Synthesis and physical properties of α,ω-bis[Co2(CO)6{μ-η2:η2-C(R)≡C}]oligothiophenes

Article abstract of DOI:10.1016/S0022-328X(00)00003-6

α,ω-Bis[Co₂(CO)₆{μ-η ²:η²-C(R)≡C}]oligothiophene derivatives (6-10), in which two dicobalt hexacarbonyl acetylides are π-conjugated onto both terminals of the oligothiophene, were prepared by the reaction of the

Full text of DOI:10.1016/S0022-328X(00)00003-6

www.elsevier.nl/locate/jorganchem
Journal of Organometallic Chemistry 599 (2000) 232–237
Synthesis and physical properties of
a,v-bis[Co2(CO)6{m-h2:h2-C(R)ꢀC}]oligothiophenes
Taeg Sung Jung a, Joo Hwan Kim b, Eun Kyung Jang a, Dong Hyun Kim a,
Yoon-Bo Shim b, Bongjin Park c, Sung Chul Shin a,*
a Department of Chemistry and Di6ision of Applied Life Science, Gyeongsang National Uni6ersity, Chinju 660-701, South Korea
b Department of Chemistry, Pusan National Uni6ersity, Pusan 609-735, South Korea
c Department of Chemistry, Sunmoon Uni6ersity, Tangjung Myun Kalsanli 100, Asan, Choongnam 336-840, South Korea
Received 9 November 1999; received in revised form 21 December 1999; accepted 24 December 1999
Abstract
a,v-Bis[Co2(CO)6{m-h2:h2-C(R)ꢀC}]oligothiophene derivatives (6–10), in which two dicobalt hexacarbonyl acetylides are
p-conjugated onto both terminals of the oligothiophene, were prepared by the reaction of the a,v-bis(alkynyl)oligothiophenes
(1–5) with Co2(CO)8. The molecular structures of new compounds were identified by spectroscopic methods and elemental
analysis. In cyclic voltammetry of the clusters 6–10, two oligothiophene-based oxidation processes (one for 7) occur between
−0.2 and 1.5 V, and the one reductive process of the metal cluster moieties occurs between 0.0 and −1.6 V, which is not present
for the oligothiophenes (1–5). The silence of the expected electronic communication of the clusters 6–10 may be attributed to the
reduction process followed by fast chemical reactions at ambient temperature. The clusters 6–10 commonly exhibit three
characteristic bands: a moderately intense, high-energy band, strong medium-energy band and weak-low energy band. The
high-energy bands are attributed to the a p–p* localized excitation. The medium- and low-energy bands may be ascribed to the
metal-to-ligand (dCo–pl*igand) charge-transfer transitions of the cluster moiety. © 2000 Elsevier Science S.A. All rights reserved.
Keywords: Cyclic voltammetry; Conducting polymers; Cluster; Oligothiophenes
organo-transition-metal moieties into the oligothio-
phene should provide interesting models that possess
unique properties, being impossible via classical organic
functionalities. Specific properties of such molecular
systems will result primarily from the ability for the
synergistic interaction of the transition-metal d-orbital
with the conjugated p-orbital of the oligothiophene
[5–9]. Limited examples of the oligothiophene-based
organo-transition metals have been reported [3,10–12].
In order to investigate how the organocobalt cluster
unit can modulate the physical properties of the olig-
othiophenes, we have prepared a series of a,v-
bis[Co2(CO)6{m-h2:h2-C(R)ꢀC}]oligothiophene deriva-
tives, in which two dicobalt hexacarbonyl acetylides are
p-conjugated onto both terminals of the oligothio-
phene, and studied their spectroscopic and electrochem-
ical behavior.
1. Introduction
There is currently a widespread interest in thiophene-
based conducting polymers because of their interesting
physicochemical properties and potential applications
to molecular devices [1,2]. Many properties of the poly-
thiophenes have been studied extensively via oligothio-
phenes because they exhibit similar electrochemical
behaviors, and their well-defined molecular structure
can be related directly to the observed properties of the
corresponding polythiophenes [3,4]. A variety of sub-
stituents have been grafted into the oligothiophenes to
tune their physical properties [3,4]. p-Conjugation of
* Corresponding author. Fax: +82-591-7616022.
E-mail address: scshin@nongae.gsnu.ac.kr (S.C. Shin)
0022-328X/00/$ - see front matter © 2000 Elsevier Science S.A. All rights reserved.
PII: S0022-328X(00)00003-6

T.S. Jung et al. / Journal of Organometallic Chemistry 599 (2000) 232–237
233
2. Experimental
thienyl). 13C-NMR: l 14.0, 19.8, 22.4, 31.0, 73.9, 95.3,
124.7, 131.0. IR: 2228 cm−1. MS: m/z 244 [M+].
HRMS: m/z Anal. Calc. for C16H20S, 244.1286; Found,
244.1279%.
2.1. Materials
Reagent grade tetrahydrofuran (THF) was dried and
distilled under nitrogen from sodium benzophenone
ketyl, and diisopropylamine was degassed prior to use.
All other chemicals were purchased from the Aldrich
Chemical Co. and were used as received. Column chro-
matography was performed on Kiesel gel 60 (230–400
mesh). 2,5-Dibromothiophene, 2,5%-dibromobithio-
phene, and 2,5%%-dibromoterthiophene were prepared
according to the known procedures [13].
2.3.2. 2,5-Bis(phenylethynyl)thiophene (2)
The same procedure used with 1 was performed from
2,5-dibromothiophene (2.4 g, 1.2 mmol) and phenyl-
acetylene (2.2 g, 2.3 mmol), affording 1.9 g (67%) of 2
1
as yellow solids. m.p.: 83–83.5°C. H-NMR: l 7.14 (s,
2H, thienyl), 7.32–7.52 (m, 10H, phenyl). 13C-NMR: l
82.9, 94.6, 123.2, 125.2, 129.0, 129.2, 132.0, 132.4. IR:
2197 cm−1. MS: m/z 284 [M+]. HRMS: m/z Anal.
Calc. for C20H12S, 284.0660; Found, 284.0661%.
2.2. Measurements
2.3.3. 2,5%-Bis(1-hexynyl)bithiophene (3)
1
Melting points was uncorrected. H-NMR and 13C-
The same procedure used with 1 was performed from
2,5%-dibromobithiophene (6.48 g, 20 mmol) and 1-
hexyne (6.57 g, 80 mmol), affording 4.2 g ( 64%) of 3 as
yellow solids. m.p.: 33–33.5°C. 1H-NMR: l 0.94 (t,
J=7.3 Hz, 6H, ꢁCH3), 1.44–1.60 (m, 8H, ꢁCH2ꢁ), 2.43
(t, J=7.1 Hz, 4H, ꢀCꢁCH2ꢁ), 6.96 (dd, J=3.8, 4.0 Hz,
4H, thienyl). 13C-NMR: l 13.6 19.5, 22.0, 30.6, 73.6,
96.0, 97.7, 123.4, 131.7, 136.9. IR: 2220 cm−1. MS: m/z
326 [M+]. HRMS: m/z Anal. Calc. for C20H22S2,
326.1163; Found, 326.1158%.
NMR spectra in CDCl3 were recorded on a Brucker
DRX 500 spectrometer using SiMe4 as an internal
standard. Infrared spectra were taken on a Hitachi
270-50 spectrometer with KBr disc and UV–vis absorp-
tion spectra on a Gilford RESPONSETM spectropho-
tometer. Mass spectra and elemental analyses were
performed at the Analytical Center of Gyeongsang
National University. The electrochemical experiments
were performed in CH2Cl2, which was purified and
dried by distillation from CaH2 prior to use. Tetrabuty-
lammonium perchlorate (TBAP) (0.1 M) was used as a
supporting electrolyte; it was recrystallized twice from
ethanol and dried in vacuo at 100°C for 5 days. The
concentration of the solutions of the alkynylated olig-
othiophene and the acetylide clusters was 1.5 mM.
Cyclic voltammetry was performed with a Pine Instru-
ments Bipotentiostat, model AFRDE4. A platinum disc
(2 mm outside diameter) was used as a working elec-
trode, a platinum wire as a counter, and an AgꢀAgCl
wire as a reference electrodes; this was internally cali-
brated versus the chemical redox couple of fer-
roceneꢀferrocenium [14].
2.3.4. 2,5%-Bis(phenylethynyl)bithiophene (4)
The same procedure used with 1 was performed from
2,5%-dibromobithiophene (2.0 g, 6.2 mmol) and phenyl-
acetylene (1.3 g, 12.4 mmol), affording 1.7 g (62%) of 4
1
as yellow solids. m.p.: 164–164.5°C. H-NMR: l 7.13
(dd, J=3.8, 4.0 Hz, 4H, thienyl), 7.34–7.52 (m, 10H,
phenyl). 13C-NMR: l 82.5, 94.6, 122.7, 122.8, 124.0,
128.4, 128.6, 131.4, 132.8, 138.1 IR: 2194 cm−1. MS:
m/z 366 [M+]. HRMS: m/z Anal. Calc. for C24H14S2,
366.0540; Found, 366.0545%.
2.3.5. 2,5%%-Bis(1-hexynyl)terthiophene (5)
The same procedure used with 1 was performed from
2,5%%-dibromoterthiophene (2.0 g, 5 mmol) and 1-hexyne
(0.93 g, 11 mmol), affording 1.5 g (73%) of 5 as yellow
solids. m.p.: 93–93.5°C. 1H-NMR: l 0.95 (t, J=7.3
Hz, 6H, ꢁCH3), 1.45–1.61 (m, 8H, ꢁCH2ꢁ), 2.44 (t,
J=7.1 Hz, 4H, ꢀCꢁCH2ꢁ), 6.97–7.02 (m, 6H, thienyl).
13C-NMR: l 13.6 19.5, 22.1, 30.6, 73.6, 96.1, 123.2,
123.3, 124.5, 131.8, 136.0, 137.0. IR: 2228 cm−1. MS:
m/z 408 [M+]. HRMS: m/z Anal. Calc. for C24H24S3,
408.1040; Found, 408.1035%.
2.3. Preparations
2.3.1. 2,5-Bis(1-hexynyl)thiophene (1)
To a mixture of 2,5-dibromothiophene (4.80 g, 20
mmol), Pd(dppf)Cl2 (0.33 g, 2 mol%), and CuI (114 mg,
3 mol%) in degassed diisopropylamine (300 ml) was
added 1-hexyne (4.93 g, 60 mmol). The reaction mix-
ture was refluxed with stirring for 12 h under N2
atmosphere. Water was poured onto the reaction mix-
ture and extracted with CH2Cl2. The extract was dried
over magnesium sulfate, and the solvent was removed
under reduced pressure. The residue was chro-
matographed on silica gel column using n-hexane to
2.3.6. 2,5-Bis[Co2(CO)6{v-p2:p2-C(C4H9)ꢀC}]thiophene
(6)
To a THF solution (20 ml) of Co2(CO)8 (4.2 mmol)
was added 2,5-bis(1-hexynyl)thiophene (1) (0.49 g, 2.0
mmol) at room temperature (r.t.) under N2 atmosphere,
and after confirmation of the disappearance of the
1
give 3.0 g (61% yield) of 1 as a yellow oil. H-NMR: l
0.93 (t, J=7.3 Hz, 6H, ꢁCH3), 1.43–1.60 (m, 8H,
ꢁCH2ꢁ), 2.41 (t, J=7.1 Hz, 4H, ꢀCꢁCH2ꢁ), 6.90 (s, 2H,

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T.S. Jung et al. / Journal of Organometallic Chemistry 599 (2000) 232–237
starting 1 by TLC ( in most case within 1 h), the solvent
was removed under reduced pressure. The residue was
chromatographed on a silica gel column using n-hexane
to give 1.57 g (96% yield) of 6 as dark-red solids. m.p.:
46–47°C. 1H-NMR: l 1.01 (br, t, 6H, ꢁCH3), 1.55–1.75
(br, m, 8H, ꢁCH2ꢁ), 2.98 (br, t, 4H, ꢁCH2ꢁ), 7.12 (br, s,
2H, thienyl). 13C-NMR: l 13.9, 22.8, 33.7, 34.0, 81.3,
101.2, 129.9, 142.7, 199.3. IR: 2088, 2050, 2026, 2005
cm−1. MS: m/z 816 [M+], 815 [M−1], 787 [M−CO],
759 [M−2CO], 731 [M−3CO], 703 [M−4CO], 677
[M−5CO], 647 [M−6CO], 619 [M−7CO], 591 [M−
8CO], 563 [M−9CO], 535 [M−10CO], 507 [M−
11CO], 562 [M−12CO]. Anal. Calc. for C32H22Co4-
O12S2: C, 42.78; H, 2.47; S, 7.14. Found: C, 43.04; H,
2.26; S, 7.24%.
2.3.9. 2,5%-Bis[Co2(CO)6{v-p2:p2-C(Ph)ꢀC}]bithiophene
(9)
The same procedure as that used for 6 was performed
with 2,5%-bis(phenylethynyl)bithiophene (4) (0.5 g, 1.36
mmol), affording 1.1g (%) of 9 as dark-red solids. m.p.
(dec.): 178°C. 1H-NMR: l 7.13–7.69 (br. m, 14H,
thienyl+phenyl). 13C-NMR: l 81.9, 92.7, 125.4, 128.8,
129.5, 129.6, 130.2, 138.3, 138.5, 142.0, 199.2. IR: 2087,
2052, 2023, 2004 cm−1. MS: m/z 938 [M+], 937 [M−
1], 909 [M−CO], 853 [M−3CO], 825 [M−4CO], 797
[M−5CO], 769 [M−6CO], 741 [M−7CO], 713 [M−
8CO], 657 [M−10CO], 629 [M−11CO]. Anal. Calc.
for C36H14Co4O12S2: C, 46.08; H, 1.50; S, 6.83. Found:
C, 45.81; H, 1.81; S, 7.09%.
11CO],
479
[M−12CO].
Anal.
Calc.
for
C20H20Co4O12S: C, 41.20; H, 2.47; S, 3.93. Found: C,
40.94; H, 2.22; S, 3.81%.
2.3.7. 2,5-Bis[Co2(CO)6{v-p2:p2-C(Ph)ꢀC}]thiophene
(7)
The same procedure as that used for 6 was performed
with 2,5-bis(phenylethynyl)thiophene (2) (0.5 g, 1.76
mmol), affording 1.4 g (96%) of 7 as dark-red solids.
2.3.10. 2,5%%-Bis[Co2(CO)6{v-p2:p2-C(C4H9)ꢀC}]-
terthiophene (10)
1
m.p.: 97–98°C. H-NMR: l 7.26 (br, s, 2H, thiophene),
The same procedure as that used for 6 was performed
with 2,5%%-bis(1-hexynyl)terthiophene (5) (0.6 g, 1.50
mmol), affording 1.3 g (88%) of 10 as dark-red solids.
m.p.: 86–87°C. 1H-NMR: l 1.03 (br. t, 6H, ꢁCH3),
1.56–1.75 (br. m, 8H, ꢁCH2ꢁ), 3.00 (br. t, 4H, ꢁCH2),
7.08–7.14 (br. m, 6H, thienyl). 13C-NMR: l 14.3, 23.3,
34.2, 34.4, 81.6, 101.6, 123.8, 125.0, 129.9, 136.7, 138.3,
141.5, 199.7. IR: 2085, 2046, 2026, 2009 cm−1. MS:
m/z 980 [M+]. Anal. Calc. for C36H24Co4O12S3: C,
44.10; H, 2.47; S, 9.81. Found: C, 43.92; H, 2.30; S,
10.14%.
7.38 (br. m, 10H, phenyl). 13C-NMR: l 81.3, 92.2,
128.2, 129.0, 129.3, 129.9, 137.9, 143.3, 198.8. IR: 2084,
2054, 2030, 1998 cm−1. MS: m/z 856 [M+], 828 [M−
CO], 800 [M−2CO], 772 [M−3CO], 744 [M−4CO],
715 [M−5CO], 687 [M−6CO], 659 [M−7CO], 632
[M−8CO], 604 [M−9CO], 547 [M−10CO], 519
[M−11CO]. Anal. Calc. for C32H12Co4O12S: C, 44.90;
H, 1.41; S, 3.75. Found: C, 45.03; H, 1.33; S, 3.94%.
2.3.8. 2,5%-Bis[Co2(CO)6{v-p2:p2-C(C4H9)ꢀC}]-
bithiophene (8)
The same procedure as that used for 6 was performed
with 2,5%-bis(1-hexynyl)bithiophene (3) (0.5 g, 1.53
mmol), affording 1.3 g (94%) of 8 as dark-red solids.
3. Results and discussion
1
m.p.: 101–102°C. H-NMR: l 1.02 (br. t, 6H, ꢁCH3),
1.56–1.75 (br. m, 8H, ꢁCH2ꢁ), 2.99 (br. t, 4H, ꢁCH2),
7.09–7.13 (br, dd, 4H, ꢁCH2ꢁ). 13C-NMR: l 13.5, 22.5,
33.4, 33.6, 80.8, 100.7, 124.4, 129.2, 137.5, 140.9, 198.9.
IR: 2087, 2052, 2003, 2019 cm−1. MS: m/z 898 [M+],
870 [M−CO], 842 [M−2CO], 814 [M−3CO], 786
[M−4CO], 730 [M−6CO], 702 [M−7CO], 674 [M−
8CO], 646 [M−9CO], 619 [M−10CO], 590 [M−
3.1. Synthesis
The acetylide clusters (6–10) were synthesized in a
two-step procedure involving the preparation of the
alkynylated oligothiophenes (1–5) using the Heck-type
coupling [15] followed by organocobaltization as shown
in Scheme 1. Thus, the oligothiophenes 1–5 were ob-
Scheme 1. Reaction conditions: (i) RꢁCꢀCH, Pd(dppf)Cl2, CuI, diisopropylamine, reflux; (ii) Co2(CO)8, THF, r.t.

T.S. Jung et al. / Journal of Organometallic Chemistry 599 (2000) 232–237
235
Table 1
Cyclic
3.2. Spectroscopy
voltammetry
data
in
CH2Cl2
for
a,v-bis(1-
alkynyl)oligothiophenes (1–5) and a,v-bis[Co2(CO)6{m-h2:h2-
C(R)ꢀC}]oligothiophenes (6–10) a
The IR spectra of the clusters 6–10 exhibit four
characteristic bands (five bands for 6) in the terminal
carbonyl stretching region, as reported previously for
similar acetylide clusters [16]. The CꢀC stretching band
of the oligothiophenes is merged into the strong car-
bonyl peaks of the acetylide clusters. The 1H-NMR
spectra of the clusters 6–10 show line-broadening of all
the peaks due to the quadrupolar relaxation of the
59Co-nuclei [17]. All ring protons of the clusters 6–10
are shifted downfield slightly from those of the corre-
sponding alkynylated oligothiophenes, due to the
strong electron-withdrawing effect of the cobalt car-
bonyl moieties. The shift amount of the alkyl reso-
nances of the clusters 6, 8 and 10 decreases gradually as
they get farther from the cluster moiety. The 13C-NMR
spectra of the clusters 6–10 also show downfield shift
of the resonances and one unique, broad signal due to
the carbonyl groups bound directly to cobalt metal
around 200 ppm, respectively. As generally observed
for metal carbonyl complexes, the mass spectra of the
clusters 6–10 exhibit in addition to the molecular ion,
successive CO losses (except for 10) and a peak consis-
tent with the loss of one hydrogen atom [18–20].
E1p.a (V) b
E2p.a (V) b
Ep.c (V) c
1 d
2 d
3 d
4 d
5 d
6
7
8
9
10
1.67
1.56
1.30
1.31
1.14
0.74
0.87
0.89
0.78
0.72
1.44
1.16
−1.06
−0.97
−1.08
−1.07
−0.96
1.15
0.96
1.28
a Measured at room temperature with a scan rate of 100 mV s−1 in
0.1 M TBAP at a Pt electrode.
b Anodic peak potentials for these irreversible processes.
c Cathodic peak potentials for these irreversible processes.
d No reduction processes were observed this compound between 0
and −1.6 V.
3.3. Electrochemical studies
The cyclic voltammetric (CV) data of the oligothio-
phenes 1–5 and clusters 6–10 are given in Table 1, and
as a typical CV of 7 are presented in Fig. 1. The CVs of
the oligothiophenes 1–3 and 5 in dichloromethane solu-
tion exhibit one highly irreversible oxidation process
(two for 4), respectively. In comparison with previous
reports for other a-capped oligothiophenes, the oxida-
tions are consistent with processes that result in radical
cation for 1–3 and 5, and sequential formation of
radical cation and dication for 4 [11,21–23]. The oxida-
tion potential for the formation of radical cation de-
creases gradually on going from 1 to 3 to 5 in the
hexynyl substituted oligothiophenes and from 2 to 4 in
the phenethynyl substituted those, indicating the de-
crease of the p-conjugation length in serial order.
The clusters 6–10 exhibit two oligothiophene-based
oxidation processes (one for 7) between −0.2 and 1.5
V, and the one reductive process of the metal cluster
moieties between 0.0 and −1.6 V that is not present
for the oligothiophenes 1–5. The systems in which two
transition-metal redox centers are covalently spanned
by p-conjugated organic spacer often undergo an exten-
sive electronic mixing between the metal d-orbitals and
the spacer p-orbitals. Those systems generally produce
two well-resolved waves in their CVs as the result of the
electronic communication between the metal centers
[24–27]. Since the present clusters 6–10 undergo only a
single irreversible reduction process, the redox centers
Fig. 1. Cyclic voltammograms of the cluster 7 in CH2Cl2, 0.1 M
TBAP, at 100 mV s−1 at a Pt electrode.
tained in 61–73% yields by coupling of a,v-dibro-
mooligothiophenes with 1-alkynes in the presence
of [1,1%-bis(diphenylphosphino)ferrocene]dichloropalla-
dium(II)] [Pd(dppf)Cl2] and CuI in diisopropylamine,
respectively. The oligothiophenes 1–5 were treated with
two equivalents of Co2(CO)8 at r.t. in THF within 1 h
to give the clusters 6–10 in nearly quantitative yields,
respectively. In all cases the reactions were monitored
by TLC, showing the disappearance of the starting
oligothiophene. All the clusters 6–10, as dark-red
solids, were purified by chromatography. They are sta-
ble in air as solids, highly soluble in nonpolar organic
solvents and slightly soluble in polar solvents.

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T.S. Jung et al. / Journal of Organometallic Chemistry 599 (2000) 232–237
of clusters appear not to see each other. The silence of
the electronic communication may be attributed to the
reduction process followed by fast chemical reactions:
i.e. an EC mechanism. This is compared with DE° for
the closely related systems [RꢁCꢀCꢁ(R)ꢁCꢀCꢁR]-
[Co2(CO)6]2 (R=Ph, ferrocenyl, (R)=naphthyl etc.)
[12], whose competing EC reactions involving the pri-
mary radical anions are quenched below −80°C and
two distinct reversible couples (electronic communica-
tion between the two equivalent Co2(CO)6 centers) can
be discerned. The result of Ref. [12] suggests that there
might be a possibility to suppress the EC reactions of
the present clusters and observe their electronic com-
munications at very low temperature. However, the
low temperature experiment could not be carried out
because of our facility limitation.
gradually on going from 1 to 3 to 5 in alkynylated
oligothiophenes and from 2 to 4 in phenethynyl substi-
tuted those. The umax values of the lower-energy bands
are significantly red-shifted on going from 1 to 3 to 5
and from 2 to 4 while the high-energy bands nearly
unshifted. The clusters 6–10 commonly exhibit three
characteristic bands; a moderately intense high-energy
band, strong medium-energy band and weak low-en-
ergy band. The high-energy bands are attributed to the
a p–p* localized excitation. The medium- and low-en-
ergy bands may be ascribed to the metal-to-ligand
(dCo–p*ligand) charge transfer transitions of the cluster
moiety. The possibility that the medium-energy bands
come from the p–p* transition is excluded because
their energies are lower than those of the correspond-
ing oligothiophenes 1–5. Since orthogonal incorpora-
tion of the cluster to the CꢀC triple bond vector
partially breaks the p-conjugation, their umax should
blue-shift from those of the alkynylated oligothio-
phenes. The p–p* transitions of the cluster conjugated
systems cannot be identified due to their merging into
3.4. UV–6is absorption studies
The electronic spectral data for the energy maxima
and the absorption coefficients of the oligothiophenes
1–5 and the clusters 6–10 in dichloromethane are
listed in Table 2, together with those of the corre-
sponding oligothiophene for comparison. Absorption
coefficients were obtained from Beer’s law studies and
determined from at least four dilution points. They
basically exhibit a moderately intense high-energy
transition and a very intense lower-energy transition.
These two bands are generally observed for oligothio-
phenes; the high-energy bands are attributed to a p–
p* localized excitation of the heteronucleus while the
broader, lower-energy band is attributed to p–p* tran-
sition of the conjugated p-system [28]. They exhibit
many fine structures whose numbers are decreased
the strong transitions of dCo–p*
.
ligand
Acknowledgements
This work was supported by the Basic Science Re-
search Institute program, Ministry of Education, Ko-
rea, 1995 (Project no. BSRI-96-3441), and KOSEF,
Korea, 1999 (Grant no. 1999-2-122-001-3).
References
[1] J. Roncali, Chem. Rev. 92 (1992) 711.
Table 2
[2] J. Roncali, Chem. Rev. 97 (1997) 173.
UV–vis data for a,v-bis(1-alkynyl)oligothiophenes (1–5) and a,v-
[3] D.D. Graf, K.R. Mann, Inorg. Chem. 36 (1997) 150.
[4] D.D. Graf, R.G. Duan, J.P. Campbell, L.L. Miller, K.R. Mann,
J. Am. Chem. Soc. 119 (1997) 5888.
bis[Co2(CO)6{m-h2:h2-C(R)ꢀC}]oligothiophenes (6–10)
Compounds
umax (nm)
m
CH2Cl2 solutions
[5] T.P. Pollagi, T.C. Stoner, R.F. Dallinger, T.M. Gilbert, M.D.
Hopkins, J. Am. Chem. Soc. 113 (1991) 703.
(103 M−1 cm−1
)
a
[6] J.C. Calabrese, L.-T. Cheng, J.C. Green, S.R. Marder, W. Tam,
J. Am. Chem. Soc. 113 (1991) 7227.
Thiophene
243
Bithiophene
Terthiophene 245 (13)
243 (11)
302 (12)
355 (25)
[7] L.K. Meyers, C. Langhoff, M.E. Thompson, J. Am. Chem. Soc.
114 (1992) 7560.
1
2
3
4
5
6
7
8
9
305 (19)
252 (18)
257 (3)
253 (7)
254 (10)
[8] D.L. Lichtenberger, S.K. Renshaw, R.M. Bullock, J. Am. Chem.
Soc. 115 (1993) 3276.
[9] D.L. Lichtenberger, S.K. Renshaw, A. Wong, C.D. Tagge,
Organometallics 12 (1993) 3522.
[10] D.D. Graf, N.C. Day, K.R. Mann, Inorg. Chem. 34 (1995) 1562.
[11] D.D. Graf, K.R. Mann, Inorg. Chem. 36 (1997) 141.
[12] N. Duffy, J. McAdam, C. Nervi, D. Osella, M. Ravera, B.
Robinson, J. Simpson, Inorg. Chim. Acta 247 (1996) 99.
[13] P. Ba¨uerle, F. Wu¨rthner, G. Go¨tz, F. Effenberger, Synthesis
(1993) 1099.
364 (11)
357 (13)
385 (16)
386 (28)
260 (13) b 377 (4) b
265 (22) b 368 (11)
254 (11) b 403 (8)
274 (18) b 403 (14)
260 (14) b 423 (14)
582 (1)
583 (2)
576 (2)
582 (2)
565 (3)
10
[14] A.J. Bard, I.R. Faulkner, Electrochemical Methods, Fundamen-
tals and Applications, Wiley, New York, 1980.
[15] R.F. Heck, Palladium Reagents in Organic Synthesis, Academic
Press, New York, 1990.
a Reported values of m are not corrected for overlap with other
absorption bands.
b Shoulder.

T.S. Jung et al. / Journal of Organometallic Chemistry 599 (2000) 232–237
237
[16] G. Centini, O. Gambino, R. Rosetti, E. Sappa, J. Organomet.
Chem. 8 (1967) 149.
[17] S. Aime, G. Gervasio, L. Milone, E. Rosenberg, Transition Met.
Chem. 1 (1976) 177.
[18] D.A. Harbourne, F.G.A. Stone, J. Chem. Soc. (A) (1968) 1765.
[19] I.-Y. Jung, Y.-J. Yoon, K.S. Rhee, G.C. Shin, S.C. Shin, Chem.
Lett. (1994) 859.
[23] P. Bauerle, U. Segelbacher, K.-L. Gaudl, D. Huttenlocher, M.
Mehring, Angew. Chem. Int. Ed. Engl. 32 (1993) 76.
[24] J.-M. Lehn, in: A.F. Williams, C. Floriani, A.S. Merbach (Eds.),
Perspectives in Coordination Chemistry, VCH, New York, 1992,
p. 447.
[25] A. Harriman, R. Ziessel, Chem. Commun. (Cambridge) (1996)
1707.
[20] C.A. Meric, D. Xu, S.I. Khan, Organometallics 11 (1992) 412.
[21] Y. Yu, E. Gunic, B. Zinger, L.L. Miller, J. Am. Chem. Soc. 118
(1996) 1013.
[26] N. LeNarvor, L. Toupet, C. Lapinte, J. Am. Chem. Soc. 117
(1995) 7129.
[27] N. LeNarvor, C. Lapinte, Organometallics 14 (1995) 634.
[28] J.N. Murrell, J. Chem. Soc. (1956) 3779.
[22] Y. Yu, E. Gunic, L.L. Miller, Chem. Mater. 7 (1995) 255.
.