[RSiO1.5]n Nanobuilding Blocks for Photonic and
Electronic Applications
R. M. Laine, J.H. Jung, J. Furgal, S. Sulaiman, J. Zhang
JS. Clark, T. Goodson, T. Mizuno
Materials Sci. & Eng., Macromolecular Sci. & Eng.; Chemistry
Supported by:
DOE, Office of Naval Research, U.S. Army Natick,
Mayaterials, Canon, Boeing, Intel
Mayaterials.com = commercial source of silsesquioxanes
Outline
•  Why silsesquioxanes (SQs)?
•  Vinyl8T8 SQs 2nd Generation
–  Syntheses
–  Photophysics
•  Mixed functional SQs
•  Beads on a Chain Polymers
-  [PhSiO1.5]xVinylSiO1.5]10/12-x
-  [VinylSiO1.5]10/12
-  Photophysics
-  More BOCs
•  Conclusions
2
Why Silsesquioxanes (SQs)?"
•  Robust, typically stable to > 300 °C"
•  Also UV stable"
R
R
R
Si
•  Easily purified because their 3-D nature"
imbues high solubility"
R
O
O
O
Si O
O
Si
O
Si
O
O
Si
O
GEN1 T8
Si
R
O
O
Si
R
O
Si
R
R
R
• High symmetry allows well"
ordered 3-D assembly via multiple"
bonding modes."
R
R
R
R
GEN1 T10
•  Opportunity to functionalize 8, 10, 12, 16, 24 times"
R
R
R
•  3-D conjugation in excited state via cage center"
offers potential to assemble rigid 3-D hybrid structures"
with semiconducting behavior. "
R
R
R
R
R
R
GEN1 T12
This is unique for organic and/or hybrid materials!
R
R
"
•  Already a review on use of SQs as OLED components "
Where their use can greatly enhance electron and hole transport "
"
R
R
R
R
R
Why Silsesquioxanes (SQs)?
o-Br8OPS
2,5-Br16OPS
8, 16 or 24 functional groups in 1.5 nm sphere
Higher than any Gen 1-3 Dendrimer
J. Mater. Chem. Web Published
Br24OPS
Cross coupling allows mix and match functional groups
R
R
Br
Br
O
Si
O
O
Si BrO
Br
O
Si
Si
O
O
Si
Br
R
Si
O
O
O
Br
O
+8
Si
Si
Heck coupling
O
O
Si
Pd catalyst
R
Si
O
R
R
O
O
O
Si
Si
Si
Br
R = OAc, NH2, NHBOC, CH3,OCH3, Cl, Ph,
O
Si
Br
O
Si
Br O
O
O
Br
Si
Si
O
O
Si
O
O
Si
Br
O
Si
O
Br
Si
Br
O
16 Functional groups
Br
Br
+ 16
O
R
Pd catalyst
Br
Heck coupling
Si
O
O
O
Si
Si
O
O
O
O
Si
O
Si
O
24 Functional groups
Br
Br
Br
Br
Br
Br
Si
Br
O
Si
Br O
O
O
O
Si
Si
O
Si
O
O
Br
Si
O
O
Br
O
Si
O
Si
Br
Br
Br
Si
O
Br
Pd catalyst
+ 24
Br
R
Heck coupling
Si
Br
Br
O
O
O
Si
Br
O
Si
Br
Br
Si
Si
O
Br
Br
O
Si
Br
Br
8 Functional groups
R
Br
Br
Si
O
R
Br
Br
Br
Si
O
R
Br
J. Mater. Chem
Web published
O
O
O
O
Br
Si
O
O
O
Si
Si
O
O
O
O
Si
Si
O
Photophysics indicates 3-D conjugation in the excited state
300 nm
405 nm
353 nm
310 nm
Si
1
vs
p-MeStilbene Abs.
p-MeStilbene Em.
o-MeStyr8OPS Abs.
o-MeStyr8OPS Em.
p-MeStyr8OPS Abs.
p-MeStyr8OPS Em.
Normalized Intensity
0.8
0.6
0.4
0.2
0
250
O
O
Si O
O
Si
O
Si
O
O
Si
O
Si
O
O
O
Si
O
Si
o-MeStyrOPS
300
350
400
450
500
550
600
650
Wavelength (nm)
Red shift of 50 nm: 3-D conjugation in excited state
Roll Sulaiman et al J. Am. Chem. Soc. 2010, 132 3708
Compound
ΦPL (%)
p-MeStilbene
9
o-MeStyr8OPS
4
p-MeStyr8OPS
4
6
Bonding in SQs
HOMO
LUMO
7
Roll, Sulaiman, J. Am. Chem. Soc. 2010, 132 3708–3722.
OctaStyrylSQ, GEN1
Cl
Cl
Si
H2O/EtOH
Si
-HCl
Cl
O
Si O O
O
Si
O
Si
O
O
O
Si
Si
O
Yield 40 %
O Si
O
Si
O
R
R
R
Si
O O
Si O
O
Si
O
Si
O
O
O
Si
Si
R
Si
O O
Si O
O
O Si
O
Si
O
Si
O
Si O
O
1st Gen.
Grubbs
Catalyst
R = H, p-Me,-OMe, -Cl, Br
m-NO2
R
R
See also Feher et al, Sellinger et al,
Marciniec et al
R
O
Yield ≈ 100 %
O Si
Si
O
O
O
Si
Si
O
R
R
8
Sulaiman et al Chem Mater. 20 5563 (2008).
[StilbeneVinylSiO1.5]8 GEN2
R1
Br
Br
Br
Si
O O
Si O
R1
Br
O
Si
O
Si O
Br
R1
Si O Si
O
O
Si OO Si O
R1
O
O
Br
R1
O Si
Si
O
O
O
Si
Si
O
Br
R1= H, Me, OMe
Pd catalyst
R1
Si OO Si
O
O
Si
O Si
R1
Br
R1
Heck rxns
Yield ≈ 100 %
3-D Styrenyl SQ
R1
R = H, Me, OMe, NH2
Sulaiman et al Chem Mater. 20 5563 (2008).
9
Photonic Motivation GEN2 (CH2Cl2)
335 nm
387 nm
H
H
H
H
Si O Si
O O O
Si O Si O
O
H
Si OO Si
O
O
Si O Si
H
H
H
10
Solvent polarity affects emission λmax
•  Proof of CT behavior
–  45-nm red-shift with increasing solvent polarity
507 nm
NHnm
360
2VinylStilbeneOS
460 nm
Normalized intensity
1
0.8
Abs. in CH2Cl2
Em. in CH2Cl2
Abs. in CH3CN
Em. in CH3CN
0.6
H2N
NH2
H2N
0.4
NH2
Si O Si
O O O
Si O Si O
O
0.2
H2N
Si OO Si
O
O
Si O Si
NH2
0
250
300
350
400
450
500
550
600
650
H2N
NH2
Wavelength (nm)
11
Two Photon Absorption Cross-sections
N
N
N
N
N
N
Si
O
Si OO
O
Si
Si
O O O
Si
Si
O
O
O O
Si
Si
Si
N
O
Si
Si
O
O
Si
Si
O
N
Si
N
Si
O
O
O
Si
O
Si
N
O
O Si
O
O
Si
N
Si
N
Sample
MeStil8OS
Me2NStil-corner
Me2NStil-half
δ (GM)
11
12
δ/moiety (GM)
1.2
12
30
Me2NStil8OS
StilbenevinylOS
N
7.5
λmax nm
735
780
790
φf
0.06
0.08
0.09
211
25
26
3
755
705
0.03
0.36
p-MeOStilvinylOS
110
14
705
0.12
p-NH2StilvinylOS
810
101
720
0.05
Thus, excellent charge separation and long lifetime
Roll, Sulaiman, J. Am. Chem. Soc. 2010, 132 3708–3722.
Beads on a Chain Polymers Motivation
Control no. of xlinks
•  1 x-linking group – pendant or end-cap groups
Li, et. al. J. Inorg. Organomet. Polym. 2002
Phillips, et. al. Curr. Opin.
Solid State & Matl. Sci. 2004
•  8 cx-linking groups – complete network
Laine et. al, JACS 2001, 123, 12416.
Chem. Mater. 2003, 15, 793.
Macromol. 2004, 37, 99
13
Control no. of xlinks
•  2 xlink groups – linear polymer with SQs in backbone
Target structure:
“Beads on a Chain” polymers
≡
Few literature examples of
difunctional silsesquioxanes
Disilanol available in
15% yield after 12
weeks!
Lichtenhan, et. al. Macromol. 1993
14
Control no. of xlinks
•  2 xlink groups – linear polymer with SQs in backbone
Double Decker Chemistry
•  Higher yields,
•  Variety of copolymers …much work in progress
Kakimoto et al “Hydrosilylation Polymerization of Double-Decker-Shaped
Silsesquioxanes” Macromolecules 39, 3473-5 (2006).
Kawakami et al” Polysiloxanes with Periodically Distributed Isomeric Double-Decker
Silsesquioxane in the Main Chain” Macromolecules, 42 3309–331(2009).
F- ion inside SQ – Bassindale
R
R
OSi O Si
R
RSi
O Si
O
O OSi O
R R
O SiOR
Si OO
Si RO R
RSi OSiOO
Si O - Si- O
O O
OF Si O Si
SiF F-Si
O
OO Si OO OSi R
R R
OSiO
OR R
RSi Si
O
O
Si O
Si RSi
R
O O
R R
RR
R
OR'
OR'
OR'
R
Si
R
Si OR'
OR'
R
Si
OR'
OR'
OR'
OR'
TBAF
TBAF
TBAF
R
N+
N+
Bassindale, et.al., Organomet., 2004
•  R = vinyl, p-tolyl
•  Reaction conditions:
–  2.5mmol TBAF for 6.52 mmol –Si(OR’)3 – 3 mmol F- for 1 mmol SQ
–  Solvent: toluene
•  Yield: 55% (p-tolyl), 60% (vinyl)
16
F- ion inside SQ – Mabry, Bowers
R
O
R
R
Si
Si
R O O
O
R
Si O
Si
O
O Si
Si
O
R
R
O
O
Si
O Si
R
R
TMAF
O
R
R
RT
R
O
Si
Si
O O
O
R
Si O
Si
O
SiF O Si
O
Si
O
R
O
O
Si
O
N+
N+
F-
TMAF
R
R
Mabry, Bowers et.al., Chem. Mater., 2008
•  Requires stoichiometric F•  Works for R = e- withdrawing (vinyl, phenyl, styrenyl, Rf)
•  Not e- donating groups (alkyl)
•  Not simple insertion of F- Complex rearrangement
17
F- ion inside SQ – Mabry, Bowers
←
29Si-NMR
data
•  Not stable in solution
–  F-@OPS and F-@OVS
form new structures in
solution (e)
–  Non-F-@ cages also form
mixed systems (f)
–  Indicates scrambling of
cage structures
18
Can we make mixed-functionality SQs?
O
Si
Si
O O
O
Si O
Si
O
O
O Si
Si
O
O
O
Si
O Si
Phenyl8T8
O
Si
Si
O O
O
Si O
Si
O
O
O Si
Si
O
O
O
Si
Si
O
Vinyl8T8
TBAF
O
Si
Si
O O
O
Si O
Si
O
O
O Si
Si
O
O
O
Si
Si
O
Target product
•  Reaction conditions:
–  Equimolar Phenyl8T8 and Vinyl8T8
–  Solvent: THF
–  2 mol% TBAF (of total SQ cage)
–  RT/24 h
19
Equilibrating Phenyl8T8 + Vinyl8T8
MALDI-ToF
T10
T12
T10
T12
T20 - T22
1000
1200
1400
1600
1800
m/z
(Ag+2000
)
m/z (Ag+)
2200
2400
2600
2800
20
Metathesis Reaction Scheme
Metathesis w/Brstyrene -> Br-Ph for further functionalization
Metathesis with Br-styrene MALDI-ToF
T10
T12
Ph10
BrStyr2Ph8
BrStyr2Ph10
BrStyr1Ph11
BrStyr1Ph9
1200
1300
1400
1500
1600
m/z Ag+
1700
1800
1900
Beads on a Chain, BOCs?
≡
Cages linked by
conjugated tethers
•  Photoluminescent
•  Soluble
Asuncion et al JACS. 2010, 132 3723–3736.
Synthesis of Model Compound
Compare UV/PL absorption/emission spectra
to Heck oligomer
Asuncion et al JACS. 2010, 132 3723–3736.
Absorption / Emission
UV Absorb./PL Emission
235
Heck Cpd Absorption
≈ 60 nm red-shift from model cpd
≈ 120 nm red-shift from absorption
Heck Model Cpd Absorption
Heck Cpd Emission
Heck Model Cpd Emission
Excitation Wavelength = 265 nm
Solvent: THF
285
335
385
435
485
535
Wavelength (nm)
Asuncion et al JACS. 2010, 132 3723–3736.
Gen 1 Vinyl10 and Vinyl12
  Cross-metathesis reaction
1st generation Grubbs catalyst
40℃ / CH2Cl2
X = 10, 12
(Ph)
(MePh)
(MeOPh)
OMe
Br
(CH2ClPh)
(BrPh)
(Np)
(BiPh)
Jae Hwan Jung
Gen 2 Vinyl10 and Vinyl12
1st generation Grubbs catalyst
40℃ / CH2Cl2
SiO1.5
Br
x
X = 10, 12
Br
OMe
R
R
NH2
R
R
SiO 1.5
R
R
R
x
R
R
R
R
X = 10, 12
R = H,
Me,
OMe,
NH2
Jae Hwan Jung
Gen 2 Vinyl10 and Vinyl12
GPC
SiO1.5
R
x
X = 10, 12
X = 10, 12
R = H, Me, OMe, NH2
BrStyrenyl SQ (GEN1)
GEN2 (H)
GEN2 (Me)
GEN2 (Ome)
GEN2 (NH2)
27
28
29
Time (min)
30
31
32
Jae Hwan Jung
Gen 2 Vinyl10 and Vinyl12
MALDI
G202A_5D
G202A_5D 12 (0.438)
100
TOF LD+
4.13e3
3361.8
T12
SiO1.5
R
x
2820.2
R = Me
T10
2821.1
%
T14
3902.9
0
2200
2400
2600
2800
3000
3200
3400
3600
3800
4000
4200
m/z
TGA
H
Me
O Me
N H 2
80
60
Weight ( % )
100
40
SiO1.5
20
R
x
0
400
800
o
T e m p e ra tu re ( C )
R
Ceramic Yield (%)
(Experimental)
Ceramic Yield (%)
(Theoretical)
Td (5%) (oC)
H
23.3
23.4
390
Me
21.5
22.1
385
OMe
20.8
20.9
325
NH2
22.1
22.1
390
Gen 2 Vinyl10 and Vinyl12
Jae Hwan Jung/Joe Furgal
Solvent Effects
465 nm
517 nm
Gen 2 C6F5 Vinyl10 and Vinyl12
TPA Data for T10/T12 SQ’s
SiO1.5
R
x
Gen 2 Vinyl10 and Vinyl12
Cyclic Voltammetry Studies
-2
-2.6
E (eV)
-3
-2.6
-2.5
NH2
-5
P3HT
-6
-4.2
H
Me
OMe
PCBM
-5.7
-6
5F
-4.9
-5.2
-2.6
LUMO
-3.2
-4
-2.2
-5.6
HOMO
-5.5
-6.2
=> To replace PCBM, GEN 2 LUMO should be < -3.2 eV
Uv Vis of Gen 2 and with addition of Cyanophenyl (GEN 3)
5F
Pd/t-Bu3
5F_CN
OMe
OMe_CN
Gen 2 and 3 Vinyl10 and Vinyl12 + Ph-CN
-2
First efforts to modify LUMO brings it half-way to target
-2.6
E (eV)
-3
-4
-2.5
-2.9
-2.8
-3.2
P3HT
-5
-4.2
5F
(A)
5F-CN
(A-A)
OMe
(D)
OMe-CN
(D-A)
PCBM
HOMO
-5.2
-5.5
-6
-6.0
LUMO
-6.2
-6.0
-5.6
D : Donor
A : Accepter
=> To replace PCBM, GEN 2 LUMO should be < -3.2 eV
Gen 3