International Winter School on Chemistry and Physics of ...
Schegolev Memorial Symposium Chernogolovka, Russia, 12-15 October 2009 Organic-Inorganic Layer Salts as Molecular Functional Materials: Peter DayChirality
Multilayers and UCL and Royal Institution, London, UK Layered structures foundation of micro-electronics (MOS etc) Fabricated by top down methods Molecular beam epitaxy
Laser ablation Spin coating etc etc But is it possible to make multilayers by self-assembly? YES A self-assembled multilayer Insulatin g layer
Metallic layer Insulating layer An old story of layers soluble ferromagnets (CnH2n+1NH3)2CrX4 Bellitto and Day
1978 Halide Layer Conductors from metals to insulators Mitzi et al. 1995 Conducting multilayers BEDT-TTF charge transfer salts
The BEDT-TTF molecule Electrochemical crystal growth Organic-Inorganic Charge Transfer Salts First paramagnetic molecular superconductor -(ET)4[(H3O)Fe(C2O4)3].C6H5CN
Day, Kurmoo, Graham 1995 What we want to do next. First objective - Superlattices of layers D+X- salts form layers: DXDXDX. Make e.g. DXDXDXDX. D, D same molecule, different packing
D, D different molecules Multi-layers means multifunctions. An early example of DXDX stacking (ET)4[(H3O)Ga(C2O4)3].PhCH2CN D X
D X Akutsu, Day et al. 2003 D Different layers have different
functions metallic proton conductor H3O+-crown ether layer: proton conducting ET layer: electron conducting Akutsu, Day et al. Superstructure with purely inorganic layer Na+ and H2O
Martin, Day et al 2007 Second objective Chiral organic-inorganic multilayers Why? Maybe novel properties magneto-chiral anisotropy (Rikken) chiral Fermi surface? chiral superconductor?? How? chiral anions
chiral donor molecules chiral guest molecules chiral solvents Chiral anions [M(C2O4)3]3-(ET)4[M(C2O4)3]C6H5CN Each anion layer contains one enantiomer Day, Kurmoo, Graham 1995
Chiral anions [M(C2O4)3]3Two polymorphs of (ET)4[(H3O)M(C2O4)3]C6H5CN C2/c is superconducting; Pbcn is semiconducting! Anion layers Cation layers Turner, Day, Howard et al 2001
Incorporating a chiral donor molecule -(TM-ET)2.7[MnCr(C2O4)3]CH2Cl2 chiral tetra(methyl)-BEDT-TTF S S
S Ferromagnetic S Metallic S S
S S Ferromagnet ic Gomez-Garcia, Giminez-Sal, Wallis & Coronado
Chiral guest molecules - DXDX superstructure (R)- and (S)-sec-phenyl alcohol Martin, Day, Akutsu et al 2007 Anion layers contain NH4+, [Fe(C2O4)3]3- and guest molecules
Martin, Day, Akutsu et al 2007 Crystals with chiral (R)- or racemic (R,S)- guest molecules Single crystal resistivities Disorder of guest molecules in (R,S)- crystal
Martin, Day, Akutsu et al (R) (R,S) Chiral solvent Crystallising (NH4)3[Fe(C2O4)3] with 18C6 gives chiral [(NH4)(18C6)]3[Fe(C2O4)3].9H2O containing only one enantiomer of the anion.
[Fe(C2O4)3] and H2O 3- Helical array of [(NH4)(18C6)]+ In an achiral solvent the same reactants crystallize in a racemic polymorph with a
different structure [(NH4)(18C6)]3[Fe(C2O4)3].6H2O Martin 2008 ET salts from chiral solvent: ET3[(Na)-Cr(C2O4)3].CH2Cl2 Martin, Day et al, 2009
ET3[(Na)-Cr(C2O4)3].CH3NO2 Polymorph I P212121 Anion layer ET layer M Martin, Day et al 2009
ET3[(Na)-Cr(C2O4)3].CH3NO2 Polymorph 2 P21 Anion layer ET layer Martin, Day et al 2009
What have we learned? Multi-layers of alternating organic and inorganic components can be crystallized with defined superstructures. Each layer can have its own properties (metallic, superconducting, magnetic etc). Chirality can be built into the structures by crystal engineering.
Collaborators Lee Martin, NottinghamTrent University, UK - synthesis, structures and properties Hiroki Akutsu; Akane Akutsu-Sato, Hyogo University, Japan structures and properties John Wallis, Nottingham Trent University, UK new donor molecules Mike Hursthouse; Peter Horton; Sussex
University, UK crystal structures Carlos Gomez, Valencia University, Spain physical properties Amalia Coldea, Bristol University, UK magnetoresistance Our funding Engineering and Physical Sciences Research Council (UK) European Commission: MAGMANet;
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