Dušanka Ž. Obadović

Nickel (II) and cobalt (II) complexes of the hydrazide of 1-naphthylacetic acid

SummaryThe hydrazide of 1-naphthylacetic acid forms both bis- and tris-(ligand) high-spin nickel(II) and cobalt(II) complexes possessing an octahedral configuration. The compositions of the complexes are influenced not only by the metal-ligand stoichiometry but also by the nature of the inorganic anion. A physico-chemical investigation showed that the ligand is neutral and bidentate, coordinated through amido-nitrogen and carbonyl oxygen. The compounds were characterized by elemental analysis, magnetic measurements, i.r. and diffuse-reflection spectra and molar conductivity.

Effect of the chiral chain length on structural and phase properties of ferroelectric liquid crystals

Studies of structural and phase properties obtained on several ferroelectric liquid crystalline materials with 2-alkoxypropionate group used as a chiral centre and without any lateral substitution are presented. In dependence on the chiral chain length these compounds exhibit the cholesteric N* phase, the ferroelectric smectic C* and a low-temperature SmX phase. Values of the spontaneous polarization and spontaneous tilt angle have been determined within the whole range of the SmC* phase. A low-temperature SmX phase has been identified as the orthogonal hexatic SmB* phase. The molecular parameters, namely the layer spacing in the SmC* and SmB* phases and the average intermolecular distances (D) between neighbouring parallel molecules in all investigated phases have been determined using the results of the X-ray diffraction obtained on non-oriented samples. The effect of the chiral chain length on mesomorphic, structural and physical properties of the studied ferroelectric liquid crystalline materials is discussed.

The Structure of Mesophases of Binary and Multicomponent Mixtures of some Cholesteric Liquid Crystals

Abstract We present the results of the study of binary and multicomponent mixtures of cholesteryl enanthate with cholesteryl nonanoate and cholesteryl formiate. The aim of the study is the preparation of the system with phase transition temperature close to room temperature. Phase diagrams of binary mixtures are formed on the basis of data obtained by the optical microscopy and DS calorimetry and the shift of phase transition points of order 30–50° with respect to initial components was established. In the case of three- and four-component mixtures, we have identified the presence of enantiomorphic phase transitions of smectic and cholesteric type respectively. X-ray diffraction data have enabled the characterization of the structure of smectic or cholesteric mesophase and the calculation of molecular parameters: apparent length of the molecules l and the average intermolecular distance (D).

Thermal decomposition of octahedral Ni(II) complexes with 1-Naphthylacetic acid hydrazide

The thermal decompositions of the octahedral complexes of Ni(II) with 1-naphthylacetic acid hydrazide (L), of the type NiLnX2·mH2O, wheren=2 and 3,m=2 and 4, andX=Cl, Br, I, NCS, OAc and 1/2 SO4, were studied in both air and nitrogen atmospheres at temperatures up to 1000 ‡C. The most probable mechanism of the process was proposed.ZusammenfassungIn dieser Arbeit wurde die thermische Zersetzung oktaedrischer Ni(II)-Komplexe mit Hydraziden der 1-Naphthylessigsäure (L) des Types NiLnX2·mH2O untersucht, wobein=2 bzw. 3,m=2 bzw. 4 undX=Cl, Br, I, NCS, OAc bzw. 1/2 SO4 ist. Die thermische Zersetzung wurde in Luftbzw. Stickstoffatmosphäre bis zu Temperaturen von 1000 C durchgefürt und der wahrscheinlichste Mechanismus des Prozesses gegeben.РЕжУМЕпРОВЕДЕНО ИсслЕДОВА НИЕ тЕРМИЧЕскОгО РАжлОжЕНИь ОктАЁДРИ ЧЕскИх кОМплЕксОВ НИкЕль с гИДРАжИДОМ 1-Н АФтИлУксУсНОИ кИслО ты (L) тИпА NiLnX2·mH2O, гДЕn=2 И 3,m=2 И 4, АX=Cl, Br, I, NCS, OAc И 1/2SO4. тЕРМИЧЕскОЕ Р АжлОжЕНИЕ пРОВЕДЕНО В АтМОсФЕРЕ ВОжДУхА И АжОтА ДО тЕМпЕРАтУРы 1000‡. пРЕДлОжЕН НАИБОлЕЕ ВЕРОьтНыИ МЕхАНИжМ т ЕРМИЧЕскОгО РАжлОжЕНИь.

Study of binary cholesteric liquid crystalline mixtures doped with some chiral nonmesogenic estradiol derivatives

We investigated the influence of some estradiol derivatives on the thermal and structural properties of binary mixtures of cholesteryl enantate and cholesteryl myristate. The characterization of the mesophases was made by polarizing optical microscopy, differential scanning calorimetry and X-ray diffraction. A considerable shift of the phase transition temperature I→Ch, as well as the temperature of formation of the SmA* phase was observed. Besides phase sequences and phase transition temperatures the measurements enabled the determination of some molecular parameters of the mixtures: the thickness of smectic layers and the longitudinal spacing distance in the cholesteric phase (d) and the average distance between the long axes of neighboring molecules (D).

X‐ray and Dielectric Spectroscopy Studies Of Chiral Ferroelectric Liquid Crystals With Keto Group

Series of ferroelectric liquid crystals with the keto group attached to the molecule core and one lactate group as the chiral centre have been studied by X‐ray and dielectric spectroscopy. The thickness of smectic layers and the average distance between the long axes of neighboring molecules increases with increase of both chains.

Study of ferroelectric liquid crystals with 2-alkoxypropionate chiral group by X-ray measurements

We present the X-ray study of three series of ferroelectric liquid crystalline materials with a 2-alkoxypropionate chiral group in order to establish the connection of physical properties and the number of carbon atoms in the non-chiral chain. All materials have the ferroelectric SmC∗ phase in a broad temperature range. Using X-ray diffraction of non-oriented samples we have identified low temperature non-tilted SmX phase as the SmB phase. The thickness of smectic layers and value of the average distance between the long axes of neighbouring molecules were determined. The temperature dependence of the layer spacing was studied in all phases.

Powder diffraction data and mesomorphic properties of 4-butyloxyphenyl 4′-decyloxybenzoate

Unit cell parameters calculated from X-ray powder diffraction data are presented for the crystalline phase of a liquid crystal 4-butyloxyphenyl 4′-decyloxybenzoate: a = 23.098 (4) Å, b = 5.974 (6) Å, c = 12.357 (10) Å, β = 121.5283 (788)°, unit-cell volume V = 1453.56 Å3. Temperature dependent X-ray diffraction data confirmed the existence of smectic A and smectic C mesophases and a more ordered, tilted crystalline smectic phase. Possibility of existence of previously reported smectic B phase as well as another crystalline phase was refuted.

Phase behaviors of binary mixtures composed of banana-shaped and calamitic mesogens

In this work, five mixtures with different concentrations of banana-shaped and calamitic compounds have been prepared and subsequently studied by polarizing optical microscopy, differential scanning calorimetry, and X-ray diffraction on non-oriented samples. The phase sequences and molecular parameters of the binary systems are presented.

The study of phase transition in some irradiated cholesteric liquid crystalline mixtures

We present the study of binary and multicomponent cholesteric mixtures undertaken with the aim of forming a system with the temperature of the phase transition close to the room temperature, which could be suitable for the detection of ionizing radiation. The phase diagrams were established on the basis of data from the optical microscopy and differential scanning calorimetry (DSC). The mixtures were exposed to the continual spectrum of X-Ray radiation in the period of 30/60 min. The mixtures react by changing the color of the mesophase, and a shift of the mesophase transition towards lower temperatures. The duration of the effects exceeds six months.