Karl Gatterer, Festkörperspektroskopie und … · Synthese, Struktur und Magnetismus von...
Transcript of Karl Gatterer, Festkörperspektroskopie und … · Synthese, Struktur und Magnetismus von...
Institute of Physical and Theoretical Chemistry
Habilitierte Mitglieder des Institutes und ihre Arbeitsgebiete:
Karl Gatterer, Festkörperspektroskopie und Magnetochemie in Material
Science
Georg Gescheidt, Paramagnetische Systeme
Günter Grampp, EPR und Photochemie
Stephan Landgraf, Spektroskopie und Elektrochemie
Franz A. Mautner, Strukturforschung
Michael Ramek, Quantenchemie
Institute of Physical and Theoretical Chemistry
Research Group Solid State Spectroscopy and Magnetochemistry in Material Science.
Prof. Dr. K. Gatterer
Current Fields of Research.
General.
The research activities of the group focus on the spectroscopic and magnetic investigation of rare-earth and transition metal ions in diverse solids. Four topics can presently be identified:
Glasses;
Crystalline nano- or mesostructured materials;
Spectroscopy and energy transfer in cubic hexachloro elapsolites;
Molecular magnetism.
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Equipment and facilities of the Group.
UV-VIS-NIR spectrometer (Omega 10, Bruins Instruments, fully computerised) for transparent materials in the 200-1500 nm range. A continuous flow helium cryostat (ROK-10, Leybold-Heraeus) can be attached to the spectrometer to cover the temperature range from 10 to 300 K.
UV-VIS-NIRspectro-reflectometer with integrating sphere (DK 2A, Beckmann Instruments, interfaced to PC) for non-transparent materials in the 200-2500 nm range. A liquid nitrogen flow cryostat (CF-200, Oxford Instruments) can be attached to the integrating sphere to cover the temperature range from 77 to 300 K.
IR spectrometer (325, Perkin Elmer, interfaced to PC) for IR transmission and reflection measurements in the 400-4000 cm-1 region and the temperature range from 10 to 300 K.
DC magnetic susceptometer (SUS-10, PAAR KG, interfaced to PC) operating from 0-1.4 Tesla within the 77-500 K range.
AC/DC susceptometer, together with the research group Molecular Magnetism at the ICTOS at the Graz University of Technology (Model 7221, LAKE SHORE CRYOTRONICS, fully computerised) in the 0-1 Tesla range for DC and AC measurements. Temperature range 300-4.2 K.
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Arbeitsbereich Strukturforschung: Aktuelle Arbeitsgebiete.
Prof. Dr. F. Mautner
Kristallstrukturen von Übergangsmetallverbindungen (Dr. Mautner) – In Zusammenarbeit mit Prof. Goher (Unversität Kuwait) werden Kristallstrukturanalysen
an Komplexverbindungen an Übergangsmetallen (insbesondere mit Cu(I)-Zentralatomen) mit (Pseudo)-halogenid-Liganden durchgeführt.
Strukturchemie von Aziden (Dr. Mautner) – In Kooperation mit Prof. Massoud (Alexandria University) und Prof. Goher (Unversität
Kuwait) erfolgen Kristallstrukturanalysen von komplexen Festkörperaziden.
Molekulare magnetische Materialien (Dr. Mautner, Dr. Abu-Youssef) – Im Rahmen der wissenschaftlich-technischen Zusammenarbeit Österreich-Spanien
(Acciones Integradas) werden in Kooperation mit Prof. Escuer und Prof. Vicente(Universität Barcelona) Untersuchungen zu Struktur und Magnetismus von Koordinationsverbindungen durchgeführt. Das zu diesem Themenbereich laufende Nationalbank-Jubiläumsfondsprojekt Projekt Nr. 6630 mit dem Titel "Magnetische Materialien auf molekularer Basis. Synthese, Struktur und Magnetismus von Azid-Brückensystemen" wurde vor kurzem abgeschlossen und das gleichlautende Nachfolgeprojekt Nr. 7967 begonnen.
Institute of Physical and Theoretical Chemistry
Hoch- und Tieftemperatur-Pulverdiffraktion;
Strukturuntersuchungen an polykristallinen
Materialien (Dr. Bitschnau) – Dem Arbeitsbereich stehen mehrere Pulverdiffraktionsanlagen für
verschiedene Temperaturbereiche (11 K bis 2000°C) zur
Verfügung. Phasenübergänge und Temperaturabhängigkeiten im
Hoch- und Tieftemperaturbereich werden untersucht (z. B.
Piezomaterialen, Hochtemperatursupraleiter). Die Möglichkeiten
zur Bestimmung und Verfeinerung von Kristallstrukturen mittels
Pulveraufnahmen wurden weiter ausgebaut (neue Methoden,
Software) und an verschiedenen Substanzen (Minerale, organische
Verbindungen, Gast-Wirt-Systeme) durchgeführt. Die
Zusammenarbeit mit der Anton Paar GmbH zur Entwicklung von
Röntgen-Hochtemperatur-Pulverkammern wurde fortgeführt.
Institute of Physical and Theoretical Chemistry
Arbeitsbereich Quantenchemie / Quantum Chemistry Group.
Leiter / Head:
– Prof. Dr. Michael Ramek.
MitarbeiterInnnen / Co-worker:
– Ass.-Prof. Dr. Anne-Marie Kelterer
Institute of Physical and Theoretical Chemistry
Arbeitsbereich Quantenchemie: Aktuelle Arbeitsgebiete.
Hauptarbeitsgebiet des Arbeitsbereiches sind quantenchemische Molekülberechnungen, die zur Untersuchung von polyfunktionellen Molekülen eingesetzt werden.
Verwendete Methoden:
– ab initio Verfahren, Kraftfeldmethoden, Dichtefunktionaltheorie, Fourieranalyse der Potenzialflächen, semiempirische Methoden.
Berechnete Eigenschaften:
– Potenzialflächen (Struktur der stationären Punkte, Energie, Reaktionsbarrieren, Reaktionsverhalten), Hyperfeinkopplungskonstanten, elektronische Effekte.
Institute of Physical and Theoretical Chemistry
Untersuchte Systeme:
– Disaccharide und deren Modellsysteme [in Kooperation mit Dr. Alfred D. French, Southern Regional Research Center, New Orleans, LA (USA)]: Sucrose und Trehalose, Cellobiose, Glucosyl-(1,4)-galactopyranose, nichtglykosidische THP-O-THP Dimere;
Organische Radikalionen: Paraphenylendiamin-Radikalkationen mit verschiedenen Substituenten (H, Me, Et, n-Propyl, n-Butyl, i-Butyl, Pyrrolidin) und Cyclooktatetraen-Anionen;
Modell Di- und Tripeptide [in Zusammenarbeit mit Prof. Lothar Schäfer, University of Arkansas, Fayetteville, AR (USA)];
Auxine: 3-Indolessigsäure (IAA) sowie chlorierte und alkylierte Derivate dieser Verbindung [in Kooperation mit Dr. Sanja Tomic und Dr. Biserka Kojic-Prodic, Institut Rudjer Boskovic, Zagreb (Kroatien)];
Aminobuttersäure (GABA) und -Hydroxybuttersäure (GHB) [in Kooperation mit Prof. Peter Nagy, University of Toledo, Toledo, OH (USA)].
Institute of Physical and Theoretical Chemistry
Overview of current research activities
1. ESR-spectroscopy
2. Photochemical methods
3. MARY-Spectroscopy (Magnetic Field Effects in Chemistry)
4. Electrochemical methods
5. Other kinetic methods
G. Grampp, S. Landgraf
Spectroscopy, Photochemistry and Chemical Kinetics
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Research activities
1. Electron Spin Resonance (ESR)-Spectroscopy
- Kinetics of electron transfer reactions by ESR linebroadening
- Intra- and intermolecular charge transfer reactions (Uni Würzburg/D)
- ESR-spectroscopy inside nanotubes (DFG, TU Darmstadt/D)
Nanotechnology.
- Biradicals (RAS, Moscow)
- Spectroscopy in ionic liquids (MPI Mainz/D)
High Pressure Chemistry:
- Chemical kinetics up to 1000 bar in solution. ESR- and UV-VIS-spectroscopy.
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Introduction
Observables: Rate constants, activation parameters (DG* / DV*),
solvent dynamics (friction)
Our Aim: To investigate possible factors that may
influence a simple electron transfer reaction
Marcus-Theory of Electron Transfer. Nobel-Prize 1992.
Variables: reactants: redox potential, size
solvent: physical and chemical properties,
additives (liquid mixtures, electrolytes)
surroundings: temperature, pressure
(also changes solvent properties)
Method: ESR line broadening experiments
Time-resolved Laser- Spectroscopy
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Mixed-valence charge-transfer (MV-CT)
N
O
O
N
O
O
bridge
+
N
O
O
N
O
O
bridge
+
k et
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ESR – linebroadening
(emim)EtSO4, 440K
1mT
kobs =1.0X107 s-1
kobs = 1.8x107 s-1
kobs = 4.9 x107 s-1
[MV++] = 9.5x10-3 M
[MV++] = 1.8x10-2 M
[MV++] = 5.0x10-2 M
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2. Photochemistry
•Time-resolved laser spectroscopy (excimer, dye-laser,
laserdiodes:
Resolution: 40 ps.
•Absorption, emission, fluorescence and photoconductivity
detection.
•Modulated Fluorescence Spectroscopy (LED)
•Single Photon Counting Spectroscopy (SPC)
•Flash Photolysis (triplet states)
•Gas Phase Fluorescence Detection
•Static and time-resolved fluorescence quenching
•Viscosity dependence of photoinduced electron transfer
•Photoinduced electron transfer reactions (PET)
•Burshtein theory of diffusion
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4. Electrochemistry
• Cyclic Voltammetry
• Rotating Disc Electrode (RDE)
• Photomodulated Voltammetry
• Redox potentials of donors and acceptors
• Redox potentials of shorted-living radicals
• Redox potentials of excited states
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Photomodulated voltammetry
Principles and instrumentations
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Weitere Infos:
Wann? Jederzeit
Wo? Bei mir (PC-Z2)
Grau ist alle Theorie, anschauen ist besser!
Laborbesichtigung
möglich? Jederzeit
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UV-VIS time resolved absorption spectroscopy
Photochemical methods
Xe-lamp
tungsten lamp
XeCl excimer-laser
308 nm; 100 mJ; ~15 ns
dye laserBiBuQ/Dioxan 388nm, 11% eff.
mo
no
ch
rom
ato
r
PMT
sample
digital
storage
oscilloscope
LED
ph
oto
dio
de
PC
GP
IB
Laser
Teflon
Teflontubes
sample
+400 VepoxyHJS101
0 V
Au plate0.25 mm
transient absorption (>10 ns)
Photoconductivity
(>10 ns)
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The electron self-exchange reaction
Non-degenerate
electron transferElectron self-exchange
A ex dK kk- - - -+A ++A ++A +A¾ ¾ ¾® ¾ ¾ ¾® ¾ ¾¾®¬ ¾ ¾¾A A A Ag g g g
precursor
complexsuccessor
complex
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ESR-Linebroadening Effects on
Electron-Self Exchange
[DDQ -] = 0,5 mM
D) [DDQ] = 9,5 mM
C) [DDQ] = 2,5 mM
B) [DDQ] = 1,5 mM
A) [DDQ] = 0 mM
Cl
Cl
O
O
CN
CN
DDQ =
3265 3266 3267 3268 3269 3270
D
C
B
A
B [10-4 T]
For example: The DDQ/DDQ _.
-couple
Institute of Physical and Theoretical Chemistry
ESR – Measurements : 1,2-
dicyanobenzene
aH1 = 0.041 mT, aH2 = 0.415 mT, aN = 0.176 MT
Electrolytic reduction in PC at 298K using a flow through cell
0.5 mT
0.5 mT
0.5 mT
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Structures of ionic liquids
N
N X
N
N EtSO4
X - = BF4- or PF6
-
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Electron transfer and high pressure
The volume of activation:
D
‡ ln et
T
kV RT
P
D D D D D D‡ ‡ ‡ ‡ ‡ ‡
IR SR coul DH SDV V V V V V
D D
D
D
D
‡ ‡
‡
‡
‡
and : inner and solvent (outer) reorganization
: coulombic work term
: Debye-Hückel effects
: solvent dynamics
IR SR
coul
DH
SD
V V
V
V
V
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Our high pressure system
Beryllium copper
Glass: quartz, Duran
o.d. 8,0-8,2 mm, i.d. 0,6-1,4 mm
etched with 5% HF
oil coated
teflon protection cover
Pressure transmission fluids:
petrol ether, ethylene glycol
Range: 0,1-60(80) MPa
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Results - acetone
0 10 20 30 40 50
21,95
22,00
22,05
22,10
22,15
ln k
et
pressure / MPa
‡ 3
expΔ V = 7,7 cm /mol
D ‡ 3
, 5,8 cm /molSR calcV
D ‡ 3
, 4,7 cm /molSD calcV
‡ 3
calcΔ V = 10,5 cm /mol
O
O
Cl
Cl
NC
NC
DDQ/DDQ.- in acetone
[DDQ.-] = 0,1 mM
[DDQ] = 0 - 10 mM
P = 0,1 - 50 MPa
ket = (1,8 - 2,1) x109 M-1 s-1
2,2 2,4 2,6 2,8 3,0 3,2
175
180
185
190
195
200
linew
idth
/ m
G
h-1 / (cP)
-1
0 10 20 30 40 50
175
180
185
190
195
200
linew
idth
/ m
G
pressure / MPa
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ESR Spectra
1 mT 1 mT
CH2Cl2CH2Cl2
260 K310 K
1 x aN = 8.46 G 2 x aN = 4.00 G
Fast exchangeSlow exchange
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0.5 mT
in oDCB in MeCN
330 K
a1 (4H) a2 (2H) a3 (2H) a4 (4H) a5 (6H) a6 (H) a7(H) a8 (3H) a9 (N)
oDCB 1.75 1.59 0.78 0.47 1.01 0.52 0.22 0.84 8.62
MeCN 1.88 1.59 0.78 0.53 1.01 0.53 0.12 0.92 8.68
330 K
pumpn
260 KENDOR TRIPLE 260 K
1 mT
1 kHz
N
O
O
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38
260 280 300 320 340 360 380 400 420
0
20
40
60
80
100
UV
-LE
D 3
65
nm
UVTOP$ 270 300 310 325 340 nm
UV-LED
380 nm
LE
D 3
93
nm
LE
D 4
00
nm
LE
D 3
50
nm
LE
D 4
50
nm
(C
)
UV-LED
385 nm#
UV
-LE
D 3
70
nm
#
UV-LED 370 nm
+UG1 filter#
I LE
D =
30
mA
; $2
0 m
A;
#1
5 m
A
VISUV
Spectral response of the LEDs available (UV)
rel. I
nte
nsity
[nm]
Institute of Physical and Theoretical Chemistry
400 500 600 700
0
20
40
60
80
100
VISUV
Spectral response of the LEDs available, I=30 mA
370#
370UG1#
385#
450*
450
460
470
500
525
565
585
610
6201
6202
630
660# 15 mA *450C
rel. I
nte
nsity
[nm]
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7. UV-VIS Determination of fluorescence lifetimes
Photochemical methods
S. Landgraf, Spectrochimica Acta A 2001, 57, 2029-2048.
Spectrometer:SPT / EG&G
320-800 nm excitation
350-850 nm emission
Resolution: 0.2-2 ns
SPT / PicoQuant
375-630 nm excitation
400-850 nm emission
Resolution: 0.2-1 ns
Modulation fluorometry
350-670 nm excitation
370-850 nm emission
Resolution: 0.1-0.5 ns
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3. Magnetic Field Effects in Chemistry
• Magnetic field dependence of fluorescence
• M.A.R.Y.-spectroscopy
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Introduction
Introduction
The Experiment: Equipment and Results
The Theory: Basic Strategy and Density Matrix Model
Comparison of Theory and Experiment
Summary and Outlook
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Why Study Electron Self-Exchange?
ESR:
Non-degenerate
electron transferElectron self-exchange
MARY:
AHFI
1 + –D A• •• •
3 + –D A• •• • + A
HFI1 + –
D A• •• •3 + –
D A• •• •
+ DHFI
1 + –D A• •• •
3 + –D A• •• • + D
HFI1 + –
AD • •• •3 + –
AD • •• •
Institute of Physical and Theoretical Chemistry
MaryschemaMagnetic Field Effect and Electron Self-Exchange
h
1 D … A *
•
kdiss k'diss
1D + A
1
Energ
y / e
V
0
3
2
1
4
Magnetic field dependent process
Photoproducts
HFI
1D* + A
1
h ''
h '
•• •1 + –
D A• •• •
Exciplex
Radical ion pair
HFI ... Hyperfine Interaction (electron - nuclear)
MARY:
AHFI
1 + –D A• •• •
3 + –D A• •• • + A
HFI1 + –
D A• •• •3 + –
D A• •• •
+ DHFI
1 + –D A• •• •
3 + –D A• •• • + D
HFI1 + –
AD • •• •3 + –
AD • •• •
EPR: • A + A– • D +
+ D• D + D
+ •or
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8. UV-VIS magnetic field dependent fluorescence
and transient absorption
Equipment:
3. Photochemical methods
Anregung
Beobachtung
Thermostat
Mono-chromator
Magnet
Filter
Gaussmeter
DC-Quelle (Offset)
L. G.L. G.S. H.
L. G. Lichtleiter (260 nm < < 650 nm) S. H. Probenhalter H. P. Hallsonde
H. P.
Offset/Modul
Photomultiplier
Filter
I=f(B) =f(B)
Computer
Magnet
Offset/Modul
AC-Quelle(Modulation)+Feldscan
dIdBAnregungs-
lichtquelle
6 x
L. G.
S. H.
H. P.
Resolution:0.2 % static
0.01% modulated
200 mG = 20 µT
M. Justinek et al. JACS
2004, 126, 5635-5646.
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Origin of the MARY Spectrum
Zeeman-splitting
of radical pair spin levels
in a magnetic field
MARY spectrum
T-
T+
S, T0
0 B
EHFI
B1/2
B1/2
0
0
1I
I0
B
saturation
half-saturation
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-10 -5 0 5 10
147.0
147.5
148.0
148.5
149.0
149.5
PM
T-S
ignal [m
V]
B [mT]
-10 -5 0 5 10
-200
0
200
400 DBpp
(b)
(a)
B [mT]
dI/dB
DCB1,2-1,3-1,4-
CN
CN
pyrene
Measurement without (a)
and with (b) modulation of
the magnetic field
0,1 mM pyrene +0,02 M 1,2-DCB
in PC (propylencarbonate)
scan 3 mT/min, mod. 1 mT
=> simulation of a Lorentzian line
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Energy Broadening of Spin Levels
T-
T+
S, T0
0 B
EHFI
DE
B1/2 (0) B c1/2 ( )
Heisenberg:
ckt
E exel
D
D
H. Staerk, R. Treichel and A. Weller,
Chem. Phys. Lett.,1983, 96, 28.
ckg
BcB ex
B
)0()( 2/12/1
0.00 0.01 0.02
22
23
24
25
[1,2-DCNB] (M)
B1/2 (G)ex
B
kg
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Generation of radicals
Directly: Photolysis of an
adequate compound, like a
symmetric ketone:
-1500 -1000 -500 0 500 1000
-0.15
-0.10
-0.05
0.00
0.05
0.10
Eox
1/2= 388 mV
Ered
1/2=-1108 mV
i [
µA
]
E [mV/SCE]
1,1,3,3 Tetraphenylacetone 5mM in a 0.08M Bu4NBF
4/CH
3CN solution,
gold electrode, v = 10 mV/s; f = 120Hz, f = 00; t = 1s
O
h2. + CO
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counter electrode
inert gas inlet
cell Luggin cappilary
reference electrode
MOTOR
WE working electrodeRE reference electrodeCE counter electrode
Scheme
of the system
for RDE experiments
working electrode
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0,0E+00
1,0E-06
2,0E-06
3,0E-06
4,0E-06
5,0E-06
6,0E-06
7,0E-06
8,0E-06
9,0E-06
1,0E-05
0,0 10,0 20,0 30,0 40,0 50,0
temperature / oC
dif
fusi
on c
oeff
icie
nt /
cm
2 s
-1
TMPPD - e - TMPPD+
5,87 E-0635,0
8,85 E-0645,0
6,57 E-0630,0
5,50 E-06 *25,0
4,76 E-0615,0
2,29 E-065,0
DIFFUSION COEFFICIENT
/ cm2 s-1
TEMPERATURE
/ oC ± 0,1oC
(1st oxidation step)
-500 0 500 1000
0,00000
0,00004
0,00008
0,00012
0,00016
0,00020
0,00024
0,00028
curr
ent
/ A
potential / mV vs. SCE
T=25oC
w
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Co-operations
K. A. McLauchlan and P. Hore, University of Oxford, UK.
A. Burshtein, Weizmann-Institute, Chemical Physics, Rehovot, Israel.
N. Lukzen, Russian Academy of Science (RAS), Novosibirisk, Russia.
J. Schneider. Darmstadt University of Technology, Germany.
P. Jacques. Universite Haute Alsace, Mulhouse, France.
Ch. Lambert, University of Würzburg, Germany.
B. Herold, Technical University Lisbon, Portugal.
R. W. Fawcett, University of Davis, CA, U.S.A.
A. Kokorin, Institute of Chemical Physics, RAS, Moscow, Russia.
Institute of Physical and Theoretical Chemistry
Habilitierte des Institutes und ihre Arbeitsgebiete:
Karl Gatterer, Festkörperspektroskopie und Magnetochemie in Material
Science
Georg Gescheidt, Paramagnetische Systeme
Günter Grampp, EPR und Photochemie
Stephan Landgraf, Spektroskopie und Elektrochemie
Franz A. Mautner, Strukturforschung
Michael Ramek, Quantenchemie