A Nanoball Switch
Jaebum Lim
Miljanić Group Meeting / Literature
U n i v e rs 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 th 2 0 0 9
Specialists in Monash University
Assoc. Prof. S. R. Batten
Prof. Keith S Murray
PhD, Manc. 1966; FRACI
Personal Chair in Chemistry, 1997
Magnetic Materials Group
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 o C in summer; 6–13 o C 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
• 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
• This compound was made by using a “bottomup” 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.
[{CuI(Tp4-py)(CH3CN)}8{FeII(NCS)2}10/3{FeII(NCS)(CH3CN)}8/3]∙(ClO4)8/3∙(CH3CN)n
Murray, K. S. et al. Angew. Chem. Int. Ed., 2008, 47, xxxx–xxxx.
Bottom-Up Approach to the Metal-Organic Nanoball
a) ligand (Tp4-py)-
b) metalloligand: [CuI(Tp4-py)(CH3CN)
+ CuI
Batten, S. R. et. al. Dalton Trans. 2005, 1910.
d) solid-state packing
+ FeII(NCS)2
c) Supramolecular nanoball
crystallization
Murray, K. S. et al. Angew. Chem. Int. Ed., 2008, 47, xxxx–xxxx.
Nanoball Structure as Determined by Single Crystal XRD
(a)
(a)
(b)
(c)
(d)
(e)
(d)
(e)
ORTEP representation (30%) of the asymmetric unit of the Fe-nanoball.
[Fe(NCS)2(py)4] (left) and [Fe(NCS)(MeCN)(py)4] (right)
Structural representation of one entire Fe-nano
A rhombic dodecahedron
The intersection of a cube and an octahedron
Murray, K. S. et al. Angew. Chem. Int. Ed., 2008, 47, xxxx–xxxx.
Important Detection Methods of SCO of Nanoball
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 (◊).
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.
Important Detection Methods of SCO of Nanoball
3. Spin Transition Curve
4. Mössbauer Spectroscopy
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.
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.
Murray, K. S. et al. Angew. Chem. Int. Ed., 2008, 47, xxxx–xxxx.