Javelin-, Hockey Stick-, and Boomerang-Shaped Liquid Crystals
J. Phys. Chem. B, Vol. 105, No. 37, 2001 8859
denser, and argon inlet was charged (under argon atmosphere)
with 1,4-dibromobenzene (5) (4.08 g, 5 mmol) and 6 mol %
tetrakis(triphenylphosphine)palladium(0) (0.69 g, 0.6 mmol). A
volume of 10 mL of dimethoxyethane (DME) was added and
this yellow solution was stirred for 10 min at room temperature.
4-Biphenylboronic acid (2) (2.97 g, 15 mmol) and 10 mL of 2
M Na2CO3 were added and this mixture was refluxed under
argon atmosphere for 24 h. After cooling to room temperature
the reaction mixture was diluted with 50 mL of water and
filtered. The solids were washed with acetone and dichlo-
romethane and vacuum-dried overnight at 60 °C. Pure p-
quinquephenyl (I), 1.49 g (78%), was obtained as colorless
platelets after three recrystallizations from hot 1,2,4-trichlo-
robenzene. IR (KBr) νmax: 1476, 1449, 1399, 1001, 818, 754,
388.1286), confirmed elemental composition: C28H20S. Low-
resolution MS: 388 (M+), 343, 194, 44. λmax (nm) (CH2Cl2)
) 326.0.
2-Quaterphenyl-4-yl-thiophene (PPPPT; II). Slight yellow
platelets from 1,2,4-trichlorobenzene, yield ) 0.043 g (62%);
IR (KBr) νmax: 1479, 1425, 1398, 995, 843, 810, 760, 681 cm-1
.
High-resolution MS: (M+) ) 388.1283 (theoretical 388.1286),
confirmed elemental composition: C28H20S. Low-resolution
MS: 388 (M+), 344, 194, 44. λmax (nm) (CH2Cl2) ) 324.0.
2-Terphenyl-4-yl-5-phenyl-1,3,4-oxadiazole (PPPOP; VII).
Colorless platelets from CH2Cl2, yield ) 0.54 g (72%); IR (KBr)
ν
max: 1610, 1578, 1546, 1481, 1448, 1400, 1082, 1069, 1002,
964, 922, 828, 766, 739 cm-1. Low-resolution MS: 374 (M+),
345, 317, 306, 241, 226, 187, 165, 153. TLC (CH2Cl2), one
spot (silica gel, tr ) 0.1). λmax (nm) (CH2Cl2) ) 311.0.
2-Phenyl-5-terphenyl-4-yl-oxazole (PPPO′P; VIII). Colorless
687 cm-1 36
. High-resolution MS: (M+) ) 382.1725 (theoretical
382.1722), confirmed elemental composition: C30H22. Low-
resolution MS: 382 (M+), 344, 302, 192, 191, 44. λmax (nm)
(CH2Cl2) ) 309.4.
Analytical Data. 2,5-Bisbiphenyl-4-yl-thiophene (PPTPP;
IV). Bright yellow platelets from 1,2,4-trichlorobenzene, yield
) 1.7 g (88%); IR (KBr) νmax: 1481, 1443, 1404, 1132, 937,
835, 795, 758, 714, 685 cm-1. High-resolution MS: (M+) )
388.1286 (theoretical 388.1286), confirmed elemental composi-
tion: C28H20S. Low-resolution MS: (M+): 388 (M+), 194,
44. λmax (nm) (CH2Cl2) ) 356.0.
platelets from CH2Cl2, yield ) 0.18 g (75%); IR (KBr) νmax
:
1541, 1481, 1449, 1401, 1136, 952, 844, 830, 823, 767, 732,
711, 692 cm-1. Low-resolution MS: 373 (M+), 345, 317, 306,
241, 228, 187, 173, 165. TLC (CH2Cl2), one spot (silica gel, tr
) 0.28). λmax (nm) (CH2Cl2) ) 335.1.
2-Terphenyl-4-yl-5-phenyl-oxazole (PPPO′′P; IX). Colorless
platelets from CH2Cl2, yield ) 0.18 g (72%); IR (KBr) νmax
:
.
1480, 1399, 1260, 1098, 1021, 950, 844, 826, 768, 743, cm-1
Low-resolution MS: 373 (M+), 345, 317, 306, 241, 228, 187,
173, 165. TLC (CH2Cl2), one spot (silica gel, tr ) 0.3). λmax
(nm) (CH2Cl2) ) 329.0.
1-Terphenyl-4-yl-3-phenyl benzene (PPPMP; X). Colorless
platelets from 1,2,4-trichlorobenzene, yield ) 0.13 g (54%);
IR (KBr) νmax: 1483, 1470, 1387, 1074, 1001, 824, 795, 752,
692, 610, 486 cm-1. High-resolution MS: (M+) ) 382.1719
(theoretical 382.1722), confirmed elemental composition: C30H22.
Low-resolution MS: 382 (M+), 191. λmax (nm) (CH2Cl2) )
300.0.
1,3-Bisbiphenyl-4-yl-benzene (PPMPP; XI). Colorless plate-
lets from 1,2,4-trichlorobenzene, yield ) 0.28 g (73%); IR (KBr)
ν
max: 1591, 1574, 1472, 1379, 1121, 999, 841, 789, 754, 719,
687, 557, 496 cm-1. High-resolution MS: (M+) ) 382.1729
(theoretical 382.1722), confirmed elemental composition: C30H22.
Low-resolution MS: 382 (M+), 191. λmax (nm) (CH2Cl2) )
285.1.
Representative Procedure for the Synthesis of Asymmetric
Model Compounds. 2-Terphenyl-4-yl-5-phenyl thiophene
(PPPTP; III). A 25 mL two-neck flask equipped with magnetic
stir bar, reflux condenser, and argon inlet was charged (under
argon atmosphere) with 4-bromo-p-terphenyl (4) (0.21 g, 0.68
mmol) and 5 mol % tetrakis(triphenylphosphine)palladium(0)
(0.04 g, 0.03 mmol). A volume of 5 mL of dimethoxyethane
(DME) was added and this yellow solution was stirred for 10
min at room temperature. 2-Phenyl-5-thiopheneboronic acid (12)
(0.14 g, 0.7 mmol) and 5 mL of 2 M Na2CO3 were added and
this mixture was refluxed under argon atmosphere for 24 h.
After cooling to room temperature the reaction mixture was
diluted with 20 mL of water and filtered. The solids were
washed with acetone and dichloromethane and vacuum-dried
overnight at 60 °C. Pure 2-terphenyl-4-yl-5-phenyl thiophene
(III), 0.23 g (89%), was obtained as yellow platelets after three
recrystallizations from hot 1,2,4-trichlorobenzene. IR (KBr)
Acknowledgment. This work was supported by NSF grant
DMR-9971143. The authors thank Dr. Peter S. White for the
X-ray crystallographic studies. Mass spectra were obtained at
the Mass Spectrometry Laboratory for Biotechnology. Partial
funding for the facility was obtained from the North Carolina
Biotechnology Center and the National Science Foundation
Grant 9111391.
Supporting Information Available: Complete crystal-
lographic information for PPTPP (IV) and PPOPP (VII),
including atomic coordinates for all atoms, bond lengths and
angles, anisotropic displacement parameters, and torsion angles.
This material is available free of charge via the Internet at http://
pubs.acs.org.
ν
max: 1483, 1449, 1398, 822, 799, 751, 748, 721, 687 cm-1
.
References and Notes
High-resolution MS: (M+) ) 388.1281 (theoretical 388.1286),
confirmed elemental composition: C28H20S. Low-resolution
MS: 388 (M+), 194, 44. λmax (nm) (CH2Cl2) ) 348.0.
(1) (a) Collings, P. J.; Patel, J. S. Introduction to the Science and
Technology of Liquid Crystals. In Handbook of Liquid Crystal Research;
Collings, P. J., Patel, J. S., Eds.; Oxford University Press: New York, 1997;
Chapter 1. (b) Collings, P. J.; Hird, M. Introduction to Liquid Crystals,
Chemistry and Physics; Taylor and Francis: Bristol, 1997; Chapter 3.
(2) Vorla¨nder, D. Z. Phys. Chem. 1927, 449, 126.
(3) (a) Irvine, P. A.; Wu, D. C.; Flory, P. J. J. Chem. Soc., Faraday
Trans. 1 1984, 80, 1795; (b) Flory, P. J.; Irvine, P. A. J. Chem. Soc., Faraday
Trans. 1 1984, 80, 1807; (c) Irvine, P. A.; Flory, P. J. J. Chem. Soc., Faraday
Trans. 1 1984, 80, 1821.
(4) SPARTAN, version 5.0; Wave function Inc.: Irvine, CA, 1997.
(5) Joule, J. A.; Mills, K.; Smith, G. F. Heterocyclic Chemistry;
Chapman and Hall: New York, 1995; Chapter 5.
(6) Gronowitz, S.; Ho¨rnfeldt, A.-B. Physical Properties of Thiophene
Derivatives. In The Chemistry of Heterocyclic Compounds; Taylor, E. C.,
Ed.; Wiley: New York, 1991; Vol. 44, Part 4, Chapter 1, p 13.
(7) Hedrick, J. L. Polym. Bull. 1991, 25, 543.
Analytical Data. 3-Terphenyl-4-yl-5-phenyl thiophene
(PPPT′P; V). Colorless platelets from 1,2,4-trichlorobenzene,
yield ) 0.23 g (85%); IR (KBr) νmax: 1478, 1447, 1398, 882,
818, 754, 685, 472 cm-1. High-resolution MS: (M+) )
388.1287 (theoretical 388.1286), confirmed elemental composi-
tion: C28H20S. Low-resolution MS: 388 (M+), 194. λmax (nm)
(CH2Cl2) ) 299.0.
2-Terphenyl-4-yl-4-phenyl thiophene (PPPT′′P; VI). Colorless
platelets from 1,2,4-trichlorobenzene, yield ) 0.18 g (69%);
IR (KBr) νmax: 1478, 1447, 1398, 882, 816, 760, 725, 691, 472
cm-1. High-resolution MS: (M+) ) 388.1277 (theoretical