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EPR-spectroscopy for systems with S = 1 and S = 3/2
Advanced Inorganic Chemistry – WS 2011/2012
• Martina Bühringer, Marco Gruber, Sarah Burchert, Mellanie Wallisch, Katrin Ludwig, Nadine Weber and Stephanie Kindt - 01.02.2012
EPR-spectroscopy for systems with
S = 1 and S = 3/2
[1]
Fundamental basics of EPR-spectroscopy
EPR-spectroscopy for spin systems S = 1
EPR-spectroscopy for S = 3/2 spin systems
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Abstract EPR-spectroscopy for systems with S = 1 and S = 3/2
[3]
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Basics of EPR-spectroscopy EPR-spectroscopy for systems with S = 1 and S = 3/2
• Method for studying chemical species having one or more unpaired electrons
(free radicals, complexes with transition metal ion) • Basic concepts are analogous to that of NMR (NMR: nuclear spin // EPR: electron spin!!!)
Zeeman effect
= g * mb * B
Resonance condition:
DE = h * n = g * mb * B
[2]
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Basics of EPR-spectroscopy EPR-spectroscopy for systems with S = 1 and S = 3/2
X-Band EPR ~9.5 GHz
for “normal” systems S = ½ and for spectra where g values are close to 2.0. ΔE = hν transitions for ν = 9.5 GHz occur at ΔE value of ~0.3 cm-1 . Q-Band EPR ~35 GHz
for systems of S > ½ for which g values are large (Energy of the transition is very high) (g values as high as 6 and 7) ΔE = hν = ~1 cm-1 .
[3]
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EPR-spectroscopy for spinsystems S = 1 and S = 3/2 EPR-spectroscopy for systems with S = 1 and S = 3/2
[4]
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EPR-spectroscopy for systems with S = 1 and S = 3/2
EPR-spectroscopy for spinsystems S = 1 and S = 3/2
or VIII , d2
or CrIII , d3
[4]
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EPR-spectra for S = 1 EPR-spectroscopy for systems with S = 1 and S = 3/2
[4]
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EPR-spectra for S = 1 EPR-spectroscopy for systems with S = 1 and S = 3/2
[5]
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EPR-spectroscopy for systems with S = 1 and S = 3/2
Examples of EPR-spectra for S = 1
[6]
EPR-spectrum of VBr3(thf)3
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Examples of EPR-spectra for S = 1 EPR-spectroscopy for systems with S = 1 and S = 3/2
[4]
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EPR-spectroscopy for systems with S = 1 and S = 3/2
Examples of EPR-spectra for S = 1
[5]
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EPR-spectra for S = 3/2 EPR-spectroscopy for systems with S = 1 and S = 3/2
• Systems with d3 or d7 high spin: Cr(III), Fe(V), Co(II), …
• Rhombogramm for S = 3/2:
axial fully rhombic slightly rhombic
[7]
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EPR-spectroscopy for systems with S = 1 and S = 3/2
Isopenicillin N synthase (~ fully axial)
Fe – Mo cluster of Nitrogenase (slightly rhombic)
FeIIIFeII(bpmp)(OPr)2
(fully rhombic)
@ 3K
EPR-spectra for S = 3/2
[7]
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EPR-spectroscopy for systems with S = 1 and S = 3/2
Fe(V)(NH3)5N S = 3/2
g = 4
g = 2
x
y
z
Examples of EPR-spectra for S = 3/2
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EPR-spectroscopy for systems with S = 1 and S = 3/2
Examples of EPR-spectra for S = 3/2
[Co(C6H5O7)2]4-
S = 3/2
Typical rhombic g-values: g1 = 8,32 g2 = 2,18 g3 = 1,45
Cobalt(II) citrate complex
[8]
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EPR-spectroscopy for systems with S = 1 and S = 3/2
EPR-spectra for S = 3/2
[4] [4]
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EPR-spectroscopy for systems with S = 1 and S = 3/2
Examples of EPR-spectra for S = 3/2
4 4 2
[9]
Combination to remember!!!
g-values for S = 3/2
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References
• Gunnar Jeschke: Einführung in die ESR-Spektroskopie (Vorlesungsscript), 1996, Mainz • Lecture script (Prof. Dr. Meyer) • Brenda A. Frazier, Erika R. Bartholomew, Peter T. Wolczanski, Serena DeBeer, Mitk’El Santiago-Berrios,
Hector D. Abruna, Emil B. Lobkovsky, Suzanne C. Bart, Susanne Mossin, Karsten Meyer, and Thomas R. Cundari, Inorg. Chem. 2011, 50, 12414−12436.
[1] http://www.chemgapedia.de/vsengine/vlu/vsc/de/ch/15/thc/quantenspek/ eprspek/tc060_eprpek.vlu/Page/vsc/de/ch/15/thc/quantenspek/eprspek/ mspek_55.vscml.html [2] http://www.mrc-mbu.cam.ac.uk/node/209 [3] http://en.wikipedia.org/wiki/File:EPR_splitting.jpg [4] http://www.chem.tamu.edu/rgroup/hughbanks/courses/634/lecturenotes/lecturenotes.html [5] Kozhanov K. A., Bubnov M. P. Doklady Chemistry, 2006, 407, 35-38 [6] Krzystek J., Fiedler A. T., Brunel L-C., Telser J. Inorg. Chem., 2004, 43, 5645-5658 [7] Lecture script (Prof. Dr. Meyer) [8] Matzapetakis M., Dakanali M., Salifoglu S. JBIC 2000, 5, 469-474 [9] Kostka, K. L.; Fox, B. G. Hendrich, M. P.; Collins, T. J.; Rickard, C. E. F.; Wright, L. J. Münck, E.; J. Am. Chem. Soc 1993, 115, 6746-6757
EPR-spectroscopy for systems with S = 1 and S = 3/2
