M i l j a n i ć G r o u p M e e ti n g / L i t e r a t u r eU n i v e r s i t y o f H o u s t o n ▪ H o u s t o n , T X ▪ J a n u a r y 9 t h 2 0 0 9

Jaebum L im

A Nanoball Switch

Specialists in Monash University

Magnetic Materials Group

Prof. Keith S MurrayPhD, Manc. 1966; FRACI Personal Chair in Chemistry, 1997

Assoc. Prof. S. R. Batten

Dr. Suzanne Neville Martin Duriska (PhD student)

Dr. Boujemaa Moubaraki

Melbourne Has Good Environment

• Melbourne is the second most populous city in Australia (3.8 million in 2007)• Oceanic climate: 14–26 oC in summer; 6–13 oC in winter; 54 mm of precipitation• The largest university in Australia is Monash University

about 55,000 students, UH about 36,000 students• The cultural and sport capital of Australia

Street Art in Melbourne, 1956 Summer Olympics games

The Concept of Molecular Switch Is Simple

t2g

eg

Low-spin 1A1g S = 0

High-spin 5T2g S = 2

t2g

egT, P, hv

• Molecular-switching can occur by spin-crossover (SCO) phenomenon• A crossover between a low-spin and a high-spin state is observed from some molecular species containing an octahedrally coordinated transition metal ion with the 3dn (4 ≤ n ≤ 7) electronic configuration

Kahn, O. C.; Martinez, J. Science, 1998, 279, 44–48.

• When the compounds shows repetitive cycling of a metastable HS state (switching “on”) and a stable LS state (switching “off”) through external stimuli, they are able to behave like molecular switch

Murray, K. S. et al. Angew. Chem. Int. Ed., 2008, 47, xxxx–xxxx.

A New Nanoscale Molecular Switch Was Reported

[{CuI(Tp4-py)(CH3CN)}8{FeII(NCS)2}10/3{FeII(NCS)(CH3CN)}8/3] (ClO∙ 4)8/3 (CH∙ 3CN)n

• This compound was made by using a “bottom-up” approach.• It shows a magnetic response to a range of external stimuli such as temperature, light, and solvent molecules. • An “on” or “off” magnetic state is able to be selected by wavelength variation. • Its possible application is a light-sensitive magnetic device. • The control of the electronic state is possible through solid-state guest exchange and removal.

Murray, K. S. et al. Angew. Chem. Int. Ed., 2008, 47, xxxx–xxxx.

Bottom-Up Approach to the Metal-Organic Nanoball

B-H

NN

NN

N

N

NN

N

a) ligand (Tp4-py)-

+ CuI

b) metalloligand: [CuI(Tp4-py)(CH3CN)

+ FeII(NCS)2

c) Supramolecular nanoball

crystallization

d) solid-state packing

Batten, S. R. et. al. Dalton Trans. 2005, 1910.

Murray, K. S. et al. Angew. Chem. Int. Ed., 2008, 47, xxxx–xxxx.

Nanoball Structure as Determined by Single Crystal XRD

(a)

(d)

(e)(a) ORTEP representation (30%) of the asymmetric unit of the Fe-nanoball.

(b) [Fe(NCS)2(py)4] (left) and [Fe(NCS)(MeCN)(py)4] (right)(c) Structural representation of one entire Fe-nano(d) A rhombic dodecahedron(e) The intersection of a cube and an octahedron

Murray, K. S. et al. Angew. Chem. Int. Ed., 2008, 47, xxxx–xxxx.

1. Magnetic susceptibility study

Plot of χMT versus temperature over the range 10 – 275 K for the thermal and LIESST effect. (○: thermal spin transition, ◊: irradiation at 532 nm followed by relaxation)

a) Plot of χMT versus T per FeII ion for the CH3CN-sorbed (○)and desorbed species(●). b) Plot of χMT versus temperature per FeII ion for sorbed solvents: CH3CN (○), acetone (□), ethanol ( ), and methanol (◊).△

Important Detection Methods of SCO of Nanoball

Murray, K. S. et al. Angew. Chem. Int. Ed., 2008, 47, xxxx–xxxx.

Important Detection Methods of SCO of Nanoball

2. Synchrotron Radiation Study

Powder X-ray diffraction peak position evolution (240–80–240 K) showing the shift from HS to LS states. Associated with this change the sample goes from a yellow color in the HS state to purple in the LS state.

Plot of the unit cell a-axis and volume versus temperature for each PXRD pattern fit (240-80 K)

Murray, K. S. et al. Angew. Chem. Int. Ed., 2008, 47, xxxx–xxxx.

Reversible switching between HS and LS states through stimulation with laser light – The LIESST effect. Green lines represent excitation and red lines represent extinction of the HS state.

3. Spin Transition Curve

Important Detection Methods of SCO of Nanoball

Murray, K. S. et al. Angew. Chem. Int. Ed., 2008, 47, xxxx–xxxx.

4. Mössbauer Spectroscopy

Mössbauer spectra of Fe-nano at (a) at liquid nitrogen (77 K) and (b) liquid helium (4.2 K) temperatures for the solvated sample and (c) at liquid helium (4.2 K)temperature for the desolvated sample. HS: red and LS: blue.