![Fine-Tuning of Fluorinated Thieno[3,4-b]thiophene Copolymer for … · 2015-02-02 · Fine-Tuning of Fluorinated Thieno[3,4-b] ... of electroactive and photoactive polymers are collectively](https://static.fdocuments.net/doc/165x107/5e934d51074b41012d481b53/fine-tuning-of-fluorinated-thieno34-bthiophene-copolymer-for-2015-02-02-fine-tuning.jpg)
Dendrimers and light: towards electroactive and photoactive dendrimers
55
Dendrimers and light: towards electroactive and photoactive dendrimers Jean M.J. Fréchet, Dept. of Chemistry, UC Berkeley AFOSR MURI Program (Dr. C. Lee) Graduate Students: Alex Adronov, Adam Freeman, Stefan Hecht, Patrick Malenfant. Postdoctoral Fellow: Lysander Chrisstoffels. Collaborators: Prof. M. Thompson, USC Prof. P. Prasad, SUNY Buffalo Dr. S. Gilat, Lucent Bell Labs Prof. G. Fleming, UC Berkeley \ Dr. D. Robello, Kodak
-
Upload
raymond-conrad -
Category
Documents
-
view
50 -
download
1
description
Dendrimers and light: towards electroactive and photoactive dendrimers. Jean M.J. Fréchet, Dept. of Chemistry, UC Berkeley AFOSR MURI Program (Dr. C. Lee) Graduate Students: Alex Adronov, Adam Freeman, Stefan Hecht, Patrick Malenfant. - PowerPoint PPT Presentation
Transcript of Dendrimers and light: towards electroactive and photoactive dendrimers
Dendrimers and light:towards electroactive and photoactive dendrimers
Jean M.J. Fréchet, Dept. of Chemistry, UC BerkeleyAFOSR MURI Program (Dr. C. Lee)
Graduate Students: Alex Adronov, Adam Freeman, Stefan Hecht, Patrick Malenfant.
Postdoctoral Fellow: Lysander Chrisstoffels.
Collaborators: Prof. M. Thompson, USCProf. P. Prasad, SUNY BuffaloDr. S. Gilat, Lucent Bell LabsProf. G. Fleming, UC Berkeley \Dr. D. Robello, Kodak
e-
e-
e-
1. Light Harvesting
2. EnergyTransfer
Relay
3. Charge Separation
ChlorophyllBound to Protein
Reaction Center
Lipid Bilayer
Natural photosynthetic processes
• Design & synthesis of a dendritic light harvesting “antenna”• Demonstration of efficient through-space energy transfer• Study of the effect of increasing dendrimer generation on ...the energy transfer efficiency
The dendritic antenna
OSi
OO
O
O
O
O
NN O
N
NNO
NN
O
N
NN
O
O
O
O
O
NNO
N
N NO
NN
O
N
N N
O
• Efficient light harvesting and energy transfer (>90%) in dendritic systems have been demonstrated.
• Synthesized molecules have been fully characterized and energy transfer was studied by both steady-state and time-resolved techniques.
• The synthetic approach has a modular design that provides versatility in the choice of core acceptor and surface donor dyes (coumarins, oligothiophenes, two-photon chromophores).
Antennas for Light Harvesting and Energy Transfer
O
O
N
N
NN
O
OO
O
OO
OO
OO
O
O
N
OO
O
O
O
O
O O
N
N
N
N
O
O OO
O
O
O OOO
N
N
N
N
O
OOO
O
O
OO
O
O
N
N
N N
O
O O
O
O O
OO
SS
SS
SS
S
OO
C8H17H17C8
ON
OO
NOO
ON
OO
N O O
O
O
NOON
OO
O
O
N O ON
OO
300320
340360
380400
420440
460480
500
360380
400420 440 460 480 500 520
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
ON O
O
OH
Donor Dye Acceptor Dye
G-4 Dendrimer
Compound acc (ps)
ET (ps) D-A Distance (Å) ET (%)
G-1 2266 <30 11.7 98%G-2 2422 <30 13.6 97%G-3 2455 <30 14.3 97%G-4 2636 <50 17.8 >93%
Summary of initial energy transfer results
ON OH
O
O
N
N
NN
O
OO
O
OO
OO
OO
O
O
N
OO
O
O
O
O
O O
N
N
N
N
O
O OO
O
O
O OOO
N
N
N
N
O
OOO
O
O
OO
O
O
N
N
N N
O
O O
O
O O
OO
Synthetic strategy
nucleophilic
electrophilic
nucleophilicattackN
O
O
N
O
O
N
O
O
N
O
OOH
O O
N
O
O
N
O
O
N
O
OOH
O O
Br
Br Br
OTBDPSO
OHR
R =
O
O
HN
ON OS
SS
SS
C8H17
SS
SS
SS
S
C8H17H17C8
(C2)8-[G-3]-CH2OH
(C2)4-[G-2]-CH2OH
(C2)2-[G-1]-CH2OH
O
OO
N
N
O
O
O
O
NOON
OO
O
OO
N
N
O
O
O
O
N O ON
OO
OH59%
3. (Br)2-[G-1]-CH2OTBDPS4. TBAF
2. NaOH/EtOH1. K2CO3/CH3CN
OO
OSO2C16H33
Br
Br
Br
Br
OO
N
N
N
N
OO
O O
OO
O O
OH
72%
81%
83%
2. TBAF1. (Br)2-[G-1]-CH2OTBDPS
OO NN
OH
O O
1. K2CO3/CH3CN2. NaOH/EtOH
BrBr
OSO2C16H33
BrBr
OTBDPS
2. TBAF1. K2CO3/CH3CN
OO NN O O
OH
+ON
HO
Peripheral laser-dye donor functionalization
Identical reactionscan be carried out to link the penta-
thiophene cores tothe donor dendrons
(C2)8-[G-3]-CH2OT7
(C2)4-[G-2]-CH2OT7
(C2)2-[G-1]-CH2OT7
89%
EDC/DMAPCH2Cl2
EDC/DMAPCH2Cl2
89%
87%
EDC/DMAPCH2Cl2
OO
N
N
N
N
OO
O O
OO
O O
O
SS
SS
SS
S
O
H17C8 C8H17
SS
SS
SS
S
OO
H17C8 C8H17
OO NN O O
(C2)2-[G-1]-CH2OH
(C2)4-[G-2]-CH2OH
(C2)8-[G-3]-CH2OH
SS
SS
SS
S
OHO
SS
SS
SS
S
OO
C8H17H17C8
ON
OO
NOO
ON
OO
N O O
O
O
NOON
OO
O
O
N O ON
OO
Core acceptor functionalization
Thiophene-core fully dye-labeled dendrons
(C2)2-[G-1]-CH2OT5
(C2)4-[G-2]-CH2OT5(C2)8-[G-3]-CH2OT5
(C2)2-[G-1]-CH2OT7
(C2)4-[G-2]-CH2OT7
(C2)8-[G-3]-CH2OT7
S
S
S
S
S
H17C8
OO
OO
N
N
N
N
OO
O O
OO
O O
OO NN O O
O
S
S
S
S
S
H17C8
O
S
S
S
S
S
H17C8
OO
O
OO
N
N
O
O
O
O
NOON
OO
O
OO
N
N
O
O
O
O
N O ON
OO
SS
SS
SS
S
OO
H17C8 C8H17
OO NN O O
OO
N
N
N
N
OO
O O
OO
O O
O
SS
SS
SS
S
O
H17C8 C8H17 SS
SS
SS
S
OO
C8H17H17C8
ON
OO
NOO
ON
OO
N O O
O
O
NOON
OO
O
O
N O ON
OO
MALDI-TOF of T7-labeled dendrons
1500 2000 2500 3000 3500 4000 4500 5000
Mass (m/z)
1403 (1408)
2075 (2079)
3411 (3420)
G-1
G-2
G-3
0
1
2
3
4
5
6
300 350 400 450 500 550 600 650
0
50
100
150
200
250
300
Absorption
Absorption
Emission
Emission
Wavelength (nm)
Ex
tin
cti
on
co
eff
icie
nt
(x 1
0-4,
M-1
cm
-1)
Em
iss
ion
In
ten
sit
y (
a.u
.)
SS
SS
SS
S
HOO
H17C8 C8H17
Large overlap between donor emission and acceptorabsorption enables efficient energy transfer.
Spectral properties of the models
OO
N
N
N
N
OO
O O
OO
O O
OH
0
20000
40000
60000
80000
100000
120000
300 350 400 450 500 550
T7
G-1
G-2
G-3
Wavelength (nm)
Ex
tin
cti
on
co
eff
icie
nt
(M-1
cm
-1)
“Light Harvesting” capacity doubles with generation.
Light harvesting: G-1 to G-3
SS
SS
SS
S
OO
C8H17H17C8
ON
OO
NOO
ON
OO
N O O
O
O
NOON
OO
O
O
N O ON
OO
0
100000
200000
300000
400000
500000
600000
700000
350 400 450 500 550 600 650
T7
G-1
G-2
G-3
Wavelength (nm)
exc = 343 nmconc. = 5.06 x 10-6 M
Em
iss
ion
in
ten
sit
y (
a.u
.)
Beyond G-1, sensitized fluorescence becomes much moreintense than fluorescence from direct excitation of the core.
Energy transfer: G-1 to G-3
SS
SS
SS
S
OO
C8H17H17C8
ON
OO
NOO
ON
OO
N O O
O
O
NOON
OO
O
O
N O ON
OO
Direct Core Emissionmax = 425 nm
T5-core dendrons as antennas
0
20000
40000
60000
80000
100000
120000
300 350 400 450 500 550 300 350 400 450 500 550 600 650
100000
200000
300000
Wavelength (nm) Wavelength (nm)
Ex
tin
cti
on
co
eff
icie
nt
(M-1c
m-1)
Em
iss
ion
in
ten
sit
y (
a.
u.)
T5
G-1
G-2
G-3
G-1
G-2
G-3
exc = 343 nmconc. = 3.93 x 10-6 M
T5
Direct Core Emissionexc = 425 nm
The observed absorption and fluorescence emission spectra of the G-1 to G-3 pentathiophene core dendrons were very similar to
those for the series of heptathiophene core dendrons.
S
S
S
S
S
H17C8
OO
O
OO
N
N
O
O
O
O
NOON
OO
O
OO
N
N
O
O
O
O
N O ON
OO
Energy transfer efficiency
Compound max ()
Donors
max ()
AcceptorsEmission
Range
ET
(%)T7-Bn 423 (48 000) 520-580G1-T7 341 (43 500) 426 (47 500) 520-580 99%G2-T7 343 (66 000) 426 (43 500) 520-580 99%G3-T7 344 (103 000) 425 (38 500) 520-580 99%T5-Bn 422 (42 000) 520-580G1-T5 345 (37 000) 423 (40 000) 520-580 99%G2-T5 344 (57000) 423 (35 000) 520-580 99%G3-T5 344 (104 000) 423 (37 000) 520-580 99%
It is possible to tune the dendrimer emission wavelength by changing the core functionality. Also, by mixing the different types of dendrimers (no dye at core, coumarin 343 at core, and oligothiophene at core), it is possible to obtain broadband emission by exciting at a single wavelength (max of donor dye -
343 nm).
Wavelength (nm) Wavelength (nm)E
mis
sio
n i
nte
ns
ity
(a
. u
.)
Em
iss
ion
in
ten
sit
y (
a.
u.)
0
50000
100000
150000
200000
250000
350 400 450 500 550 600 650 7000
40000
80000
120000
160000
350 400 450 500 550 600 650 700
Tunable emission
OO NN O O
OH
N N
O
OOO O
O
O
O
N
SS
SS
SS
S
OO
H17C8 C8H17
OO NN O O
NN
O
N
NN
O
OH
O
OHHO
O
OSi
NNO
N
NNO
OO
OO
OSi
NN O
N
NN O
+EDC/DMAP
G-1
Investigation of cooperativity effects of two-photon chromophores when arranged in a branched structure
Incorporation of two-photon dyes
A collaboration with Prof. Paras Prasad.
NNO
N
NNO
OO
OO
OH
NN O
N
NN O
BrBr
OSi
OSi
OO
O
O
O
O
NN O
N
NNO
NN
O
N
NN
O
O
O
O
O
NNO
N
N NO
NN
O
N
N N
O
+K2CO3
18-Crown-6
G-2
Two-photon dendrimers
Collaboration with Prof. Paras Prasad
O OHO
O ONH
CF3
O OHO
C OH
O
N C O
Future directions:dendritic energy transfer relay
320 nm
380 nm
390 nm
470 nm
480 nm510 nm
A
A
AA
A A
A
A
A
h h
h ’h ’
Energy Transfer
• Self-assembly of individualdonor dendrons and acceptor dyes simplifies the preparation of antennas.
• Energy transfer on surfaces opens avenues for the fabrication of novel photonic devices.
• Variation of photoactive donors and acceptors allows for numerous applications, ranging from sensors to solar cells and new devices.
Surface-confined energy transfer
O
O
N
Si SiSi
Si
O
O
NH
SiOO O
Si
O
NN
O
O
O
O
O
NH
Si
O
O
NH
Si OOO
O
NN
OO
OO
O
Si
O
O
NH
SiOO
O
Si
O
NN
OO
OO
O
NH
Si
O
O
O
O
N
O
NH
SiO
OO
Si
O
NN
O
OO
O
O
O
Si SiSi
O
Si
NHO
O
O
N
NHO
O
O
N
h
• Self-assembled monolayers of chromophores with different aspect ratios were prepared on silicon wafers by using siloxane chemistry.• Complete quenching of the donor emission as well as efficient energy transfer from the assembled coumarin-2 (donor) dyes to the coumarin-343 (acceptor) dyes was observed.• The photophysical properties are tuned by varying the molar ratio of assembled donor and acceptor chromophores on the surface.
h’
Energy transfer on self-assembled surfaces
Synthesis of adsorbates
Donor chromophore
Acceptor chromophore
+MeCN
O
O
O
N N
OOO O
HO
OO
O
N N
OOO O
HO
EDC / DPTS
CH2Cl2
DMAP
(85%) (69%)
SiOO
O
O
NH
O
N N
OOO O
O
Si O
O O
NH2
+
OHO
OO
N
EDC / DPTS
CH2Cl2(73%)
Si O
O O
NHO
OO
N
Si O
O O
NH2
Physisorption of coumarin-343 onto amino-terminated SAMs
0
10000
20000
30000
40000
400 500 600
em
(nm)
Emission scan
cps ( s -1 )
ex = 420 nm
I
II
III
OHO
OO
N
CH2Cl2 CH2Cl2
NEt3
I III
II
SiSi
SiO
H2N
SiOO O
Si
H2N
Si
H2N
Si OOO
OO
Si Si
H2N
Si
O-O
OO
N
O-O
OO
N
SiSi
SiO
+H3N
SiOO O
Si
H2N
Si
+H3N
Si OOO
OO
Si Si
H2N
Si
1 2 (nm)
0
0.25
0.5
0.75
1
320 370 420 470 520 570
em
A.U.
Excitation spectra and Emission spectra of SAMs of 1 or 2
1
2 2 1
Photophysical properties of coumarin-derivatized SAMs
SiOO
O
O
NH
O
N N
OOO O
O
Si O
O O
NHO
OO
N
Energy transfer within SAMs of mixed monolayers of coumarin chromophores
Emission spectra from mixed monolayer of 1 and 2 (1:2 ratio)
1 2
0
20000
40000
60000
80000
350 400 450 500 550 600
em (nm)
cps (s-1
)
ex = 420 nm
ex = 370 nm
Si O
O O
NHO
OO
N
SiOO
O
O
NH
O
N N
OOO O
O
Ae De
Ae DeAe De
Ae De
Ae De
Ae De AeDe
Ae De
h h
e-
e-e-
e-
Electron Transfer
E lectron Injectioninto SemiconductingSubstrate
• Light harvesting event is followed by electron transfer.
• The excited state of secondary donor (De) transfers an electron instead of emitting light.
• Electron acceptor can inject an e- into a semi-conducting substrate.
Energy transfer on surfaces… The next step
1. Light Harvesting & Energy Transfer
h
+
-+ -
S
S'
2. Charge Separation
3. Charge Transport
4. Subsequent Reaction
Light harvesting and electron transfer:the concept
Electroactive core is capable of donating an electron to attached acceptor;this effects charge separation that may be followed by charge transport
and subsequent [email protected]
1. Light Harvesting
2. Energy Transfer
3. Electron Transfer
+ +
N
OO
OO
OO
NN
N
OO
N
OO
N O O
NOO
OO
N O O
O
ON
N
N
OO
NOO
Ru2+
N
N R N N CH3
e-
O
OO
N
N
O
O
O
O
NOON
OO
O
OO
N
N
O
O
O
O
N O ON
OO
S
S
S
S
O
O
O
O
N
N
+
+
e-
Clark, D. C. et. al. J. Am. Chem. Soc. 1997, 119, 10525-10531
N
N
NNR = (CH2)n, n = 2-8
+ +Ru2+
N
N R N N CH3
Light harvesting and electron transfer:the molecules
Why use dendrimers in OLEDs?
Site-isolatedlight emittingchromophore
“Insulating”building block
Hole or electrontransporting moiety
Preorganization of active components and building blocksA collaboration with Prof. M. Thompson, USC
h h
Metal cathodeITO anode
Glass substrate
Dendrimers in single layer OLED’s
O
NO
O
N
N
OO
N
O
OO
O
O
N
O
O
N
N
O
O
N
OO
OO
O
NO
O
N
N
OO
N
O
OO
O
O
N O
O
O
NN
O
A collaboration withProf. M. Thompson, USC
Synthesis of Dye-Labeled Cores
Coumarin 343 (C343)max(abs) = 425 nm
max(em) = 478 nm
N O
OH
O
O
Br
Br
Br
Br
+O
Br
Br
Br
N O
O
O
KHCO318-crown-6
acetoneCH2Cl2,
71%
"pentathiophene" (T5)max(abs) = 425 nmmax(em) = 550 nm
SS S
S SOH
O
C8H17
Br
Br
Br
Br
O
Br
Br
BrS
S SS S
O
C8H17KHCO3
18-crown-62-butanoneCH2Cl2,
64%
Synthesis of HT-Labeled Monodendrons
OHHO
OH
+
K2CO318-crown-6
acetone, 71% O O
OH
NO
O
N
NO
O
N
N
O
N
O
Br
+
OHHO
OH
N
O
N
O
OH
NBr
K2CO318-crown-6
acetone, 79%
TAA2-[G-1]-OH
CBr4, PPh3THF
0 °C - rt83%
PPh3, Br2CH2Cl2
96%
BrOH Br O O N
O O
O
PPTS
CH2Cl296%
(Naph)PhNHPd2(dba)3
DPPF
NaOtBu
toluene, 95° C98%
Synthesis of Reactive Monodendrons
TAA2-[G-1]-OHDCC, DPTSCH2Cl2, 97%
TAA4-[G-2]-OHDCC, DPTSCH2Cl2, 94%
HO
O
OH
O
OH
SiO
SiO
O O
OSi O
Si
HO
O
OH
OTBDMSClimidazole
DMF87%
AcOHH2O
THF82%
N
O
O
N
N
O
O
N
O
O
O
O
OSi
N
O
O
N
O
O
N
OO
N
O
N
O
O
N
O
O
N
OO
N
O
O O
OSi
Synthesis of Fully-Labeled Dendrimers
RO
NO
O
N
N
OO
N
O
OO
O
O
N
O
O
N
N
O
O
N
OO
OO
O
NO
O
N
N
OO
N
O
OO
O
O
N
O
O
N
N
O
O
N
OO
OO
O Si
K2CO3, KF18-crown-6
acetone, THF
RO
Br
Br
Br
SS S
S SO
C8H17
N O
O
OR = 40%
59%R =
Single-Layer OLEDs
ITO
DENDRIMER + PBD
Mg-Ag CATHODE
h
All devices herein were single-layer, twocomponent devices consisting of the fully-labeled dendrimers (for HT and emission) andthe molecular electron transporter, PBD.
1. Spin cast a glyme solution of thecomponents (~ 10 mg/mL) onto a patternedITO substrate. @ 2000 rpm for 40seconds, pinhole free films with an averageellipsometric thickness were ~ 900 Åproduced.
2. A Mg-Ag cathode (9:1) was vapordeposited to a thickness of 500 Å andsubsequently capped with an additional1000 Å of Ag.
3. Typical turn-on voltages for these deviceswere 12-15 V, and most could be driven atvoltages exceeding 30 V.
PBD (electron transport)
NN
O
A collaboration with Prof. M. Thompson, USC
Device Fabrication
glass
ITO
photoresist,insulating strip
Teflontape
Working deviceTop View
Mg:Agwith Ag cap
(+)
(-)
(+)
(-)
light out
Working deviceBottom View
Patterned ITOPrior to vapor deposition
A collaboration with Prof. M. Thompson, USC
0
0.2
0.4
0.6
0.8
1
1.2
300 400 500 600 700 800
wavelength (nm)
inte
nsity
(a.u
.)
PL ( TAA only )
PL ( dendrimer only )
PL ( dendrimer + PBD )EL ( dendrimer + PBD )
TAA = TAA2-[G-1]-OH
Photo- and electroluminescenceof C343 labeled dendrimers
O
NO
O
N
N
OO
N
O
OO
O
O
N
O
O
N
N
O
O
N
OO
OO
O
NO
O
N
N
OO
N
O
OO
O
O
N O
O
O
NN
OPBD =A collaboration with Prof. M. Thompson, USC
0
0.2
0.4
0.6
0.8
1
1.2
300 400 500 600 700 800
wavelength (nm)
inte
nsi
ty (
a.u
.)
PL ( dendrimer only)PL ( dendrimer + PBD)
EL ( dendrimer + PBD)
Photo- and Electroluminescenceof T5 Labeled Dendrimers
O
NO
O
N
N
OO
N
O
OO
O
O
N
O
O
N
N
O
O
N
OO
OO
O
NO
O
N
N
OO
N
O
OO
O
OS
S SS S
O
C8H17
NN
OPBD =
A collaboration with Prof. M. Thompson, USC
Color Tunable OLEDs by Mixing Dendrimers
0
0.2
0.4
0.6
0.8
1
1.2
300 400 500 600 700 800
wavelength (nm)
inte
ns
ity
(a
.u.)
C343 only
C343 : T5
5 : 1
3 : 1
2 : 1
1 : 1
C343T5
O
NO
O
N
N
OO
N
O
OO
O
O
N
O
O
N
N
O
O
N
OO
OO
O
NO
O
N
N
OO
N
O
OO
O
O
N O
O
O
O
NO
O
N
N
OO
N
O
OO
O
O
N
O
O
N
N
O
O
N
OO
OO
O
NO
O
N
N
OO
N
O
OO
O
OS
S SS S
O
C8H17
The smalldendrimer
affords partialsite-isolation
Increasing the size of the dendrimer will increase site isolation of the central lumophore; this should lead to enhanced color
tunability of devices containing mixtures of dendrimers.
Surface (HT)chromophores
Centrallumophore
Interior “insulating”monomer layers
Towards enhanced properties…
Increasing dendrimer size for enhanced site-isolation
DYE
N
O
Ar
Ar
N
O
Ar
Ar
N
O
Ar
Ar
N
O
Ar
Ar
OO
OO
O
N
O
Ar
Ar
NO
Ar
Ar
N
O
Ar
Ar N
O
Ar Ar
OO
O
O
O
O
O
N
O
Ar
Ar N
O
Ar Ar
N
O
Ar
Ar
N OAr
Ar
O
OO
O
DYE O
O
O
O
OO
NArAr
N ArAr
O
O O
NAr
ArN
ArAr
O
O
O
ONAr
Ar
NAr
ArO
O
O
N
Ar
Ar
N
Ar
Ar
O
OO
OO
NArAr
N ArAr
O
O O
NAr Ar
NAr Ar
O
O
O
ONAr
Ar
N
Ar
ArO
O
O
N
Ar
Ar
N
Ar
Ar
O
OO
O
O
N
Ar
Ar
N
ArAr
O
O
O
N Ar
Ar
N
Ar
Ar
OO
O
O
N
Ar
Ar
N
Ar
Ar
O
O
O
N Ar
Ar
NAr
Ar
OO
O
Current status of project
• A new family of fully-labeled dendrimers has been successfully prepared via a modular approach.
• Photoluminescence studies indicate that efficient Forster energy transfer between peripheral and core chromophores occurs within these dendrimers.
• Analogous energy conveyance processes occur in single-layer OLEDs containing these dendrimers and exclusive emission from the core chromophores is observed.
• Site isolation of chromophoric dyes within the dendrimer affords some degree of color tunability.
Porphyrin-core stars as photo- and electroactive polymers
peripheral functionalities(chromophores or solubilizing groups)
porphyrin-core unit(energy sink and catalytic site)
polymer backbone(UV-transparent and redox-stable)
advantages: ease and flexibility of preparation/modification efficient shielding of the core (site isolation) solvent-induced change of shape and size potential: photoresponsive devices and sensors, catalysts
Solar Energy Concentration and Conversion
water-soluble micellar structure solvophobically-driven catalysis
substratesubstrate productproduct
Toward Light-driven Supermolecular Catalysis
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
OO
O
O
OO
O
OOO
O
OOO
O
HN
OO
O
O
O
O
HN
OO
O
O
O
O
O
NH
O
O
O O
O
O O
OOO
HN
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
OO
O
O
OO
O
OOO
O
OOO
O
O
O
NH
OO
O
O
O
O NH
OO
O
O
O
O
O
NH
O
O
O O
O
O O
OOO
HN
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
OO
O
O
OO
O
OO O
O
OO O
O
HN
OO
O
O
O
OHN
OO
O
O
O
O
O
NH
O
O
OO
O
OO
O OO
NH
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
OO
O
O
OO
O
OO O
O
OO O
O
O
O
NH
OO
O
O
O
ONH
OO
O
O
O
O
O
NH
O
O
OO
O
OO
O OO
NH
O
O
Fe NNN N
Myoglobin Mimics - Oxygen Binding in Artificial Enzymes:
see also: Jiang and Aida Chem. Commun. 1996, 1523 (polyether dendrimers)
dioxygen binding affinity: 1500 times higher than hemoglobin (T-state)
Collman, Fu, Zingg, and DiederichChem. Commun. 1997, 193
Encapsulated porphyrins - a retrospective
Pollak, Leon, Fréchet, Maskus, Abruña Chem. Mater. 1998, 10, 30
O
O
O
OO
OO
O
O
O
OO
O
O
O
O
O
OO
O
O
O
O
O
O
O O
O
O
O
Zn
N
N
N
N
O
O
O
OO
O
O
O
O
O
O
O
O
O
O
O
O
OO
O
O
O
O
O
O
O
O
O
O
O
O
O
O
OO
O
O
O
O
O
O
O
O
O
O
O
O
OO
O
O
O
O
O
O
O
O
O
O
O
O
O
O
OO
OO
O
O
O
OO
O
O
O
O
O
OO
O
O
O
O
O
O
O O
O
O
O
Hemeprotein Mimics - Tuning of Redox properties by Isolation of the Core:
see also: Diederich and coworkers Angew. Chem. Int. Ed. Engl. 1994, 33, 1739; Angew. Chem. Int. Ed. Engl. 1995, 34, 2725; Helv. Chim. Acta 1997, 80, 1773
Jin, Aida, Inoue Chem. Commun. 1993, 1260Aida and coworkers Macromolecules 1996, 29, 5236
Encapsulated porphyrins - a retrospective
HO
HO
O
O
OHOH
OO
OH
OH
O
O
OH OH
O O
NH
HN
N
N
OHOH
OO
HO
HO O
O
HOHO
OO
HOHO
OO
HO
HO O
O
OHOH
OO
OH
OHO
ONH
HN
N
NO
OH
OHO
HO
OH
OH
OH
NH
HN
N
N
OH
HO
HO
HO
HO
OH
OHNH
HN
N
NOH
Por
Por
O
OCO2H
1.
DIC, DPTS (THF, CH2Cl2)
2. 2 M H2SO4
(THF, MeOH)
O
O
n
Sn(Oct)2
105 oC
branched initiators star polymers
Synthesis of branched porphyrin-core star polymers
OO
O O
O
O
OH
NNHN HN
n-1
chain ends
repeat units1H NMR Analysis:
Characterization of porphyrin-core star polymers
free base star
coumarin star
core modification (metalation): end-group modification (esterification):
16-armstar
O
OO
O
OO
O
OO
O
OO
O
OO
O
OO
O
OO
O
OO
O
O O
O
OO
O
OO
O
O O
O
OO
O
OO
O
O O
O
O O
O(
O)
O
O(
O)
O
O
O
O(
O)
O
O(
O)
O
)O
(O
O
)O
(O
O
OO
OO
OO
O
)O
(O
O
)O
(O
O
OO
NH
HN
N
N
O O(
O)
O
O(
O)
O
O
)O
(O
O
)O
(O
O
O
)O
(O
O
)O
(O
O
O O(
O)
O
O(
O)
O
O
n/16
n/16
n/16
n/16
n/16
n/16
n/16
n/16
n/16
n/16
n/16n/16
n/16
n/16
n/16
n/16
O O
O
Cl
DMAP(CH2Cl2, pyridine)
O(
O)
O
HO(
O)
O
H
OO
O(
O)
O
HO(
O)
O
H
)O
(O
O
H )O
(O
O
H
OO
OO
OO
O
)O
(O
O
H )O
(O
O
H
OO
N
N
N
N
O O(
O)
O
HO(
O)
O
H
O
)O
(O
O
H )O
(O
O
H
O
)O
(O
O
H )O
(O
O
H
O O(
O)
O
HO(
O)
O
H
O
Zn
n/16
n/16
n/16
n/16
n/16
n/16
n/16
n/16
n/16
n/16
n/16
n/16n/16
n/16
n/16
n/16
Zn(OAc)2
(CHCl3, MeOH)
Modification of porphyrin-core star polymers
300 400 500 600 700
0.0
0.2
0.4
0.6
0.8
1.0 free base star Zn star coumarin star
abso
rban
ce /
a.u.
wavelength / nm
500 550 600 650
x 5
Q
q1 k [Q]
Stern-VolmerAnalysis
enhanced shielding of the core moiety by the polymer backbonedegree of site isolation is a function of the chain length
fluorescence quenching experiments: employing methyl viologen in acetonitrile
Accessibility of the zinc porphyrin core
Förster, Fluoreszenz Organischer Verbindungen, Vandenhoech and Ruprech: Göttingen, 1951
τkΦ ETET 6
22
ETkDA
AD
R
μμ )J(ε
R
kκk A
DA
oD
6
2
ETk
distancespectraloverlap
O
OO
O
OO
O
OO
O
OO
O
OO
O
OO
O
OO
O
OO
O
O O
O
OO
O
OO
O
O O
O
OO
O
OO
O
O O
O
O O
O(
O)
O
O(
O)
O
O
O
O(
O)
O
O(
O)
O
)O
(O
O
)O
(O
O
OO
OO
OO
O
)O
(O
O
)O
(O
O
OO
NH
HN
N
N
O O(
O)
O
O(
O)
O
O
)O
(O
O
)O
(O
O
O
)O
(O
O
)O
(O
O
O O(
O)
O
O(
O)
O
O
n/16
n/16
n/16
n/16
n/16
n/16
n/16
n/16
n/16
n/16
n/16n/16
n/16
n/16
n/16
n/16
300 350 400 450 500 550 600 650
acceptor(Porphyrin)
donors(coumarins)
wavelength / nm
Energy transfer in coumarin-terminatedporphyrin-core star polymers
correlation between energy transfer efficiency and average donor-acceptor distance
quenched donor emission in chloroform:
Influence of the chain length on the energy transfer
solvation-induced change of average donor-acceptor distance:
bad solvent (MeCN)collapsed conformation
good solvent (CHCl3)extended conformation
Influence of the solvent on the energy transfer
The role of concentration - trivial vs. non-trivial energy transfer
Photo and electroactive dendrimers: some conclusions
• Dendrimers are ideally suited for the design of nanometer scale antennas.• Through space energy transfer is very efficient.• Site isolation of chromophores at the core of dendrimer provides for unique behaviors not achievable with ordinary chromophores or polymers.• Energy transfer on surfaces opens avenues for the fabrication of novel photonic devices.• Applications include photonic devices, solar cells, OLEDs, sensors, light-powered reactors, etc.
