Title of Invention	HIGH TEMPERATURE LIQUID CRYSTALLINE AZOXY COMPOUNDS AND METHOD OF PREPARATION
Abstract	The invention particularly relates to a novel 14 member hornolougous series of azoxy compounds and a simple, cheap, and environmentally friendly synthetic methodology employed to reach the same. More specifically, the members of the presently invented series of azoxy compounds exhibit a wide mesophase range. The invention particularly relates to these azoxy compounds as represented hereunder by the Formula 1 and also to a simple and cost-effective manner of its manufacture wherein R represents CH3 to C14H29; a 14 member homologous series of the new azoxy liquid crystalline compounds. The present invention thus favours providing a 14 member set of liquid crystalline compounds having a wide mesophase range that would be stable upto a temperature of 280 °C for wide industrial application and use including formulating substances for display devices which can be operated under extreme conditions such as in deserts and the like.

Title of Invention

HIGH TEMPERATURE LIQUID CRYSTALLINE AZOXY COMPOUNDS AND METHOD OF PREPARATION

Abstract

The invention particularly relates to a novel 14 member hornolougous series of azoxy compounds and a simple, cheap, and environmentally friendly synthetic methodology employed to reach the same. More specifically, the members of the presently invented series of azoxy compounds exhibit a wide mesophase range. The invention particularly relates to these azoxy compounds as represented hereunder by the Formula 1 and also to a simple and cost-effective manner of its manufacture wherein R represents CH3 to C14H29; a 14 member homologous series of the new azoxy liquid crystalline compounds. The present invention thus favours providing a 14 member set of liquid crystalline compounds having a wide mesophase range that would be stable upto a temperature of 280 °C for wide industrial application and use including formulating substances for display devices which can be operated under extreme conditions such as in deserts and the like.

Full Text	FIELD OF THE INVENTION The invention particularly relates to a novel 14 member homolougous series of azoxy compounds and a simple, cheap, and environmentally friendly synthetic methodology employed to reach the same. More specifically, the members of the presently invented series of azoxy compounds exhibit a wide mesophase range. The invention particularly relates to these azoxy compounds as represented hereunder by the Formula I and also to a simple and cost-effective manner of its manufacture wherein R represents CH3 to C14H29; a 14 member homologous series of the new azoxy liquid crystalline compounds. The present invention thus favours providing a 14 member set of liquid crystalline compounds having a wide mesophase range that would be stable upto a temperature of 280 °C for wide industrial application and use including formulating substances for display devices which can be operated under extreme conditions such as in deserts and the like. BACKGROUND ART Aromatic azoxy compounds are key materials for electronic display devices based on their mesomorphic properties. This invention relates to the ester-azoxy compounds and more particularly to the ester-azoxy compounds having a nematic liquid crystal phase. thereby improving liquid crystal display elements including the compositions. Liquid crystal display devices have many advantages over a luminescence-type display. The liquid crystal display unit including the driver circuit is small and flat, can be driven at low voltage by a small power source and provide a visual display which is far superior to the luminescence-type display. In view of these advantages, liquid crystal display devices have become widely used for computer terminals, POS terminals, video displays and the like in place of conventional cathode ray tubes. Liquid crystal materials used in liquid crystal display cells are generally of the nematic type. It is generally known that nematic liquid crystal compounds are characteristic in that the electro-optical effect, such as light-scattering, double refraction and the like, changes greatly under the influence of an electric field. In view of these characteristics, nematic liquid crystals are used widely for liquid crystal display devices based on various display principles. The particular characteristics required of a liquid crystal material in order to be utilized in the above mentioned display principles differ from each other. However, several conditions are required to for all of them. First, the material must be chemically stable, secondly it must be in the nematic state over a wide range of temperature and thirdly, the method of synthesis of such compound should be cost-effective, convenient and environment friendly. There has been a continuing need in the art to achieve such form of liquid crystal materials which would meet the above requirements of the art As regards the angle of mesophase range, it is known that the maximum mesophase range of 47.8 °C is observed for [C6H13-O-Ph-N(O)=N-Ph-0-C6H13] of the closest known azoxy derivative series [R-O-Ph-N(O)=N-Ph-O-R]. It is noteworthy to mention that C2H5-SOC-Ph-N=N(O)-Ph-COS-C2H5 and C7H15-OOC-CH=CH-Ph-N N(O)-Ph- CH=CH-COO-C7H15 from two different azoxy series which show maximum thermal ranges 111.4 °C and 100.5 °C respectively. From the synthesis point of view of these liquid crystalline azoxy compounds, the known synthetic routes to prepare the symmetrical 4,4'-n-dialkyl/aikyloxyazoxybenzene.s are the oxidation of the corresponding 4,4'-n-dialkyl/alkyloxy azobenzenes (Scheme 1). electrochemical reduction of 4-(n-alkyloxybenzoyloxy)-4'-nitrobenzene by electrochemical method (Scheme 2) and oxidation of the 4-n-alkoxy anilines using 30% hydrogen peroxide (Scheme 3). The disadvantages associated with all the above processes are that they suffer from: a) Multiple steps b) Prolonged reaction time c) Multiple products that prevent easy separation It would be clearly apparent from the above that there remain two types of basic- problems associated with the liquid crystalline known azoxy homologues: i) Absence of liquid crystalline azoxy compounds having a wide mesophase range, ii) Absence of simple, cheap and environment friendly synthetic method for the synthesis of such compounds. There thus is a continuous need in the art to provide liquid crystalline azoxy compounds having a wide mesophase range with a relatively cheap synthetic pathway. OBJECTS OF THE INVENTION It is therefore a primary object of this invention to provide for liquid crystalline azoxy compounds having a broad mesomorphic range covering temperatures above and below room temperature. Another object of the present invention is directed to provide for liquid crystalline azoxy compound and liquid crystal composition including the same as a dopant or when used as a base of a liquid crystal material would improve or increase the liquid crystal temperature range or in other words will have the widest range of mesophases at a cost- effective manner of producing the same for wide and diverse applications and end uses. Another object of the invention is to provide cost-effective and easy synthesis liquid crystalline azoxy compounds having a broad mesomorphic range covering temperatures above and below room temperature.. Accordingly, it is an object of the invention to provide novel ester-azoxy compounds having a broad mesomorphic range covering temperatures above and below room temperature. It is another object of the invention to provide for selective members of a new homologous series of liquid crystalline bis-[4-(n-alkyloxybenzoyloxy)phenyl]diazene oxides which are 14 members of the homologous series having carbon numbers 1-14 in the alkoxy chain which would have the widest range of mesophases. It is a further object of the invention to provide the ester azoxy compounds with a high clearing temperature and mesophase stability temperature of 280 °C which is rare for the azoxy derivatives of other homologous series. Still another object of the invention is to provide a synthetic methodology of the novel azoxy compounds of the present invention. Still another object of the invention is to provide a more economic, single step and environment friendly synthetic transformation leading to these novel azoxy compounds. Yet another object of the invention is to provide the novel azoxy compounds which mabe used to formulate mixtures that will be useful to display devices to be operated in extreme temperature conditions such as in desert. Still other objects and advantages of the invention will in part be obvious and in part be apparent from the specification. SUMMARY OF THE INVENTION Thus according to the basic aspect of the invention there is provided a liquid crystalline compound and/or a homologous series of compounds of general Formula 1; [R-O-Ph- COO-Ph-N(O)=N-Ph-OOC-Ph-O-R] which is structurally represented as: wherein R of the alkoxy group has 1 to 14 carbon atoms starting from CH3 to C14H29; a 14 member homologous series identified as Compounds 1-1 to Compound 1-14. Importantly, the present invention is directed to a above new group of azoxy compounds [R-O-Ph-COO-Ph-N(O)=N-Ph-OOC-Ph-O-R] incorporating two additional phenyl rings linked via two ester linkage to the known azoxy core [R-O-Ph-N(O)=N-Ph- O-R] . Preferably, the liquid crystalline compound and/or a homologous series of compounds comprises aromatic azoxy ester and having the required very high thermal stability of upto about 285°C. Advantageously, the liquid crystalline compound and/or a homologous series of compounds of the invention exhibits liquid crystalline behaviour over a wide range of temperature 100 to 150°C. In particular, the above disclosed liquid crystalline compound and/or a homologous series of compounds according to the invention have a maximum thermal range of 168.6 C for which is the Compound I-10-and a minimum thermal range of 85.7°C which is the Compound 1-3. More particularly, the liquid crystalline compound and/or a homologous series of compounds according to the invention include compounds as per Formula-I which include: i) Compounds 1-2 to 1-7 which show nematic phase on melting up to isotropic temperature and on reversal cooling (below isotropic temperature) the nematic phase remains upto crystallization temperature. ii) Compounds 1-9 to 1-13 which show smectic phase followed by nematic phase upto isotropic temperature,the nematic phase enters into smectic phase on reverse cooling and continues upto solidification temperature. iii) Compound 1-14 which shows only nematic phase. It is also identified by way of the present invention that in the the liquid crystalline homologous series of compounds of the invention, the mesogenic behaviour of compound 1-1, the lowest member of the series, is similar to that of compounds 1-9 to I- 13 The mesogenic behaviour of 1-8 is unique within this series, said compound 1-8 showing only nematic phase on heating, but showing nematic phase followed by smectic phase during cooling. In accordance with another aspect of the invention there is provided a process for the manufacture of the liquid crystalline compound of Formula-I comprising: (i) providing 4-(n-alkyloxybenzoyIoxy)-4'-nitrobenzenes;and (ii) converting the said 4-(n-alkyloxybenzoyloxy)-4'-nitrobenzenes to corresponding bis- [4-(n-alkyloxybenzoyloxy)phenyl]diazene oxides [R-O-Ph-COO-Ph-N(O) N-Ph-OOC- Ph-O-R], In the above process for the manufacture of the liquid crystalline compound of Formula-1 the said conversion of said 4-(n-alkyloxybenzoyloxy)-4'-nitrobenzenes to corresponding bis-[4-(n-alkyloxybenzoyloxy)phenyl]diazene oxides [R-O-Ph-COO-Ph-N(O) N-Ph- OOC-Ph-O-R] is done by zinc-ammonium chloride in ethanol-water mixture preferably about 328 to 338 preferably 333K. In accordance with a preferred aspect of the invention in the above process for the manufacture of the liquid crystalline compound of Formula-1 the said ethanol-water ratio is about 8.5:1.5 to 9.5:0.5 preferably 9:1 (v/v). In accordance with yet another aspect of the present invention there is provided a liquid crystal formulation for display devices and the like comprising anyone or more of the homologous series of compounds of general Formula-I; [R-O-Ph-COO-Ph-N(O) N-Ph- OOC-Ph-O-R] which is structurally represented as: wherein R of the alkoxy group has 1 to 14 carbon atoms starting from CH3 to C14H2: a 14 member homologous series identified as Compounds 1-1 to Compound 1-14. Advantageously, the above liquid crystal formulation for display devices and the like is adapted to be stable at extreme temperatures. DETAILED DESCRIPTION OF THE INVENTION Thus according to the basic aspect of the present invention, there is provided a new group of azoxy compound having the general Formula I ; [R-O-Ph-COOPh-N(O) N-Ph- OOC-Ph-O-R] as depicted below by a novel synthetic methodology as outlined in Scheme I: The present invention leads over others in two aspects: i) Mesophase range ii) Synthesis The presently invented series of mesogens exhibit a larger mesophase range compared to the corresponding members of the homologous series of the other azoxy derivatives. The mesophases are stable up to around 280 °C which is rare for the other azoxy derivatives of other homologous series The starting material used in the above synthesis i.e. the 4-(n-alkyloxybenzoyloxy)-4'- nitrobenzene was synthesized following the procedure as shown in Scheme 11 hereunder: The above schemes I and II clearly reveal the advantages residing in the synthesis of this new 14 member homologous series of liquid crystalline bis-[4-(n- alkyloxybenzoyloxy)phenyl]diazene oxides and the merits of such synthetic method as follows: a) Handling is very easy and safe b) Low cost due to cheap reagents like ammonium chloride and zinc duct and also aqueous ethanol as solvent c) Solvent system of ethanol and water mix is environment friendly d) One step conversion e) Single product which is purified by recrystallisation Thus the above invention relates to the provision and synthesis of a new group of azoxy compounds by a simple, cheap and green method and encompassing a wider mesophase range, more specifically exhibiting nematic phase over a wide range of temperature. This group of compounds has a very high potential for wide application based on their wide thermal range of nematic phase. These novel ester-azoxy compounds having the general Formula I; [R-O-Ph-COO-Ph-N(O)=N-Ph-OOC-Ph-O-R] serve better than many prior art compounds with the known azoxy core [R-O-Ph-N(O)=N-Ph-O-R] in terms of possessing a wider mesophase range and a simple synthetic pathway. Preferably, the protocol followed for quantitative testing of the liquid crystalline behaviour of these novel compounds as its end characteristics are through Optical Polarising Microscopy, Differential Scanning Calorimetry and Small Angle Xray Diffraction method. Further, these materials can be used as a base component to develop a wide range of commercial liquid crystal mixture since these materials have a wide range of mesophase. With a high clearing temperature of 280 °C these compounds may be used to formulate mixtures that will be useful for display devices to be operated in extreme temperature conditions such as, in deserts. The details of the invention its objects and advantages are explained hereunder in greater detail in relation to non-limiting exemplary illustrations as per the following Examples: EXAMPLES: Example I: Synthesis of Starting materials: Synthesis of the starting materials, 4-(n-alkyloxybenzoyloxy)-4'-nitroben/ene was done as shown schematically in Scheme 11 above. n-Alkoxybenzoic acids were prepared by usual technique. Other required chemicals viz. 4nitrophenol, dicyclohexylcarbodiimide (DCC), N, N dimethylaminopyridine (DMAP) were purchased from E. Merck Ltd., India and used without further purification. 4-(p-alkyloxybenzoyloxy)-4'-nitrobenzene: All the 4-(n-alkyloxybenzoyIoxy)-4'-nitrobenzenes were synthesized following the same procedure. A mixture of 4-octyloxy benzoic acid (2 g; 7.96 mmol), 4-nitrophenol (1.12 g; 7.96 mmol), dicyclohexylcarbodiimide (DCC) (1.64 g: 7.96 mmol) and N, N- dimethylaminopyridine (0.1 g; 0.79 mmol) in 25 mL of dichloromethane was stirred at room temperature for 12 h. The reaction mixture was filtered off and the solution evaporated under reduced pressure. The solid was crystallized from ethanol. filtered and dried under vacuum. A very pale yellow solid was obtained. (Yield: 2.5 g: 85 %). Example II: Synthesis of bis-[4-(naIkyloxybenzoyloxy)phenyl] diazene oxides For the purpose the synthesis the starting materials, 4-(n-alkyloxybenzoyloxy)-4'- nitrobenzenes, was used as obtained above under Example I as per Scheme II. Ammonium chloride and zinc dust were purchased from E. Merck Ltd., India and were used without further purification. All the bis-[4-(nalkyloxybenzoyloxy)phenyl] diazene oxides were synthesized following the same procedure. As a representative case, the synthesis of bis-[4-(n- octyloxybenzoyloxy)phenyl] diazene oxide is given below. To a solution of 4-(n-octyloxybenzoyloxy)-4'-nitrobenzene (3.71 g; 10 mmol) in a mixture (100 mL) of ethanol and water (9:1 v/v), warmed to 333 °K, ammonium chloride (1.07 g; 20 mmol) was added. Further heating was stopped and zinc powder (1.96 g; 30 mmol) was added to the reaction mixture very slowly over 10 minutes with stirring. The reaction mixture was further stirred for lh. The resulting reaction mixture was diluted with equal volume of cold water and then filtered. The yellow residue was extracted with dichloromethane. Evaporation of the solvent afforded the novel compound of Formula I as very pale yellow solid. The resulting compound was purified by recrystallization from dichloromethane and ethanol (1:5 v/v), (Yield: 1.83 g; 52.80%). (Scheme I) The phase transition temperatures (°C) for bis [4-(n-alkyoxybenzoyloxy)phenyl]diazene oxides (Compounds 1-1 to 1-14) obtained as above were next tested and the results are provided hereunder in Table 1: All the members of this family show thermotropic mesogenic behaviour over a good temperature range, which is wider than that of the corresponding member of bis-(4-alkyloxyphenyl)diazene oxides. 2) Compounds 1-2 to 1-7 show nematic phase on melting up to isotropic temperature. On reversal cooling (below isotropic temperature) the nematic phase remains upto crystallization temperature. 3) Compounds 1-9 to 1-13 show smectic phase followed by nematic phase upto isotropic temperature. The nematic phase enters into smectic phase on reverse cooling and continues upto solidification temperature. 4) Compound 1-14 shows only nematic phase. 5) Interestingly the mesogenic behaviour of compound 1-1, the lowest member of the series, is similar to that of compounds 1-9 to 1-13 6) The mesogenic behaviour of 1-8 is unique within this series. Compound 1-8 shows only nematic phase on heating, but it shows nematic phase followed by smectic phase during cooling. 7) The maximum thermal range is 168.6 °C for 1-10 and the minimum thermal range is 75.8 °C for 1-3. Therefore, the members of this series exhibit very wide range of mesophase. It is thus possible by way of the present invention to provide for the liquid crystalline homologues having a wide mesophase range and also involving a simple , cost-effective and environment friendly synthetic method for the synthesis of such compounds. Advantageously the compounds according to the invention which have a clearing temperature as high as about 280°C would favour its use in display devices especially those required to be operated under extreme conditions such as in desert and favour a wide industrial application in the related field. We claim: 1. A liquid crystalline compound and/or a homologous series of compounds of general Formula-I; [R-O-Ph-COO-Ph-N(O)=N-Ph-OOC-Ph-O-R] which is structurally represented as: wherein R of the alkoxy group has I to 14 carbon atoms starting from CH2, to C14H29; a 14 member homologous series identified as Compounds 1-1 to Compound 1-14.. 2. A liquid crystalline compound and/or a homologous series of compounds according to claim 1 wherein the compound is aromatic azoxy ester. 3. A liquid crystalline compound and/or a homologous series of compounds according to anyone of claims 1 or 2 comprising very high thermal stability of upto about 285°C. 4. A liquid crystalline compound and/or a homologous series of compounds according to anyone of claims 1 to 3 which exhibits liquid crystalline behaviour over a wide range of temperature 100 to 150°C. 5. A liquid crystalline compound and/or a homologous series of compounds according to anyone of claims 1 to 4 having a maximum thermal range of 168.6°C for which is the Compound I-10-and a minimum thermal range of 85.7 C which is the Compound 1-3. 6. A liquid crystalline compound and/or a homologous series of compounds according to anyone of claims 1 to 5 wherein the said i) Compounds 1-2 to 1-7 show nematic phase on melting up to isotropic temperature and on reversal cooling (below isotropic temperature)the nematic phase remains upto crystallization temperature. ii) Compounds 1-9 to 1-13 show smectic phase followed by nematic phase upto isotropic temperature,the nematic phase enters into smectic phase on reverse cooling and continues upto solidification temperature. iii)Compound 1-14 shows only nematic phase. 6. A liquid crystalline compound and/or a homologous series of compounds as claimed in anyone of claims 1 to 5 wherein the mesogenic behaviour of compound 1-1. the lowest member of the series, is similar to that of compounds 1-9 to 1-13 7. A liquid crystalline compound and/or a homologous series of compounds as claimed in anyone of claims 1 to 6 wherein the mesogenic behaviour of 1-8 is unique within this series, said compound 1-8 showing only nematic phase on heating, but showing nematic phase followed by smectic phase during cooling. 8. A process for the manufacture of the liquid crystalline compound of Formula-I as claimed in anyone of claims 1 to 6 comprising: (i) providing 4-(n-alkyloxybenzoyloxy)-4'-nitrobenzenes;and (ii) converting the said 4-(n-alkyloxybenzoyloxy)-4'-nitrobenzenes to corresponding bis- [4-(n-alkyloxybenzoyloxy)phenyl]diazene oxides [R-O-Ph-COO-Ph-N(O) N-Ph-OOC- Ph-O-R]. 9. A process for the manufacture of the liquid crystalline compound of Formula-1 as claimed in claim 7 wherein said conversion of said 4-(n-alkyloxybenzoyloxy)-4'- nitrobenzenes to corresponding bis-[4-(n-alkyloxybenzoyloxy)phenyl]diazene oxides [R- O-Ph-COO-Ph-N(O)=N-Ph-OOC-Ph-O-R] is done by zinc-ammonium chloride in ethanol-water mixture preferably 328 to 338 preferably 333K. 10. A process for the manufacture of the liquid crystalline compound of Formula-I as claimed in anyone of claims 8 or 9 wherein the said ethanol-water ratio is about 8.5:1.5 to 9.5:0.5 preferably 9:1 (v/v). 11. A liquid crystal formulation for display devices and the like comprising anyone or more of the homologous series of compounds of general Formula-l; [R-O-Ph-COO-Ph- N(O)=N-Ph-OOC-Ph-O-R] which is structurally represented as: wherein R of the alkoxy group has 1 to 14 carbon atoms starting from CH; to C14H29; a 14 member homologous series identified as Compounds 1-1 to Compound 1-14. 12. A liquid crystal formulation for display devices and the like as claimed in claim 1 1 which is adapted to be stable at extreme temperatures. 13. A liquid crystalline compound and/or a homologous series of compounds of general Formula-I; [R-O-Ph-COO-Ph-N(O)=N-Ph-OOC-Ph-O-R] substantially as herein described and illustrated with reference to the accompanying examples. The invention particularly relates to a novel 14 member hornolougous series of azoxy compounds and a simple, cheap, and environmentally friendly synthetic methodology employed to reach the same. More specifically, the members of the presently invented series of azoxy compounds exhibit a wide mesophase range. The invention particularly relates to these azoxy compounds as represented hereunder by the Formula 1 and also to a simple and cost-effective manner of its manufacture wherein R represents CH3 to C14H29; a 14 member homologous series of the new azoxy liquid crystalline compounds. The present invention thus favours providing a 14 member set of liquid crystalline compounds having a wide mesophase range that would be stable upto a temperature of 280 °C for wide industrial application and use including formulating substances for display devices which can be operated under extreme conditions such as in deserts and the like.

Full Text

FIELD OF THE INVENTION
The invention particularly relates to a novel 14 member homolougous series of azoxy
compounds and a simple, cheap, and environmentally friendly synthetic methodology
employed to reach the same. More specifically, the members of the presently invented
series of azoxy compounds exhibit a wide mesophase range. The invention particularly
relates to these azoxy compounds as represented hereunder by the Formula I and also to
a simple and cost-effective manner of its manufacture

wherein
R represents CH3 to C14H29; a 14 member homologous series of the new azoxy liquid
crystalline compounds.
The present invention thus favours providing a 14 member set of liquid crystalline
compounds having a wide mesophase range that would be stable upto a temperature of
280 °C for wide industrial application and use including formulating substances for
display devices which can be operated under extreme conditions such as in deserts and
the like.
BACKGROUND ART
Aromatic azoxy compounds are key materials for electronic display devices based on
their mesomorphic properties. This invention relates to the ester-azoxy compounds and
more particularly to the ester-azoxy compounds having a nematic liquid crystal phase.
thereby improving liquid crystal display elements including the compositions.

Liquid crystal display devices have many advantages over a luminescence-type display.
The liquid crystal display unit including the driver circuit is small and flat, can be driven
at low voltage by a small power source and provide a visual display which is far superior
to the luminescence-type display. In view of these advantages, liquid crystal display
devices have become widely used for computer terminals, POS terminals, video displays
and the like in place of conventional cathode ray tubes. Liquid crystal materials used in
liquid crystal display cells are generally of the nematic type.
It is generally known that nematic liquid crystal compounds are characteristic in that the
electro-optical effect, such as light-scattering, double refraction and the like, changes
greatly under the influence of an electric field. In view of these characteristics, nematic
liquid crystals are used widely for liquid crystal display devices based on various display
principles.
The particular characteristics required of a liquid crystal material in order to be utilized in
the above mentioned display principles differ from each other. However, several
conditions are required to for all of them. First, the material must be chemically stable,
secondly it must be in the nematic state over a wide range of temperature and thirdly, the
method of synthesis of such compound should be cost-effective, convenient and
environment friendly. There has been a continuing need in the art to achieve such form of
liquid crystal materials which would meet the above requirements of the art
As regards the angle of mesophase range, it is known that the maximum mesophase
range of 47.8 °C is observed for [C6H13-O-Ph-N(O)=N-Ph-0-C6H13] of the closest known
azoxy derivative series [R-O-Ph-N(O)=N-Ph-O-R]. It is noteworthy to mention that
C2H5-SOC-Ph-N=N(O)-Ph-COS-C2H5 and C7H15-OOC-CH=CH-Ph-N N(O)-Ph-
CH=CH-COO-C7H15 from two different azoxy series which show maximum thermal
ranges 111.4 °C and 100.5 °C respectively.

From the synthesis point of view of these liquid crystalline azoxy compounds, the known
synthetic routes to prepare the symmetrical 4,4'-n-dialkyl/aikyloxyazoxybenzene.s are the
oxidation of the corresponding 4,4'-n-dialkyl/alkyloxy azobenzenes (Scheme 1).
electrochemical reduction of 4-(n-alkyloxybenzoyloxy)-4'-nitrobenzene by
electrochemical method (Scheme 2) and oxidation of the 4-n-alkoxy anilines using 30%
hydrogen peroxide (Scheme 3).

The disadvantages associated with all the above processes are that they suffer from:
a) Multiple steps
b) Prolonged reaction time
c) Multiple products that prevent easy separation

It would be clearly apparent from the above that there remain two types of basic-
problems associated with the liquid crystalline known azoxy homologues:
i) Absence of liquid crystalline azoxy compounds having a wide mesophase
range,
ii) Absence of simple, cheap and environment friendly synthetic method for the
synthesis of such compounds.
There thus is a continuous need in the art to provide liquid crystalline azoxy compounds
having a wide mesophase range with a relatively cheap synthetic pathway.
OBJECTS OF THE INVENTION
It is therefore a primary object of this invention to provide for liquid crystalline azoxy
compounds having a broad mesomorphic range covering temperatures above and below
room temperature.
Another object of the present invention is directed to provide for liquid crystalline azoxy
compound and liquid crystal composition including the same as a dopant or when used
as a base of a liquid crystal material would improve or increase the liquid crystal
temperature range or in other words will have the widest range of mesophases at a cost-
effective manner of producing the same for wide and diverse applications and end uses.
Another object of the invention is to provide cost-effective and easy synthesis liquid
crystalline azoxy compounds having a broad mesomorphic range covering temperatures
above and below room temperature..

Accordingly, it is an object of the invention to provide novel ester-azoxy compounds
having a broad mesomorphic range covering temperatures above and below room
temperature.
It is another object of the invention to provide for selective members of a new
homologous series of liquid crystalline bis-[4-(n-alkyloxybenzoyloxy)phenyl]diazene
oxides which are 14 members of the homologous series having carbon numbers 1-14 in
the alkoxy chain which would have the widest range of mesophases.
It is a further object of the invention to provide the ester azoxy compounds with a high
clearing temperature and mesophase stability temperature of 280 °C which is rare for the
azoxy derivatives of other homologous series.
Still another object of the invention is to provide a synthetic methodology of the novel
azoxy compounds of the present invention.
Still another object of the invention is to provide a more economic, single step and
environment friendly synthetic transformation leading to these novel azoxy compounds.
Yet another object of the invention is to provide the novel azoxy compounds which mabe used to formulate mixtures that will be useful to display devices to be operated in
extreme temperature conditions such as in desert.
Still other objects and advantages of the invention will in part be obvious and in part be
apparent from the specification.
SUMMARY OF THE INVENTION

Thus according to the basic aspect of the invention there is provided a liquid crystalline
compound and/or a homologous series of compounds of general Formula 1; [R-O-Ph-
COO-Ph-N(O)=N-Ph-OOC-Ph-O-R] which is structurally represented as:

wherein
R of the alkoxy group has 1 to 14 carbon atoms starting from CH3 to C14H29; a 14
member homologous series identified as Compounds 1-1 to Compound 1-14.
Importantly, the present invention is directed to a above new group of azoxy
compounds [R-O-Ph-COO-Ph-N(O)=N-Ph-OOC-Ph-O-R] incorporating two additional
phenyl rings linked via two ester linkage to the known azoxy core [R-O-Ph-N(O)=N-Ph-
O-R] .
Preferably, the liquid crystalline compound and/or a homologous series of compounds
comprises aromatic azoxy ester and having the required very high thermal stability of
upto about 285°C.
Advantageously, the liquid crystalline compound and/or a homologous series of
compounds of the invention exhibits liquid crystalline behaviour over a wide range of
temperature 100 to 150°C.

In particular, the above disclosed liquid crystalline compound and/or a homologous
series of compounds according to the invention have a maximum thermal range of
168.6 C for which is the Compound I-10-and a minimum thermal range of 85.7°C
which is the Compound 1-3.
More particularly, the liquid crystalline compound and/or a homologous series of
compounds according to the invention include compounds as per Formula-I which
include:
i) Compounds 1-2 to 1-7 which show nematic phase on melting up to isotropic
temperature and on reversal cooling (below isotropic temperature) the nematic
phase remains upto crystallization temperature.
ii) Compounds 1-9 to 1-13 which show smectic phase followed by nematic phase upto
isotropic temperature,the nematic phase enters into smectic phase on reverse cooling
and continues upto solidification temperature.
iii) Compound 1-14 which shows only nematic phase.
It is also identified by way of the present invention that in the the liquid crystalline
homologous series of compounds of the invention, the mesogenic behaviour of
compound 1-1, the lowest member of the series, is similar to that of compounds 1-9 to I-
13
The mesogenic behaviour of 1-8 is unique within this series, said compound 1-8 showing
only nematic phase on heating, but showing nematic phase followed by smectic phase
during cooling.
In accordance with another aspect of the invention there is provided a process for the
manufacture of the liquid crystalline compound of Formula-I comprising:
(i) providing 4-(n-alkyloxybenzoyIoxy)-4'-nitrobenzenes;and

(ii) converting the said 4-(n-alkyloxybenzoyloxy)-4'-nitrobenzenes to corresponding bis-
[4-(n-alkyloxybenzoyloxy)phenyl]diazene oxides [R-O-Ph-COO-Ph-N(O) N-Ph-OOC-
Ph-O-R],
In the above process for the manufacture of the liquid crystalline compound of Formula-1
the said conversion of said 4-(n-alkyloxybenzoyloxy)-4'-nitrobenzenes to corresponding
bis-[4-(n-alkyloxybenzoyloxy)phenyl]diazene oxides [R-O-Ph-COO-Ph-N(O) N-Ph-
OOC-Ph-O-R] is done by zinc-ammonium chloride in ethanol-water mixture preferably
about 328 to 338 preferably 333K.
In accordance with a preferred aspect of the invention in the above process for the
manufacture of the liquid crystalline compound of Formula-1 the said ethanol-water ratio
is about 8.5:1.5 to 9.5:0.5 preferably 9:1 (v/v).
In accordance with yet another aspect of the present invention there is provided a liquid
crystal formulation for display devices and the like comprising anyone or more of the
homologous series of compounds of general Formula-I; [R-O-Ph-COO-Ph-N(O) N-Ph-
OOC-Ph-O-R] which is structurally represented as:

wherein
R of the alkoxy group has 1 to 14 carbon atoms starting from CH3 to C14H2: a 14
member homologous series identified as Compounds 1-1 to Compound 1-14.

Advantageously, the above liquid crystal formulation for display devices and the like is
adapted to be stable at extreme temperatures.
DETAILED DESCRIPTION OF THE INVENTION
Thus according to the basic aspect of the present invention, there is provided a new group
of azoxy compound having the general Formula I ; [R-O-Ph-COOPh-N(O) N-Ph-
OOC-Ph-O-R] as depicted below by a novel synthetic methodology as outlined in
Scheme I:

The present invention leads over others in two aspects:
i) Mesophase range ii) Synthesis
The presently invented series of mesogens exhibit a larger mesophase range compared to
the corresponding members of the homologous series of the other azoxy derivatives. The
mesophases are stable up to around 280 °C which is rare for the other azoxy derivatives
of other homologous series

The starting material used in the above synthesis i.e. the 4-(n-alkyloxybenzoyloxy)-4'-
nitrobenzene was synthesized following the procedure as shown in Scheme 11 hereunder:

The above schemes I and II clearly reveal the advantages residing in the synthesis of this
new 14 member homologous series of liquid crystalline bis-[4-(n-
alkyloxybenzoyloxy)phenyl]diazene oxides and the merits of such synthetic method as
follows:
a) Handling is very easy and safe
b) Low cost due to cheap reagents like ammonium chloride and zinc duct and also
aqueous ethanol as solvent
c) Solvent system of ethanol and water mix is environment friendly
d) One step conversion
e) Single product which is purified by recrystallisation
Thus the above invention relates to the provision and synthesis of a new group of azoxy
compounds by a simple, cheap and green method and encompassing a wider mesophase

range, more specifically exhibiting nematic phase over a wide range of temperature. This
group of compounds has a very high potential for wide application based on their wide
thermal range of nematic phase. These novel ester-azoxy compounds having the general
Formula I; [R-O-Ph-COO-Ph-N(O)=N-Ph-OOC-Ph-O-R] serve better than many prior
art compounds with the known azoxy core [R-O-Ph-N(O)=N-Ph-O-R] in terms of
possessing a wider mesophase range and a simple synthetic pathway.
Preferably, the protocol followed for quantitative testing of the liquid crystalline
behaviour of these novel compounds as its end characteristics are through Optical
Polarising Microscopy, Differential Scanning Calorimetry and Small Angle Xray
Diffraction method.
Further, these materials can be used as a base component to develop a wide range of
commercial liquid crystal mixture since these materials have a wide range of mesophase.
With a high clearing temperature of 280 °C these compounds may be used to formulate
mixtures that will be useful for display devices to be operated in extreme temperature
conditions such as, in deserts.
The details of the invention its objects and advantages are explained hereunder in greater
detail in relation to non-limiting exemplary illustrations as per the following Examples:
EXAMPLES:
Example I: Synthesis of Starting materials:
Synthesis of the starting materials, 4-(n-alkyloxybenzoyloxy)-4'-nitroben/ene was done
as shown schematically in Scheme 11 above. n-Alkoxybenzoic acids were prepared by
usual technique. Other required chemicals viz. 4nitrophenol, dicyclohexylcarbodiimide

(DCC), N, N dimethylaminopyridine (DMAP) were purchased from E. Merck Ltd., India
and used without further purification.
4-(p-alkyloxybenzoyloxy)-4'-nitrobenzene:
All the 4-(n-alkyloxybenzoyIoxy)-4'-nitrobenzenes were synthesized following the same
procedure.
A mixture of 4-octyloxy benzoic acid (2 g; 7.96 mmol), 4-nitrophenol (1.12 g; 7.96
mmol), dicyclohexylcarbodiimide (DCC) (1.64 g: 7.96 mmol) and N, N-
dimethylaminopyridine (0.1 g; 0.79 mmol) in 25 mL of dichloromethane was stirred at
room temperature for 12 h. The reaction mixture was filtered off and the solution
evaporated under reduced pressure. The solid was crystallized from ethanol. filtered and
dried under vacuum. A very pale yellow solid was obtained. (Yield: 2.5 g: 85 %).
Example II: Synthesis of bis-[4-(naIkyloxybenzoyloxy)phenyl] diazene oxides
For the purpose the synthesis the starting materials, 4-(n-alkyloxybenzoyloxy)-4'-
nitrobenzenes, was used as obtained above under Example I as per Scheme II.
Ammonium chloride and zinc dust were purchased from E. Merck Ltd., India and were
used without further purification.
All the bis-[4-(nalkyloxybenzoyloxy)phenyl] diazene oxides were synthesized following
the same procedure. As a representative case, the synthesis of bis-[4-(n-
octyloxybenzoyloxy)phenyl] diazene oxide is given below.
To a solution of 4-(n-octyloxybenzoyloxy)-4'-nitrobenzene (3.71 g; 10 mmol) in a
mixture (100 mL) of ethanol and water (9:1 v/v), warmed to 333 °K, ammonium chloride

(1.07 g; 20 mmol) was added. Further heating was stopped and zinc powder (1.96 g; 30
mmol) was added to the reaction mixture very slowly over 10 minutes with stirring. The
reaction mixture was further stirred for lh. The resulting reaction mixture was diluted
with equal volume of cold water and then filtered. The yellow residue was extracted with
dichloromethane. Evaporation of the solvent afforded the novel compound of Formula I
as very pale yellow solid. The resulting compound was purified by recrystallization from
dichloromethane and ethanol (1:5 v/v), (Yield: 1.83 g; 52.80%). (Scheme I)
The phase transition temperatures (°C) for bis [4-(n-alkyoxybenzoyloxy)phenyl]diazene
oxides (Compounds 1-1 to 1-14) obtained as above were next tested and the results are
provided hereunder in Table 1:

All the members of this family show thermotropic mesogenic behaviour over a
good temperature range, which is wider than that of the corresponding member of
bis-(4-alkyloxyphenyl)diazene oxides.
2) Compounds 1-2 to 1-7 show nematic phase on melting up to isotropic temperature.
On reversal cooling (below isotropic temperature) the nematic phase remains upto
crystallization temperature.
3) Compounds 1-9 to 1-13 show smectic phase followed by nematic phase upto
isotropic temperature. The nematic phase enters into smectic phase on reverse
cooling and continues upto solidification temperature.
4) Compound 1-14 shows only nematic phase.
5) Interestingly the mesogenic behaviour of compound 1-1, the lowest member of the
series, is similar to that of compounds 1-9 to 1-13
6) The mesogenic behaviour of 1-8 is unique within this series. Compound 1-8 shows
only nematic phase on heating, but it shows nematic phase followed by smectic
phase during cooling.
7) The maximum thermal range is 168.6 °C for 1-10 and the minimum thermal range
is 75.8 °C for 1-3. Therefore, the members of this series exhibit very wide range
of mesophase.
It is thus possible by way of the present invention to provide for the liquid crystalline
homologues having a wide mesophase range and also involving a simple , cost-effective
and environment friendly synthetic method for the synthesis of such compounds.
Advantageously the compounds according to the invention which have a clearing
temperature as high as about 280°C would favour its use in display devices especially
those required to be operated under extreme conditions such as in desert and favour a
wide industrial application in the related field.

We claim:
1. A liquid crystalline compound and/or a homologous series of compounds of general
Formula-I; [R-O-Ph-COO-Ph-N(O)=N-Ph-OOC-Ph-O-R] which is structurally
represented as:

wherein
R of the alkoxy group has I to 14 carbon atoms starting from CH2, to C14H29; a 14
member homologous series identified as Compounds 1-1 to Compound 1-14..
2. A liquid crystalline compound and/or a homologous series of compounds according to
claim 1 wherein the compound is aromatic azoxy ester.
3. A liquid crystalline compound and/or a homologous series of compounds according to
anyone of claims 1 or 2 comprising very high thermal stability of upto about 285°C.
4. A liquid crystalline compound and/or a homologous series of compounds according to
anyone of claims 1 to 3 which exhibits liquid crystalline behaviour over a wide range of
temperature 100 to 150°C.

5. A liquid crystalline compound and/or a homologous series of compounds according to
anyone of claims 1 to 4 having a maximum thermal range of 168.6°C for which is the
Compound I-10-and a minimum thermal range of 85.7 C which is the Compound 1-3.
6. A liquid crystalline compound and/or a homologous series of compounds according to
anyone of claims 1 to 5 wherein the said
i) Compounds 1-2 to 1-7 show nematic phase on melting up to isotropic temperature
and on reversal cooling (below isotropic temperature)the nematic phase remains upto
crystallization temperature.
ii) Compounds 1-9 to 1-13 show smectic phase followed by nematic phase upto
isotropic temperature,the nematic phase enters into smectic phase on reverse cooling
and continues upto solidification temperature.
iii)Compound 1-14 shows only nematic phase.
6. A liquid crystalline compound and/or a homologous series of compounds as claimed
in anyone of claims 1 to 5 wherein the mesogenic behaviour of compound 1-1. the lowest
member of the series, is similar to that of compounds 1-9 to 1-13
7. A liquid crystalline compound and/or a homologous series of compounds as claimed
in anyone of claims 1 to 6 wherein the mesogenic behaviour of 1-8 is unique within this
series, said compound 1-8 showing only nematic phase on heating, but showing nematic
phase followed by smectic phase during cooling.
8. A process for the manufacture of the liquid crystalline compound of Formula-I as
claimed in anyone of claims 1 to 6 comprising:
(i) providing 4-(n-alkyloxybenzoyloxy)-4'-nitrobenzenes;and
(ii) converting the said 4-(n-alkyloxybenzoyloxy)-4'-nitrobenzenes to corresponding bis-
[4-(n-alkyloxybenzoyloxy)phenyl]diazene oxides [R-O-Ph-COO-Ph-N(O) N-Ph-OOC-
Ph-O-R].
9. A process for the manufacture of the liquid crystalline compound of Formula-1 as
claimed in claim 7 wherein said conversion of said 4-(n-alkyloxybenzoyloxy)-4'-
nitrobenzenes to corresponding bis-[4-(n-alkyloxybenzoyloxy)phenyl]diazene oxides [R-
O-Ph-COO-Ph-N(O)=N-Ph-OOC-Ph-O-R] is done by zinc-ammonium chloride in
ethanol-water mixture preferably 328 to 338 preferably 333K.
10. A process for the manufacture of the liquid crystalline compound of Formula-I as
claimed in anyone of claims 8 or 9 wherein the said ethanol-water ratio is about 8.5:1.5 to
9.5:0.5 preferably 9:1 (v/v).
11. A liquid crystal formulation for display devices and the like comprising anyone or
more of the homologous series of compounds of general Formula-l; [R-O-Ph-COO-Ph-
N(O)=N-Ph-OOC-Ph-O-R] which is structurally represented as:

wherein
R of the alkoxy group has 1 to 14 carbon atoms starting from CH; to C14H29; a 14
member homologous series identified as Compounds 1-1 to Compound 1-14.
12. A liquid crystal formulation for display devices and the like as claimed in claim 1 1
which is adapted to be stable at extreme temperatures.
13. A liquid crystalline compound and/or a homologous series of compounds of general
Formula-I; [R-O-Ph-COO-Ph-N(O)=N-Ph-OOC-Ph-O-R] substantially as herein
described and illustrated with reference to the accompanying examples.

The invention particularly relates to a novel 14 member hornolougous series of azoxy
compounds and a simple, cheap, and environmentally friendly synthetic methodology
employed to reach the same. More specifically, the members of the presently invented
series of azoxy compounds exhibit a wide mesophase range. The invention particularly
relates to these azoxy compounds as represented hereunder by the Formula 1 and also to
a simple and cost-effective manner of its manufacture

wherein
R represents CH3 to C14H29; a 14 member homologous series of the new azoxy liquid
crystalline compounds.
The present invention thus favours providing a 14 member set of liquid crystalline
compounds having a wide mesophase range that would be stable upto a temperature of
280 °C for wide industrial application and use including formulating substances for
display devices which can be operated under extreme conditions such as in deserts and
the like.

Documents:

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Patent Number

277274

Indian Patent Application Number

1957/KOL/2008

PG Journal Number

48/2016

Publication Date

18-Nov-2016

Grant Date

16-Nov-2016

Date of Filing

05-Nov-2008

Name of Patentee

UNIVERSITY OF NORTH BENGAL

Applicant Address

SILIGURI

Inventors:

#	Inventor's Name	Inventor's Address
1	BISWAS, ACHINTESH NARAYAN	EX-SRF (CSIR), DEPARTMENT OF CHEMISTRY, UNIVERSITY OF NORTH BENGAL, SILIGURI 734013
2	DAS, PURAK	SRF (SDT), DEPARTMENT OF CHEMISTRY, UNIVERSITY OF BENGAL, SILIGURI 734013
3	MANDAL, PRADIP KUMAR	PROFESSOR, DEPARTMENT OF PHYSICS, UNIVERSITY OF NORTH BENGAL, SILIGURI 734013
4	BANDYOPADHYAY, PINAKI	READER, DEPARTMENT OF CHEMISTRY, UNIVERSITY OF NORTH BENGAL, SILIGURI 734013

PCT International Classification Number

C07F7/02;C09K19/40;C07C67/00

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA