The synthesis and characterisation of a novel thiophene-based liquid crystal exhibiting ferro- ferri- and antiferro-electric phase types David J. Byron,' Lachezar Komitov,b Avtar S. Matham,*' Ian McSherry' and Rqbert C. Wilson' 'Department of Chemistry and Physics,. The Nottingham Trent University Clifton Lane Nottingham UK NG11 8NS bDepartment of Physics Chalmers University of Technology S-412 96 Goteborg Sweden The synthesis and liquid crystal properties of (R)-(-)-4-( 1-methylheptyloxycarbony1)phenyl5-( 4-decyloxyphenyl) thiophene-2- carboxylate is reported.. This material exhibits the following phase types ("C) I 97.4 SA 92.2 Sc* 81.4 ferri 78.8 antiferroelectric 48.6 glass state (characterised by thermal optical microscopy and differential scanning calorimetry). Results from electro-optical investigations for example field-induced transitions temperature and voltage dependence and current and electro-optic response clearly illustrate the presence of the Sc* ferro- ferri- and antiferro-electric phase types.Recently there has been considerable interest in the synthesis and liquid crystal properties of compounds which may exhibit antiferroelectric and ferrielectric in an attempt to promote the development of novel fast-switching electro-optic display devices. Chandani et aL4 reported the occurrence of such phases in MHPOBC 1 1 which are particularly important because they exhibit the phenomenon of tristate switching i.e. the electric field-induced phase transition between the antiferroelectric and ferroelec- tric phases.The structure of the antiferroelectric phase is regarded as a herringbone arrangement of molecules in which the molecules tilt in opposite directions in adjacent layers. Hence the overall spontaneous polarisation of the antiferroelectric phase averages to zero. However the structure of the ferrielectric phase is rather more complex. One possible situation may be such that the molecules in every third or fourth layer are tilted in the opposite direction to those in the remaining layers.. Thus the magnitude of the spontaneous polarisation in the ferri-electric phase is smaller than the one associated with the S,*(ferroelectric) phase. Investigation of the liquid crystal properties of thiophene- based heterocyclic compounds has shown that their properties are dependent on the linearity of the ~ystem.~-~ Hence thio- phene systems are generally lower melting than their analogous 1,4-phenylene counterparts due to a reduced packing efficiency of the molecules.In addition thiophene-based systems possess a strong lateral dipole within their structure which promotes negative dielectric anisotropy thus eliminating the need for lateral cyano and fluoro substituents which tend to increase the molecular breadth and possibly the viscosity of the system. Here we report the synthesis of (R)-(-)-4-( 1-methyl- heptyloxycarbonyl )phenyl 5-( 4-decyloxyphenyl) thiophene-2- carboxylate 2 2 in order to assess the validity of the 'bent' or relatively non-linear 2,5-disubstituted thiophene moiety as a suitable * Author for correspondence.mesogenic core capable of exhibiting the ferro- ferri- and antiferroelectric phase types. Synthesis The preparative route undertaken for the synthesis of (R)-(-)-4-( 1-methylheptyloxycarbony1)phenyl 5-( 4-decyloxypheny1)-thiophene-2-carboxylate 2 is outlined in Scheme 1. The Grignard reagent of 4-bromoanisole 3 was treated with an excess of trimethyl borate at -78 "C to afford the corre- sponding 4-methoxyphenylboronic acid 4. Commercial 2-bromothiophene was cross-coupled* with compound 4 in the presence of a catalytic amount of tetrakis( tripheny1phosphine)- palladium(0) to give 2-( 4-methoxyphenyl) thiophene 5 which was then demethylated with boron tribromide' to yield the intermediate hydroxy compound 6.Alkylation of 6 with 1-bromodecane followed by lithiation in the presence of N,N,N',N'-tetramethylethylenediame (TMEDA) and car-bonation of the intermediate alkoxy compound 7 gave the corresponding 5-( 4-decyloxyphenyl ) thiophene-2-carboxylic acid 8. The desired chiral phenol 13 was prepared uia a series of protection/deprotection" steps on 4-hydroxybenzoic acid 9 followed by esterification with (R)-(-)-octan-2-01. Alternatively compound 13 may also be prepared using analogous methods reported by Chin et al." which involve protection of 4-hydroxybenzoic acid with methyl chloroformate.. The thio- phene-based carboxylic acid 8 was esterified12 with compound 13 in the presence of 1,3-dicyclohexylcarbodiimide(DCC) and 4-dimethylaminopyridine (DMAP) as catalyst to afford the desired (R)-(-)-4-( 1-methylheptyloxycarbony1)phenyl 5-( 4-decyloxyphenyl) thiophene-2-carboxylate 2.Results and Discussion Optical microscopy differential scanning calorimetry and miscibility studies The liquid crystal transition temperatures and thermodynamic data for compound 2 are listed in Table 1. Phase identification was best achieved by compressing the sample between two pre-treated glass substrates (cell gap of approximately 4 pm) which causes the molecules to adopt homeotropic alignment. In this situation the SA phase appears as the homeotropic texture i.e. optically extinct when the sample is placed between crossed polarisers. At the SA-Sc* transition a dramatic textural change is observed whereby the dark homeotropic texture of the S phase gives rise to a blue J.Muter. Chem. 1996 6( 12) 1871-1878 1871 Reagents and conditions i Mg I THF then B(OMe) THF -78 "C; ii 2-bromothiophene Pd(PPh,) 2 M Na,CO reflux; iii BBr CH2C12 -78°C to room temp.; iv C,,H2,Br K2C03 acetone reflux; v TMEDA 1.6~ butyllithium then COz H'; vi BnBr K2C03,acetone reflux; vii aq. EtOH KOH reflux; viii (R)-(-)-octan-2-ol DCC DMAP CH2Cl,; ix H 10% Pd-C EtOH room temp.; x DCC DMAP CH2C12 Table 1 Liquid crystal transition temperatures and thermodynamic data for (R)-(-)-4-( 1 -methylheptyloxycarbonyl)phenyl5-(4-decyloxy-phenyl )thiophene-2-carboxylate 2 T/"C (AH/kJ mol-I)" I-SA SA-S,* S,*-Ferri Ferri-Anti Anti-Glass 97.4 92.2 81.4 78.8 48.6 (5.48) (0.60) (0.014) (-Ib (19.84) For each compound the first row gves transition temperatures and the second row (in parentheses) gives enthalpies of transition on cooling (DSC scan rate 1O'C min-').bThe enthalpy of the transition was too small to be evaluated. petal-like texture characteristic of the Sc* phase i.e. selective light reflection (Plate 1).. The blue coloration is indicative of a helical system which possesses an extremely short pitch (less than 0.3 pm) and a helix axis perpendicular to the sample plates.. The onset of the S,*(ferri) phase culminates in the appearance of an intense shimmering milky-white texture (Plates 2 and 3) associated with a substantial increase in the pitch.Similarly the S,*(ferri j-S,*(antiferro) transition was characterised by the loss of the shimmering texture which was superseded by the appearance of a red-brown (selective reflec- tion) coloration (Plate 4) indicative of the shortening of the pitch when compared to the ferrielectric phase. However 1872 J. Muter. Chem. 1996 6( 12) 1871-1878 Plate 1 Texture of a 4 pm thick sample of 2 with surface treatment for a homeotropic alignment at 85 "C [S,*(ferroelectric) phase] Plate 2 Texture of a 4 pm thick sample of 2 with surface treatment for a homeotropic alignment at 81 "C (just entering in the ferrie- lectric phase) Plate 3 Texture of a 4 pm thick sample of 2 with surface treatment for a homeotropic alignment at 79 "C [S,*(ferrielectrici phase] compared with the ferroelectric phase the pitch in the antiferroelectric phase is 10nger.I~ Study of these phase types by differential scanning calor- imetry (DSC) is difficult because of the small enthalpy associ- ated with the transitions hence some peaks may not be observed.However Fig. 1shows the DSC thermogram (second cool 10°Cmin-l) for compound 2 whereby the enthalpy of the SA-Sc*(ferro) transition is sufficiently large. measurable and corresponds to a first order transition (0.60 kJ mol-I). The peak corresponding to the S,*(ferro)-S,*(ferri) transition is rather small but nevertheless equates to a second-order Plate 4 Texture of a 4 pm thick sample of 2 with surface treatment for a homeotropic alignment at 75 "C [S,*(antiferroelectric) phase] Fig.1 DSC thermogram showing the second cool cycle for (R)-(-)-4-( 1-methylheptyloxycarbonyl )phenyl 5-( 4-decylox yphenyl )thiophene-2-carboxylate 2 recorded at 10"C min-' transition (0.014 kJ mol-'). Although the transition of the ferri-to the antiferro-electric phase was detected by DSC unfortunately it was too small to be evaluated with any great certainty.. This shows the importance of using complementary techniques i.e. thermal optical microscopy coupled with DSC as well as the behaviour of some important physical param-eters during phase identification. The existence of these phases was further confirmed by miscibility studies with (R)-(-)-1-methylheptyl 4'-(4-decyloxy-benzoyloxy)biphenyl-4-carboxylate 14 as the standard mate-rialI4 [transitions ('C) is0 123.7 SA 103.9 Sc* 91.7 ferrielectric 74.5 antiferroelectric 47.2 J*).14 The binary phase diagram for mixtures of compound 2 with the standard 14 is depicted in Fig. 2 and shows continuous miscibility across the entire composition range for the SA Sc* (ferroelectric) S,*(ferrielectric) and S,*(antiferroelectric) phases thus confirming the identification of the phases. Field-induced transitions temperature and voltage dependence and current and electro-optic response The investigations on the electro-optic response apparent tilt angle and spontaneous polarisation were performed using sandwich cells of 2 pm thickness inserted in a special holder allowing application of a unidirectional mechanical shear to the cells..Thus the liquid crystal layer was aligned in a bookshelf geometry with smectic layers perpendicular to the Fig. 2 Miscibility diagram for various compositions of (R)-(-)-4-( 1-methylheptyloxycarbony1)phenyl 5-(4-decyloxyphenyl)thiophene-2-carboxylate 2 with the standard (R)-(-)-1-methylheptyl 4-(4-decyloxybenzoyloxy)biphenyl-4-carboxylate 14 glass substrates. During the measurements the texture of the layer was kept uniform. The field-induced transition either from the ferri-or anti-ferro-electric phase to the ferroelectric phase can also be characterised by an increase in the birefringence of the sample which is linked to changes in the sample colour. Plates 5-8 show clearly the textural changes indicative of the field-induced transition of the antiferroelectric phase to the ferroelectric phase at varying applied voltages.Domains along the smectic layers were formed during this transition. The apparent tilt angle Oapp was measured under a low frequency square voltage (quasi dc conditions) by suitable movement of the turntable of a polarizing microscope i.e. the smectic C cone angle or twice the tilt angle was determined by detecting the position of the two minima in the transmitted light through the sample as it was rotated between crossed polarisers.. The spontaneous polarisation Ps was measured according to the capacitance bridge method.I5 The temperature dependence of the apparent tilt angle Oapp and spontaneous polarisation P is shown in Fig.3 and 4 Plate 5 Field-induced changes of a sample of 2 at 75 "C (antiferroelec-tric phase) where E=O V pm-' J. Mater. Chem. 1996 6(12) 1871-1878 1873 Plate 6 Field-induced changes of a sample of 2 at 75 "C (antiferroelec-tric phase) where E =7 V pm Plate 7 Field-induced changes of a sample of 2 at 75 "C (antiferroelec-tric phase) where E =7 5 V pm Plate 8 Field-induced changes of a sample of 2 at 75 "C (antiferroelec-tric phase) where E=9 V pm-I (ferroelectric state) respectively Fig 3 reveals that the material possesses a large Oapp in the field-induced Sc* phase. The temperature depen- dence of Ps at 60 "C(Fig 4),which has been measured at high enough voltages to be safely in the ferroelectric state during the temperature scan reveals a maximum value of approxi- mately 140 nCcm-' for the spontaneous polarisation In addition Oapp and Ps have rather large values at the Sc*-SA phase transition which coupled with the DSC measurements further suggests the first-order nature of this transition The voltage dependence of the spontaneous polarisation P at different temperatures is shown in Fig 5(u-c) In the Sc*(ferro) phase a very low field is required in order to unwind 1874 J Muter Chem 1996 6( 12) 1871-1878 c -I a? 26 ~~~11111 11~1 11 11 1 11 111 1111~1 ~~ 2055 60 65 70 75 80 85 90 95 TI'C Fig. 3 Temperature dependence of the apparent tilt angle Oapp for 2 at an applied electric field of E =32 V pm 14017--7120 1001 0 0 0 0 0 6o i Fig.4 Temperature dependence of the spontaneous polarisation P for 2 the helix and hence achieve saturation of the P [Fig 5(u)] Monitoring the voltage dependence of P at 79°C [Fig 5(b)] reveals clearly the presence of the ferrielectric phase 1 e at very low values of the applied electric field P increases steadily and then reaches a short-lived plateau (threshold voltage Vc= 9 V) Ps then increases rapidly and reaches a second stable saturation point whereby the sample is in the field-induced ferroelectric state Importantly the value of P at the threshold voltage is about 35 nC cmP2 which is approximately one third of the value corresponding to the P of the field-induced ferroelectric state which is in agreement with the suggested structure of the ferrielectric phase.The threshold behaviour of Ps in the ferrielectric phase is further illustrated in Fig 6 which depicts a characteristic current hysteresis loop at lower and higher voltages with respect to V Similarly Fig 5(c) shows the voltage dependence of P at 60°C (antiferroelectric phase) In this situation at low voltages the P is very small compared to the corresponding value (saturation) at high voltages which is attained following an extremely sharp thresh- old voltage. The rather small value for P at low voltages may be attributed to incomplete relaxation of the antiferroelectric phase . Monitoring of the current and electro-optic response charac- teristics of a liquid crystal material is a useful method which may be used to aid the process of phase assignment As depicted in Fig 7(u,b) compound 2 at 65 "C exhibits a double electro-optical hysteresis loop double current peak and electro- optical response with three states typical of the antiferroelectric state 1 e one field-off stable antiferroelectric state and two field-induced ferroelectric states Each of these peaks are associated with certain changes in the shape of the electro- optical response Fig 8(u-d) show the changes which take place in the current response trace on moving from the antiferro- to the ferro-electric phase via the ferrielectric state Fig.5 Voltage dependence of P at (a) 88°C [short pitch S,*(.ferroelectric) phase] (b) 79 "C (ferrielectric phase) and (c) 60 "C (antiferroelectric phase) Fig. 6 Current hysteresis loops at T=79 "Cfor two different strengths of the applied field less (E= 5 V pm-'),smaller hysteresis loop and higher (E= 13 V pm-') larger hysteresis loop Fig.7 (a)Electro-optical and current response for a 2 pm thick sample in the antiferroelectric phase.. The traces 1,2 and 3 are the applied voltage optic and current response respectively. (b) Electro-optical hysteresis loop for a 2 pm thick sample in the antiferroelectric phase The second current response peak observed in the antiferroelec- tric phase is no longer observed for the ferrielectric phase.. The remaining current response peak appears to be a combination of several peaks which is usually the case when the liquid crystal material is in the ferrielectric phase. Finally in the ferroelectric phase only one peak is present in the current response.Experimental Structural confirmation of the structures of the intermediates and the products was obtained by H NMR spectroscopy (JEOL FX60Q 270 MHz spectrometer) with tetramethylsilane as internal standard and infrared spectroscopy ( Perkin-Elmer FT 1605 spectrophotometer). Mass spectra were determined with an A.E.I. MS 902s spectrometer equipped with a Mass Spectrometry Services 200 console and an INCOS 2300 data system.. Thermal optical microscopy was carried out with a Vickers M75 polarising microscope in conjunction with a Mettler FP52 hot stage and FP5 control unit.. Thermodynamic data were recorded using a Perkin-Elmer DSC7 differential scanning calorimeter.4-Methoxyp henyl boronic acid 4 In an atmosphere of nitrogen commercial 4-bromoanisole 3 (107 g 0.57 mol) in dry tetrahydrofuran (100ml) was added Fig. 8 Electro-optical and current response for 2 pm thick sample of 2 at (a) T=55 C (antiferroelectric phase) (b) T=77 C (near the antiferroelectric-ferrielectric transition) (c) T= 79 8 "C (ferrielectric phase) and (d) T =90 C (ferroelectric phase) when a voltage of Up =65 V and f=2 Hz is applied to the cell dropwise to a stirred mixture of magnesium turnings (15 8 g 0 65 mol) a single crystal of iodine and dry tetrahydrofuran (50 ml) at such a rate that the tetrahydrofuran boiled gently After stirring for an additional 4 h the resultant solution of the Grignard reagent was transferred to a pressure equalising funnel and was then added dropwise to a vigorously stirred solution of trimethyl borate (1 15 mol 129 ml) in dry tetra- hydrofuran (100 ml) maintained at -78 "C.The ensuing white suspension was stirred for a further 1 h at -78 "C and then allowed to warm to room temperature overnight. The reaction mixture was then hydrolysed with 4 M aqueous hydrochloric acid and stirred for 1 h at room temperature and the product was extracted with diethyl ether (3 x 150 ml) dried (MgSO,) and the solvent removed zn uucuo to give an off-white solid The crude product was purified by recrystallisation from water to afford pure 4-methoxyphenylboronic acid 4 (43 65 g 50%) as a white solid mp 201-203 "C 6,(CDCl,-[2H,]DMSO) 4 9 (3H s CH,O) 68-82 (4H m ArH) [B(OH) protons not detected] ~~~~(KBr)/cm-~ 3465 (0-H str) 2966 1604 1374 1340 1247 1171 1111 1020 747 2-(4-Methoxyphenyl) thiophene 5 In a nitrogen atmosphere a solution of 4-methoxyphenyl-boronic acid 4 (5 5 g 0 084 mol) in ethanol (30 ml) was added to a vigorously stirred mixture of 2-bromothiophene (5 1 g 0 031 mol) tetrakis( triphenylphosphine)palladium(O) (0 3 mol%) 2 M aqueous sodium carbonate (30 ml) and ben- zene (30 ml). The reaction mixture was heated under reflux for 16 h cooled extracted into diethyl ether (3 x 100 ml) dried (MgSO,) and the solvent evaporated to yield a brown oil Purification was achieved by column chromatography on silica gel eluting with 3 1 light petroleum (bp 40-60 "C)-chloroform followed by recrystallisation from ethanol to afford the desired 2-( 4-methoxyphenyl) thiophene 5 (54 g 55%) as a white solid mp 107-108 "C (lit ,I7 105-106"C) GH(CDC1,) 3 8 (3H s CH,O) 72 (7H m ArH) vrn,,(KBr)/cm-l 3446 3098 2960 2834 1605 1500 1292 1261 1246 1184 1031 810 705 2-( 4Hydroxyphenyl) thiophene 6 In an inert atmosphere of nitrogen boron tribromide (2 10 ml 0 023 mol) was added dropwise to a stirred solution of 2-(4-methoxypheny1)thiophene 5 (4 9 g 0 015 mol) in dry dichloro- methane (17 ml) at such a rate ensuring that the reaction temperature remained at -78 "C.The reaction mixture was then allowed to warm to room temperature overnight recooled to -78"C and the excess of boron tribromide was then destroyed by the addition of methanol (5 ml).The mixture was acidified (4 M HCl) extracted with diethyl ether (3 x 50 ml) washed with water dried (MgS0,) and the solvent removed zn uacuo. The resulting green solid was purified by 1876 J Mater Chem 1996 6(12) 1871-1878 flash chromatography on silica gel eluting with 1 4 ethyl acetate-light petroleum (bp 40-60 "C),to yield the desired 2- (4-hydroxypheny1)thiophene6 (1 3 g 36%) mp 140-142 "C (lit ,I8 143-145 "C) hH(CDCl3) 7 1 (7H m ArH) 8 7 (lH br s OH disappears on D20 shake) vmax(KBr)/cm-' 3376 (0-H str) 1609 1501 1255 1173 817 688 2-( CDecyloxyphenyl )thiophene 7 Commercial 1-bromodecane (0 0017 mol) was added to a vigorously stirred mixture of 2-(4-hydroxyphenyl) thiophene 6 (040 g 0 0013 mol) anhydrous potassium carbonate (048 g 0 0034 mol) and dry acetone (20 ml).The reaction was heated under reflux for 24 h cooled filtered to remove any insoluble material and the filtrate evaporated to dryness. The crude product was recrystallised from ethanol to yield the desired 2- (4-decyloxyphenyl) thiophene 7 (0 36 g 88%) mp 74-75 "C as a white solid d,(CDCl,) 0 9 (3H t CH,) 12-1 4 (14H m alkyl) 1 8 (2H quintet CH2CH20) 3 9 (2H t CH20) 6 6-7 6 (7H m ArH) v,,,(KBr)/cm ' 2930 2860 1620 1530 1500 1470 1290 1250 1040 850 700 5-(4-Decyloxyphenyl ) thiophene-2-carboxylic acid 8 In an inert atmosphere of nitrogen 1 6 M butyllithium (2 1 ml 0 0032 mol) was added to a stirred solution of tetramethyl- diaminomethane (TMEDA) (034 g 0 003 mol) in dry hexane (50 ml).The resulting mixture was stirred at room temperature for 30 min after which 2-( 4-decyloxyphenyl) thiophene 7 (0 003 mol) in dry hexane (50 ml) was added dropwise and the reaction mixture was heated under reflux for 4 h. The reaction mixture was then cooled poured onto a large excess of solid carbon dioxide and allowed to stand overnight. The resulting slurry was acidified (4 M HCl) extracted with diethyl ether dried (MgSO,) and the solvent removed zn uucuo to yield the crude carboxylic acid 8 which was used for the next step without further purification Benzyl4-benzyloxybenzoate 10 Compound 10 was prepared from benzyl bromide (495g 0 29 mol) commercial 4-hydroxybenzoic acid (20 0 g 0 15 mol) anhydrous potassium carbonate (55 7 g 0 40 mol) and dry acetone (200ml) using the method described pre- viously for the synthesis of 24 4-decyloxyphenyl) thiophene 7 (71%) mp 127-128 "C dH(CDC1,) 5 0-5 3 (4H d 2 x CH20) 69-80 (14H m ArH) v,,,(KBr)/cm-l 3455 2951 2876 1698 1604 1509 1272 1169 1002 857 QBenzyloxybenzoic acid 11 Benzyl 4-benzyloxybenzoate 10 (24 0 g 0 075 mol) potassium hydroxide (38 g 0 68 mol) and 80% aqueous ethanol (300 ml) were heated under reflux for 4 h.The resulting white solid was filtered off acidified (4~ HCl) extracted with diethyl ether (3 x 50 ml) dried (MgSO,) and the solvent was removed zn ljucuu to give a white solid Purification was achieved by crystallisation from ethanol to afford the desired 4-benzyl- oxybenzoic acid 11 (99"/0) mp 188-190°C as a white solid dH(CDC13-[2H,]DMSO) 5 2 (2H s CH20) 7 0-8 0 (9H m ArH) 12 3 (lH br s OH disappears on D20shake) v,,,(KBr) 3463-2867 (0-H str) 1686 (C=O str) 1606 1512 1453 1304 1258 1169 1014 848 782 695.(R)-(-)-1-Me th ylhept y 1 4-benz ylox ybenzoa te 12 4-Benzyloxybenzoic acid 11 (6 0 g 0 026 mol) (R)-(-)-octan- 2-01 (3 4 g 0 026 mol) and 4-dimethylaminopyridine (DMAP) (10 mol%) were dissolved in dry dichloromethane (180 ml) stirred for 5 min at 0 "C and 1,3-dicyclohexylcarbodi1mide (5 4 g 0 026 mol) was then added. The reaction was then stirred for 6 h at room temperature the white insoluble solid produced during this period was filtered off and discarded and the filtrate evaporated to dryness. The crude residue was purified by column chromatography on silica gel eluting with 9 1 chloroform-light petroleum (bp 40-60 "C).The desired fractions were collected and the solvent removed in uucuo to give the desired (R)-(-)-1-methylheptyloxy 4-benzyloxybenzo- ate 12 (%YO) as a clear oil GH(CDCl,) 09 (3H t CH,) 1 2-1 4 (13H m CHCH3 and alkyl) 5 2 (3H m CH20 and CHCH,) 7 5 (9H m ArH) v,,,(thin film)/cm-' 2958 2857 1711 (C=O str) 1605 1276 1250 1102 846 (R)-(-)-4-( 1-Methylheptyloxycarbonyl)phenol 13 (R)-(-)-1-Methylheptyl 4-benzyloxybenzoate 12 (2 5 g 0 007 mol) was added to a stirred suspension of 10% Pd-C in ethanol (100 ml) and hydrogenated at room temperature and atmospheric pressure.After uptake of the appropriate amount of hydrogen (ca 24 h) the catalyst was filtered off and the filtrate was evaporated to dryness to afford the desired (R)-(-)-4-( 1-methylheptyloxycarbony1)phenol13 (89Y0) as a clear oil d,(CDCl,) 1 3 (16H m alkyl) 5 2 (1H m CHCH,) 7 6 (5H m ArH) v,,,(thin film)/cm-' 3356 (0-H str) 2930,2858 1710 (C=O str) 1605 1281 1165 1113 851 (I?)-( -)-4-(1-Methylheptyloxycarbonyl)phenyl5-(4decyloxyphenyl) thiophene-2-carboxylate 2 5-( 4-Decyloxyphenyl )thiophene-2-carboxylic acid 8 (0 00069 rnol) (R)-(-)-4-( I-methylheptyloxycarbony1)phenol13 (0 11 g 0 00069 mol) and 4-dimethylaminopyridine (DMAP) (10 mol%) were dissolved in dry dichloromethane (25 ml) stirred for 5 min at 0 "C and 1,3-dicyclohexylcarbodiimide (0 14 g 0 00069 mol) was then added Treatment as for com- pound 12 gave a crude residue which was purified by column chromatography on silica gel eluting with 3 1 chloroform- light petroleum (bp 40-60 "C) followed by several recrystalli- sations from ethanol to give the desired (R)-(-)-44 1 -methyl- heptyloxycarbony1)phenyl 5-(4-decyloxyphenyl)thiophene-2-carboxylate 2 (0 35 g 86%).The melting point and transition temperatures for compound 2 are listed in Table 1 (Found C 73 01 H 8 15 C36H4805S requires C 72 97 H 8 1lY0) dH(CDC1,) 0 9 (6H t 2 x CH,) 1 2-1 4 (27H m alkyl) 1 75 (2H m CH2CH20) 40 (2H t CH,O) 5 1 (lH m CHCH,) 69-76 (4H dd ArH) 7 15 (4H m ArH) 72 and 785 (2H dd ArH) vmax(KBr)/cm-' 2961 2923 1720 (C=O) 1605 1448 1261 1197 1078 1021 803 Conclusion.From our microscopic thermal and electro-optical investi- gations we can conclude that (R)-(-)-4-( l-methylheptyloxycar- bony1)phenyl 5-( 4-decyloxyphenyl) thiophene-2-carboxylate 2 exhibits the S,*ferro- fern- and antiferro-electric phase types . This is the first known example of a thiophene-based material which exhibits these phase types It is envisaged that other homologues derived from 5-( 4-alkoxyphenyl) thiophene-2- carboxylic acid 9 and (R)-(-)-4-( 1-methylheptyloxycarbony1)-phenol 13 are likely to exhibit similar phase types To this effect we are currently synthesising members of an homologous series of (R)-(-)-4-( 1-methylheptyloxycarbony1)phenyl 5-( 4- decyloxyphenyl)thiophene-2-carboxylates together with more elaborate physical-electro-optical studies.The results of this work will be published in a later communication . 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