Browsing by Author "Sachin Kumar Singh"

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A Liquid-Crystal-Based System for Differentiating Structurally Related Analytes
(Wiley-Blackwell, 2018) Kirtika Mishra; Sachin Kumar Singh; Bachcha Singh
We report a new approach for differentiating structurally related analytes using a liquid crystal (LC) based system. In this work we have combined two principles (analyte-surfactant interactions and host-guest inclusion) at LC/aqueous interface to differentiate structurally related analytes methyl red (MR) and methyl orange (MO). On introducing MR/MO in aqueous solution containing sodium dodecyl sulfate (SDS), the optical response of 4-cyano-4′-pentylbiphenyl (5CB) changes from dark to bright in presence of MR but remains same in the presence of MO. This observation implies interaction of analyte (MR) and surfactant (SDS), thus effectively displacing SDS adsorbed at the 5CB/aqueous interface. Further, competitive inclusion complex formation of β-cyclodextrin (β-CD) with SDS or with analyte (dye, MR/MO) was visualized through changes in the optical response of 5CB at SDS-laden 5CB/aqueous interface. On addition of MR/MO to the SDS-β-CD complex solution the optical response of 5CB changes from bright to dark in presence of MO but remains same in the presence of MR. This implicates that homeotropic orientation of 5CB resulted due to the reorganization of displaced SDS molecules from β-CD cavity at the 5CB/aqueous interface. Overall, this LC based system demonstrates differentiation of structurally related analytes in the absence and presence of β-CD. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Advances in Lung Cancer Treatment Using Nanomedicines
(American Chemical Society, 2023) Akshansh Sharma; Devanshi Shambhwani; Sadanand Pandey; Jay Singh; Hauzel Lalhlenmawia; Murali Kumarasamy; Sachin Kumar Singh; Dinesh Kumar Chellappan; Gaurav Gupta; Parteek Prasher; Kamal Dua; Deepak Kumar
Carcinoma of the lungs is among the most menacing forms of malignancy and has a poor prognosis, with a low overall survival rate due to delayed detection and ineffectiveness of conventional therapy. Therefore, drug delivery strategies that may overcome undesired damage to healthy cells, boost therapeutic efficacy, and act as imaging tools are currently gaining much attention. Advances in material science have resulted in unique nanoscale-based theranostic agents, which provide renewed hope for patients suffering from lung cancer. Nanotechnology has vastly modified and upgraded the existing techniques, focusing primarily on increasing bioavailability and stability of anti-cancer drugs. Nanocarrier-based imaging systems as theranostic tools in the treatment of lung carcinoma have proven to possess considerable benefits, such as early detection and targeted therapeutic delivery for effectively treating lung cancer. (Figure presented) Several variants of nano-drug delivery agents have been successfully studied for therapeutic applications, such as liposomes, dendrimers, polymeric nanoparticles, nanoemulsions, carbon nanotubes, gold nanoparticles, magnetic nanoparticles, solid lipid nanoparticles, hydrogels, and micelles. In this Review, we present a comprehensive outline on the various types of overexpressed receptors in lung cancer, as well as the various targeting approaches of nanoparticles. © 2022 The Authors.
Concept and role of immunomodulatory medicinal plants used in Ayurvedic health care system
(EnPress Publisher, LLC, 2024) Sachin; Vineet Kumar; Mohit Sharma; Vaishnavi; Priyanka Chaudhary; Saurabh Singh; Kalvatala Sudhakar; Bimlesh Kumar; Narendra Kumar Pandey; Sachin Kumar Singh; Anand Kumar Choudhary; Dileep Singh Baghel
The statement "prevention is better than cure" and its applications is not a new for Ayurvedic health care system. The statement defines the aim and objectives of Ayurvedic health care system in a nutshell "swasthasya swasthya rakshanam aaturasya vikara prashamanam". The immune system is certainly considered one of our most discreet biological systems withinside the body. Immunizations may be obtained by us actively or passively. Active immunization includes stimulating with an antigen to generate immunological defenses against a destiny exposure, rather than passive vaccination, which includes administering antibodies to someone who has already been exposed to an antigen. Both plant and animal sources produce immunomodulatory effects to boost the body’s immunological reactivity against infections by engaging the non-specific immune system. Herbal immunomodulators are substances that either activate or suppress innate and adaptive immune responses in the body. Different ailments including allergies, asthma, rheumatoid arthritis, cancer, and other infectious disorders are caused by immune system failure. Therefore, regulating the many infectious illnesses requires significant immune response modification. Global scientific study is currently focused on how various medicinal plant components might alter the immune system. Numerous Indian and "Rasayana" and medicinal plants may have immunomodulatory characteristics. Some of these plants are Tinospora cordifolia, Morus alba, Acacia catechu, Allium sativum, and Mangifera indica. There are many more that are still undiscovered and offer space for greater study. © 2024 by author(s).
Effect of alkoxy chain density on the mesogenic properties of aroylhydrazone based liquid crystals: synthesis, characterisation, photophysical and gelation behaviour
(Taylor and Francis Ltd., 2020) Priyanka Kanth; Hemant Kumar Singh; Vijay Kumar; Sachin Kumar Singh; D. S. Shankar Rao; S. Krishna Prasad; Bachcha Singh
Three series of ester linkage containing aroylhydrazone based compounds have been synthesised where density and length of alkoxy chains are varied sequentially at ester end, keeping amide end of the molecule the same to investigate the effect of alkoxy chain density. The series of the compounds with single alkoxy chain at 4- position at ester terminal show nematic mesophase. The series with two alkoxy chains at 3- and 5- positions exhibit columnar rectangular mesophase and the series with three alkoxy chains at 3-, 4- and 5- positions show columnar oblique mesophase. It was observed that increasing the number of alkoxy chains at ester terminal, self-assembly of molecules changes and leads to a change from nematic to columnar mesophase and also significant enhancement in the mesomorphic range. Temperature dependent Raman studies confirm the presence of intermolecular hydrogen bonding which assist the self-assembly and gelation properties of molecules. All the series show similar photophysical properties despite the fact that the series vary in their molecular structures. Representative compounds of each series exhibited gelation in hydrocarbon solvents. FESEM images of the gels showed interwoven network of nanofibers of several micrometres length. These supergelators may be good candidates for applications in electronic devices. © 2020 Informa UK Limited, trading as Taylor & Francis Group.
Effect of regioisomerism on the self-assembly, photophysical and gelation behavior of aroylhydrazone based polycatenars: Synthesis and characterization
(Elsevier B.V., 2019) Priyanka Kanth; Hemant Kumar Singh; Vijay Kumar; Sachin Kumar Singh; D.S. Shankar Rao; S. Krishna Prasad; Bachcha Singh
In this paper we report five series of aroylhydrazone based polycatenars differing from each other in number and position of alkoxy chains on one end of the core; keeping other end the same. A systematic variation in the structures was carried out to understand the effect of position and chain length on the mesophase behavior. In the case of single alkoxy chain at 4-position, there is a transition from Smectic C to Smectic A mesophase during cooling and Smectic A to Smectic C transition in heating cycle in all the homologues except n = 6 & n = 8. In the case of two alkoxy chains at 3-, 5-positions, the compounds are non-mesogenic in nature. On changing the position of alkoxy chains from 3-, 5-positions to 3-, 4-positions, intermolecular forces weaken and these compounds become liquid crystalline and show columnar rectangular mesophase resulting from the effect of regioisomerism. Moving on to the series with three alkoxy chains, it was observed that 2-, 3-, 4-trialkoxy substituted compounds exhibit columnar rectangular mesophase except lower chain length (n = 6 & 8) while 3-, 4-, 5-trialkoxy substituted aroylhydrazones show columnar rectangular mesophase; except n = 10 which shows columnar oblique mesophase. Thus it was established that on increasing density of alkoxy chains around one terminal, mesophase changes from smectic to columnar mesophase. Temperature dependent Raman studies confirm the presence of intermolecular hydrogen bonding. Further, effect of substitution pattern did not show much influence on the photophysical properties of the mesogenic series in solid and solution state. However, the non-mesogenic series showed a different absorption and emission transition from the mesogenic series in solid and solution state. Solid state fluorescence studies show almost similar emission maxima in all the series. However, it was also noticed that non-mesogenic series show maximum red shifted emission maxima in solid state as compared to that of solution. All the series showed good gelation properties with less than 1% CGC (wt%) suggesting the strong ability of molecules to form gel. These H-bonded liquid-crystalline gels have immense potential for applications in emissive displays. © 2019 Elsevier B.V.
Exploring a solid polymorphism and phase transitions in 4-cyano-4′-pentylbiphenyl (5CB) and rGO-doped 5CB using temperature dependent Raman spectroscopy
(Elsevier B.V., 2025) Ummer Bashir Khoja; Chandan Bhai Patel; Pankaj Kumar Tripathi; Rajesh Kumar; Soni Mishra; Sachin Kumar Singh; Ranjan Kumar Singh; Kunwar Vikram
Raman spectroscopy is used to examine the temperature-dependent phase transition behaviour of the liquid crystalline system 4-cyano-4′-pentylbiphenyl (5CB) and its nanocomposite with reduced graphene oxide (5CB@rGO) over the temperature range of −160 °C to 90 °C. First time, such a broad temperature range study of 5CB and 5CB@rGO has been reported. The structural and intermolecular interaction characteristics of the liquid crystal 5CB and its behaviour in the presence of reduced graphene oxide (rGO) are examined in depth by the temperature-induced Raman spectra and DFT calculations. To assess the phase transitions in 5CB and 5CB@rGO, the significant bands associated with the polar C[tbnd]N group and phenyl rings were thoroughly examined. A new crystal-crystal (solid polymorphism) phase transition is investigated first time, occurring between −120 °C and −100 °C. Another significant new crystal-crystal phase transition in 5CB and 5CB@rGO is also exposed, taking place between −20 °C and −10 °C. Differential scanning calorimeter (DSC) measurements confirm this new phase transition in 5CB and temperature sensitivity fairly matches Raman analysis. To evaluate the structural as well as change in intermolecular interactions in each phase, the detailed DFT study is performed on the 5CB molecule to establish the spectra-structure relation. The detailed spectra-structure correlation is discussed in this study. The spectra-structure correlation and change in spectral parameters are used to investigate the structure and intermolecular interaction of each phase. © 2025 Elsevier B.V.
Fabrication of liquid crystal based sensor for detection of hydrazine vapours
(Elsevier B.V., 2014) Rajib Nandi; Sachin Kumar Singh; Hemant Kumar Singh; Bachcha Singh; Ranjan K. Singh
A novel liquid crystal (LC) based sensor to detect trace level amount of hydrazine vapour has been developed. The LC 4′-pentyl-4-biphenylcarbonitrile (5CB) doped with 0.5 wt% 4-decyloxy benzaldehyde (DBA) shows dark to bright optical texture upon exposure of hydrazine vapours as revealed by polarizing optical microscopy under crossed polarizers. The hydrazine interacts with the doped DBA and form diimine compound which disrupt the orientation of aligned 5CB. The interaction between DBA and hydrazine has been also studied by Raman spectroscopy. © 2014 Elsevier B.V. All rights reserved.
Fabrication of Liquid Crystal Optical Sensors Using Cyclodextrin Polymer for Real Time, Selective and Visible Detection of Industrial Dyes in Contaminated Natural Water Samples
(Wiley-VCH Verlag, 2025) Madeeha Rashid; Satyabratt Pandey; Vishal Singh; Chandan Bhai Patel; Ranjan Kumar Singh; Sachin Kumar Singh
Industrial wastewater release of dyes poses serious environmental and health risks when introduced into natural water systems. Herein, a cyclodextrin-based polymer sensor (Ech-CDP) is developed for real-time, visible detection of harmful methylene blue (MB) and methyl orange (MO) dyes in distilled and contaminated natural water samples. The sensor works through a competitive host-guest mechanism between sodium dodecyl sulphate (SDS) and Ech-CDP, altering liquid crystal alignment. Initially, SDS induces homeotropic ordering, which shifts to a tilted state upon binding with Ech-CDP. The presence of MB or MO displaces SDS, reverting the alignment and causing a visible bright-to-dark transition under polarizers. The sensor exhibits high selectivity, with detection limits of 0.03 mM for MB and 0.05 mM for MO in aqueous solutions, and 0.08 mM for MB and 0.26 mM for MO in real water samples, remains effective for 3 days, and is unaffected by pH variations between 4.8 and 9.1. Additionally, the sensor demonstrates an on–off switching capability, suggesting potential applications for molecular logic gates and advancing environmental monitoring techniques in dye-polluted waters. © 2025 Wiley-VCH GmbH.
In vitro anti-inflammatory and antioxidant activities of Hinguleswara rasa-based herbomineral formulations
(Innovare Academics Sciences Pvt. Ltd, 2018) Abhishek Chatterjee; Dileep Singh Baghel; Amit Mittal; Saurabh Singh; Bimlesh Kumar; Narendra Kumar Pandey; Sachin Kumar Singh; S. Tamilvanan; Shruti Chopra; Amit Bhatia; Anand Kumar Chaudhary
Objective: The aims of the present investigation were to develop the herbal and/or herbomineral formulations of Hinguleswara rasa and to compare their anti-inflammatory and antioxidant activities, in vitro, with that of standard drug samples. Methods: This study was an interventional investigation in three samples: In the first sample, Hinguleswara rasa (HR1) was prepared as per methodology described in Rasatarangini using Shuddha Hingula (10 g), Shuddha Vatsanabha (10 g), and Pippali (10 g). In the second and third sample, respectively, Hinguleswara rasa was prepared by replacing Shuddha Hingula with Kajjali where Kajjali made from Hingulotha parada and Sodhita parada constitutes two varieties of Hinguleswara rasa, i.e. HR2 and HR3. In vitro antioxidant activity was studied using 2,2-diphenyl-1-picrylhydrazyl, and the absorbance was recorded at 517 nm. For evaluating the in vitro anti-inflammatory studies, the inhibition of albumin denaturation technique was performed. Results: The results showed that the formulation of Hinguleswara rasa has shown dose-dependent activity which was observed in 100 µg concentration. HR1, HR2, and HR3 showed 36.11, 17.22, and 16.11% radical scavenging activity. Conclusion: It could be concluded that the changes made in the formulations did not affect the in vitro anti-inflammatory and antioxidant effects of the herbomineral formulations. © 2018, Innovare Academics Sciences Pvt. Ltd. All rights reserved.
Investigation of coordination properties of isolated adenine to copper metal: A systematic spectroscopic and DFT study
(Elsevier B.V., 2013) Om Prakash; Sachin Kumar Singh; Bachcha Singh; Ranjan K. Singh
The coordination properties of copper with adenine have been studied by the analyzing the changes in Fourier Transform Infra-red (FTIR) and Raman spectra of adenine and adenine-copper complex. The geometry of adenine and adenine copper complex were optimized and theoretical Infra-red and Raman spectra of the optimized structures were calculated using Density Functional Theory (DFT). During synthesis of adenine-copper complex specific procedure was adopted to attach the Cu atom with particular N-atom of adenine (N9). The results of Raman and DFT confirmed the attachment. The Raman bands at 625, 330 and 230 cm-1 of adenine-copper complex contain significant contribution of the vibrational motions of Cu metal coordinated to N9 and Cl atoms. The DFT calculations give additional vibrational modes containing the Cu, N9 and N9/ atoms, which are not observed in FTIR and Raman spectra. The Raman, IR and DFT study confirm that Cu metal has good binding affinity to the isolated adenine base. © 2013 Elsevier B.V. All rights reserved.
Investigation of liquid crystalline property of a new calamitic liquid crystalline system methyl 4-(4ʹ-(4ʹʹ-(decyloxy)benzyloxy) benzylideneamino)benzoate
(Taylor and Francis Ltd., 2017) Rajib Nandi; Hemant Kumar Singh; Sachin Kumar Singh; D. S. Shankar Rao; S. Krishna Prasad; Bachcha Singh; Ranjan K. Singh
A new polar calamitic liquid crystal, methyl 4-(4ʹ-(4ʺ-(decyloxy)benzyloxy) benzylideneamino)benzoate (M3BA) containing ether and Schiff base groups as linker with terminal polar ester group, has been synthesised and mesomorphic properties are studied by differential scanning calorimetry, polarising optical microscopy, density functional theory, temperature-dependent X-ray diffraction and temperature-dependent micro- Raman study. The smectic A (SmA) mesophase with focal conic texture has been observed with wide mesomorphic range. Layer thickness in SmA phase is greater than the optimised length of the molecule, indicating partially bilayer SmA phase. Analysis of Raman marker bands of C–H in-plane bending of phenyl rings, C=C stretching of rings, C=N stretching and C=O stretching shows structural changes at molecular level at Cr → SmA phase transition and provides proper intermolecular interactions responsible for dimeric unit in partially bilayer SmA phase. © 2016 Informa UK Limited, trading as Taylor & Francis Group.
Liquid crystal based sensor system for the real time detection of mercuric ions in water using amphiphilic dithiocarbamate
(Elsevier B.V., 2016) Sachin Kumar Singh; Rajib Nandi; Kirtika Mishra; Hemant Kumar Singh; Ranjan Kumar Singh; Bachcha Singh
We developed a simple, sensitive, label-free and real time detection method for mercuric ions (Hg2+) in water using liquid crystals (LCs). In this system, newly synthesized amphiphilic potassium N-methyl-N-dodecyldithiocarbamate (MeDTC) was doped in 4-cyano-4′-pentyl biphenyl (5CB) LC, which align LC molecules at aqueous interface and polar head group of the amphiphile acts as mecuric ion specific chelating ligand. When this sensor system was incubated in the aqueous solution containing Hg2+ ions, a dark to bright transition of the image of LCs was observed. This was caused due to rapid and stable complex formation between dithiocarbamate chelating group of MeDTC with Hg2+ ions at aqueous interface, which disrupted the orientation of LCs giving bright texture. The limit of detection of the system for aqueous Hg2+ ion is 0.5 μM. This sensor did not respond to other metal ions like Pb2+, Cd2+, Cu2+, Zn2+, Na+, Mg2+ and Ca2+, which are common environmental interference in water. We also demonstrated that this sensor is capable of detecting Hg2+ ions in real water samples (tap water). The very simple and effective procedure reported here should facilitate the development of real time, portable and reliable LC based sensor for mercury pollution control. © 2015 Elsevier B.V. All rights reserved.
Liquid crystalline properties of 3-[4-(4′- alkoxybenzoyloxybenzylidene) amino]-1,2,4-triazines: Synthesis and characterization
(2010) Bachcha Singh; Ashwini Pandey; Sachin Kumar Singh
A new series of 3-[4-(4′-alkoxybenzoyloxybenzylidene)amino]-1,2,4- triazines, C3H2N3N=CHC6H 4OCOC6H4OCmH2m+1 where m=6, 7, 8, 9, 10, 11, 12, 14, and 16 have been synthesized. These compounds have been characterized by elemental analyses, FT-IR, UV-visible, 1H, and 13C NMR spectroscopy. Mesomorphic properties of these compounds were studied by differential scanning calorimetry and polarizing microscopy. The mesomorphic nature of these compounds is dependent on the alkoxy chain length. The compounds (m=6, 7) do not exhibit mesomorphism while the compounds (m=8, 9, 11, 12, 14) show a monotropic nematic mesophase in cooling cycle. The 3-[4-(4′-decyloxybenzoyloxybenzylidene)amino]-1,2,4-triazine displays an enantiotropic nematic mesophase and the hexadecyloxy compound exhibits the smectic A mesophase. Copyright © Taylor & Francis Group, LLC.
Mesomorphic and DFT studies of terminal ester containing salicylaldimines and their copper (II) complexes
(Taylor and Francis Inc., 2017) Hemant Kumar Singh; Sachin Kumar Singh; Vijay Kumar; Priyanka Kanth; Kirtika Mishra; Bachcha Singh
In this article, we report synthesis and characterization of a novel homologous series of butyl 4-(4′-(alkoxy)-2-hydroxybenzylideneamino)benzoates, CnLH (n = 6, 8, 10, 12, 14, 16) and their copper(II) complexes. The mesomorphic properties of these compounds were investigated by differential scanning calorimetry (DSC), polarizing optical microscopy (POM) and powder X-ray diffraction (XRD) studies. The ligands and their copper(II) complexes exhibit wide range of enantiotropic smectic A mesophase as confirmed by their typical optical texture under polarizing microscope. Thermal stability of the compounds is determined by thermo gravimetric analyses. DFT calculations have been performed using GAUSSIAN-09 program at B3LYP level to obtain the stable electronic structure of the ligand and its copper(II) complex. © 2017 Taylor & Francis Group, LLC.
Mesomorphic, micro-Raman and DFT studies of new calamitic liquid crystals; Methyl 4-[4-(4-alkoxy benzoyloxy)benzylideneamino]benzoates
(Elsevier, 2014) Rajib Nandi; Hemant Kumar Singh; Sachin Kumar Singh; Bachcha Singh; Ranjan K. Singh
The mesomorphic properties of newly synthesized homologous series of calamitic liquid crystals; methyl 4-[4-(4-alkoxy benzoyloxy)benzylideneamino] benzoates, H2n+1CnOC 6H4COOC6H4C(H)N C6H 4COOCH3; n = 6, 8, 10, 12, 14, 16 (MABBAB-n) containing ester and Schiff base groups as linker have been studied by temperature dependent micro-Raman study, differential scanning calorimetry (DSC) and polarizing optical microscopy (POM). All members of this series exhibit enantiotropic smectic A (SmA) mesophase with oily streak and focal conic textures. Analyses of Raman marker bands of phenyl rings, Schiff base and ester groups of MABBAB-10 confirm the phase transitions. The Raman study also gives an evidence of breaking of weak intermolecular hydrogen bonds associated with ester groups and formation of new hydrogen bonds through CN bond at Cr → SmA phase transition. The monomer and dimer were optimized and vibrational assignment of MABBAB-10 was also done with density functional theoretical (DFT) technique to understand the experimental results. © 2014 Elsevier Ltd. All rights reserved.
Metal Containing Liquid Crystalline Polymers
(Springer International Publishing, 2015) Bachcha Singh; Sachin Kumar Singh
Design and synthesis of multifunctional single molecules stabilizing liquid-crystalline phases are significant from both fundamental research and application point of views. This task seems to be fulfilled, in part, by metallomesogenic polymers or metal containing liquid crystal polymers (MLCPs) due to two promising elements- liquid crystallinity and metal centre in a single molecular unit with the processability of polymers. The variety of readily available metals incorporated into these mesogenic polymers introduces new physical properties and, consequently, new applications in the field of polymeric materials traditionally based on a few elements (C, H, N, O, halogens, S, P). In recent years enormous growth has occurred in the field of science and technology of metallomesogenic polymers as evident from a large number of publications on these materials. The present chapter will firstly describe general concept of metal containing liquid crystal polymers followed by classification of MLCPs in terms of their mesogenic behaviour (thermotropic and lyotropic) and chemical structures. A brief introduction of synthetic strategies i.e. molecular engineering of MLCPs will be presented in next section to draw a clear concept behind the designing of these functional materials. A special section will be devoted to recent advances including borderline cases in the field of metal containing liquid crystal polymers followed by concluding remarks and future perspective. © Springer International Publishing Switzerland 2016.
Microwave-assisted synthesis and mesomorphic investigations of p-substituted aroylhydrazones and their nickel(II) and copper(II) complexes
(Taylor and Francis Ltd., 2015) Sachin Kumar Singh; Vijay Kumar; Rajib Nandi; Hemant Kumar Singh; Ranjan K. Singh; Bachcha Singh
The present study is focused on the development of green microwave process for the synthesis of mesogenic substituted aroylhydrazones and their nickel(II) and copper(II) complexes. The compounds have been synthesised by microwave-assisted as well as thermal methods for comparison purpose. The compounds were structurally characterised by using suitable spectroscopic techniques. The mesomorphic properties were studied by differential scanning calorimetric analysis and polarising optical microscopy. The stable molecular structures of the mesogenic methylidenehydrazinato-nickel(II) complex have been obtained by density functional theoretical method to understand the structural origin responsible for the mesomorphic property. © 2015, Taylor & Francis.
Microwave-assisted synthesis, characterisation and mesomorphic investigations of novel disubstituted aroylhydrazones
(Taylor and Francis Ltd., 2015) Sachin Kumar Singh; Vijay Kumar; Hemant Kumar Singh; Priyanka Kanth; Bachcha Singh
The present study is focused on the development of green microwave process for the synthesis of mesogenic substituted aroylhydrazones and their structure–mesophase relationship study. Two new liquid crystalline series of disubstituted aroylhydrazones with (ABB(OH)H-n) and without lateral hydroxyl group (ABBH-n) (n = 6–16) have been synthesised by microwave-assisted methods. The compounds were structurally characterised by using suitable spectroscopic techniques. The mesomorphic properties of the series of aroylhydrazones were examined using differential scanning calorimetric analysis and polarising optical microscopy. The relationship between structure and mesogenic properties was analysed by comparison of the present series and earlier reports on homostructural series of aroylhydrazones. Thus, the effects of substitution of phenyl rings with ester and ether linking group at both terminals and introduction of hydroxyl group at lateral position on stability of mesophase and their width were investigated. In general, all substituted aroylhydrazone derivatives exhibit SmC mesophase, and substitution of terminal and lateral group has considerably increased the stability and broadened the width of mesophase of the compounds. © 2015 Taylor & Francis.
Molecular approach to phase transitions in a calamitic ester substituted aroylhydrazone liquid crystal
(John Wiley and Sons Ltd, 2016) Rajib Nandi; Sachin Kumar Singh; Hemant Kumar Singh; D.S. Shankar Rao; S. Krishna Prasad; Bachcha Singh; Ranjan K. Singh
Temperature dependent Raman and X-ray diffraction studies of a calamitic ester substituted aryolhydrazone liquid crystal (LC) system; N-[4-(4ʹ-decyloxy)benzoyloxy benzylidene]-Nʹ-[4ʹ-decyloxybenzoyl]hydrazine (DB2H) have been performed to investigate the molecular arrangement and intermolecular interaction environment in LC phase. X-ray diffraction study with the help of density functional theoretical study gives the information of molecular tilt angle in SmC layer. Prominent Raman signatures of crystal I → crystal II, crystal II → SmC and SmC → Isotropic phase transitions were identified in terms of changes in peak position and linewidth as well as Raman intensity. Analysis of Raman marker bands gives evidence of residual intermolecular hydrogen bonds between amide groups responsible for tilting arrangement in SmC phase. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.
Monitoring the temperature-induced phase transition in a calamitic liquid crystal MABAB-12 via temperature-dependent Raman and DFT study
(Taylor and Francis Ltd., 2025) Sunny Shukla; Monalisha Nayak; Sachin Kumar Singh; Chandan Bhai Patel; Ranjan Kumar Singh
The calamitic liquid crystal methyl 4-(4’-12-alkoxybenzylideneamino) benzoate (MABAB-12) containing a Schiff base as linking group has been synthesised. Mesomorphic properties and phase transition temperatures were probed through temperature-dependent Raman spectroscopy and analysed using density functional theory (DFT). Analysis of Raman marker bands of C-H in-plane bending, C=C stretching of phenyl rings and C=N stretching of the linker gives evidence of phase transitions. To understand the molecular changes more clearly, an in situ Raman measurement of C-H in-plane bending has also been performed. The temperature-dependent Raman study of MABAB-12 reveals the intra-molecular rotation-induced coplanarity of phenyl rings during the Cr→SmA transition. As a result of intra-molecular rotation, significant charge transfer from the phenyl rings to the linking group is observed. Rotational conformational analysis of MABAB-12 has also been performed through density functional theory (DFT), which also supports induced coplanarity of phenyl rings at the Cr→SmA transition. The analysis of Raman spectra reveals the melting of the hitherto rigid core. © 2025 Informa UK Limited, trading as Taylor & Francis Group.