TY - JOUR
T1 - Syntheses and properties of graphyne fragments
T2 - Trigonally expanded dehydrobenzo[12]annulenes
AU - Tahara, Kazukuni
AU - Yamamoto, Yuki
AU - Gross, Dustin E.
AU - Kozuma, Hiroyoshi
AU - Arikuma, Yoko
AU - Ohta, Koji
AU - Koizumi, Yoshiko
AU - Gao, Yuan
AU - Shimizu, Yo
AU - Seki, Shu
AU - Kamada, Kenji
AU - Moore, Jeffrey S.
AU - Tobe, Yoshito
PY - 2013/8/19
Y1 - 2013/8/19
N2 - We present herein the synthesis and properties of the largest hitherto unknown graphyne fragment, namely trigonally expanded tetrakis(dehydrobenzo[12] annulene)s (tetrakis-DBAs). Intramolecular three-fold alkyne metathesis reactions of hexakis(arylethynyl)DBAs 9 a and 9 b using Fürstner's Mo catalyst furnished tetrakis-DBAs 8 a and 8 b substituted with tert-butyl or branched alkyl ester groups in moderate and fair yields, respectively, demonstrating that the metathesis reaction of this protocol is a powerful tool for the construction of graphyne fragment backbones. For comparison, hexakis(arylethynyl)DBAs 9 c-g have also been prepared. The one-photon absorption spectrum of tetrakis-DBA 8 a bearing tert-butyl groups revealed a remarkable bathochromic shift of the absorption cut-off (λ cutoff) compared with those of previously reported graphyne fragments due to extended π-conjugation. Moreover, in the two-photon absorption spectrum, 8 a showed a large cross-section for a pure hydrocarbon because of the planar para-phenylene-ethynylene conjugation pathways. Hexakis(arylethynyl)- DBAs 9 c-e and 9 g and tetrakis-DBA 8 b bearing electron-withdrawing groups aggregated in chloroform solutions. Comparison between the free energies of 9 e and 8 b bearing the same substituents revealed the more favorable association of the latter due to stronger π-π interactions between the extended π-cores. Polarized optical microscopy observations, DSC, and XRD measurements showed that 8 b and 9 e with branched alkyl ester groups displayed columnar rectangular mesophases. By the time-resolved microwave conductivity method, the columnar rectangular phase of 8 b was shown to exhibit a moderate charge-carrier mobility of 0.12 cm2 V-1 s-1. These results indicate that large graphyne fragments can serve as good organic semiconductors.
AB - We present herein the synthesis and properties of the largest hitherto unknown graphyne fragment, namely trigonally expanded tetrakis(dehydrobenzo[12] annulene)s (tetrakis-DBAs). Intramolecular three-fold alkyne metathesis reactions of hexakis(arylethynyl)DBAs 9 a and 9 b using Fürstner's Mo catalyst furnished tetrakis-DBAs 8 a and 8 b substituted with tert-butyl or branched alkyl ester groups in moderate and fair yields, respectively, demonstrating that the metathesis reaction of this protocol is a powerful tool for the construction of graphyne fragment backbones. For comparison, hexakis(arylethynyl)DBAs 9 c-g have also been prepared. The one-photon absorption spectrum of tetrakis-DBA 8 a bearing tert-butyl groups revealed a remarkable bathochromic shift of the absorption cut-off (λ cutoff) compared with those of previously reported graphyne fragments due to extended π-conjugation. Moreover, in the two-photon absorption spectrum, 8 a showed a large cross-section for a pure hydrocarbon because of the planar para-phenylene-ethynylene conjugation pathways. Hexakis(arylethynyl)- DBAs 9 c-e and 9 g and tetrakis-DBA 8 b bearing electron-withdrawing groups aggregated in chloroform solutions. Comparison between the free energies of 9 e and 8 b bearing the same substituents revealed the more favorable association of the latter due to stronger π-π interactions between the extended π-cores. Polarized optical microscopy observations, DSC, and XRD measurements showed that 8 b and 9 e with branched alkyl ester groups displayed columnar rectangular mesophases. By the time-resolved microwave conductivity method, the columnar rectangular phase of 8 b was shown to exhibit a moderate charge-carrier mobility of 0.12 cm2 V-1 s-1. These results indicate that large graphyne fragments can serve as good organic semiconductors.
KW - alkynes
KW - dehydrobenzoannulenes
KW - graphyne
KW - metathesis
KW - self-assembly
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U2 - 10.1002/chem.201300838
DO - 10.1002/chem.201300838
M3 - Article
C2 - 23821553
AN - SCOPUS:84882280040
SN - 0947-6539
VL - 19
SP - 11251
EP - 11260
JO - Chemistry - A European Journal
JF - Chemistry - A European Journal
IS - 34
ER -