 17.3, � 2 = 11.7 

Better lattice energy 

Higher density (� = 1.75) 

Industrial development in progress 

[M. U. Schmidt, P. Kempter, R. Born, European Patent 1199309 A1 (2002) 

M. U. Schmidt, P. Kempter, C. Plüg, R. Born, European Patent 1201718 A2 (2002)]

Example 4: Diaryl Pigments 

CH 3 

O 

Cl 

H N 

H O 

R2 N N 

N N R2 

O H 

N H 

Cl 

O 

H C 3 

R4 R5 

Name R2 R4 R5 rel. Colour strength (�) 

P. Yellow 12 H H H 100 % 

P. Yellow 13 CH 3 CH 3 H 141 % 

P. Yellow 14 CH 3 H H ca. 106 % (not fully optimized) 

P. Yellow 83 O-CH 3 Cl O-CH 3 138 % 

Production: 65 000 t / year 

Sales: > 300 Mio € / year) 

R5 

R4


CH 3 

O 

Cl 

H N 

H O 

R2 N N 

N N R2 

O H 

N H 

Cl 

O 

H C 3 

R4 R5 



P. Yellow 13 CH 3 CH 3 H 141 % 



QM calculations (single molecules): 

R = H / CH 3: no influence on � 

R5 

R4


CH 3 

O 

Cl 

H N 

H O 

R2 N N 

N N R2 

O H 

Cl � 

N 

H C 3 

H 

O 

R4 R5 



P. Yellow 13 CH 3 CH 3 H 141 % 





�� = 0°: good conjugation of � systems => high � 

�� = 40°: hindered conjugation => low � 

R5 

R4


CH 3 

O 

Cl 

H N 

H O 

R2 N N 

N N R2 

O H 

Cl � 

N 

H C 3 

H 

O 

R4 R5 



P. Yellow 13 CH 3 CH 3 H 141 % 







R5 

R4 

CSD: 

� 50 % 

� 50 %


CH 3 

O 

Cl 

H N 

H O 

R2 N N 

N N R2 

O H 

Cl � 

N 

H C 3 

H 

O 

R4 R5 



Hypothesis: 



R5 

R4 

Are the colour strengths differences 

caused by the crystal structures? 

=> Structure determination from powder data 

CSD: 

� 50 % 

� 50 %

<strong>Crystal</strong> structure of Pigment Yellow 12 

Twisted molecules 

Herringbone packing 

[M.U. Schmidt, R.E. Dinnebier, H. Kalkhof, J. Phys. Chem. B 111 (2007), 9722-9732] 

P2 1/c, Z = 4 

a = 17.878(4) Å 

b = 7.365(2) Å 

c = 24.365(5) Å 

� = 112.8(2)º 

Rigid-Body 

Rietveld refinement: 

R p = 9.12 % 

R wp = 12.69 % 

R F2 = 14.62 % 

� 2 = 3.8

Pigment Yellow 14: Structure solution by 

lattice energy minimization using CRYSCA 

60000 

50000 

40000 

30000 

20000 

10000 

0 

Intensity / 

Counts 

Experimental 

X-ray powder 

diagram 

(Lab data) 

10 15 20 25 30 35 2� / ° 

[M.U. Schmidt, R.E. Dinnebier, H. Kalkhof, J. Phys. Chem. B 111 (2007), 9722-9732]



60000 

50000 

40000 

30000 

20000 

10000 

0 

Intensity / 

Counts 

Experimental 

X-ray powder 

diagram 

(Lab data) 

10 15 20 25 30 35 2� / ° 


Indexing 

Unit cell 

Possible SG: 

– 

P 1 or P 1, Z = 1



60000 

50000 

40000 

30000 

20000 

10000 

0 

Intensity / 

Counts 

Experimental 

X-ray powder 

diagram 

(Lab data) 

10 15 20 25 30 35 2� / ° 


Indexing 

Unit cell 

Possible SG: 

– 

P 1 or P 1, Z = 1 

Lattice energy 

minimizations 

by CRYSCA (in P 1) 

a, b, c, �, �, �, fixed 

Packing and 

5 intramol. torsions 

optimized



60000 

50000 

40000 

30000 

20000 

10000 

0 

Intensity / 

Counts 

Experimental 

X-ray powder 

diagram 

(Lab data) 

10 15 20 25 30 35 2� / ° 


Indexing 

Unit cell 

Possible SG: 

– 

P 1 or P 1, Z = 1 




a, b, c, �, �, �, fixed 

Packing and 


optimized 

Best minimum (P 1) 

–



60000 

50000 

40000 

30000 

20000 

10000 

0 

Intensity / 

Counts 

Experimental 

X-ray powder 

diagram 

(Lab data) 

Calculated 

10 15 20 25 30 35 2� / ° 

Indexing 

Unit cell 

Possible SG: 

– 

P 1 or P 1, Z = 1 




a, b, c, �, �, �, fixed 

Packing and 


optimized 

– 

Best minimum (P 1) 

Calculation of X-ray 

powder diagram

Pigment Yellow 14: 

Synchrotron data and Rietveld refinement 

Intensität (Counts) 

Diff. 

experimental 

calculated 

NSLS Brookhaven�� = 1.149 Å 

Refinement of 

individual x, y, z, and B iso 

for all atoms (except H) 

was possible 

R p = 8.53 %, R wp = 12.87 %, R F 2 =17.60%, � 2 = 3.3

Pigment Yellow 13 and 14 

Planar molecules 

Layer packings 


P.Y.13: 

P1, Z = 2 

a = 8.3691(1) Å 

b = 8.7650(2) Å 

c = 12.8167(3) Å 

� = 112.054(1)º 

� = 92.920(2)º 

� = 105.691(1)ºP 

P.Y.14: 

P1, Z = 2 

a = 8.21420(6) Å 

b = 9.33011(5) Å 

c = 11.78471(8) Å 

� = 112.6805(3)º 

� = 98.1609(4)º 

� = 105.4338(4)º

<strong>Crystal</strong> structure of Pigment Yellow 83 

Planar molecules 

Herringbone packing 


P2 1/n, Z = 2 

a = 5.18907(9) Å 

b = 20.6106(4) Å 

c = 16.9954(4) Å 

� = 98.186(1)º 

R p = 7.38 % 

R wp = 11.6 % 

R F2 = 16.04 % 

� 2 = 2.63

Diaryl pigments: 

Structure-property relationships 

Compd. Col. strength Conform. Packing 

P. Yellow 12 100 % twisted herring bone P2 1/c, Z = 4 

P. Yellow 13 141 % planar 

P. Yellow 14 

(106 %) planar 

layer 

P. Yellow 83 138 % planar herring bone P2 1/c, Z = 2 


P1, Z = 1


Understanding the crystal structures 




P. Yellow 14 

Twisted conformation 

preferred for single molecules 


layer 



P1, Z = 1






P. Yellow 14 




layer 


Planar conformation 

unfavorable for single molecules 


P1, Z = 1






P. Yellow 14 





Planar conformation 

unfavorable for single molecules 

Why not a 

packing like 

P.Y. 12? 


Compd. Col. strength Conform. SG, Z Packing 



P. Yellow 14 



Lattice energy minimizations: 

P.Y. 13 / 14 / 83 with a packing like P.Y.12 

Lattice energy reduced by +7 to +15 kJ/mol 

Density reduced 

=> Unfavorable packings 





Why not a 

packing like 

P.Y. 12? 


Diaryl pigments: <strong>Crystal</strong> <strong>Engineering</strong> 

Compd. Col. strength Conform. Packing SG, Z 



P. Yellow 14 


layer P1, Z = 1 


Can P.Y. 12 adopt the planar structure of P.Y. 13/14 ? 






P. Yellow 14 






Lattice energy only slightly worse => Second polymorph? 






P. Yellow 14 



Experiments: 


Polymorph found [Ciba SC, European Patent, 1997] 

Requires special additives: H C 37 18 

NH 




N 

H 

N 

H 

NH 2



P. Yellow 12 (�) 100 % twisted herring bone P2 1/c, Z = 4 

P. Yellow 12 (�) ... planar 


P. Yellow 14 



Experiments: 


Polymorph found [Ciba SC, European Patent, 1997] 

Requires special additives: H C 37 18 

NH 



N 

H 

N 

H 

NH 2






P. Yellow 14 




Are there solid solutions of P.Y.12 and P.Y.13/14 ? 







P. Yellow 14 





Lattice energy minimizations: Yes! 







P. Yellow 14 





Lattice energy minimizations: Yes! 

Experiments: Yes! 

Color strength 150% ! 





Solid solution of P.Y.12 and P.Y.14 

150 % planar 



P. Yellow 14 






Compd. Col. strength Conform. Selling price 

P. Yellow 12 (�) 100 % twisted low 


150 % planar high 


P. Yellow 13 141 % planar high 

P. Yellow 14 





Compd. Col. strength Conform. Selling price Costs 

P. Yellow 12 (�) 100 % twisted low low 


150 % planar high 


P. Yellow 13 141 % planar high high 

P. Yellow 14 




N 

H 

N 

H 

CH 3 

CH 3





150 % planar high medium 



P. Yellow 14 




N 

H 

N 

H 

CH 3 

CH 3








P. Yellow 14 



High selling price for lower costs. 

The solid solution is produced industrially. 


N 

H 

N 

H 

CH 3 

CH 3








P. Yellow 14 



High selling price for lower costs. 

The solid solution is produced industrially. 

=> <strong>Crystal</strong> <strong>Engineering</strong> may even help to reduce the costs. 


N 

H 

N 

H 

CH 3 

CH 3

Crystal Engineering on Organic Pigments

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