Design, synthesis and characterization of a linear hydrogen bonded homologous series

A linear hydrogen bonded liquid crystalline homologous series has been synthesized and characterized. Hydrogen bond is formed between p-n-dodecyloxy benzoic acid and various p-n-alkyl benzoic acids whose alkyl chain vary from octyl to ethyl. Synthesized complexes are characterized by FTIR, ¹H NMR and ¹³C NMR studies for inferring the formation of hydrogen bonds. Polarizing Optical Microscopy (POM) and DSC studies reveal various mesophases and their corresponding transition temperatures along with respective enthalpy values. All the seven synthesized complexes exhibit rich liquid crystalline mesomorphism. A new phase namely smectic X has been observed in five of the complexes with a narrow thermal range. This phase has been characterized by optical textural, DSC, tilt angle and helicoidal pitch studies. Smectic X is sandwiched between traditional smectic C and re-entrant smectic C (designated as C_R) phases. Homeotropic transition in nematic phase is observed in all the mesogens and thus these materials can be used as thermally controlled optical shutters. Tilt angle in smectic C, smectic X and smectic C_R phases have been experimentally elucidated for all the mesogens.     

Systematic studies on eight homologous series of supramolecular hydrogen bonded liquid crystals

Design, synthesis and characterization of hydrogen bonded liquid crystals (HBLC) formed by alkyloxy benzoic acids (referred as nOBA?:?ABOm) are discussed. Eight such homologous series of HBLC are synthesized with varying the carbon chain length from 5 to 12 referred as nOBA?:?ABOm. These complexes are characterized by polarizing optical microscope (POM), differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FTIR) studies. Phase diagrams of the individual series have been constructed from the data of POM and DSC respectively. The effect of the chain length on the phase formation is discussed. Thermodynamic evaluation of nOBA?:?ABOm homologues series has been carried out. It is observed that the entire eight homologous series possess thermodynamically equilibrium energy states. The results of phase variance influence of chain length, phase transitions and corresponding enthalpy values are discussed.     

Design and characterization of hydrogen bonded ferroelectric liquid crystals: A study of light modulation in nematic and smectic orderings

A novel series of hydrogen bonded ferroelectric liquid crystals (HBFLC) have been isolated. Phase transition temperatures obtained by differential scanning calorimetry (DSC) and textural observations elicited by polarizing optical microscope (POM) studies are discussed. Phase diagram is constructed from the above data. Salient feature of the present work is observation of a light modulation due to field induced transitions (FiT) in nematic and smectic C* phases. Tilt angle measurements in various FiT of smectic C* phase are discussed. One of the mesogens in nematic phase behaves like an optical modulator; helical pitch measurements support the above observation.     

EPR characterization of a nanoporous metal-organic framework exhibiting a bulk magnetic ordering

Magnetic properties of the open-framework structure [Cu₃(PTMTC)₂(py)₆(CH₃CH₂OH)₂(H₂O)] as well as those of a related evacuated sample have been analyzed on the basis of combined SQUID and EPR measurements. Such combined experiments demonstrate unambiguously the key role played by the radical ligand PTMTC in the promotion in both molecular magnets of magnetic exchange interactions through the open-framework structure.     

Study and characterization of the smectic X* phase in binary mixtures of thermotropic double hydrogen bonded ferroelectric liquid crystals

Thermotropic double hydrogen bonded ferroelectric liquid crystals (DHBFLCs) composed of N-carbamyl-L-glutamic acid (CGA) and p-n-alkyloxy benzoic acids (BAO) have been investigated. Variation in the molar proportion of X and Y (where X = CGA + 5BAO and Y = CGA + 6BAO, CGA + 7BAO, and CGA + 8BAO) composed of three series yielded 27 binary mixtures. Optical and thermal properties of these mixtures are meticulously studied in the present article. A novel smectic ordering, namely smectic X*, is observed in all the three series. The aim of the investigation is to obtain an abundance occurrence of smectic X* and hence the proportions of the binary mixtures are so chosen that the preamble task is accomplished. Phase diagrams of three series are constructed from the data obtained from polarizing optical microscope (POM) and differential scanning calorimetry (DSC) studies. Odd–even effect, order of the phase transition, thermal stability factor, thermal equilibrium, and optical tilt angle are also premeditated.     

Investigation of polar and nonpolar ordering in a smectic liquid crystal layer

A molecular-statistical theory that describes a smectic layer where short molecular axes have both polar and nonpolar orders has been developed. Several types of dependences of each order parameter on temperature and external field were obtained, and all possible phase states of the layered structure were determined.     

Induced anticlinic ordering and nanophase segregation of bow-shaped molecules in a smectic solvent

Recent experiments indicate that doping low concentrations of bent-core molecules into calamitic smectic solvents can induce anticlinic and biaxial smectic phases. We have carried out Monte Carlo simulations of mixtures of rodlike molecules (hard spherocylinders with length/breadth ratio L(rod)/D = 5) and bow-shaped molecules (hard spherocylinder dimers with length/breadth ratio L(ban)/D = 5 or 2.5 and opening angle psi). We find that a low concentration ( 3%) of L(ban)/D = 5 dimers induces anticlinic ( SmC(A)) ordering in an untilted smectic ( SmA) phase for 100 < or = psi < 150. For L(ban)/D = 2.5, no tilted phases are induced. However, with decreasing psi we observe a sharp transition from intralamellar nanophase segregation (bow-shaped molecules segregated within smectic layers) to interlamellar nanophase segregation (bow-shaped molecules concentrated between smectic layers) near psi = 130.     

Structure and stability of a homologous series of tin oxides

The structures and stabilities of a series of nonstoichiometric SnO2-x compounds, which are yet unknown experimentally, are predicted using the cluster expansion technique combined with first-principles calculations. A homologous series of Sn(n+1)O(2n) in which oxygen vacancies are layered on (101) planes of the rutile lattice is discovered. The homologous crystals are composed of divalent and quadrivalent Sn atoms. No trivalent Sn atoms are formed.     

Electron scattering studies of DMS,DMDS and DMSO homologous series

The present paper reports ionisation, elastic and total cross section for the first three members of dimethyl sulphide, dimethyl disulphide and dimethyl sulphoxide family of molecules. The multi-scattering centre spherical complex optical potential formalism is applied for integral elastic and inelastic cross section calculations. From the inelastic part, ionisation cross section is derived using complex scattering potential-ionisation contribution method. The total cross section is then obtained from the sum of elastic and inelastic contributions. A reasonably good agreement is obtained for elastic cross section, wherever comparison is available. The ionisation and total cross section calculation for the complete set of molecules has been performed for the first time.     

Correlation between the molecular chirality index and the spontaneous polarisation in series of smectic C* liquid crystals

A correlation between spontaneous polarisation and the chirality index of the constituent molecules, multiplied by the molecular transverse dipole, has been considered for five series of ferroelectric smectic C* liquid crystals. A good correlation has been found within each series, and it has been shown that the scaled chirality index may be used to estimate the spontaneous polarisation in a series of smectic C* mesogens with small systematic changes of the molecular structure. At the same time one cannot expect any significant correlation between the polarisation and the chirality index for smectic C* materials of sufficiently different structure because the spontaneous polarisation may be significantly effected by some details of the molecule's structure including the orientation of the transverse dipole with respect to the primary short molecular axis.     

Comparative study of liquid-crystalline ordering in a monomer,linear polymer,and graft copolymer by the photon transmission technique

The photon transmission technique was used to study the phase transitions of a liquid crystalline acrylate monomer, 6-(4-cyanobiphenyl-4′oxy)hexyl acrylate (LC6), its homopolymer (PLC6) and its graft copolymer (GLC6) with polytetrahydrofuran grafts. The phase transitions were also confirmed by DSC and polarizing microscopy. We observed the phase transition sequence isotropic–nematic–smectic A–smectic C in the LC6 monomer. In PLC6 and GLC6 polymers, the nematic and smectic A phases appear dominant. The apparent nematic–smectic A transition is of first order in PLC6 and of second order in GLC6, with the transition temperature remaining the same. The effects of quenched random constraints introduced in GLC6 are consistent with the theory of quenched random interactions. The critical exponents were also evaluated.     

Design, synthesis and characterization of a highly luminescent Eu-complex monomer featuring thenoyltrifluoroacetone and 5-acryloxyethoxymethyl-8-hydroxyquinoline

A multi-functional ligand, 5-acryloxyethoxymethyl-8-hydroxyquinoline (Hamq), was synthesized, which contained a polymerizable C=C double bond for the copolymerization with other vinyl monomers and acted as photon antenna able to transfer energy to Eu³⁺ ions effectively. The triplet state energy of Hamq was determined to be 22,370 cm⁻¹ via the phosphorescence spectra of Hamq and its gadolinium complex. The title complex monomer Eu(tta)₂(amq) was prepared by coordination reaction of Hamq with europium isopropoxide and 2-thenoyltrifluoroacetone (Htta) in dry organic solvents under argon atmosphere and characterized by elemental analysis and IR spectrum. The photophysical properties of the complex were studied in detail with UV-vis, luminescence spectra, luminescence lifetime and quantum yield. The complex exhibited nearly monochromatic red emission at 612 nm, a remarkable luminescence quantum yield at room temperature (30.6%) upon ligand excitation and a long ⁵D₀ lifetime (389 μs), which indicated that the ligand Hamq could sensitize the luminescence of Eu(III) ion efficiently in Eu(tta)₂(amq), resulting in a strong luminescence of its copolymer poly[MMA-co-Eu(TTA)₂(amq)] under UV excitation. The excellent luminescence properties of the complex made it not only a promising light-conversion molecular device but also an excellent luminescent monomer.     

Realization and characterization of a two-photon four-qubit linear cluster state

We report on the experimental realization of a four-qubit linear cluster state via two photons entangled both in polarization and linear momentum. This state was investigated by performing tomographic measurements and by evaluating an entanglement witness. By use of this state we carried out a novel nonlocality proof, the so-called "stronger two observer all-versus-nothing" test of quantum nonlocality.     

Synthesis and structural characterization of a series of lanthanide stannate pyrochlores

A simple hydrothermal method has been employed to prepare a series of lanthanide stannate pyrochlores Ln₂Sn₂O₇ (Ln=Y, La, Pr-Yb) at a relatively low temperature of less than 200 °C successfully. On the basis of structural characterizations by X-ray powder diffraction (XRD), Fourier transform infrared (FT-IR) absorption spectroscopy and Raman spectroscopy, it was found that the positions of bands in vibrational spectra are sensitive to the ionic radius of Ln³⁺, and the linear relationship can be seen between the frequency of Sn-O stretching mode and the lanthanide ionic radius in IR spectrum, as well as the frequency of O-Sn-O bending mode and the lanthanide ionic radius in Raman spectrum.     

Thermal and optical characterization of a novel series of supramolecular liquid crystals

Supramolecular hydrogen bonded liquid crystal (SMHBLC) homologous series is synthesized and characterized. Hydrogen bond is formed between p-n-alkyloxy benzoic acids (nOBA, where n=7 to 12) and Iodo substituted benzoic acid (I_mBA) respectively. The isolated homologs are characterized by various techniques like Polarizing Optical Microscopy (POM), Differential Scanning Calorimetry (DSC), ¹H Nuclear Magnetic Resonance Spectroscopy (NMR) and Fourier Transform Infrared Spectroscopy (FTIR). From the POM and DSC studies phase diagram has been constructed and discussed. A new smectic ordering, labeled as smectic R, has been characterized which exhibits a ribbon like texture. This phase is observed in a complex pertaining to the undecyloxy carbon number. Tilt angle in smectic R phase and in traditional smectic C of all the complexes have been experimentally deduced and the results are fitted and so obtained β value concurrences with the Mean field theory predicted value.     

Organic high-spin systems: synthesis, electrochemical and ETSF studies of a series of tetraaryl-meta-phenylenediamines

A series of N,N,N′,N′-tetraaryl-1,3-phenylenediamines with various substituents at the para-position of peripheral rings were designed and synthesized. Electrochemical and novel electron transfer stopped-flow methods were invoked for characterizing the absorption spectra of the corresponding short-lived mono- and dicationic states. Both thermodynamic and kinetic stabilization are required to extend the lifetime of the dicationic states. Useful molecular design rules for stabilizing the dicationic states of N,N,N′,N′-tetraaryl-1,3-phenylenediamines as precursors for positively charged high-spin systems were elucidated.