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Supramolecular Chemistry
– Hydrogen-Bonded Networks
Christoph Janiak
University of Düsseldorf, Germany
Email: janiak@uni-duesseldorf.de
Hydrogen-bonded frameworks
M
N
N D
A
MN
N
D
A
M
N
ND
A
M N
N
D
A
D = hydrogen donorA = hydrogen acceptor
Cl
Cl Cl
Cl
M HCl
Cl Cl
Cl
MHN N
Supramolecular interactions (hydrogen-bonding, p-stacking)
in metal-organic networks
MLx
MLx
MLx
LxM
LxM
LxM
hydrogen bonding p-p stacking van der Waals hydrophobic hydrophilic interactions
inter-polymer packing
MLx
LxM
MLx
LxM
intra-polymer packing
=polymer-solvent
MLx
MLx
MLx
-anion packing
(template)
Aromatic...aromatic interactions
3.3-3.8 Å > 4.8 Å
p-stacking, "p-p interaction" C-H...p interaction
face-to-face offset, slipped T-shaped
p-Stacking between metal-pyridine fragments
N
planenormal
N
P, plane 2
x
x
M
M
centroid-centroid distance
P, plane 1
intermolecular contact3.0 < centroid-centroid distance < 4.6 Å
Constraints:
J. Chem. Soc., Dalton Trans. 2000, 3885
CSD search setup:
p-Stacking between metal-pyridine fragments
centroid-centroid distance [Å] interplanar angle [°]
frequency
J. Chem. Soc., Dalton Trans. 2000, 3885
p-Stacking between metal-pyridine fragments
frequency
plane normal - centroid-centroid angle [°]
N
planenormal
N
x
x
M
M
centroid-centroiddistance
J. Chem. Soc., Dalton Trans. 2000, 3885
p-Stacking between metal-pyridine fragments
pla
ne n
orm
al -
centr
oid
-centr
oid
angle
[°]
centroid-centroid distance [Å]
N
planenormal
N
x
x
M
M
centroid-centroiddistance
J. Chem. Soc., Dalton Trans. 2000, 3885
p-Stacking between metal-ligand fragments
NM
N
M
OM
OO
M
M
M
M
X M
XM
x
x
~3.80 Å
>20°
plane-planedistance: ~3.6 Å
>1.30 Å
lateral shift
J. Chem. Soc., Dalton Trans. 2000, 3885
Aromatic...aromatic interactions
face-to-face offset, slipped T-shaped
p-p
repulsion
H
H
+
+
-p
attraction
H+-p
attraction
Hunter, Sanders, J. Am. Chem. Soc. 1990, 112, 5525
p...p or C-H...p ?
Type of weak bond Interaction type Interaction energy[kJ/mol]
O-H···ON-H···O
electrostatic
dispersive
16-60
cation···p
C-H···O
C-H···p
p···p
van der Waals
5-80
<16
<2-20
<4-10
<5
Desiraju, Steiner, The Weak Hydrogen Bond, Oxford, 1999
Nishio et al., The CH/p Interaction, Wiley-VCH, 1998
Steed, Atwood, Supramolecular Chemistry, Wiley, 2000
Schneider, Yatsimirski, Principles and Methods in Supramolecular Chemistry, Wiley, 2000
Janiak, (p-p stacking), J. Chem. Soc., Dalton Trans. 2000, 3885
Non-covalent supramolecular interactions
How do we analyze for non-covalent interactions?
http://www.cryst.chem.uu.nl/platon/
Program PLATON: A. L. Spek, Acta Crystallogr. A, 1990, 46, C34.
(current) PLATON Version 1.12, 29-10-07.
Windows implementation: L. J. Farrugia, University of Glasgow, Scotland, 2007.
How do we analyze for non-covalent interactions?
How do we analyze for non-covalent interactions?
How do we analyze for non-covalent interactions?
From metal-organic networks
to hydrogen-bonded Networks
M
N
N D
A
MN
N
D
A
M
N
ND
A
M N
N
D
A
D = hydrogen donorA = hydrogen acceptor
Metal-organic networks H-bonded networks
M M M M1D chains
M M M
M M M
M M M
2D nets
M M M
M M M
M M MM
M M M
M M M
MM3Dframeworks
covalent
less flexible
more directional
network
electrostatic
more flexible
less directional
network
Introduction
pyrazolylborate ligands
Trofimenko, Scorpionates, Imperial College Press, London 1999
N
B
N N
N
H
N
N
N
N
N
NB
HH
hydro-tris(pyrazolyl)borate dihydro-bis(pyrazolyl)borate
- molecular chelate complexes
KBH4 + n H-azolyl K[H4-nB(azolyl)n] + n H2
D
Modified poly(pyrazolyl)borate ligands
N
B
N N
N
H
N
N
N
NN
N
NN
B
HH
tris(pyrazolyl)borate
bis(triazolyl)borate
N
N
B
N
N
H
N
N
tris(indazolyl)borate
N
B
N N
NNN
H
N
NN
N
NN
N
NN
NN
B
HH
tris(triazolyl)borate
bis(tetrazolyl)borate
Chem. Commun. 1994, 545; Chem. Eur. J. 1995, 1, 637; Z. Anorg. Allg. Chem. 2000, 626, 2053
NB
N N
NNN
H
N
NN
B
N
NM
N
NN
N
H
N
NN
M2+ + 2 N3–H2O
M = Fe, Co, Ni, Zn
H2O·2H2O
2OH2·OH2
two-dimensional
water/ice substructure
Hydrogen-bonded frameworks
with tris(triazolyl)borate N3
J. Am. Chem. Soc. 2002,
124, 14010
two-dimensional
complex layer
Polyhedron 2003,
22, 1123
Two-dimensional complex layer
CH···N bonds
Polyhedron 2003, 22, 1123
Polyhedron 2003, 22, 1123
Two-dimensional complex layer
CH···N bonds
Fe-N3
spin crossover
NB
N N
NNN
H
N
NN
B
N
NFe
N
NN
N
H
N
NN
low-spin high-spin
1A1g5T2g
FeII, d6T1/2 ~ 62 °C
temperature variable magnetic measurements
Moessbauer spectroscopy
UV/Vis spectroscopy
DSC
magnetic dilution
2
4
6
8
10
12
20 40 60 80
Temperature [°C]T
1 [
s]
20
30
40
50
60
70
80
90
20 40 60 80
Temperature [°C]
T1
[s
]
temperature variable T1-measurements on H2O
NB
N N
NNN
H
N
NN
B
N
NFe
N
NN
N
H
N
NN
H2O in 99.8% D2O
+
[Fe]
in mmol/l
1.24
2.26
4.87
Fe-N3
spin crossover
NB
N N
NNN
H
N
NN
B
N
NFe
N
NN
N
H
N
NN
H2OOH2
OH2
H2O
H2O
outer-sphere relaxation mechanism
Fe-N3
spin crossover
Two-dimensional water/ice substructure
J. Am. Chem. Soc. 2002, 124, 14010(neutron diffraction)
Two-dimensional water/ice substructure
J. Am. Chem. Soc. 2002, 124, 14010(neutron diffraction on [Ni(N3)2] · 6 D2O )
263 K
Pmnb
(Pmna)
20 K
P21nb
(Pna21)
DT
278 K
Cmce
(Cmca)
k2 t2
Two-dimensional water/ice substructure
J. Am. Chem. Soc. 2002, 124, 14010
263 K 20 K
DT
= crystallographic disorder
(neutron diffraction on [Ni(N3)2] · 6 D2O )
Two-dimensional water/ice substructure
J. Am. Chem. Soc. 2002, 124, 14010
(neutron diffraction)
263 K 20 K
DT
Two-dimensional water/ice substructure
J. Am. Chem. Soc. 2002, 124, 14010
(neutron diffraction)
263 K 20 K
DT
Other (modified) poly(pyrazolyl)borato ligands
N
B
N N
N
H
N
N
N
NN
N
NN
B
HH
tris(pyrazolyl)borate bis(triazolyl)borate
N
N
B
N
N
H
N
N
tris(indazolyl)borateN2inda
3-D coordination polymer
P212121
B
N
N N
H
chiral crystal structure
H
N
NN
Tl (Tl)
TlTl
NLO-effect
Polyhedron 2002, 21, 553
Main-group metal chemistry
(modified) poly(pyrazolyl)borato ligands
chiral crystal structure
NN
B
HNN
NN
Tl
N N
B
HN N
NN
Tl
C2 axis
p---p stacking, chiral pairs
C2
NLO-effect
Inorg. Chem. Commun. 2000, 3, 271
Main-group metal chemistry
(modified) poly(pyrazolyl)borato ligands
Main-group metal chemistry
(modified) poly(pyrazolyl)borato ligands
NB
N N
N
H
N
N
3D coordination polymer
P212121
TlB
N
N N
H
NB
NN
N
H
N
N
Tl
Tl+---p(azolyl) interactions
P21chiral crystal structure
Z. Anorg. Allg. Chem. 1998, 624, 755
H
N
NN
Tl (Tl)
Tl Tl
NN
BH
NN
NNTl
N N
BH
N N
N NTl
C2 axis
p---p stacking, chiral pairs
C2
Inorg. Chem. Commun. 2000, 3, 271
Polyhedron 2002, 21, 553
NLO-effectspontaneous resolution
N
N
B
N
N
H
N
N
Cu
N
N
B
N
N
H
N
N
crystallizationwith 2.5THF
5 Å
Supramolecular assemblies with MOF-type structures
based on modified poly(pyrazolyl)borate ligands
26% pot. solvent volume
Eur. J. Inorg. Chem. 2000, 1229
M = Fe,Co16 Å
2 Å 6 Å
N
N
B
N
N
H
N
N
M
N
N
B
N
N
H
N
N
crystallization
with 3.5CHCl3
38% pot. solvent volume
Eur. J. Inorg. Chem. 2000, 1229
Supramolecular assemblies with MOF-type structures
based on modified poly(pyrazolyl)borate ligands
N
N
B
NN
H
N
N
M
N
N
B
NN
H
N
N
with 1.67 dioxane
crystallization
29% channel volume
M = Ni,Zn4 Å
Supramolecular assemblies with MOF-type structures
based on modified poly(pyrazolyl)borate ligands
Eur. J. Inorg. Chem. 2000, 1229
Hydrogen-bonded framework
with isonicotinamide and Ag+: {Ag(INA)2(µ-NO3)}2
N
OH2N
isonicotinamideINA
Ag–Ag 3.1429(5) Å
Aust. J. Chem. 2006, 59, 22.
Bis(isonicotinamide)silver nitrate,
{Ag(INA)2(µ-NO3)}2
light-stability: after 30 min irradiation with a 15 W energy saving lamp at a distance of 5 cm
{Ag(INA)2
(µ-O3SCF3)}2
untreated
filter paper
{Ag(INA)2
(µ-NO3)}2
filter papers
impregnated
with 0.1 mol/l
solutions
AgNO3
INA
stabilization by
- hydrogen bonding
- NO3 clamping
- Ag-Ag contact
Aust. J. Chem. 2006, 59, 22.
Hydrogen-bonded framework
with isonicotinamide and Ag+: {Ag(INA)2(µ-NO3)}2
dissolution behavior:
- pH dependent
- slower at more acidic pH
- faster at more basic pH
due to
- low base strength of INA
(pKa = 3.67)
- H-bonding network in
solid {Ag(INA)2(µ-NO3)}2
Aust. J. Chem. 2006, 59, 22.
0
500
1000
1500
2000
30 min 5 h
pp
m
pH = 4.1
pH = 7.0
H-Brücken-Gitter
mit Isonicotinamid und Ag+
– slow release of Ag+:
Hydrogen-bonded framework
with isonicotinamide and Ag+: {Ag(INA)2(µ-NO3)}2
N
OH2N
isonicotinamideINA
Anion recognition
here: perchlorate, ClO4–
Chem. Commun. 2003, 902
Anion recognition
here: perchlorate, ClO4–
Chem. Commun. 2003, 902
Chiral building blocks for
supramolecular, hydrogen-bonded networks
N N
H2N NH2
5,5'-diamino-2,2'-bipyridineDABP
N
NNH2
H2N
NN
Fe
NH2
H2N
D-[Fe(DABP)3]2+
N
N
NH2
H2N 1,1'-bi-2-naphtholBINOL
OH
OH
–2H+
BINOLAT2–
R(S)
N
NNH2
H2N
NN
Fe
NH2
H2N
D-[Fe(DABP)3]2+
N
N
NH2
H2N
Tris(bipyridine)metal complexes
with diaminobipyridine, DABP
M = Fe, Ni, (Cu) Zn, Cd
Eur. J. Inorg. Chem. 1999, 1507
Inorg. Chim. Acta 2003, 343, 366
Z. Anorg. Allg. Chem. 2004, 630, 1564
M2+ + 3 DABP
N
NNH2
H2N
O
O2N
NN
Fe
NH2
H2N
O
D-[Fe(DABP)3]2+
O2N
N
N
NH2
H2N
O
O2NO NO2
O
NO2
O
NO2
Second-sphere hydrogen bonding
with [Fe(DABP)3]2+
CrystEngComm 2004, 6, 126
Fe2+ + 3 DABPnitrophenolate
Molecular paneling through hydrogen-directed assembly
CrystEngComm 2004, 6, 126
Molecular paneling through hydrogen-directed assembly
CrystEngComm 2004, 6, 126
Molecular paneling through hydrogen-directed assembly
CrystEngComm 2004, 6, 126
-[Fe(DABP)3]2+
D-
[Fe(DABP)3]2+
D-
[Fe(DABP)3]2+
polar space group: P31c
Molecular paneling through hydrogen-directed assembly
CrystEngComm 2004, 6, 126
-[Fe(DABP)3]2+
D-
[Fe(DABP)3]2+
D-
[Fe(DABP)3]2+
polar space group: P31c
Molecular paneling through hydrogen-directed assembly
CrystEngComm 2004, 6, 126
-[Fe(DABP)3]2+
D-
[Fe(DABP)3]2+
D-
[Fe(DABP)3]2+
polar space group: P31c
Molecular paneling through hydrogen-directed assembly
CrystEngComm 2004, 6, 126
-[Fe(DABP)3]2+
D-
[Fe(DABP)3]2+
D-
[Fe(DABP)3]2+
polar space group: P31c
O
OP
O
OH
Hydrogen-bonded (and metal-organic) frameworks:
Our interest: Chiral, enantiomeric structures
OH
OHR(S)
1,1'-binaphthalene-
2,2'-diyl phosphoric acid
BNPPAH
rac or R
–H+
BNPPA–
- inexpensive ligand enantiomers
1,1'-bi-2-naphthol
BINOL
–2H+
BINOLAT2–
Hydrogen-bonded networks
with rac-BINOL
M = Cu, x = 5
Ni, Cd, x = 6
Zn, x = 4[M(NH3)x]
2+[BINOLAT]2–(BINOL)2M2+ + 3 BINOL
conc. NH3
MeOH
O
O
H
H
H
H
BINOLAT2–BINOL
HO
H
OH
H
O
O
O
O
O
O
Hydrogen-bonded strands
with rac-BINOL
M = Cu, x = 5
Ni, Cd, x = 6
Zn, x = 4[M(NH3)x]
2+[BINOLAT]2–(BINOL)2M2+ + 3 BINOL
conc. NH3
MeOH
c
strand
+
cavities
O
O
H
H
H
H
BINOLAT2–BINOL
M
H3N NH3
NH3H3N
NH3H3N
M = Ni, Cd
or
NH3
MH3N
NH3
NH3
M = Zn
2+
2+
HO
H
OH
H
O
O
O
O
O
O
Hydrogen-bonded strands
with rac-BINOL
M = Cu, x = 5
Ni, Cd, x = 6
Zn, x = 4[M(NH3)x]
2+[BINOLAT]2–(BINOL)2M2+ + 3 BINOL
conc. NH3
MeOH
CrystEngComm 2004, 6, 293
Hydrogen-bonded strands with rac-BINOL
Molecular paneling through hydrogen-directed assembly
strand+
cavities
Molecular paneling through hydrogen-directed assembly
CrystEngComm 2004, 6, 293
strand
Molecular paneling through hydrogen-directed assembly
CrystEngComm 2004, 6, 293
strand
100 200 300 400 500 600
dm
/dT
, Dm
, DT
,
ion
ic f
low
in
arb
itra
ry u
nits
temperature [°C]
m/z=268
–27.4
–55.0
–6.3
endo
Tp=302
Tp=443
Tp=116
DTG
TG
DTA
m/z=17
m/z=44
m/z=286
Supramolecular M-BINOL Strands:
thermischal behavior of [M(NH3)6]2+[BINOLAT]2–(BINOL)2
–6NH3
– ~2OH
OH
O–
–CO2,
DTG, TG, DTA and MS-trend-scan
CrystEngComm 2004, 6, 293
Hydrogen-bonded strands
with rac-BINOL
S
R
R R
S
S
R
S
Hydrogen-bonded strands
with rac- and S-BINOL
[Cd(S-BINOLAT)(NH3)4]0(S-BINOL)2(H2O)(MeOH)2
Cd2+ + 3 S-BINOL
conc. NH3
MeOH
chiral crystal structure: C2
[M(NH3)x]2+[rac-BINOLAT]2–(rac-BINOL)2
M2+ + 3 rac-BINOL
conc. NH3
MeOH
space group: C2/c
CrystEngComm 2005, 7, 309
Hydrogen-bonded strands
with rac-BINOL
c
R
RS
S
S
O
O
HH
HH
-BINOLAT2–-BINOL
HO
H
OH H
O
O
O
O
O
O
rac
O
O
H
H
-BINOLAT2–-BINOL
H
OH
O
O O
S
HH
O O
HOH
O
Hydrogen-bonded strands
with S-BINOL
c
S
SS
S
S
[Cd(S-BINOLAT)(NH3)4]0(S-BINOL)2(H2O)(MeOH)2Cd2+ + 3 S-BINOL
conc. NH3
MeOH
no matchanymore inH-bonding
CrystEngComm 2005, 7, 309
O
O
H
H
-BINOLAT2–-BINOL
H
OH
O
O O
S
HH
O O
HOH
O
Hydrogen-bonded strands
with S-BINOL
c
S
SS
S
S
[Cd(S-BINOLAT)(NH3)4]0(S-BINOL)2(H2O)(MeOH)2Cd2+ + 3 S-BINOL
conc. NH3
MeOH
strand
+
cavities
translocation along c
O
O
H
H
-BINOLAT2–-BINOL
H
OH
O
O O
S
HH
O O
HOH
O
Cd
H3N NH3
NH3H3N
2+
Hydrogen-bonded strands
with S-BINOL
c
S
SS
S
S
[Cd(S-BINOLAT)(NH3)4]0(S-BINOL)2(H2O)(MeOH)2Cd2+ + 3 S-BINOL
conc. NH3
MeOH
CrystEngComm 2005, 7, 309
Metal coordination
with S-BINOL
CrystEngComm 2005, 7, 309
Hydrogen-bonded strands
with S-BINOL
strand
+
cavities
Hydrogen-bonded strands
with S-BINOL
strand
+
cavities
Molecular paneling through hydrogen-directed assembly
strand
CrystEngComm 2005, 7, 309
Hydrogen-bonded strands
with (S)-BINOL
[Ag(NH3)2]+[S-BINOLAT]–(S-BINOL)(EtOH)Ag+ + 2 S-BINOL
conc. NH3
EtOH
Ag+ + 2 rac-BINOL
conc. NH3
EtOH[Ag(NH3)2]
+[S(R)-BINOLAT]–(S(R)-BINOL)(EtOH)
spontaneous resolution, ~40%ee
chiral crystal structure: P1
CrystEngComm 2004, 6, 293
CrystEngComm 2005, 7, 309
BINOLAT – BINOL
Ag NH3H3N
+O
O
H
H
H
O
O
H
H
O
O
O
O
H
BINOLAT –BINOL
[Ag(NH3)2]+[S-BINOLAT]–(S-BINOL)(EtOH)Ag+ + 2 S-BINOL
conc. NH3
EtOH
strand
Hydrogen-bonded strands
with (S)-BINOL
Molecular paneling through hydrogen-directed assembly
U-shaped channels
CrystEngComm 2005, 7, 309
Molecular paneling through hydrogen-directed assembly
CrystEngComm 2005, 7, 309
100 200 300 400 500 600
dm
/dT
, Dm
, DT
,
ionic
flo
w in a
rbitra
ry u
nits
temperature [°C]
Tp=323
Tp=211
Tp=116
Tp=319
Tp=114
–75.3
–8.9
DTG
TG
DTA
m/z=17
m/z=46
m/z=286
H-bonded strands
with (S)-BINOL and Ag+
–2NH3
–EtOHOH
OH
DTG, TG, DTA und MS-trend-scan
CrystEngComm 2005, 7, 309
10 15 20 25 30 35 40 45 50
silver
heated to 130 °C
(S)-BINOL
calculated
inte
nsity
2 Theta (°)
H-bonded strands
with (S)-BINOL and Ag+
D
130 °C
CrystEngComm 2005, 7, 309CrystEngComm 2005, 7, 309
Hydrogen-bonded (and meta-organic) frameworks:
Our interest: Chiral, enantiomeric structures
1,1'-binaphthalene-
2,2'-diyl phosphoric acid
BNPPAH
rac or R
–H+
BNPPA–
O
OP
O
OH
- inexpensive ligand enantiomers
OH
OHR(S)
1,1'-bi-2-naphthol
BINOL
–2H+
BINOLAT2–
Hydrogen-bonded frameworks
with bi-naphthol phosphate BNPPA
O
OP
O
O–
rac
BNPPA–
NH2H2N
NH2
+
CuH3N
H3N NH3
NH3
. HOCH3
. HOCH3
2+
CuH3CO
H
. HH3CO
HOCH3
OCH3H
OH2
OH2
2+
NiH2N
H2N OH2
OH2
NH2
NH2
2+
cations:
(compressed
octahedron !)
New J. Chem. 2006, 30, 156.
Hydrogen-bonded frameworks
with bi-naphthol phosphate BNPPA
- common feature
hydrophobic layers
hydrophilic layers
New J. Chem. 2006, 30, 156.
inverse bilayer
hydrophilic interior
hydrophobic exterior
hydrophobic exterior
stacking
weak interactions thin plate
thin-plate crystal dimension= longest crystallographic axis
OO
POO –
Inverse bilayers through strong O/N–H···O hydrogen bonding
and very weak C–H···p interactions
New J. Chem. 2006, 30, 156.
inverse bilayer
hydrophilic interior
hydrophobic exterior
hydrophobic exterior
stacking
weak interactions thin plate
thin-plate crystal dimension= longest crystallographic axis
OO
POO –
Inverse bilayers from BNPPA
"normal" bilayer
water
water water
liposome
H2O
- hydrophilic exterior- hydrophobic interior
inverse bilayer
hydrophilic interior
hydrophobic exterior
hydrophobic exterior
stacking
weak interactions thin plate
thin-plate crystal dimension= longest crystallographic axis
OO
POO –
Inverse bilayers through strong O/N–H···O hydrogen bonding
and very weak C–H···p interactions
only very weak
C–H···p interactions,
no p-p interactions
New J. Chem. 2006, 30, 156.
Inverse bilayers from BNPPA
inverse bilayer
hydrophilic interior
hydrophobic exterior
hydrophobic exterior
stacking
weak interactions thin plate
thin-plate crystal dimension= longest crystallographic axis
OO
POO –
New J. Chem. 2006, 30, 156.
Hydrogen-bonded (and metal-organic) frameworks:
Our interest: Chiral, enantiomeric structures
- inexpensive ligand enantiomers
- amino acid chiral pool
HO NH
O
Ph
N-phenylglycine =
2-(phenylamino)acetic acid
(*)HN
O
R
O
NH
R
*
*
HO
O
OH
O
R = -CH3 (L-Ala)
= -CH(CH3)2 (L-Val)
= -CH2-indol (L-Trp)
= -CH2CH(CH3)2 (L-Leu)
= -CH2Ph (L-Phe)
NH2
Rh
HO
Ph
S*
NH2
Rh
HO
O R
R = MeR = Ph
S*
–O2CMe
+
NH
Rh
O
O
R
R/S
*
Higher element of chirality
– homochiral helices
Chiral cod-Rh(aminocarboxylato) and chiral cod-Rh(amino alcohol) complexes:
- amino acids as chiral ligands
Dalton Trans. 2009, 3698.
Eur. J. Inorg. Chem. 2006, 2146.
HO NH
O
Ph
Higher element of chirality
– homochiral helices
N-phenylglycine =
2-(phenylamino)acetic acid
(*)
spontaneous
resolution
upon crystallization
(M) 43-helical chains
– homochiral –
R-complex →
chiral space group: P43
NH
Rh
O
O
Ph
(R/S)
*
Higher element of chirality
– homochiral helices
Transfer of chirality?
N-H···O hydrogen bonding R complexes into 43-helical chain
intra-chain homochirality
Higher elements of chirality – homochiral helices
through hydrogen bonding and van der Waals interactions
Transfer of chirality?
43-helix
corrugated van der Waals surface homochiral assembly of 43-helices in crystal
inter-chain homochirality
Eur. J. Inorg. Chem. 2006, 2146.
only very weak C–H···p interactions,
no p-p interactions
Higher elements of chirality – homochiral helices
through hydrogen bonding and van der Waals interactions
R complex left-handed M-
43-helix
P43
Higher elements of chirality – homochiral helices
through hydrogen bonding and van der Waals interactions
R complex left-handed M-
43-helix
S complex right-handed P-
41-helix
P43 P41
Dalton Trans. 2009, 3698.Eur. J. Inorg. Chem. 2006, 2146.
Higher elements of chirality – homochiral helices
through hydrogen bonding and van der Waals interactions
R complex left-handed M-
43-helix
S complex right-handed P-
41-helix
P43 P41
crystal ensemble =
racemic mixture
Dalton Trans. 2009, 3698.Eur. J. Inorg. Chem. 2006, 2146.
Hydrogen-bonded (and metal-organic) frameworks:
Our interest: Chiral, enantiomeric structures
- inexpensive ligand enantiomers
- amino acid chiral pool
HO NH
O
Ph
N-phenylglycine =
2-(phenylamino)acetic acid
(*)HN
O
R
O
NH
R
*
*
HO
O
OH
O
R = -CH3 (L-Ala)
= -CH(CH3)2 (L-Val)
= -CH2-indol (L-Trp)
= -CH2CH(CH3)2 (L-Leu)
= -CH2Ph (L-Phe)
Chiral, enantiomeric ligand for chiral coordination polymers,
molecular trigonal prism with Cu2 as SBU
Chirality
Porosity ?
trigonal space group R3
CrystEngComm 2008, 10, 461
Molecular trigonal prism with Cu2 as SBU
Chirality
Porosity ?
~30 Ǻ
CrystEngComm 2008, 10, 461
Chiral, enantiomeric molecular trigonal prism with three Cu2 units:
[Cu2(μ4-TBPhe)2(EtOH)(H2O)]3 · ~28(H2O/0.33EtOH)
~30 Ǻ
electron density in the interior
of the trigonal prism
cannot be clearly localized
- solvent of crystallization highly disordered
crystal solvent O atoms refined
- simultaneously with their occupancies
- isotropically
- with "anti-bumping"
restraints, BUMP in SHELXLCrystEngComm 2008, 10, 461
Chiral, enantiomeric molecular trigonal prism with three Cu2 units
23.4%
potential solvent area volume
calculated by
PLATON for WindowsTotal potential solvent area volume
3275 Å3
per unit cell volume
13955 Å3
Molecular trigonal prism with Cu2 as SBU
Chirality
Porosity ?
solution study:
ESI-mass
UV/VIS
NMR
CD spectroscopy
CrystEngComm 2008, 10, 461
Molecular trigonal prism with Cu2 as SBU
solution study:
ESI-mass
UV/VIS
NMR
CD spectroscopy
light scattering
channels through
crystal lattice
Molecular trigonal prism with Cu2 as SBU
channels through
crystal lattice
trigonal space group R3
a = b = 39.7978(3) Å
c = 10.1735(2) ÅCrystEngComm 2008, 10, 461
Molecular trigonal prism with Cu2 as SBU
solution study:
ESI-mass
UV/VIS
NMR
CD spectroscopy
~30 Ǻ
= ~3 nm
TEM from MeOH solution:
Molecular trigonal prism with Cu2 as SBU
solution study:
ESI-mass
UV/VIS
NMR
CD spectroscopy
~30 Ǻ
= ~3 nm
Light scattering in MeOH solution:
4.2–5.6 nm
av. 4.85 nm
Chiral molecular trigonal prism with Cu2 as SBU:
Magnetism
0 50 100 150 200 250 300T (K)
0
2
4
6
8
10
12
(m
em
u/a
sym
. unit)
g = 2,29
J = -214 K
= 4 %
TIP= 0.23 memu/asym. unit
C54H58.66Cu2N6O17.33
0 50 100 150 200 250 300T (K)
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
T (
em
uK
/asym
. unit)
C54H58.66Cu2N6O17.33
CrystEngComm 2008, 10, 461
Type of weak bond Interaction type Interaction energy[kJ/mol]
O-H···ON-H···O
electrostatic
dispersive
16-60
cation···p
C-H···O
C-H···p
p···p
van der Waals
5-80
<16
<2-20
<4-10
<5
Desiraju, Steiner, The Weak Hydrogen Bond, Oxford, 1999
Nishio et al., The CH/p Interaction, Wiley-VCH, 1998
Steed, Atwood, Supramolecular Chemistry, Wiley, 2000
Schneider, Yatsimirski, Principles and Methods in Supramolecular Chemistry, Wiley, 2000
Janiak, (p-p stacking), J. Chem. Soc., Dalton Trans. 2000, 3885
Non-covalent supramolecular interactions:
From strong to weak hydrogen bonds
X-ray crystallography and solid state NMR:
Palladacycle pseudo-polymorphs and a vanishing polymorph
Chronology:
The first observation: 12 from toluene
2 symmetry independent molecules in the asymmetric unit, Z' = 2, P1
(Z' > 1 structure)
- the start: Short CH3···CH3 contact (3.256 Å) ?
CrystEngComm 2008, 1928
X-ray crystallography and solid state NMR:
Palladacycle pseudo-polymorphs and a vanishing polymorph
Chronology:
Why
2 symmetry independent molecules in the asymmetric unit, Z' = 2?
(Z' > 1 structure) – Conformational difference?
overlay of
molecule Pd1-Pd2
and
molecule Pd3-Pd4
NMe2
Pd
O NMe2
Pd
O
N
CrystEngComm 2008, 1928
X-ray crystallography and solid state NMR:
Palladacycle pseudo-polymorphs and a vanishing polymorph
Chronology:
Why
2 symmetry independent molecules in the asymmetric unit, Z' = 2?
(Z' > 1 structure) – the full structure with disordered solvent
~2 x 0.25 = ~0.5 toluene per 2 Pd2 molecules (= 12)
CrystEngComm 2008, 1928
Z' > 1 structures: A crystal "on the way"?
Matter of discussion
Desiraju: On the presence of multiple molecules in the crystal asymmetric unit (Z' > 1)
(CrystEngComm 2007, 9, 91-92)
Anderson and Steed: Comment on "On the presence of multiple molecules in the
aymmetric unit"
(CrystEngComm 2007, 9, 328-330)
Nichol and Clegg: Further thoughts on crystal structures with Z' > 1: analysis of ...
(CrystEngComm 2007, 9, 959-960)
Babu and Nangia: High Z' polymorphs have shorter C–H···O interactions and O–H···O
hydrogen bonds
(CrystEngComm 2007, 9, 980-983)
Gavezotti: Structure and energy in organic crystals with two molecules in the asymmetric
unit: causality of chance?
(CrystEngComm 2008, 10, 389-398)
Chronology:
Verification of Z' = 2 by CPMAS NMR
NMe2
Pd
O NMe2
Pd
O
N
1
12 · 0.5 C6H5-CH3
- each C-signal appears in pairs
- 16 out of 18 signals for the above non-aromatic C atoms of 12 are resolved
- two toluene positions in crystal
X-ray crystallography and solid state NMR:
Palladacycle pseudo-polymorphs and a vanishing polymorph
CrystEngComm 2008, 1928
Chronology:
changing the solvent for verification
of toluene-CH3 assignment
NMe2
Pd
O NMe2
Pd
O
N
1
12 · 0.5 C6H5-CH3
12 · 0.5 C6D5-CD3
from C6H5CH3:
from C6D5CD3:
X-ray crystallography and solid state NMR:
Palladacycle pseudo-polymorphs and a vanishing polymorph
CrystEngComm 2008, 1928
Chronology:
2 independent molecules in the asymmetric unit
because of solvent loss during crystal mounting?
~2 x 0.25 = ~0.5 toluene per 2 Pd2 (= 12)
X-ray crystallography and solid state NMR:
Palladacycle pseudo-polymorphs and a vanishing polymorph
Chronology:
2 independent molecules in the asymmetric unit
because of solvent loss during crystal mounting? Crystallization from C6D6: P1
~2 x 0.25 = ~0.5 toluene per 2 Pd2 (= 12) 1.5 benzene per Pd2 (= 1), Z' = 1
X-ray crystallography and solid state NMR:
Palladacycle pseudo-polymorphs and a vanishing polymorph
CrystEngComm 2008, 1928
X-ray and CPMAS NMR:
Pd pseudo-polymorphs
Chronology:
verification from CPMAS: NMe2
Pd
O NMe2
Pd
O
N
1
12 · 0.5 C6H5-CH3
12 · 0.5 C6D5-CD3
1 · 1.5 C6D6
from C6H5CH3:
from C6D5CD3:
from C6D6 no splitting
Z' = 1
Chronology:
2 independent molecules in the asymmetric unit New X-ray data set of 1 from toluene,
because of solvent loss during crystal mounting? quick and careful crystal mounting
~2 x 0.25 = ~0.5 toluene per 2 Pd2 (= 12) 1.5 toluene per Pd2 (= 1), Z' = 1
P1
X-ray crystallography and solid state NMR:
Palladacycle pseudo-polymorphs and a vanishing polymorph
CrystEngComm 2008, 1928
X-ray and CPMAS NMR:
Pd pseudo-polymorphs
Chronology: attempted
verification from CPMAS: NMe2
Pd
O NMe2
Pd
O
N
1
12 · 0.5 C6H5-CH3
12 · 0.5 C6D5-CD3
1 · 1.5 C6D6
1 · 1.5 C6H5-CH3
from C6H5CH3:
crystals of 1 wet in rotor, clearly visible solvent in CPMAS 1H NMR
strong toluene smell after the experiment upon opening of rotor
splitting
Z' = 2
CrystEngComm 2008, 1928
NMe2
Pd
O NMe2
Pd
O
N
tolueneP 1
1
1 · 1.5 C7H8
P 112 · 0.5 C7H8
toluene
P 11 · 1.5 C6H6
C6H6
CH2Cl2/hexane
P21/c1 · 1 C6H14
X-ray crystallography and solid state NMR:
Palladacycle pseudo-polymorphs and a vanishing polymorph
To obtain the structure of 1 · 1.5 C7H8 or 12 · 0.5 C7H8 depends on the crystallization technique
and crystal handling:
CrystEngComm 2008, 1928
NMe2
Pd
O NMe2
Pd
O
N
tolueneP 1
1
1 · 1.5 C7H8
P 112 · 0.5 C7H8
toluene
P 11 · 1.5 C6H6
C6H6
CH2Cl2/hexane
P21/c1 · 1 C6H14
X-ray crystallography and solid state NMR:
Palladacycle pseudo-polymorphs and a vanishing polymorph
hexane
sample intoluene
technique B
hexane
sample intoluene
technique A
technique A
technique B
To obtain the structure of 1 · 1.5 C7H8 or 12 · 0.5 C7H8 depends on the crystallization technique
and crystal handling:
NMe2
Pd
O NMe2
Pd
O
N
tolueneP 1
1
1 · 1.5 C7H8
P 112 · 0.5 C7H8
toluene
P 11 · 1.5 C6H6
C6H6
CH2Cl2/hexane
P21/c1 · 1 C6H14
X-ray crystallography and solid state NMR:
Palladacycle pseudo-polymorphs and a vanishing polymorph
hexane
sample intoluene
technique B
hexane
sample intoluene
technique A
technique A
technique B
crystallization
and collection
within
3-4 days!
crystal-to-crystal transition
To obtain the structure of 1 · 1.5 C7H8 or 12 · 0.5 C7H8 depends on the crystallization technique
and crystal handling:
CrystEngComm 2008, 1928
X-ray and CPMAS NMR:
Pd pseudo-polymorphs
NMe2
Pd
O NMe2
Pd
O
N
1
1 · 1.5 C6H5-CH3
12 · 0.5 C6H5-CH3
from C6H5CH3,
technique A:
1 · 1.5 C6H5CH3
technique B:
12 ·0.5 C6H5CH3
crystal-to-crystal transition
after 30 min
after 10 h
quick
spectrum
X-ray crystallography and solid state NMR:
Pd pseudo-polymorphs and solvent mobility from 2H static CPMAS
12 · ~0.5 C6D5-CD3
toluene-d8 is immobile
CrystEngComm 2008, 1928
X-ray crystallography and solid state NMR:
Pd pseudo-polymorphs and solvent mobility from 2H static CPMAS
1 · 1.5 C6D6
benzene-d6 rotates around C6-axis
CrystEngComm 2008, 1928
NMe2
Pd
O NMe2
Pd
O
N
tolueneP 1
1
1 · 1.5 C7H8
P 112 · 0.5 C7H8
toluene
P 11 · 1.5 C6H6
C6H6
CH2Cl2/hexane
P21/c1 · 1 C6H14
X-ray crystallography and solid state NMR:
Palladacycle pseudo-polymorphs and a vanishing polymorph
1 · 1.5 C7H8 12 · 0.5 C7H8 1 · 1.5 C6H6 1 · C6H14
Independent reflections
Obs. reflect. [I > 2(I)]
Parameters refined
R1 / wR2 [I > 2(I)]
R1 / wR2 (all reflect.)
Goodness-of-fit on F2
7772
7089
452
0.0338 / 0.0793
0.0379 / 0.0814
1.082
11565
9237
757
0.0272 / 0.0598
0.0388 / 0.0618
1.008
7746
6641
473
0.0231 / 0.0519
0.0309 / 0.0548
1.034
7491
7157
422
0.0296 / 0.0717
0.0312 / 0.0725
1.135
CrystEngComm 2008, 1928
recrystallization from
CHCl3red crystals
MeOHyellow crystals
THF and acetonitrile mixture of
red and yellowcrystals
N NPd
Br Br
Pd polymorphs originating from different Br···p and C–H···Br contacts
Two polymorphic forms (dimorphs) depending on the solvent:
monoclinic, P21/c
triclinic, P1
Eur. J. Inorg. Chem. 2008, 2830
Conformational difference?
Pd polymorphs originating from different Br···p and C–H···Br contacts
Eur. J. Inorg. Chem. 2008, 2830
Pd polymorphs originating from different Br···p and C–H···Br contacts
"Dimeric units" as common "building block"
red crystals yellow crystals
Eur. J. Inorg. Chem. 2008, 2830
Pd polymorphs originating from different Br···p and C–H···Br contacts
"Dimeric units" as common "building block"
red crystals yellow crystals
Br2···N2 3.480(4) 3.780(8)
Difference in Br2···PdN2C2-heterocycle contact:
Pd polymorphs originating from different Br···p and C–H···Br contacts
Different packing of the dimeric building blocks in dimorphs:
red crystals yellow crystals
"herringbone" array
Eur. J. Inorg. Chem. 2008, 2830
Pd polymorphs originating from different Br···p and C–H···Br contacts
Different packing of the dimeric building blocks in dimorphs:
red crystals yellow crystals
"herringbone" array parallel array
Pd polymorphs originating from different Br···p and C–H···Br contacts
Difference in C–H···Br contacts (Å):
red crystals yellow crystals
Eur. J. Inorg. Chem. 2008, 2830
Pd polymorphs originating from different Br···p and C–H···Br contacts
Statistiscal analysis of C–H···Br contacts, "data mining" in Cambridge Structure Data bank:
(histogram) (scattergram)
0
500
1000
1500
2000
2500
3000
2.50 2.60 2.70 2.80 2.90 3.00 3.10 3.20 3.30
H···Br (Å)
Nu
mb
er
of
exam
ple
s
H···Br (Å)
Eur. J. Inorg. Chem. 2008, 2830
Can a single C–H···F–C hydrogen bond make a difference?
Assessing the H···F bond strength from 2D 1H-19F CP/MAS NMR
The observation: 2 symmetry independent molecules in the asymmetric unit (Z' > 1 structure)
Pd PF
F
F F
F
Pd PF
F
F F
F
molecule 1 molecule 2
asymmetric unit
CrystEngComm 2006, 8, 662
Can a single C–H···F–C hydrogen bond make a difference?
Assessing the H···F bond strength from 2D 1H-19F CP/MAS NMR
The observation: 2 symmetry independent molecules in the asymmetric unit (Z' > 1 structure)
Pd PF
F
F F
F
Pd PF
F
F F
F
molecule 1 molecule 2
asymmetric unit
What is the reason?
CrystEngComm 2006, 8, 662
Can a single C–H···F–C hydrogen bond make a difference?
Assessing the H···F bond strength from 2D 1H-19F CP/MAS NMR
Conformational difference?
overlay of
molecule 1
and
molecule 2
CrystEngComm 2006, 8, 662
Can a single C–H···F–C hydrogen bond make a difference?
Assessing the H···F bond strength from 2D 1H-19F CP/MAS NMR
Conformational difference? No!
overlay of
molecule 1
and
molecule 2
CrystEngComm 2006, 8, 662
Can a single C–H···F–C hydrogen bond make a difference?
Assessing the H···F bond strength from 2D 1H-19F CP/MAS NMR
Pd PF
F
F F
F
Pd PF
F
F F
F
molecule 1 molecule 2
asymmetric unit
Differentiating, strong intermolecular p-p or C–H···p interactions?
CrystEngComm 2006, 8, 662
Can a single C–H···F–C hydrogen bond make a difference?
Assessing the H···F bond strength from 2D 1H-19F CP/MAS NMR
Pd PF
F
F F
F
Pd PF
F
F F
F
molecule 1 molecule 2
asymmetric unit
Differentiating, strong intermolecular p-p or C–H···p interactions? No!
CrystEngComm 2006, 8, 662
Can a single C–H···F–C hydrogen bond make a difference?
Assessing the H···F bond strength from 2D 1H-19F CP/MAS NMR
Pd PF
F
F F
F
Pd PF
F
F F
F
molecule 1 molecule 2
asymmetric unit
Is the structure / space group correct? orthorhombic, Pbca
2 data sets: 100 K and 293 K
all R-values < 0.094
CrystEngComm 2006, 8, 662
Can a single C–H···F–C hydrogen bond make a difference?
Assessing the H···F bond strength from 2D 1H-19F CP/MAS NMR
Pd PF
F
F F
F
Pd PF
F
F F
F
molecule 1 molecule 2
asymmetric unit
Test for correct observation: Solid-state 19F-NMR
10 different F-signals expected
-100 -105 -110 -115 -120 -125 -130 -135 -140 -145 -150 -155 -160 -165 ppm
-16
2.4
-16
0.5
-15
8.8
-15
7.8
-15
7.4
-10
9.0
-10
7.5
-10
4.3
-10
3.9
Can a single C–H···F–C hydrogen bond make a difference?
Assessing the H···F bond strength from 2D 1H-19F CP/MAS NMR
Pd PF
F
F F
F
Pd PF
F
F F
F
molecule 1 molecule 2
asymmetric unit
Test for correct observation: Solid-state 19F-NMR
10 different F-signals expected
9/10 found
ortho-F
4 signals
meta+para-F
5/6 signals
Can a single C–H···F–C hydrogen bond make a difference?
Assessing the H···F bond strength from 2D 1H-19F CP/MAS NMR
What about C–H···F–C hydrogen bonds?
D’Oria, Novoa: " neutral C–H···F interactions have an interaction energy
around 0.4 kcal mol–1 "
(E. D’Oria, J. J. Novoa, CrystEngComm 2008, 10, 423)
Hulliger et al.: "the role of fluorine in crystal engineering is not yet clear"
"except for phenyl-perfluorphenyl p-stacking,
other observed fluorine interactions are generally weak"
(K. Reichenbächer, H. I. Süss, J. Hulliger, Chem. Soc. Rev. 2005, 34, 22)
Boese, Nangia, Desiraju et al.: "relevant C–H···F–C interactions in fluorobenzenes C6H6–nFn"
(V. R. Thalladi, H.-C. Weiss, D. Bläser, R. Boese, A. Nangia, G. R. Desiraju,
J. Am. Chem. Soc. 1998, 120, 8702)
Dunitz and Taylor: "organic fluorine (C–F) hardly ever accepts hydrogen bonds"
(J. D. Dunitz, R. Taylor, Chem. Eur. J. 1997, 3, 89)
Can a single C–H···F–C hydrogen bond make a difference?
Assessing the H···F bond strength from 2D 1H-19F CP/MAS NMR
Differentiating C–H···F–C hydrogen bonds?
A lot of intermolecular C–H···F–C hydrogen bonds between Pd1 – Pd1, Pd2 – Pd2 and Pd1 – Pd2
CrystEngComm 2006, 8, 662
Can a single C–H···F–C hydrogen bond make a difference?
Assessing the H···F bond strength from 2D 1H-19F CP/MAS NMR
Differentiating C–H···F–C hydrogen bonds?
shortest contact H40···ortho-F1 2.39 / 2.42 Å (100 K / 293 K),
second-shortest H44···para-F8 2.50 / 2.58 Å
CrystEngComm 2006, 8, 662
Can a single C–H···F–C hydrogen bond make a difference?
Assessing the H···F bond strength from 2D 1H-19F CP/MAS NMR
shortest contact H40···ortho-F1 contact is between Pd1 – Pd2 !
Can a single C–H···F–C hydrogen bond make a difference?
Assessing the H···F bond strength from 2D 1H-19F CP/MAS NMR
-500010000 5000 0 Hz
PILGRIM experiment:
assesses the strength of the 1H–19F dipol–dipol coupling
–104
–162
ppm
o-F
m/p-F
width ~ coupling strength
strongest
coupling
CrystEngComm 2006, 8, 662
Metal complexes for biopolymers
Biochemistry
Coordination
chemistry
Metal complexes for biopolymers
N
N
N
N
RuN
NL
L
2+
L = -NH2
-CO2Et
-NHCO2Et
Ruthenium(II) complexes
– photophysical properties
– energy and electron transfer
– binding to proteins
Inorg. Chim. Acta 2001, 318, 103
metal complexes with bio relevance:
Z. Anorg. Allg. Chem. 2003, 629, 2282
Z. Anorg. Allg. Chem. 2003, 629, 2585
Z. Anorg. Allg. Chem. 2004, 631, 17
2+
(PF6–)2
L:
N
NH
N
NH
N
NH
N
NH
N
NH
Ph
Ph
N N
NRu
N
N
L
NNH
NNH
NNH
Metal complexes for biopolymers
Model complexes:
Binding to cytochrome c:
+ cyt c [Ru(bipy)(terpy)(cyt c)]2+
– UV/VIS
– fluorescence
– ESI-MS
Dalton Trans. 2005, 256
– X-ray
– UV/VIS = f(pH, time)
– fluorescence
[Ru(bipy)(terpy)(cyt c)]2+
Histidin binding site:
His44 (His39)
– analysis of
trypsin digestion products
with HPLC-MS
(ESI-MS/MS)His44
His38
His31
His23
Dalton Trans. 2005, 256
NB
N N
NNN
H
N
NN
B
N
NM
N
NN
N
H
N
NN
H2O
OH2
Summary:
Hydrogen-bonded frameworks
two-dimensional
water/ice substructure
NB
N N
NNN
H
N
NN
B
N
NM
N
NN
N
H
N
NN
H2O
OH2
two-dimensional
water/ice substructure
Summary:
Hydrogen-bonded frameworks
N
OH2N
isonicotinamideINA
+ AgNO3
stabilizing formulation of solid AgNO3
Summary:
Hydrogen-bonded frameworks
OH
OH
molecular
paneling
O
OP
O
O–
BNPPA–
inverse
bilayers
BINOL/BINOLAT2–
N
N
NN
FeN
N
NH2
NH2
NH2
H2NH2N
H2N
[Fe(DABP)3]2+
Summary:
Hydrogen-bonded frameworks
spontaneous resolution molecular trigonal-prismatic hexamer
HO NH
O
Ph
HN
O
R
O
NH
R
*
*
HO
O
OH
O
Summary:
Recent case studies on non-covalent interactions
recrystallization from
CHCl3red crystals
MeOHyellow crystals
THF and acetonitrile mixture of
red and yellowcrystals
N NPd
Br Br
NMe2
Pd
O NMe2
Pd
O
N
tolueneP 1
1
1 · 1.5 C7H8
P 112 · 0.5 C7H8
toluene?
P 11 · 1.5 C6H6
C6H6
CH2Cl2/hexane
P21/c1 · 1 C6H14
?
Acknowledgements
Magnetism Prof. J. Sanchiz, Univ. La Laguna
Mössbauer Dr. H. Winkler, Univ. Lübeck
TG/MS PD Dr. C. Näther, Univ. Kiel
Neutron diffraction Dr. S. Mason, ILL Grenoble
Heat transformation S. Henninger, ISE Freiburg
Luminescence Dr. H. Höppe, Univ. Freiburg
special X-ray Prof. C. Röhr, Univ. Freiburg
NP-TEM Dr. R. Thomann, Univ. Freiburg
Au-NP Dr. M. Krüger, Dr. M. Walter, Univ. Freiburg
Finances: DFG, FCI, AvH
Dr. Khalid Abu-Shandi
Frederik Blank
Anne-Christine Chamayou
Stefan Deblon
Dr. Thomas Dorn
Prof. Dr. M. Enamullah (AvH)
Marie Genitrini
Jerôme Krämer
Dr. Paul G. Lassahn
Hesham Mena
Dr. Barbara Wisser (née Paul)
Engelbert Redel
Dr. Tobias Scharmann
Dr. Savas Temizdemir
Lars Uehlin
Jana Vieth
Christian Vollmer
Dr. Biao Wu
Dr. He-Ping Wu (AvH)
Dr. Xiao-Juan Yang
Dr. Cungen Zhang (AvH)
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