Structure Property Relationships in Crystal Structures of Molecules with Non Centrosymmetric Polymorphs Brainfest 2005 talk

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Structure-Property

Relationships in Crystal

Structures of Polar

Molecules

Graham Tizzard

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Background

 _{No. of different attractive forces}

determine packing in molecular crystals

 London forces, multipolar forces, H-

bonding, CT forces

 _{Complex interplay of these + repulsion E}

→ many local minima in crystal lattice E

 _{→ Polymorphism - the existence of more}

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Polymorphism & H-bonding

 _H-bonds:

 Highest E interactions in molecular crystals  most

important attractive force

 Multiple H-bonding sites → different H-bonding

topologies → polymorphism

 _However:

 Polymorphism also in systems w.out strong

H-bonds (D – H ∙∙∙ A; D = N, O, S; A = N, O, S, Hal)

 Weak H-bonds may exist (C – H ∙∙∙ A, C – H ∙∙∙ π)

 Importance of H-bonding in defining polymorphism

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Aims

 _{Detailed study of weak or non H-bonding}

systems

 _{Especially those w. non-centrosymmetric}

polymorphs

 _{V. important for development of}

materials w. NLO properties

 _{Electrostatic interactions expected to}

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Dataset

 _{Constructed from Cambridge Structural}

Database1 (CSD) v5.25 (November

2003)

 _{CSD mined for polymorphic clusters with}

≥ one non-centrosymmetric member

 _{835 ‘hits’ made up of 258 polymorphic}

clusters each comprising of 2-3 different polymorphs

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Analyses

 _XPac2:

 Many polymorphic families of a compound show no

similarity when analysed

 For those that do ‘structure-forming’ motif may be

able to be elucidated from results

 _{Short contact analysis (Mercury v1.2.1}3) +

modelling of electrostatic charges (Spartan’04 for windows4)

 Correlation between short contact distances &

matching of potentials would suggest these are important in a crystal structure

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4’-Bromo-trans-1,4-dihydro-4-tritylbiphenyl (BAWSAT)

 _{2 polymorphs identified from CSD: BAWSAT &}

BAWSAT01

 _{BAWSAT01 is non-centrosymmetric}

[5] [5]

Reference

1.0 0.5

Z’

2 4

Z

1167.309 2343.211

Cell Volume / Å3

90 90

γ / º

108.98 90

β / º

90 90

α / º

8.463 10.431

c / Å

16.187 17.264

b / Å

9.011 13.012

a / Å

Pc (7) Pnam (62)

Space Group (No.)

monoclinic orthorhombic

Crystal System

BAWSAT01 BAWSAT

CSD code

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XPac Analysis of BAWSAT

 _{Views of BAWSAT along the c-axis}

(top) & BAWSAT01 between the a and c axes (bottom)

 _{XPac reveals 1d chain along these}

respective axes common to both crystal structures (green)

 _{In both structures the same chain}

motif is interspaced (in different ways) between the original (dark green)

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Short Contact & Electrostatic

Charge Analyses of BAWSAT

 _{Each molecule in}

BAWSAT01 (top) &

BAWSAT (bottom) has short contacts w. 8 neighbours

 _{None of these is particularly}

strong

 _{ESC & SC data correlation:}

4/10 wrt. BAWSAT01; 0 wrt. BAWSAT

 _{Suggests electrostatic}

interactions unimportant in crystal formation

 _{Other interactions e.g.}

simple space-filling may dictate these structures.

-0.041 2.359 0.136788 H22 :7 0.155091 H4 -0.041 2.359 0.155091 H4 :8 0.136788 H22 -0.056 2.844 0.155091 H4 :8 -0.191035 C28 -0.056 2.844 -0.191035 C28 :7 0.155091 H4 -0.058 2.342 0.104592 H13 :6 0.120092 H19 -0.058 2.342 0.120092 H19 :5 0.104592 H13 -0.08 2.97 0.097207 H3 :4 -0.117756 Br1 -0.08 2.97 -0.117756 Br1 :3 0.097207 H3 -0.086 2.314 0.130679 H8 :2 0.136779 H24 -0.086 2.314 0.136779 H24 :1 0.130679 H8

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2-(α-p-Bromophenyl-β-nitroethyl)-cyclohexanone (BPNECH)

 _{2 polymorphs identified from CSD: BPNECH &}

BPNECH01

 _{BPNECH01 is non-centrosymmetric}

[7] [6]

Reference

1.0 1.0

Z’

4 4

Z

1448.175 1473.234

Cell Volume / Å3

90 90

γ / º

90 90.30

β / º

90 90

α / º

30.777 30.570

c / Å

8.495 8.560

b / Å

5.539 5.630

a / Å

P212121 (19)

P21/c (14)

Space Group (No.)

orthorhombic monoclinic

Crystal System

BPNECH01 BPNECH

CSD code

[6] M. Calligaris, F. Giordano, L. Randaccio; Ric. Sci., Parte 1; 36; 1333; 1966.

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XPac Analysis of BPNECH

 _{Views of BPNECH (top)}

and BPNECH01 (bottom) along the b-axis

 _{XPac reveals 2d sheet}

along these respective axes common to both crystal structures (green)

 _{In BPNECH both}

highlighted sheets (green & dark green) are

identical

 _{In BPNECH01 second}

sheet highlighted (red) is same sheet structure

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Short Contact & Electrostatic

Charge Analyses of BPNECH

 _{Each molecule in}

BPNECH01 (top) and

BPNECH (bottom) has short contacts w. 8 / 9 neighbours respectively

 _{Short contacts are stronger}

on the whole than in BAWSAT & BAWSAT01

 _{ESC & SC data correlate in}

both polymorphs

 _{Suggests that electrostatic}

interactions may be

significant in formation of both crystal systems

-0.059 2.661 -0.451598 O3 :2 0.12995 H2 -0.059 2.661 0.12995 H2 :1 -0.451598 O3 -0.063 2.987 0.093177 H5 :8 -0.05641 Br1 -0.063 2.987 -0.05641 Br1 :7 0.093177 H5 -0.084 2.636 -0.447545 O1 :6 0.106818 H7 -0.084 2.636 0.106818 H7 :5 -0.447545 O1 -0.124 2.596 -0.434661 O2 :4 0.130828 H1 -0.124 2.596 0.130828 H1 :3 -0.434661 O2 -0.212 2.508 0.203696 H12 :1 -0.434661 O2 -0.212 2.508 -0.434661 O2 :2 0.203696 H12 -0.222 2.498 -0.434661 O2 :2 0.166816 H13 -0.222 2.498 0.166816 H13 :1 -0.434661 O2 Length-VdW Length Electrostatic charge 2 Atom2 Electrostatic charge 1 Atom1 BPNECH01 -0.029 2.691 -0.451598 O3 :9 0.062736 H3 -0.029 2.691 0.062736 H3 :8 -0.451598 O3 -0.048 2.672 0.06238 H9 :3 -0.434661 O2 -0.048 2.672 -0.434661 O2 :4 0.06238 H9 -0.057 3.313 -0.447545 O1 :7 -0.05641 Br1 -0.057 3.313 -0.05641 Br1 :7 -0.447545 O1 -0.096 2.624 0.106818 H7 :6 -0.447545 O1 -0.096 2.624 -0.447545 O1 :5 0.106818 H7 -0.145 2.575 0.12995 H2 :3 -0.451598 O3 -0.145 2.575 -0.451598 O3 :4 0.12995 H2 -0.224 2.496 0.1308282 H12 :3 -0.434661 O2 -0.224 2.496 -0.434661 O2 :4 0.1308282 H12 -0.27 2.45 -0.434661 O2 :4 0.1308283 H13 -0.27 2.45 0.1308283 H13 :3 -0.434661 O2 -0.326 2.394 0.130828 H1 :2 -0.434661 O2 -0.326 2.394 -0.434661 O2 :1 0.130828 H1 Length-VdW Length

Electrostatic charge 2

Atom2

Electrostatic charge 1

Atom1

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Comments I

 _{Several points worth noting:}

 Overall analysis involves several techniques - hard

to draw conclusions using them in isolation

 XPac analysis uses ’top-down’ approach - data

derived from polymorph crystal structures

 Modelling of electrostatic charges is ‘bottom-up’

approach - data derived from molecule

 One goal of Comb-e-Chem project - combine data

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Comments II

 _{Major ‘bottlenecks’ throughout project have}

been workflow related:

 Data transfer from one application to another

 ‘Driving’ applications to obtain the data

 _{Methods of automation investigated:}

 perl to write data-transfer scripts

 Spreadsheets to automate calculations

 _{Ultimate aim of providing complete analysis of}

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Acknowledgements

 _{Prof. Mike Hursthouse}

 _{The Group – Dr. Simon Coles, Dr. Mark}

Light, Dr. Peter Horton, Dr. Ann

Bingham, Dr. Thomas Gelbrich, Dr. Stefan Christensen, Dr. Yang Li, Dr. David Hughes, Suzanna Ward

 _{EPSRC E-Science project}_(GR/R67729,