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Carboxamidophenylsydnone: a mesoionic mesogen for liquid crystals
February 2000
Materials Letters 42 Ž2000. 280–282 www.elsevier.comrlocatermatlet
Carboxamidophenylsydnone: a mesoionic mesogen for liquid crystals Wing Lai Chan a , Wei Han Zhang b, Yau Shan Szeto a
b,)
Department of Applied Biology and Chemical Technology, The Hong Kong Polytechnic UniÕersity, Kowloon, Hong Kong, People’s Republic of China b Institute of Textiles and Clothing, The Hong Kong Polytechnic UniÕersity, Kowloon, Hong Kong, People’s Republic of China Received 8 July 1999; accepted 4 August 1999
Abstract A new class of liquid crystals based on carboxamidophenylsydnone was synthesized by a simple reaction between 3-Ž4-aminophenyl.sydnone and appropriate aliphatic carboxylic acids in the presence of SiCl 4 . q 2000 Elsevier Science B.V. All rights reserved. Keywords: Mesoionic mesogens; Liquid crystals, Sydnones
Sydnones have been the most extensively studied heterocyclic mesoionic system w1x. Recent studies on their physical properties, spectral properties, and biological activities have been reviewed w2x and the chemistry of sydnones including the preparation of various sydnone derivatives was summarized w3x. Other investigations such as the synthesis of fusedring bissydnones w4,5x and fused-ring sydnones w6,7x were also reported. However, the mesoionic sydnonyl mesogens or mesogens derived from other
)
Corresponding author. Tel.: q852-27666446; fax: q85227731432. E-mail address: [email protected] ŽY.S. Szeto..
mesoionic compounds had not been incorporated into materials with liquid crystal properties. This paper reports the synthesis of the liquid crystal carboxamidophenylsydnone. The mesoionic sydnones were prepared as follows: silicon ŽIV. chloride in anhydrous pyridine was added dropwise to a stirring solution of a carboxylic acid and 3-Ž4-aminophenyl.sydnone in anhydrous pyridine at room temperature. The mixture was stirred overnight and then poured onto crushed ice Ž50 g.. The sticky residue collected was extracted with chloroform Ž3 = 30 ml.. The combined chloroform extract was then washed with dilute HCl Ž0.1 M, 20 ml. and brine Ž50 ml., respectively. The chloroform solution was dried over Na 2 SO4 and then evaporated to dryness. The residue was separated using chromatograph Žsilica gel. with petroleum ether–ethyl acetate as an eluent. Table 1 summarizes
00167-577Xr00r$ - see front matter q 2000 Elsevier Science B.V. All rights reserved. PII: S 0 1 6 7 - 5 7 7 X Ž 9 9 . 0 0 1 9 6 - 2
W.L. Chan et al.r Materials Letters 42 (2000) 280–282
281
Table 1 Reagents used and yields of the products Carboxylic acid
Aminosydnone
Pyridine Žml.
SiCl 4 rpyridine
Productryield Ž%.
Acrylic acid Ž0.26 g, 3.5 mmol. Pentenoic acid Ž0.15 g, 1.5 mmol. Heptenoic acid Ž0.15 g, 1.16 mmol. Undecenoic acid Ž0.20 g, 1.1 mmol. Octanoic acid Ž0.20 g, 1.4 mmol. Thioctic acid Ž0.25 g, 1.2 mmol.
0.53 g, 3.0 mmol 0.23 g, 1.3 mmol 0.17 g, 1.0 mmol 0.16 g, 1.0 mmol 0.21 g, 1.2 mmol 0.19 g, 1.1 mmol
10 5 5 5 5 5
0.51 gr5 ml 0.22 gr5 ml 0.17 gr2 ml 0.17 gr2 ml 0.20 gr2 ml 0.19 gr2 ml
2r61 3r51 4r60 5r70 6r67 7r58
the reaction conditions and reaction yields. The chemical equation of the reaction is indicated below.
The following are the spectroscopic analysis data of the mesoionic sydnones. 3-Ž4-Acrylamido.phenylsydnone Ž2.: 1 H NMR Žacetone-d 6 . d 9.6 Žbr, 1H., 7.9 Žq, 4H., 7.2 Žs, 1H., 5.8–6.2 Žm, 1H., 4.5 Žm, 2H.. Anal. calcd. for C 11 H 9 N3 O 3 : C, 57.14; H, 3.92; N, 18.17. Found: C, 57.01; H, 3.64; N, 17.95. 3-w4Ž4-Pentenamido.phenylxsydnone Ž3.: 1 H NMR Žacetone-d 6 . d 9.5 Žbr, 1H., 7.9 Žq, 4H., 7.2 Žs, 1H., 5.8 Žm, 1H., 4.9 Žm, 2H., 2.2–2.6 Žm, 4H.. Anal. calcd. for C 13 H 13 N3 O 3 : C, 60.23; H, 5.05; N, 16.21; ms Ž259.. Found: C, 59.81; H, 4.80, N, 15.86; ms ŽFAB . Ž260 M q q 1 .. 3-w4-Ž6-Heptenamido . phenylxsydnone Ž4.: 1 H NMR Žacetone-d 6 . d 9.6 Žbr, 1H., 7.95 Žq, 4H., 7.3 Žs, 1H., 5.8 Žm, 1H., 4.95 Žm, 2H., 2.3 Žm, 4H., 1.4–1.8 Žm, 4H.. Anal. calcd. for C 15 H 17 N3 O 3 : C, 62.71; H, 5.96; N, 14.62; ms Ž287.. Found: C, 62.50; H, 5.57; N, 14.78; ms ŽFAB. Ž 2 8 8 M q q 1 . . 3 - w -4 - Ž 1 0 -U n d ecen am id o . phenylxsydnone Ž5.: 1 H NMR ŽCDCl 3 . d 7.8 Žq, 4H., 6.6 Žs, 1H., 5.7 Žm, 1H., 4.9 Žm, 2H., 2.4 Žt, 2H., 1.7 Žm, 2H., 1.4 Žm, 12H.. Anal. calcd. for C 19 H 25 N3 O 3 : C, 66.45; H, 7.34; N, 12.24; ms Ž343.. Found: C, 66.13; H, 7.06; N, 11.95; ms ŽFAB. Ž344 Mqq 1.. 3-Ž4-Octanamido. phenylsydnone Ž6.: 1 H NMR Žacetone-d 6 . d 9.52 Žbr, 1H., 7.9 Žq, 4H., 7.2
Žs, 1H., 2.38 Žt, 2H., 1.2–1.8 Žm, 10H., 0.8 Žt, 3H.. Anal. calcd. for C 16 H 21 N3 O 3 : C, 63.35; H, 6.98; N, 13.85; ms Ž303.. Found: C, 63.00; H, 6.69; N, 13.60; m s Ž FA B . Ž 304 M q q 1 . . 3- w 4- Ž 6,8-D i thiooctanamido.phenylxsydnone Ž7.: 1 H NMR Žacetone-d 6 . d 9.40 Žbr, 1H., 7.8 Žq, 4H., 7.2 Žs, 1H ., 1.4 – 3.6 Žm, 13H .. Anal. calcd. for C 16 H 19 N3 O 3 S 2 : C, 52.58; H, 5.24; N, 11.50; ms Ž365.. Found: C, 52.32; H, 5.00; N, 11.21; ms ŽFAB. Ž366 Mqq 1.. It is generally necessary that organic compounds which display liquid crystal properties when the constituent molecules are elongated and contain a rigid group, a flexible tail, and a polarizable functional group w8x. The advantage of using the sydnone is its polar structure, which would be sensitive towards both electric and magnetic fields and the applications in electro-optic display would be feasible. In fact, large effort has been exerted in the study of organometallic liquid crystal materials at least partly because they can interact strongly with electric fields and because of their unusual electric properties w9,10x. The transition temperatures, Tm Žmelting point. and Tc Žclearing temperature. of the mesoionic compounds were measured using a hot stage polarizing microscope and are summarized in Table 2. All the molecules contain a permanent dipole, which is a Table 2 Transition temperatures of the mesoionic liquid crystals Compound
Tm Ž8C. Tc Ž8C.
Ž2. 3-Ž4-Acrylamido.phenylsydnone Ž3. 3-w4-Ž4-Pentenamido.phenylxsydnone Ž4. 3-w4-Ž6-Heptenamido.phenylxsydnone Ž5. 3-w4-Ž10-Undecenamido.phenylxsydnone Ž6. 3-Ž4-Octanamido.phenylsydnone Ž7. 3-w4-Ž6,8-Dithiooctanamido.phenylxsydnone
190.0 183.5 153.0 122.0 146.0 118.0
– 185.2 157.7 130.0 152.0 132.0
282
W.L. Chan et al.r Materials Letters 42 (2000) 280–282
pre-requisite for materials w11x to have a transitional mesophase. Indeed, all but compound 2 show smectic mesophases. The transition temperature of compounds 3, 4, and 5 of the same homologous series decreases as the number of carbon in the aliphatic chain is increased, which is a relationship usually found in liquid crystal materials w12x. Compound 2 does not show its liquid crystalline transition because its flexible end is too short to hold the molecule in an orderly position against its chaotic motion. In conclusion, we have discussed the synthesis of a novel class of liquid crystals based on carboxamidophenylsydnone. The liquid crystals may be very sensitive to both electric and magnetic fields because of their mesoionic nature.
Acknowledgements We thank the University Grants Committee and the Hong Kong Polytechnic University for their support.
References w1x W.D. Ollis, C.A. Ramsden, Adv. Heterocycl. Chem. 19 Ž1976. 1. w2x C.G. Newton, C.A. Ramsden, Tetrahedron 38 Ž1982. 2965. w3x C.N. Kuo, S.P. Wang, M.Y. Yeh, H.J. Tien, J. Chin. Chem. Soc. ŽTaipei. 39 Ž1992. 641. w4x H.J. Tien, Y.K. Lee, J. Chin. Chem. Soc. ŽTaipei. 35 Ž1988. 63. w5x W.L. Chan, J.A. Waite, Heterocycles 38 Ž1994. 2261. w6x W.C. Burson III, D.R. Jones, K. Turnbull, P.N. Preston, Synthesis 9 Ž1991. 745. w7x W.L. Chan, J.A. Waite, Y.H. Lin, Y.S. Szeto, Heterocycles 38 Ž1994. 2023. w8x D. Demus, Liq. Cryst. 5 Ž1989. 75. w9x H. Adams, N.A. Bailey, D.W. Bruce, R. Dhillon, D.A. Dunmur, S.E. Hunt, E. Lalinde, A.A. Maggs, R. Orr, P. Styring, M.S. Wragg, P.M. Maitlis, Polyhedron 7 Ž1988. 1861. w10x H.X. Zheng, P.J. Carroll, T.M. Swager, Liq. Cryst. 14 Ž1993. 1421. w11x T.H. Chan, L.T.L. Wong, J. Org. Chem. 34 Ž1969. 2766. w12x Y.S. Szeto, C.S. Li, X.G. Wu, W.L. Chan, Polym. Bull. 39 Ž1997. 179.
Materials Letters 42 Ž2000. 280–282 www.elsevier.comrlocatermatlet
Carboxamidophenylsydnone: a mesoionic mesogen for liquid crystals Wing Lai Chan a , Wei Han Zhang b, Yau Shan Szeto a
b,)
Department of Applied Biology and Chemical Technology, The Hong Kong Polytechnic UniÕersity, Kowloon, Hong Kong, People’s Republic of China b Institute of Textiles and Clothing, The Hong Kong Polytechnic UniÕersity, Kowloon, Hong Kong, People’s Republic of China Received 8 July 1999; accepted 4 August 1999
Abstract A new class of liquid crystals based on carboxamidophenylsydnone was synthesized by a simple reaction between 3-Ž4-aminophenyl.sydnone and appropriate aliphatic carboxylic acids in the presence of SiCl 4 . q 2000 Elsevier Science B.V. All rights reserved. Keywords: Mesoionic mesogens; Liquid crystals, Sydnones
Sydnones have been the most extensively studied heterocyclic mesoionic system w1x. Recent studies on their physical properties, spectral properties, and biological activities have been reviewed w2x and the chemistry of sydnones including the preparation of various sydnone derivatives was summarized w3x. Other investigations such as the synthesis of fusedring bissydnones w4,5x and fused-ring sydnones w6,7x were also reported. However, the mesoionic sydnonyl mesogens or mesogens derived from other
)
Corresponding author. Tel.: q852-27666446; fax: q85227731432. E-mail address: [email protected] ŽY.S. Szeto..
mesoionic compounds had not been incorporated into materials with liquid crystal properties. This paper reports the synthesis of the liquid crystal carboxamidophenylsydnone. The mesoionic sydnones were prepared as follows: silicon ŽIV. chloride in anhydrous pyridine was added dropwise to a stirring solution of a carboxylic acid and 3-Ž4-aminophenyl.sydnone in anhydrous pyridine at room temperature. The mixture was stirred overnight and then poured onto crushed ice Ž50 g.. The sticky residue collected was extracted with chloroform Ž3 = 30 ml.. The combined chloroform extract was then washed with dilute HCl Ž0.1 M, 20 ml. and brine Ž50 ml., respectively. The chloroform solution was dried over Na 2 SO4 and then evaporated to dryness. The residue was separated using chromatograph Žsilica gel. with petroleum ether–ethyl acetate as an eluent. Table 1 summarizes
00167-577Xr00r$ - see front matter q 2000 Elsevier Science B.V. All rights reserved. PII: S 0 1 6 7 - 5 7 7 X Ž 9 9 . 0 0 1 9 6 - 2
W.L. Chan et al.r Materials Letters 42 (2000) 280–282
281
Table 1 Reagents used and yields of the products Carboxylic acid
Aminosydnone
Pyridine Žml.
SiCl 4 rpyridine
Productryield Ž%.
Acrylic acid Ž0.26 g, 3.5 mmol. Pentenoic acid Ž0.15 g, 1.5 mmol. Heptenoic acid Ž0.15 g, 1.16 mmol. Undecenoic acid Ž0.20 g, 1.1 mmol. Octanoic acid Ž0.20 g, 1.4 mmol. Thioctic acid Ž0.25 g, 1.2 mmol.
0.53 g, 3.0 mmol 0.23 g, 1.3 mmol 0.17 g, 1.0 mmol 0.16 g, 1.0 mmol 0.21 g, 1.2 mmol 0.19 g, 1.1 mmol
10 5 5 5 5 5
0.51 gr5 ml 0.22 gr5 ml 0.17 gr2 ml 0.17 gr2 ml 0.20 gr2 ml 0.19 gr2 ml
2r61 3r51 4r60 5r70 6r67 7r58
the reaction conditions and reaction yields. The chemical equation of the reaction is indicated below.
The following are the spectroscopic analysis data of the mesoionic sydnones. 3-Ž4-Acrylamido.phenylsydnone Ž2.: 1 H NMR Žacetone-d 6 . d 9.6 Žbr, 1H., 7.9 Žq, 4H., 7.2 Žs, 1H., 5.8–6.2 Žm, 1H., 4.5 Žm, 2H.. Anal. calcd. for C 11 H 9 N3 O 3 : C, 57.14; H, 3.92; N, 18.17. Found: C, 57.01; H, 3.64; N, 17.95. 3-w4Ž4-Pentenamido.phenylxsydnone Ž3.: 1 H NMR Žacetone-d 6 . d 9.5 Žbr, 1H., 7.9 Žq, 4H., 7.2 Žs, 1H., 5.8 Žm, 1H., 4.9 Žm, 2H., 2.2–2.6 Žm, 4H.. Anal. calcd. for C 13 H 13 N3 O 3 : C, 60.23; H, 5.05; N, 16.21; ms Ž259.. Found: C, 59.81; H, 4.80, N, 15.86; ms ŽFAB . Ž260 M q q 1 .. 3-w4-Ž6-Heptenamido . phenylxsydnone Ž4.: 1 H NMR Žacetone-d 6 . d 9.6 Žbr, 1H., 7.95 Žq, 4H., 7.3 Žs, 1H., 5.8 Žm, 1H., 4.95 Žm, 2H., 2.3 Žm, 4H., 1.4–1.8 Žm, 4H.. Anal. calcd. for C 15 H 17 N3 O 3 : C, 62.71; H, 5.96; N, 14.62; ms Ž287.. Found: C, 62.50; H, 5.57; N, 14.78; ms ŽFAB. Ž 2 8 8 M q q 1 . . 3 - w -4 - Ž 1 0 -U n d ecen am id o . phenylxsydnone Ž5.: 1 H NMR ŽCDCl 3 . d 7.8 Žq, 4H., 6.6 Žs, 1H., 5.7 Žm, 1H., 4.9 Žm, 2H., 2.4 Žt, 2H., 1.7 Žm, 2H., 1.4 Žm, 12H.. Anal. calcd. for C 19 H 25 N3 O 3 : C, 66.45; H, 7.34; N, 12.24; ms Ž343.. Found: C, 66.13; H, 7.06; N, 11.95; ms ŽFAB. Ž344 Mqq 1.. 3-Ž4-Octanamido. phenylsydnone Ž6.: 1 H NMR Žacetone-d 6 . d 9.52 Žbr, 1H., 7.9 Žq, 4H., 7.2
Žs, 1H., 2.38 Žt, 2H., 1.2–1.8 Žm, 10H., 0.8 Žt, 3H.. Anal. calcd. for C 16 H 21 N3 O 3 : C, 63.35; H, 6.98; N, 13.85; ms Ž303.. Found: C, 63.00; H, 6.69; N, 13.60; m s Ž FA B . Ž 304 M q q 1 . . 3- w 4- Ž 6,8-D i thiooctanamido.phenylxsydnone Ž7.: 1 H NMR Žacetone-d 6 . d 9.40 Žbr, 1H., 7.8 Žq, 4H., 7.2 Žs, 1H ., 1.4 – 3.6 Žm, 13H .. Anal. calcd. for C 16 H 19 N3 O 3 S 2 : C, 52.58; H, 5.24; N, 11.50; ms Ž365.. Found: C, 52.32; H, 5.00; N, 11.21; ms ŽFAB. Ž366 Mqq 1.. It is generally necessary that organic compounds which display liquid crystal properties when the constituent molecules are elongated and contain a rigid group, a flexible tail, and a polarizable functional group w8x. The advantage of using the sydnone is its polar structure, which would be sensitive towards both electric and magnetic fields and the applications in electro-optic display would be feasible. In fact, large effort has been exerted in the study of organometallic liquid crystal materials at least partly because they can interact strongly with electric fields and because of their unusual electric properties w9,10x. The transition temperatures, Tm Žmelting point. and Tc Žclearing temperature. of the mesoionic compounds were measured using a hot stage polarizing microscope and are summarized in Table 2. All the molecules contain a permanent dipole, which is a Table 2 Transition temperatures of the mesoionic liquid crystals Compound
Tm Ž8C. Tc Ž8C.
Ž2. 3-Ž4-Acrylamido.phenylsydnone Ž3. 3-w4-Ž4-Pentenamido.phenylxsydnone Ž4. 3-w4-Ž6-Heptenamido.phenylxsydnone Ž5. 3-w4-Ž10-Undecenamido.phenylxsydnone Ž6. 3-Ž4-Octanamido.phenylsydnone Ž7. 3-w4-Ž6,8-Dithiooctanamido.phenylxsydnone
190.0 183.5 153.0 122.0 146.0 118.0
– 185.2 157.7 130.0 152.0 132.0
282
W.L. Chan et al.r Materials Letters 42 (2000) 280–282
pre-requisite for materials w11x to have a transitional mesophase. Indeed, all but compound 2 show smectic mesophases. The transition temperature of compounds 3, 4, and 5 of the same homologous series decreases as the number of carbon in the aliphatic chain is increased, which is a relationship usually found in liquid crystal materials w12x. Compound 2 does not show its liquid crystalline transition because its flexible end is too short to hold the molecule in an orderly position against its chaotic motion. In conclusion, we have discussed the synthesis of a novel class of liquid crystals based on carboxamidophenylsydnone. The liquid crystals may be very sensitive to both electric and magnetic fields because of their mesoionic nature.
Acknowledgements We thank the University Grants Committee and the Hong Kong Polytechnic University for their support.
References w1x W.D. Ollis, C.A. Ramsden, Adv. Heterocycl. Chem. 19 Ž1976. 1. w2x C.G. Newton, C.A. Ramsden, Tetrahedron 38 Ž1982. 2965. w3x C.N. Kuo, S.P. Wang, M.Y. Yeh, H.J. Tien, J. Chin. Chem. Soc. ŽTaipei. 39 Ž1992. 641. w4x H.J. Tien, Y.K. Lee, J. Chin. Chem. Soc. ŽTaipei. 35 Ž1988. 63. w5x W.L. Chan, J.A. Waite, Heterocycles 38 Ž1994. 2261. w6x W.C. Burson III, D.R. Jones, K. Turnbull, P.N. Preston, Synthesis 9 Ž1991. 745. w7x W.L. Chan, J.A. Waite, Y.H. Lin, Y.S. Szeto, Heterocycles 38 Ž1994. 2023. w8x D. Demus, Liq. Cryst. 5 Ž1989. 75. w9x H. Adams, N.A. Bailey, D.W. Bruce, R. Dhillon, D.A. Dunmur, S.E. Hunt, E. Lalinde, A.A. Maggs, R. Orr, P. Styring, M.S. Wragg, P.M. Maitlis, Polyhedron 7 Ž1988. 1861. w10x H.X. Zheng, P.J. Carroll, T.M. Swager, Liq. Cryst. 14 Ž1993. 1421. w11x T.H. Chan, L.T.L. Wong, J. Org. Chem. 34 Ž1969. 2766. w12x Y.S. Szeto, C.S. Li, X.G. Wu, W.L. Chan, Polym. Bull. 39 Ž1997. 179.