Transcript Ferrocene-capped Thiophene

Suzuki Coupling:
Aqueous and Anhydrous Synthesis of
Ferrocene-Capped Thiophene
Fe
S
Fe
Bill Mitchell
2003-04
Introduction
• Polythiophene
– p-type semiconducting organic polymer
– Tuneable electronic properties
*
S
*
n
Polythiophene
Introduction
• Applications
– Photovoltaics (solar cells)
•
•
•
•
Cheaper
Higher voltage
Activated by visible light
Tuning will improve efficiency
– Transistors, light emitting diodes
• Cheaper
• More efficient
• Smaller
*
S
*
n
Introduction
• Problem
– No cyclic voltammetry
• Polymerization
• Ferrocene
– End-cap for thiophene
– Electrochemically active
Fe
Ferrocene
Introduction
• Short chain vs. long chain
– Solubility
– Yield
– Accuracy
S
Fe
S
n
Fe
Fe
S
S
n
n= 1, 2, 3
n= 3, 4
Short chain
Long chain
Fe
Procedure 1:
Aqueous 2,5-Diferrocenyl-Thiophene
• Suzuki Coupling
– Aqueous
• Highly contaminated
• Low yield
OH
B
2
Fe
OH
Br
+
S
Br
Fe
PdCl 2(dppf)
+ 2 NaOH(aq)
In dimethoxyethane
ref lux 120 hr.
S
Fe
Side Reaction
B
Fe
+
OH
OH
HOH
Fe
+
B(OH)3
Anhydrous Coupling
Organic soluble
– Boronic ester
– Less contamination
– Higher yield
O
B
O
Fe
1-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-ferrocene
Procedure 2:
1-(4,4,5,5-Tetramethyl-1,3,2-Dioxabolan-2-yl)-Ferrocene
(Boronic Ester)
OH
O
B
HO
OH
Fe
B
O
+
HO
in pentane
Fe
+
HOH
PPh3
PPh3
Fe
S
Pd
Procedure 3:
PPh3
PPh3
Anhydrous 2,5-DiferrocenylThiophene
X
PPh3
PPh3
+
Pd
S
Br
X
2 PPh 3
Fe
X = Br,
Fe
PPh3
S
PPh3 Pd
X
Br
PPh3
PPh3
S
Pd
X
O
Br
-
B
Fe
K3PO4 +
In dioxane
Reflux 96-120 hr.
Fe
+
KBr
+
K2PO4
O
B
O
O
Results
Solv ent
Cataly st
5-10 mol%
dependant on scale
Excess Ligand Reducing Agent
Base
equiv alent
equiv alent on cataly st 3 equiav alents on
on cataly st
f ully reduced
boronic ester
Time
Y ield
(starting materials)
THF
dioxane
dioxane
dioxane
dioxane
NiBr2(PPh3)2
PdCl2(dppf )
NiBr2(PPh3)2
NiCl2(dppe)
NiCl2(dppe)
1 PPh3
none
none
2 dppe
2 dppe
2 n-BuLi
2 n-BuLi
2 n-BuLi
.5 n-BuLi
none
potassium
potassium
potassium
potassuim
potassium
72
48
72
44
18
0%
0%
0%
0%
0%
dioxane
dioxane
dioxane
PdCl2(dppf )
(PPh3)4Pd(0) open bottle
(PPh3)4Pd(0) f resh bottle
none
2 PPh3
2 PPh3
.5 n-BuLi
none
none
potassium carbonate
potassium carbonate
potassium carbonate
48 hrs
24 hrs
120 hrs
0% (~100%)
0% (~100%)
2.5% (N/A)
dioxane
dioxane
dioxane
dioxane
dioxane
NiCl2(dppe)
NiCl2(dppe)
PdCl2(dppf )
(PPh3)4Pd(0) f resh bottle
(PPh3)4Pd(0) f resh bottle
2 dppe
2 dppe
none
2 PPh3
2 PPh3
.25 added af ter 20 hr. potassium phosphate
.375 n-BuLi
potassium phosphate
.375 n-BuLi
potassium phosphate
none
potassium phosphate
none
potassium phosphate
44 hrs
120 hrs
44 hrs
96 hrs
96 hrs
0% (90%)
0% (~100%)
0% (~95%)
trace (42%)
5% (69%)
t-butoxide
t-butoxide
t-butoxide
t-butoxide
t-butoxide
hrs
hrs
hrs
hrs
hrs
(~100%)
(~0%)
(~0%)
(~0%)
(~0%)
Results:
Aqueous 2,5-Diferrocenyl-Thiophene
1H
NMR spectrum
250 MHz
Fe
S
Fe
Conclusion
• Synthesize Ferrocene-Capped Thiophene
– Aqueous method
– Chromatography eluent less polar
• 50:50 hexane:dichloromethane
• 70:30 hexane:dichloromethane
Further Research
• Make Derivatives
– Electron donating and withdrawing
– Electrochemical characterization
• Variable temperature
Applications
• Photovoltaics
• Transistors
Suzuki Coupling:
Aqueous and Anhydrous Synthesis of
Ferrocene-Capped Thiophene
Fe
S
Fe
Bill Mitchell
2003-04
Chemical Shift
observed shift (Hz)*106

6
250*10 (Hz)
