5
34
Can. J. Chem. Vol. 87, 2009
Electrochemical measurements
0.053 mmol), and CuI (0.010 g, 0.053 mmol), followed by
5-ethynyl-2,2’-bipyridine (0.230 g, 1.276 mol). The reaction
mixture was refluxed overnight until starting materials had
been consumed, as verified by TLC. The crude product
was passed through a pad of Celite, and the filtrate was
washed with brine (3 ꢀ 50 mL), and then dried with so-
dium sulfate. After concentration, the crude product was
recrystallized from acetone(hot)/water (5:1) to yield 0.258
g of a yellow solid (92% yield). Mp 141 8C. FT-IR (KBr,
Cyclic voltammetry (CV) experiments were performed
with a Bioanalytical Systems Inc. Epsilon electrochemical
workstation. Compounds were dissolved in anhydrous sol-
vent (CH Cl , CH CN, or DMF) and deareated by sparging
2
2
3
with dinitrogen gas for 20 min. Solution concentrations were
approximately 10–3 mol/L in analyte containing 0.1 mol/L
supporting electrolyte (Et NPF ). A typical three-electrode
4
6
setup was used, including a platinum working electrode, Ag
wire pseudoreference electrode, and a platinum wire auxili-
ary electrode. Ferrocene was used in all cases as an internal
standard in our setup and was oxidized at potentials
of +0.50, +0.54, and +0.70 V in CH Cl , CH CN, and
–1
cm ): 3405 (m, br), 3072 (m), 2920 (w), 2205 (m),
1717 (w), 1586 (m), 1541 (m), 1457 (s), 1433 (m),
1366 (m), 1126 (w), 1090 (w), 1019 (m), 854 (m),
1
784 (s), 739 (w), 623 (m). H NMR (300 MHz, CDCl3,
2
2
3
DMF, respectively; all potentials quoted are versus the ferro-
cene oxidation potential. Scan rates for CV experiments
were 100 mV/s.
ppm) d: 8.82 (s, 1H), 8.71 (d, 1H, J = 2 Hz), 8.43 (t, 2H,
J = 3.4 Hz), 7.94 (dd, 1H, J = 4, 1 Hz), 7.85 (td, 1H, J =
4, 1 Hz), 7.62 (d, 1H, J = 1 Hz), 7.35 (m, 2H), 7.26 (d,
1
1
1
H, J = 2 Hz). 13C NMR (600 MHz, CDCl , ppm) d:
3
55.5, 154.7, 151.5, 149.3, 139.2, 137.0, 129.8, 129.4,
25.6, 123.9, 121.7, 121.3, 120.3, 120.3, 88.6, 85.9.
Variable temperature magnetic susceptibility
measurements
Variable temperature magnetic susceptibility measure-
ments were recorded on a superconducting quantum interfer-
ence device (SQUID) magnetometer (Quantum Design
MPMS) with a 5.5 T magnet (temperature range from 2 to
+
MS (FAB+) m/z (%): 262 (M , 100). Anal. calcd. for
C H N S (%): C 73.27, H 3.85, N 10.69; found: C
16 10
2
7
2.96, H 4.07, N 10.35.
3
,3’-Bis(5-ethynyl-2,2’-bipyridine)-2,2’-bithiophene (2)
In a Schlenk flask anhydrous N,N-diisopropylamine
3
00 K) in an external field of 1000 Oe. Samples were care-
fully weighed into gelatin capsules, with empty gelatin cap-
sules above and below to eliminate background contributions
from the gelatin, which were loaded into plastic straws and
attached to the sample transport rod. Diamagnetic correc-
tions were made using Pascal’s constants.
(60 mL) was deaerated by N2 sparging for 30 min, followed
by the successive addition of 5-ethynyl-2,2’-bipyridine
(0.500 g, 2.775 mmol), 3,3’-dibromo-2,2’-bithiophene
(0.408 g, 1.261 mmol), and 3 mol% each of PdCl2(PPh3)2
(
0.58 g, 0.083 mmol) and CuI (0.015 g, 0.083 mmol). The
reaction mixture was refluxed overnight under N . Follow-
Synthesis
2
ing consumption of starting materials (TLC), the reaction
mixture was concentrated and then passed through a Celite
pad. The filtrate was concentrated under reduced pressure,
and the residue was pre-absorbed onto neutral alumina, and
then loaded onto a plug of neutral alumina. Impurities were
separated by elution with hexanes, and the product was
eluted with copious amounts of dichloromethane. The residue
was recrystallized from 4:1 hot chloroform/hexanes to pro-
duce 0.434 g (66%) of a bright yellow solid. Mp >200 8C.
5
-(Trimethylsilylethynyl)-2,2’-bipyridine
The following is a modified version of the procedure re-
5
ported by Ziessel and co-workers. 5-Bromo-2,2’-bipyridine
(1.00 g, 4.385 mmol), PdCl (PPh ) (92 mg, 0.131 mmol,
2 3 2
3
mol%), PPh (69 mg, 0.263 mmol, 6 mol%), and CuI
3
(83 mg, 0.438 mmol, 10 mol%) were added successively to
a two-necked round-bottomed flask, which was flushed with
N . Anhydrous N,N-diisopropylamine (90 mL) was syringed
into the flask, and the mixture was stirred and deareated for
2
–1
FT-IR (KBr, cm ): 3428 (s, br), 3052 (w), 2994 (w),
2918 (w), 2849 (w), 2192 (w), 1630 (w), 1572 (m),
1540 (w), 1458 (s), 1433 (s), 1364 (m), 1243 (w),
1092 (w), 1018 (m), 829 (w), 795 (s), 719 (s), 640 (m).
3
0
0 min. Lastly, ethynyltrimethylsilane (0.579 g, 6.577 mmol,
.82 mL) was added, and the reaction mixture was refluxed
for 20 h. The solvent was evaporated, and the residue was
dissolved in chloroform; pentane was used to precipitate im-
purities that were removed by gravity filtration. The filtrate
was passed through a Celite pad and concentrated. The resi-
due was dissolved in acetone, filtered, and concentrated to af-
ford 1.067 g (96%) yield of the product. Spectroscopic
properties are consistent with those reported by Ziessel and
1
H NMR (300 MHz, CDCl3, ppm) d: 8.89 (s, 2H),
8.72 (d, 2H, J = 2 Hz), 8.45 (t, 4H, J = 4 Hz), 7.99 (dd,
2H, J = 4, 1 Hz), 7.86 (t, 2H, J = 4 Hz), 7.35 (d, 4H, J =
3 Hz), 7.25 (d, 2H, J = 3 Hz). 13C NMR (600 MHz,
CDCl3, ppm) d: 155.4, 154.9, 151.4, 149.3, 139.0, 138.6,
137.0, 130.4, 124.8, 124.0, 121.3, 120.4, 120.3, 119.1,
co-workers.5 1H NMR (300 MHz, CDCl , ppm) d: 8.75 (d,
+
92.4, 89.8. MS (EI+) m/z (%): 183 [(M – C20H11N2S2) ,
3
+
+
1
H, J = 2 Hz), 8.70 (d, 1H, J = 5 Hz), 8.40 (m, 2H), 7.84
50)], 262 [(M – C16H9N2S) , 100], 522 (M , 100). Anal.
calcd. for C32H18N4S2 (%): C 73.55, H 3.47, N 10.73;
found: C 73.27, H 3.69, N 10.68.
(
m, 2H), 7.33 (m, 1H), 0.29 (s, 9H). MS (EI+) m/z (%):
+
2
52 (M , 100).
5-(3-Ethynylthienyl)-2,2’-bipyridine (1)
(1)Co(DBSQ) (3)
2
A solution of 3-bromothiophene (0.100 mL, 1.063 mmol)
in anyhydrous N,N-diisopropylamine (20 mL) was deaer-
A dry Schlenk flask was charged with Co (DBSQ)8
4
(0.114 g, 0.057 mmol) and flushed with N gas. Anhydrous
2
ated by sparging with N gas for 30 min. Five mol% of
toluene (20 mL) was added to the flask, which was
deareated for 20 min by sparging with N2 gas. Solid 1
(0.060 g, 0.229 mmol) was added to the toluene solution of
2
each of the following were successively added to the
flask: PdCl (PPh ) (0.037 g, 0.053 mmol), PPh (0.014 g,
2
3 2
3
Published by NRC Research Press