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Deconvolution of supramolecular synthons and analysis of supramolecular isomerism for wheel-and-axle silver complexes Al

Deconvolution of supramolecular synthons and analysis of supramolecular isomerism for wheel-and-axle silver complexes Alessia Bacchi, Elsa Bosetti University of Parma – Italy. Spirit of this work.

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Deconvolution of supramolecular synthons and analysis of supramolecular isomerism for wheel-and-axle silver complexes Al

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  1. Deconvolution of supramolecular synthons and analysis of supramolecular isomerism for wheel-and-axle silver complexes Alessia Bacchi, Elsa Bosetti University of Parma – Italy

  2. Spirit of this work A supramolecular synthon is a structural unit formed by intermolecular interactions (e.g. carboxylic acid H-bonded dimer) deconvolution Observed native crystal Supramolecular synthons Structural motifs Virtual mutant crystal In cerebro manipulation convolution

  3. Outline • what are wheel-and-axle silver complexes • extraction of fundamental synthons • derivation of supramolecular motifs • generation of tentative supramolecular isomers* • * Purely speculative exercise

  4. One organic model DHMB Our molecule [Ag(LOH)2]+ Wheel-and-axle (it’s ionic!!)

  5. Wheel-and-axle What a difference the anion makes… BF4- [Ag(LOH)2]BF4 + PF6- We will look at the patterns arising from the different properties of the anions [Ag(LOH)2]PF6

  6. Deconvolution of supramolecular motifs Deconvolution of supramolecular motifs: [Ag(LOH)2]BF4vs. [Ag(LOH)2]PF6 • elencation of supramolecular synthons • analysis of their assembly in supramolecular motifs • two motifs are identified 1) Hydrogen bond chains –OH…F-X-F…HO- 2) cyclic pattern comprising Ag…F, –OH…F, and Ag…p BF4- PF6-

  7. Deconvolution of supramolecular motifs Hydrogen bond chains –OH…F-X-F…HO- : cisvs.trans BF4- PF6-

  8. Deconvolution of supramolecular motifs Anion interactions/imprinting : tetrahedralvs.octahedral BF4- diamondoid PF6- hexagonal

  9. Supramolecular isomerism… “ is the existence of more than one type of network superstructures for the same molecular building blocks” “all sets of polymorphs can therefore be regarded as being supramolecular isomers of one another” B. Moulton, M.J. Zaworotko, Chem. Rev., 101, 1629-1658 (2001)

  10. Deconvolution of supramolecular motifs –OH…F-X-F…HO- synthon: cisvs.trans • tetrahedral anion: cis • e-f additional interaction • supramolecular chirality • pseudo twofold symmetry • tetrahedral imprinting (angle between molecular long axes)=109° • octahedral anion: trans • centre of symmetry • octahedral imprinting

  11. Engineering of supramolecular isomers Engineering of supramolecular isomers starting from the synthons The observed structures are generated by propagating the synthons via inversion centre on Ag atoms

  12. Engineering of supramolecular isomers We want to combine the supramolecular synthons according to other symmetry elements compatible with the molecular structure, to generate a landscape of possible alternative supramolecular formats

  13. (a) (b) (c) Engineering of supramolecular isomers In the observed structures both the cations are centrosymmetric. There are other potential symmetry conditions:

  14. Hexameric quasi-macrocyclic assembly Ring closure requires the matching of Ag atoms Engineering of supramolecular isomers BF4- Application on Ag of a two-fold symmetry axis perpendicular to the pyridine plane – anti OH –same chirality

  15. Homochiral helix (pitch 17Å), polar residues outside. Could be templated? Could use 6PE? Engineering of supramolecular isomers BF4- The influence of conformation Application on Ag of a two-fold symmetry axis perpendicular to the pyridine plane - conformationally modified (f=O-C(sp3)-Cpy-Cpy=0°)

  16. homochiral helix (pitch 50Å) polar residues are hidden along the helix folding Engineering of supramolecular isomers BF4- application on Ag of a two-fold symmetry axis belonging to the pyridine plane – syn OH – same chirality Too loose: difficult to control

  17. Pentameric quasi-macrocyclic assembly. Ring closure is symmetry forbidden. Engineering of supramolecular isomers BF4- application on Ag of a mirror symmetry perpendicular to N-Ag-N - syn OH - opposite chirality

  18. Engineering of supramolecular isomers PF6- (a) (b) (c) Potential polymorphs? Too similar: difficult to control and engineer

  19. Conclusions • local (< 3.6Å) and medium range (< 5.5 Å) metal environment is identical • Anions make the difference • BF4 gives a cis –OH…F-X-F…HO-synthon • PF6 gives a trans –OH…F-X-F…HO- synthon • Zig-zag chains of –OH…F H-bonds with cis/trans geometry are observed • other combinations have been generated to explore possible supramolecular isomerism

  20. People involved Prof. Alessia Bacchi Prof. Mauro Carcelli Dr Paolo Pelagatti Dr Dominga Rogolino Dr Elsa Bosetti Dipartimento di Chimica Generale ed Inorganica, Chimica Analitica, Chimica Fisica University of Parma A. Bacchi, E. Bosetti, M. Carcelli, P. Pelagatti, D. Rogolino, CrystEngComm, 2004, 6, 177-183

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