Effect of hydrogen-bonded supramolecular assembling on liquid crystal properties of imidazole-containing azomethines and their chelates with copper(II)

Kadkin, O.,Tae, J.,Kim, E. H.,Kim, S. Y.,Choi, M. G. Taylor Francis 2010 Supramolecular chemistry Vol.22 No.1

Liquid crystal phases generated by supramolecular self-assembly of biforked amphiphilic imidazoles

Kadkin, Oleg N.,Tae, Jigeon,Kim, So Yeon,Kim, Eun Ho,Lee, Eunji,Choi, Moon-Gun Taylor Francis 2009 Liquid crystals Vol.36 No.12

<P> Functional groups with the capability of hydrogen bonding are widely used in the molecular design and preparation of liquid crystalline supramolecular systems, a rapidly growing area of materials showing a high sensitivity towards external stimuli. A series of novel imidazole-containing Schiff's bases replenishing the family of supramolecular liquid crystals has been synthesised and characterised by proton nuclear magnetic resonance, Fourier transform infrared, and ultraviolet-visible spectroscopy, and elemental analyses. Variation of lengths of the terminal alkyl substituents in the obtained amphiphilic imidazoles within 6, 8, 10, 12, 14 and 16 carbon atoms leads to significant changes in their thermal behaviour, micro-segregation and supramolecular self-assembly. Lower homologues were non-mesomorphic, while intermediate members of the homologous series exhibited monotropic bilayered smectic and columnar mesophases. A higher homologue with 16 carbon atoms has an increased trend towards crystallisation of the aliphatic chains and did not exhibit mesomorphism again. The liquid crystalline mesophases were identified and investigated by polarised optical microscopy, differential scanning calorimetry, X-ray diffraction and thermal emission microscopy methods. According to X-ray diffraction characteristics, the smectic mesophase has a bilayered structure where the hydrophilic imidazole groups form a continuous hydrogen bonded network. The interface curvature created by the second alkyl chain leads to the appearance of columnar nanostructures in homologues with 12 and 14 aliphatic carbon atoms.</P>

Synthesis, computational modelling and liquid crystalline properties of some [3]ferrocenophane-containing Schiff's bases and β-aminovinylketone: Molecular geometry-phase behaviour relationship

Kadkin, O.N.,Han, H.,Galyametdinov, Y.G. Elsevier Sequoia 2007 Journal of organometallic chemistry Vol.692 No.25

Syntheses of series of mono- and di-substituted [3]ferrocenophane derivatives with various promesogenic molecular shapes are reported in this article. Nematic and smectic mesophases were observed in the synthesized compounds. On the base of computer-generated molecular models the molecular geometry-phase behaviour relationships were examined.

A Novel Series of Heteropolynuclear Metallomesogens: Organopalladium Complexes with Ferrocenophane-Containing Ligands

Kadkin, Oleg N.,An, Jaein,Han, Haksoo,Galyametdinov, Yuri G. WILEY-VCH Verlag 2008 European journal of inorganic chemistry Vol.2008 No.10

<P>Ferrocenophane-containing (Fcph) Schiff's bases p-C<SUB>12</SUB>H<SUB>25</SUB>O(C<SUB>6</SUB>H<SUB>4</SUB>)CH=N(C<SUB>6</SUB>H<SUB>4</SUB>)Fcph (L<SUP>A</SUP>H) and p-C<SUB>12</SUB>H<SUB>25</SUB>O(C<SUB>6</SUB>H<SUB>4</SUB>)COO(C<SUB>6</SUB>H<SUB>4</SUB>)CH=N(C<SUB>6</SUB>H<SUB>4</SUB>)Fcph (L<SUP>B</SUP>H) react with palladium(II) acetate to form μ-acetato- and chloro-bridged dimeric organopalladium complexes. By exchanging acetato-groups with the chloride anions, μ-chloro-bridged heteropolynuclear dimers are obtained that show thermotropic smectic A phases over a temperature range of 198 to 260 °C. The complexes [PdClL<SUP>A</SUP>]<SUB>2</SUB> and [PdClL<SUP>B</SUP>]<SUB>2</SUB> can be transformed into a variety of mixed-ligand Pd<SUP>II</SUP> complexes by treatment with salicylaldimine p-C<SUB>12</SUB>H<SUB>25</SUB>O(C<SUB>6</SUB>H<SUB>4</SUB>)COO(C<SUB>6</SUB>H<SUB>3</SUB>)(OH)CH=N(C<SUB>6</SUB>H<SUB>4</SUB>)Fcph (L<SUP>C</SUP>H) and β-aminovinyl ketone p-C<SUB>12</SUB>H<SUB>25</SUB>O(C<SUB>6</SUB>H<SUB>4</SUB>)COCH=CHNH(C<SUB>6</SUB>H<SUB>4</SUB>)Fcph (L<SUP>D</SUP>H). The obtained mixed-ligand heterometallic complexes [PdL<SUP>A</SUP>L<SUP>C</SUP>], [PdL<SUP>B</SUP>L<SUP>C</SUP>], [PdL<SUP>A</SUP>L<SUP>D</SUP>] and [PdL<SUP>B</SUP>L<SUP>D</SUP>] exhibit enantiotropic, thermotropic nematic phases over a broad temperature range from 71 to 205 °C. The structures of the synthesized compounds were characterized by means of <SUP>1</SUP>H NMR, IR and UV spectroscopy, as well as elemental analysis. The liquid crystalline properties were studied by polarising optical microscopy and DSC. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)</P> <B>Graphic Abstract</B> <P>Liquid crystalline heteropolynuclear complexes based on palladium(II) chelates withvarious ferrocenophane-containing ligands were synthesized. <img src='wiley_img/14341948-2008-2008-10-EJIC200700750-fig000.gif' alt='wiley_img/14341948-2008-2008-10-EJIC200700750-fig000'> </P>

Novel Tetrahedratic Smectic C and Nematic Mesophases in Unsymmetrically 1,1′-Bis-substituted Ferrocenomesogens

Kadkin, Oleg N.,Kim, Eun Ho,Rha, Young Joon,Kim, So Yeon,Tae, Jigeon,Choi, Moon-Gun WILEY-VCH Verlag 2009 Chemistry Vol.15 No.40

<B>Graphic Abstract</B> <P>Non-conventional mesophases have been observed in novel ferrocene-containing liquid crystals. The formation of helical and garland-like superstructures, and spontaneous resolution into macroscopic chiral domains occur in the lamellar mesophase. The nematic mesophase shows unusual textures and chiral nematic droplets such as those depicted. <img src='wiley_img/09476539-2009-15-40-CHEM200901349-content.gif' alt='wiley_img/09476539-2009-15-40-CHEM200901349-content'> </P>

Synthesis and liquid crystal properties of copper(II) and palladium(II) chelates with new ferrocene-containing enaminoketones

Kadkin, Oleg N.,Kim, Eun Ho,Kim, So Yeon,Choi, Moon-Gun Elsevier 2009 Polyhedron Vol.28 No.7

<P><B>Graphical abstract</B></P><P>The syntheses of a series of ferrocene-containing β-aminovinylketone complexes with Cu(II) and Pd(II) ions are described in this article. The synthesized ligands and Cu(II) complexes exhibited disordered soft crystal phases upon cooling from the isotropic liquid state, and the Pd(II) complexes showed monotropic smectic C mesomorphism.</P><ce:figure></ce:figure> <P><B>Abstract</B></P><P>Heterometallic liquid crystals are of special interest because of the possibility to combine optical, magnetic and electric properties of different metal ions in one mesogenic molecule. In order to investigate new heteropolynuclear mesogenic systems, a series of β-aminovinylketone ligands derived from acetyl ferrocene have been synthesized. Subsequently Cu(II) and Pd(II) ions were incorporated into the enaminoketone chelate core. The obtained ligands and complexes were characterized by element analysis, <SUP>1</SUP>H NMR, IR and UV–Vis spectroscopies. According to thermal polarizing microscopy and DSC studies, the ligands and Cu(II) complexes exhibit disordered soft crystal phases upon cooling from the isotropic liquid state. The Pd(II) complexes showed monotropic smectic C mesomorphism. The metal centres in the synthesized heteropolynuclear mesogens are in close vicinity to each other, which is of considerable interest from the viewpoint of the potential electron-transfer interactions between a ferrocene core and the central ions.</P>

Phase behavior of some mono-substituted ferrocene- and [3]ferrocenophane-containing nematics with the cyclohexane ring in the rigid core

Kim, S.Y.,Kadkin, O.N.,Kim, E.H.,Choi, M.G. Elsevier Sequoia 2011 Journal of organometallic chemistry Vol.696 No.11

Generally, incorporation of the cyclohexane rings into the rigid core of rod-like mesogens leads to improved technological parameters, i.e. low viscosity, ambient transition temperatures and stability of the nematic state. Taking this into consideration, a series of novel cyclohexane-containing derivatives of ferrocene has been synthesized. The effect of various structural factors on liquid crystalline behavior of the synthesized ferrocene-containing nematics has been examined. Ferrocenophane compounds exhibited enhanced liquid crystalline properties in comparison with the derivatives of unbridged ferrocene. Depending on thermal prehistory of the samples, some of the synthesized ferrocenomesogens showed remarkable migration of the phase transition temperatures. In one case such behavior led to stabilization of the initially monotropic nematic mesophase in subsequent heating cycles. In another case, the phase transition shifts caused the lowering of the crystal-to-nematic transition temperature and the broadening of the mesophase range. There was also a case of alteration from the initially enantiotropic to monotropic behavior. The obtained novel metallomesogens are important footsteps toward the development of low-viscous and low-temperature materials for liquid crystal applications possessing a chromophoric, redox-switchable, polarizable and chemically stable superaromatic ferrocene unit.