Molecular flexibility dependence on mesogenic behaviors of isomeric and nonisomeric series

A novel homologous series containing vinyl ester and azomethane central bridges and n-alkoxy as well as 3″,4″-dimethyl groups as flexible terminal/lateral groups viz. RO?C₆H₄?CH = CH?COO?C₆H₄?N?CH?C₆H₃-(CH₃)₂ have been synthesized and studied with a view to establishing the relation between molecular structure and thermotropic liquid crystal (LC) properties with reference to molecular flexibility within the series. The series consists of twelve homologues (C₁ to C₁₆). C₆ and C₇ homologues are smectogenic plus nematogenic and C₈ to C₁₆ homologues are only smectogenic, and the rest of the homologues (C₁ to C₅) are nonmesomorphic. Transition temperatures and the textures of the homologues were determined using an optical polarizing microscope equipped with a heating stage (POM). The textures of a nematic phase are threaded or Schlieren and that of a smectic phase are of the A or C type. Analytical, thermal and spectral data support the molecular structures. Smectic and nematic thermal stabilities are 116.85°C and 147.5°C, respectively. Whose Sm?N/I and N-I mesophase lengths are varied between 15°C to 21°C and 25°C to 62°C, respectively. The novel compounds are compared with structurally-similar series.     

Study of the molecular structure on liquid crystal properties with reference to thermotropic azoester derivatives

An azoester homologues series: RO?C₆H₄?COO?C₁₀H₆?N?N?C₆H₄?OC₅H₁₁ (para) as novel liquid crystalline (LC) materials has been synthesized and studied with a view to understanding and establishing the effects of molecular structure on LC properties with reference to laterally substituted phenyl ring and terminally substituted ?OR and ?OC₅H₁₁ (n) groups; including ?COO? and ?N?N? central bridges. Novel homologous series of thermotropic LC variety consists of thirteen homologues (C₁ to C₁₈). C₁ to C₃ derivatives are nonliquid crystal (NLC); C₄ is only nematogenic and C₅ to C₁₈ are smectogenic plus nematogenic. All the mesogenic homologues (C₄ to C₁₈) are enantiotropically nematogenic or/and smectogenic as confirmed by a polarizing optical microscopy (POM) equipped with a heating stage. Transition curves Cr-I/M, Sm?N, and N?I behaved in normal manner in a phase diagram. Odd-even effect is exhibited by Sm?N and N?I transition curves. Analytical, spectral and thermal data confirms the molecular structure of novel homologues. Novel azoester series is predominantly nematogenic and partly smectogenic whose mesogenic temperatures ranges minimum to maximum from 79.0°C to 162.0°C. Thermal stability for smectic and nematic are 128.2°C and 147.7 °C, respectively. Thus, it is a middle ordered melting type of novel series whose total mesophaselength ranges from 20.0°C to 56.0°C. Textures of nematic are threaded or schlieren and that of smectic are smectic A or C.     

Synthesis of novel ester series and study of its mesomorphism dependence on terminal end group with lateral –OCH3 group

Novel liquid crystal (LC) materials of ester derivatives were synthesized and studied with a view to understanding and establishing the effects of molecular structure on LC properties. The novel molecules consist of two phenyl rings bonded through –COO– central group and a laterally substituted methoxy group with –OC_nH_2n+1 as well as –COOCH₃ terminal end groups, and yielded 12 homologous members of an ester series. The C₁ to C₃ members are nonmesomorphic, the C₄ to C₁₂ members are enantiotropic nematic only, and the C₁₄ to C₁₆ members are enantiotropically smectogenic in addition to nematogenic. Transition temperatures and the textures of LC state were observed through an optical polarizing microscope (POM) equipped with a heating stage. The textures of nematic phase are threaded or Schlieren, and that of smectic phase are focal conic of the type A or C. Transition curves of a phase diagram behave in normal manner with the exhibition of an odd-even effect (only N-I). Analytical and spectral data support the molecular structures of the novel ester derivatives. The LC properties of the present series are compared with structurally similar other known series. The average thermal stability of the series is 93°C for smectic and 120.88°C for nematic and the mesogenic phase length ranges between 2°C and 46°C.     

Synthesis,characterization, and mesomorphic investigation of vinyl ester-substituted chalcones and effect of lateral ‒NO2 and ‒OCH3 group

A novel homologous series of α-4-(4′-n-alkoxy cinnamoyloxy) phenyl β-2″-nitro, 3″–4″ di methoxy benzoyl ethylenes, H_2n+1CnO?C₆H₄?CH?CH?COO?C₆H₄?CO?CH?CH?C₆H₂(NO₂) (OCH₃)₂ (n = 1–8, 10, 12, 14, 16, 18) has been synthesized. All these compounds have been characterized by suitable spectroscopic techniques. C₁ homologue is nonmesogenic, while C₂ homologue shows enantiotropic nematogenic property and the rest of the homologous (C₃?C₁₈) displayed enantiotropically smectogenic plus nematogenic phase. Phase transition temperatures and textures of the LC phase were determined by an optical polarizing microscopy (POM) equipped with a heating stage. The mesomorphic properties of these compounds were confirmed by differential scanning calorimetry (DSC) analysis.     

Mesomorphism dependence on molecular rigidity with reference to ‒CH˭CH‒ unit of central bridge

A novel ester homologous series of rich mesomorphism and low temperatures with unexpected phase behaviors of eleven homologues was synthesized and studied with a view to understanding and establishing the relation between mesomorphic behaviour and the molecular structure of a series 4-(4′-n-alkoxybenzoyloxy)-4″-chlorobenzyl cinnamates. All the members of the novel series are enantiotropically smectogenic and the octyloxy (C₈) to hexadecyloxy (C₁₆) homologues are enantiotropically nematogenic, in addition to smectogenic. Odd–even effect is observed for Sm?I/Sm?N transition curve but it is absent for N?I transition curve. Textures of nematic phase are threaded or Schlieren and that of the smectic phase are fan shaped or batonates of smectic-A type phase or Smectic-C type for C₁₆ homologues as judged directly from a heating stage of an optical polarizing microscopy. Analytical and spectral data confirmed the molecular structures of novel homologues. Mesomorphic properties of present series are compared with the structurally similar other known series. The average smectic and nematic thermal stabilities are 92.78°C and 100.8°C, respectively. Mesophase length minimum to maximum for smectic and nematic are 21.0°C to 31.1°C and 8.4°C to 42.6°C respectively. Thus, the present novel series is partly nematogenic and fully smectogenic with considerable degree of mesomorphism and low melting type.     

Study of mesomorphism and laterally substituted nitro group

A novel thermotropically mesomorphic, meta-substituted nitro group of chalconyl ester series, RO-C₆H₄-COO-C₆H₃-(NO₂)-CO-CH=CH-C₆H₄OC₁₂H₂₅(n) (para) is synthesized and studied with an aim to establish the relation between molecular structure and the mesomorphism with reference to changing molecular flexibility in presence of nitro lateral group. Novel homologous series consist of thirteen homologs (C₁–C₁₈) whose mesomorphism commences from C₅ homolog as enantiotropic nematogenic with absence of smectic property, even in the monotropic condition. Transition temperatures of novel substances were determined by an optical polarizing microscope, equipped with a heating stage (POM). Textures of a nematic phase are threaded or Schlieren. N-I transition curve exhibited narrow, sharp and short odd-even effect; with deviating trend in a phase diagram. Analytical, spectral and thermal data confirmed the molecular structures of homologs. Thermal stability for nematic is 182.89°C, whose mesophase lengths minimum to maximum ranges from 17°C to 45°C and it is an upper middle ordered melting type series. Group efficiency order for nematic is series 1 > series Y > series X, as derived from comparative study of structurally similar analogous series.     

Mesomorphism dependence on molecular rigidity and substitution of same functional group on lateral or terminal position of tailed phenyl ring

Novel liquid crystal materials (LCs) of low temperature range (53°C to 75°C) have been synthesized through a series of chalconyl derivatives consisting of two phenyl rings bonded through a –CH?CH?CO? central bridge to study the effect of molecular structure on LC properties in general and with a focus on molecular rigidity. The novel homologues series (C₁ to C₁₈) consists of thirteen homologues with general formula RO?C₆H₄?CH?CH?CO?C₆H₄?OC₁₀H₂₁(n) (meta). The C₁, C₂, C₃ homologues are nonliquid crystals (NLC) and the rest of the homologues (C₄ to C₁₈) are either monotropic or enantiotropic liquid crystals. C₄ to C₆ homologues are enantiotropicnematic and the rest of the mesomorphic homologues are (C₇ to C₁₈) monotropicsmectic in addition to monotropicnematic character. Transition and melting temperatures including textures of homologues were determined by an optical polarizing (POM) microscopy equipped with a heating stage. Textures of a nematic phase are threaded or Schlieren, and that of the smectic phase are of the type Smectic A or C as judged directly from the heating top of the microscope. Thermal stability for smectic is very poor and of the nematic is (N-I) 69.3°C whose, total mesophase length ranges between 07.0 to 14.0°C at C₈ and C₄ homologues respectively.     

Molecular structural flexibility dependence of mesomorphism through ortho-substituted bromo group

A novel series of liquid crystal (LC) materials of Schiff's bases viz. RO-C₆H₄?CH?CH?COO?C₆H₄?N?CH?C₆H₄?Br (ortho) is synthesized and studied with a views to understanding and establishing the effect of molecular structure on liquid crystal properties and to provide novel thermotropic LC material to the scientific and technological community of research interest. The novel series consists of thirteen members (C₁ to C₈, C₁₀, C₁₂, C₁₄, C₁₆ &; C₁₈). All the members of a series are enantiotropic liquid crystals. Smectic (C₁₀?C₁₈) and nematic (C₁?C₁₈) property commence from C₁₀ and C₁ homologue respectively. Transition temperatures and the textures of homologues were determined using a polarizing optical microscope (POM) equipped with a heating stage. Transition curves Cr-M, Sm-N and N-I of a phase diagram behaved in normal manner. Odd–even effect is absent for Sm-N transition curve, but it is present for N-I curve. Sm-N transition curve is extrapolated to C₈ and C₆ nonsmectogenic homologues to determine and predict their latent ability for exhibition of smectic property. Analytical and spectral data confirms the molecular structures of homologues. Thermal stabilities of smectic and nematic are 85.4°C and 130.1°C °C whose upper and lower total mesophase length vary from 58.0°C to 06.0°C at the C₁₀ and C₁ = C₅ = C₆ homologue, respectively. Textures of nematic phase are threaded or Schlieren and smectic phase are of type A or C. LC properties of present novel series are compared with structurally series known series. Thus, present novel series is predominantly nematogenic and partly smectogenic with middle ordered melting type and considerable total mesophase length range.     

Study of deviation from normal liquid crystal behavior of mesomorphic-isotropic transition curve in a chalconyl ester series with equipolar terminal end groups

A novel chalconyl ester homologous series RO.C₆H₄.COO.C₆H₄.CO-CH:CH-C₆H₄.OC₈H₁₇(p) synthesized and studied with a view to understanding and establishing the relation between molecular structure and Liquid Crystal (LC) properties of thermotropic mesomorphs. The novel series consists of eleven homologous (C₁ to C₁₆). Enantiotropicnematic type of mesophase formation commences from C₃ homologue and continued up to the last C₁₆ homologue of a novel series. Smectogenic character is totally absent for the novel series. Transition temperatures and the textures of nematic phase were determined through an optical polarizing microscopy (POM) equipped with a heating stage. Textures of nematic phase are threaded or Schlieren. Transition curve Cr-N/I and N-I behaved in normal manner except C₈ homologue which showed negligible deviation from normal behavior. N-I transition curve exhibited odd–even effect. Analytical and structural data supported the molecular structures of homologues. Average thermal stability for nematic is 98.88°C whose degree of mesomorphismvary from 12.0°C to 37.0°C. Evaluated thermometric data of present novel series are compared with structurally similar series. Group efficiency order for nematic on the basis of thermal stability, early commencement of mesophase and the degree of mesomorphism. Thus, present series is predominantly nematogenic and lower middle ordered melting type the low degree of mesomorphism.     

Molecular flexibility dependence mesomorphism

A novel series of chalconyl homologue derivatives with RO.C₆H₄.COO.C₆H₄.CO.CH:CH-C₆H₄.N.(CH₃)₂ (Para) have been synthesized and thermotropically studied with a view to understanding and establishing the effect of molecular structure on mesomorphic behavior of the novel homologues. The series consists of thirteen homologues (C₁ to C₁₈). C₇ to C₁₈ homologues are smectogenic, C₄ to C₁₈ nematogenic and C₁ to C₃ nonmesomorphic. Thus, novel chalconyl series is predominantly nematogenic and partly smectogenic. Transition temperatures and textures of mesophases were determined using an polarizing optical microscope (POM) equipped with a heating stage. Analytical and spectral data confirmed molecular structures of homologues. Phase transition curves showing phase behavior in a phase diagram behaved in normal manner. Thermal stability for smectic and nematic are relatively low at 59.6 °C and 76.6 °C respectively whose, smectogenic and nematogenic phase length vary from 12 to 16 °C and 06 to 20 °C, respectively. Mesomorphic behaviors of the present series are compared with a structurally similar known homologous series.     

Dependence of mesomorphism on geometrical shapes of isomeric and nonisomeric series of chalconyl esters

A meta substituted chalconyl ester homologous series: RO?C₆H₄?COO?C₆H₄(meta)?CO?CH?CH?C₆H₄?OC₁₂H_25(n)(para) is synthesized and studied with a view to understanding the effect of molecular substitution at meta position in a molecular structure on thermotropic liquid crystal properties. The novel homologous series consists of thirteen homologues (C₁ to C₁₈). All the homologues except the nonliquid crystal homologues C₁, C₂, C₃ are enantiotropic nematic with the absence of smectic properties. The transition and melting temperatures were determined by an optical polarizing microscopy (POM) equipped with a heating stage. Textures of a nematic phase are threaded or Schlieren. Transition curves (Cr-N/I and N-I) behave in normal manner except homologues between C₁₀ and C₁₄ of N-I curve, which show negligible deviation from normal and a smooth descending tendency. The N-I transition curve exhibits an odd-even effect up to C₁₀ homologue and then the odd-even effect disappears for higher homologues. Analytical and the spectral data support the molecular structures. Thermal stability for nematic is 107.3°C and the mesophase lengths range between 13.0°C and 35.0°C at the C₁₈ and C₁₂ homologues respectively. Group efficiency order for nematic is derived on the basis of thermal stability as ?OC₁₂H_25(n) (linear) > ?OC₁₂H_25(n) (nonlinear) > ?OC₁₆H₃₃ (nonlinear).     

Dependence of mesomorphism on tail group in combination with a lateral methoxy group

A novel homologous series of esters with a lateral methoxy group and terminal n-heptyl cinnamate group was synthesized and studied to investigate mesomorphic behavior in relation to structure. The twelve membered series consists of methoxy to pentyloxy derivatives that are nonmesomorphic and the rest of the homologs as smectegenically mesomorphic, including C₆ and C₇ monotropic smectic and C₈ to C₁₆ enantiotropic smectic without exhibition of any nematic property. The textures of smectogenic mesophases are focal conic fan shaped or batonates of the type smectic-A or Schlieren-C. An odd-even effect is exhibited by the Sm–I transition curve in the phase diagram. The Cr–Sm and Sm-I transition curves behave in a normal manner. Transition temperatures and textures were determined on an optical polarizing microscope, equipped with a heating stage. Some representative members were characterized by IR, H¹NMR, mass spectra, and elemental analysis. Analytical data support the molecular structures of the homologs. Mesomorphic properties of the present novel series are compared with the structurally similar known series. The present series is smectogenic only, whose thermal average stability is 89.8^°C and of a middle-ordered melting type.     

Crystal structure of R[UO2(CH3COO)3] (R = NH 4+ , K+, or Cs+)

The single crystal structure of NH₄[UO₂(CH₃COO)₃] (I), K[UO₂(CH₃COO)₃] (II), and Cs[UO₂(CH₃COO)₃] (III) is studied by X-ray diffraction. I and II crystallize in the tetragonal crystal system. The crystal data are as follows: a = 13.6985(3) and c = 27.5678(14) ?, V = 5173.1(3) ?³, space group I4₁/a, Z = 16, and R = 0.023 for I; a = 13.8890(5) and c = 26.0839(18) ?, V = 5031.7(4) ?³, space group I4₁/a, Z = 16, and R = 0.037 for II. Crystals III are orthorhombic, a = 18.176(2), b = 13.119(2), and c = 22.088(4) ?, V = 5267(1)?³, space group Pbca, Z = 16, and R = 0.0424. In structures I–III, the uranium-containing structural units are represented by discrete mononuclear [UO₂(CH₃COO)₃]⁻ groups, which belong to the AB ₃⁰¹ (A = UO₂²⁺, B ⁰¹=CH₃COO⁻) crystal chemical group of uranyl complexes.     

Mesomorphic dependence on molecular rigidity by central bridge and homo–hetero ring systems

A novel homologous series of thermotropic derivatives containing a heterocyclic ring was synthesized and studied with a view to understanding and establishing a relation between liquid crystal (LC) properties and the molecular structure of chalconyl derivative in general. The series comprises 12 homologues, of which smectogenic LC property commences from the decyloxy (C₁₀) homologue and continues for C₁₂, C₁₄, and C₁₆ homologues. Homologues C₁ to C₈ are non-liquid crystals. Exhibition of nematogenic mesophase is totally absent. Transition and melting temperatures were determined by an optical polarizing microscope equipped with a heating stage. Spectral and analytical data confirmed the molecular structures of homologues. The textures of smectic mesophase are A or C, and are determined by a miscibility method. The average thermal stability of the smectic phase is 113.57°C. The mesogenic phase length ranges between 4.1°C and 11.1°C. Thus, it is a middle-ordered melting-type series of shorter range of liquid crystallinity with absence of nematogenic character. Some LC properties of the present series are compared with a structurally similar known homologous series.     

Variation in Mesomorphic Characteristics with Certain Alterations in Molecular Structure: Homologous Series iso-Propyl p-(p'-n-Alkoxy CinnamoyIoxy) Benzoates and iso-Propyl p-(p'-n-AIkoxy Benzoyloxy) Benzoates

Mesomorphic characteristics of homologous series n-propyl p-(p'-n-alkoxy cinnamoyloxy)benzoates (I)¹ are quite in keeping with the general molecular structure and molecular forces accruing therefrom. Continuing the work further, the right hand terminal group of the series (I) has been replaced by a branched group with iso disposition of the alkylchain but having the same number of carbon atoms. Thus the new homologous series iso-propyl p-(p'-n-alkoxy cinnamoyloxy)benzoates (II) with all other molecular geometry the same, gets mesomorphic characteristics changed considerably. The first few members become non-mesogenic, nematic orientation is altogether eliminates and the smectic mesophase range is reduced to about one third of that of the series (I). Another new homologous series (III) with all the molecular geometry of the series (II). but with a shorter central bridge —COO— than —CH=CH—COO—receives a further jolt in its exhibition of mesomorphic characteristics. The first seven members and the last member of the series (III) become non-mesomorphic; however, some middle members exhibit monotropic smectic mesophase. The effect of the branching of the terminal substituent and shortening of the central bridge are thus quite evident and arouse good interest. The smectic texture as determined by optical microscopy and by the study of mixtures² is of fan shaped focal conic smectic A variety.     

Mesomorphism dependence on lateral substitution and central bridge

A novel ester homologous series was synthesized and studied with a view to understanding and establishing the effects of molecular structure on liquid crystal properties with a common laterally substituted –OCH3 group and changing terminal groups. The novel series consists of twelve members. The C₁ to C₃ members are not liquid crystals and the rest of the members C₄ to C₁₆ are smectogenic without exhibition of nematic character. Textures of smectic phase are focal conic fan shaped of the type A or C. The transition temperatures and textures of smectic mesophases were observed through hot stage polarizing microscopy (POM). The transition curves (Cr-I or Cr-M and Sm-I) behaved in normal manner. Analytical and spectral data support the molecular structures. Average thermal stability for smectic is 77.25°C and smectogenic mesophase ranges from 15°C to 33°C. Liquid crystal properties of the present series are compared with structurally similar homologous series. Thus, the series is smectogenic only with three homologs nonmesogenic.     

Columnar Mesomorphism of the Mixed Substituted Apolar Triphenylenes: Prognosis and Experimental Data

Abstract

The calculations of molecular parameters (MP) of triphenylene derivatives with the mixed substituents were carried out here. The prognosis of columnar mesomorphism (CM) for this series of compounds was made on the basis of the value of MP. The compounds Ia-If are synthesized, their thermotropic and lyotropic mesomorphism have been studied. The good agreement of calculation and experimental data has been found for a new series of triphenylenes.     

Role of n-alkoxy terminal end groups on mesomorphism

A homologous series RO-C₆H₄-CH:CH-COO-C₆H₄-CO-CH:CH-C₆H₄-OC₆H₁₃ (n) of novel liquid crystals (LC) has been synthesized and studied with a view to understanding and establishing the relation between molecular structure of a substance and the LC properties or behavior of thermotropic LC materials. Novel series consist of 11 homologues. C₁ and C₂ homologue derivatives are non-LCs and the rest of homologues (C₃ to C₁₆) are nematogenic without exhibition of smectic property. Transition temperatures were determined by an optical polarizing microscopy equipped with a heating stage. Transition curve Cr-N/I of a phase diagram behaved in normal manner. N/I transition curve partly deviated at C₆ and C₁₀ homologues from normal descending behavior, and exhibited very narrow and sharp odd-even effects. Textures of nematic phase are threaded or Schlieren. Thermal, analytical, and spectral data confirmed the molecular structures of novel chalconyl ester derivatives. Thermal stability for nematic is 95.77°C and the upper and lower mesophase lengths vary from 35 to 16°C at C₅ and C₈ homologues respectively. Group efficiency order derived for nematic on the basis thermal stability is -OC₁₀H₂₁ (n) > -OC₈H₁₇(n) > -OC₆H₁₃(n).     

Mesomorphism dependence on halogenated chalconyl esters in terms of molecular flexibility/rigidity

Vinyl carboxy central group containing a novel chalconyl ester homologous series: RO.C₆H₄.CH ? CH.COO.C₆H₄.CH ? CH.CO.C₆H₄.I (para) have been synthesized and studied with a view to understand and establish the relation between thermotropic liquid crystalline (LC) behaviors and the molecular structure. Novel chalconyl ester homologous series consists of thirteen homologs (C₁–C₁₈). C₁–C₃ homologs are nonmesogenic, C₄ homolog is enantiotropic nematogenic and the rest of the homologs (C₅–C₁₈) are enantiotropically smectogenic plus nematogenic. Phase transition temperatures and textures of LC phase were determined by an optical polarizing microscopy (POM) equipped with a heating stage. Cr-M/I, Sm-N, N-I transition curves in a phase diagram behaved in normal manner. Sm-N and N-I transition curves exhibited odd-even effect from C₄–C₁₀ or nearby C₁₀ homolog. Textures of nematic phase are threaded or Schlieren and that of the smectic phase are of the type smectic A or C. Analytical and spectral data confirms the molecular structure of homologs. Thermal stabilities for smectic and nematic mesophases are 155.0 and 180.7, respectively, and their corresponding mesophaselengths are varied from minimum to maximum at 17.0°C–39.0°C as well as 15.0°C–30.0°C. Thus, it is middle ordered melting type series. The group efficiency orders derived on the basis of smectic and nematic thermal stabilities are as under: Sm: -C₆H₄.I > -C₆H₄.Cl > -C₄H₃S and N:- C₆H₄.I > -C₆H₄.Cl > -C₄H₃S from comparative study of structurally similar analogous series