thiophene units stay trans to the central CPS moiety (no disorder
was found in this case) (Fig. 8). Dihedral angles between the rings
are in the range of 161–173◦. The short perpendicular distance of
8 A. Patra and M. Bendikov, J. Mater. Chem., 2010, 20, 422–433.
9 (a) K. Aydemir, S. Tarkuc, A. Durmus, G. E. Gunbas and L. Toppare,
Polymer, 2008, 49, 2029–2032; (b) K. Takimiya, Y. Kunugi, Y. Konda,
N. Niihara and T. Otsubo, J. Am. Chem. Soc., 2004, 126, 5084–5085;
(c) T. Okamoto, K. Kudoh, A. Wakamiya and S. Yamaguchi, Org.
Lett., 2005, 7, 5301–5304; (d) B. Dong, Y. Xing, J. Xu, L. Zheng, J. Hou
and F. Zhao, Electrochim. Acta, 2008, 53, 5745–5751; (e) A. Dadvand,
F. Cicoira, K. Yu. Chernichenko, E. S. Balenkova, R. M. Osuna, F.
Rosei, V. G. Nenajdenko and D. F. Perepichka, Chem. Commun., 2008,
˚
2.94 A between two mean planes of outer thiophene rings from the
adjacent molecules shows efficient p ◊ ◊ ◊ p stacking in 12, which is
˚
considerably shorter than the same in 11 (3.30 A). The C–Br ◊ ◊ ◊ O
interactions in 12 connect the molecules along the crystallographic
c-axis. The incorporation of selenium in the central moiety changes
the bond angle from ~93◦ for 11 (C5-S2-C15 - 92.4(2)) to ~88◦ (C5-
Se1-C15 - 87.7(2)) for 12. The anti-anti conformation in both the
symmetry independent molecules apparently has no influence on
the overall crystal packing in 12 when compared to the syn-anti
and anti-anti in compound 11. Although the structure of 11 has
high R value with some disorder, the structure clearly indicates to
the high preference for planarity in these class of compounds.
˙
¨
¨
5354–5356; (f) M. I. Ozkut, S. Atak, A. M. Onal and A. Cihaner, J.
Mater. Chem., 2011, 21, 5268–5272.
10 (a) M. Heeney, W. Zhang, D. J. Crouch, M. L. Chabinyc, S. Gordeyev,
R. Hamilton, S. J. Higgins, I. McCulloch, P. J. Skabara, D. Sparrowe
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H. Wijsboom, S. S. Zade, M. Li, Y. Sheynin, G. Leitus and M.
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V. Lakshmikantham and M. P. Cava, Org. Lett., 2001, 3, 4283–4285.
11 S. Das and S. S. Zade, Chem. Commun., 2010, 46, 1168–1170.
12 (a) M. Li, Y. Sheynin, A. Patra and M. Bendikov, Chem. Mater., 2009,
21, 2482–2488; (b) M. Li, A. Patra, Y. Sheynin and M. Bendikov, Adv.
Mater., 2009, 21, 1708–1711; (c) A. Patra, Y. H. Wijsboom, G. Leitus
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Conclusion
13 S. S. Zade, N. Zamoshchik and M. Bendikov, Chem.–Eur. J., 2009, 15,
8613–8624.
The paper reports an elegant manner to obtain thiophene and
selenophene capped CPS cooligomers using an efficient synthetic
approach. For comparison, we had synthesized the thiophene
capped CPT cooligomer as well as CPT. All the cooligomers
were polymerized electrochemically. Single crystal XRD and DFT
studies revealed the trimer and polymers are almost planar leading
to highly conjugated systems. Selenophene containing polymers
are having lower band gap than thiophene analogues, though the
thiophene based polymers are having deeper HOMO levels due
to higher onset oxidation potentials, which make these polymers
more resistant against unintentional doping and effective to
be applied in photovoltaic cells. Alternate copolymers of thio-
phene/selenophene (unsubstituted) with CPT/CPS (substituted)
have significantly lower values for HOMO and LUMO levels
compared to that of homopolymers of CPT/CPS.
14 S. Das, P. K. Dutta, S. Panda and S. S. Zade, J. Org. Chem., 2010, 75,
4868–4871.
15 A. Saito, Y. Matano and H. Imahori, Org. Lett., 2010, 12, 2675–2677.
16 A. Maaninen, T. Chivers, M. Parvez, J. Pietika¨inen and R. S. Laitinen,
Inorg. Chem., 1999, 38, 4093–4097.
17 We had experienced a mixture of CPT–TMS2 and CPT after column,
so it was desilylated further to get only CPT. Instead of using 3 N
HCl or usual work up, if reaction mixture was directly loaded on
triethylamine treated silica gel, CPT–TMS2 can be isolated. 1H NMR
(400 MHz, CDCl3) d 3.37 (s, 4H), 3.35 (s, 6H), 2.58 (s, 4H), 0.27 (s,
18H).
18 K. Takahashi and S. Tarutani, Heterocycles, 1996, 43, 1927–1935.
19 Gaussian 03, Revision E.01. M. J. Frisch, G. W. Trucks, H. B. Schlegel,
G. E. Scuseria, M. A. Robb, J. R. Cheeseman, J. A. Montgomery, Jr.,
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Petersson, H. Nakatsuji, M. Hada, M. Ehara, K. Toyota, R. Fukuda,
J. Hasegawa, M. Ishida, T. Nakajima, Y. Honda, O. Kitao, H. Nakai,
M. Klene, X. Li, J. E. Knox, H. P. Hratchian, J. B. Cross, C. Adamo,
J. Jaramillo, R. Gomperts, R. E. Stratmann, O. Yazyev, A. J. Austin,
R. Cammi, C. Pomelli, J. W. Ochterski, P. Y. Ayala, K. Morokuma, G.
A. Voth, P. Salvador, J. J. Dannenberg, V. G. Zakrzewski, S. Dapprich,
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K. Raghavachari, J. B. Foresman, J. V. Ortiz, Q. Cui, A. G. Baboul,
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Acknowledgements
Financial support from DST, India is gratefully acknowledged by
SSZ and CMR. AB acknowledges CSIR for research fellowship.
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