Novel ferroelectric liquid crystals based on fused thieno[3,2-b]furan and thieno[3,2-b]thiophene cores

Several series of new benzofused thieno[3,2-b]furan- and thieno[3,2-b]thiophene-based derivatives have been synthesized and their mesomorphic properties investigated. All the studied compounds exhibit a SmC* phase with very wide temperature interval. Additionally, some types of the compounds show the cholesteric, SmA or blue phase. In the ferroelectric SmC* phase we evaluated physical properties of relevance for possible applications.     

The distribution of landed property

The distribution of property is established through various mechanisms. In this paper we study the acreage distribution of land plots owned by natural persons in the Zlín Region of the Czech Republic. We show that the data are explained in terms of a simple model in which the inheritance and market behavior are combined.     

Synthesis,Characterization and Electrochemistry of New Soluble Porphyrazine Complexes Bearing Octakis 3‐Methylbutylthio Substituents

Porphyrazines, MPz (M = Mg, H, Ni, Zn and Co) with octakis 3‐methylbutylthio substituents have been synthesized starting with the corresponding unsaturated dicarbonitrile derivative. These new compounds have been characterized by UV‐Vis, FT‐IR, ¹H NMR, MS and elemental analysis methods. Voltammetric properties of the complexes were also investigated by CV, DPV and CPC techniques. Electrochemical studies show that three reversible one electron reductions and one reversible one electron oxidation processes (two for Co^IIPz) are observed for all of the complexes. The E_1/2 values are similar for the H₂Pz, Ni^IIPz and Zn^IIPz derivatives with negative shift due to the different effective nuclear charges of the central metal ion. Peak to peak separations and separation between the first reduction and first oxidation couples related with the HOMO‐LUMO gap of the complexes are in harmony with the common porphyrazine complexes.     

Synthesis and mesomorphic properties of liquid crystalline [1]benzothieno[3,2-b][1]benzothiophene derivatives

Two new series of chiral aliphatic and aromatic esters of 7-decyl[1]benzothieno[3,2-b][1]benzothiophene-2-carboxylic acid were synthesized and their mesomorphic behaviour studied. While the chiral aliphatic esters exhibited only the SmA phase, the antiferroelectric SmC_A* phase was found for esters with chiral 4-hydroxybenzoates; for one homologue a ferroelectric SmC* phase was also observed. Introduction of lateral substituents in the 3-position of the 4-hydroxybenzoic acids (methoxy, fluoro, chloro, and bromo) led to a reduction of the polymorphism and only the SmA phase remained.     

Built-up structure criticality

The built-up land represents an important type of an overall landscape. In this paper, the built-up land structure in the largest cities in the Czech Republic and some selected cities in the USA is analysed using the framework of statistical physics. We calculate the variance of the total area and of the count of the built-up land plots contained inside discs of different radii. In both cases, the variance as a function of the disc radius follows a power law with exponents that are comparable through different cities. The study is based on the cadastral data from the Czech Republic and on the building footprints from GIS data in the USA.     

Novel liquid crystals based on [1]benzothieno[3,2- b][1]benzothiophene

Four series of new [1]benzothieno[3,2- b][1]benzothiophene derivatives have been synthesized. In the non-chiral series a SmA phase occurs, while the chiral series exhibits a rather wide antiferroelectric SmC^A* phase just below the SmA phase. The SmA-SmC^A* phase transition has been studied using DSC and dielectric spectroscopy. In the SmC^A* phase the spontaneous quantities have been measured. The tilt angle shows a typical temperature dependence and the values of spontaneous polarization are rather moderate. The length of the helical pitch increases on increasing the length of the non-chiral alkyl chain.     

Strikingly Different Effects of Hydrogen Bonding on the Photodynamics of Individual Nucleobases in DNA: Comparison of Guanine and Cytosine

Ab initio surface hopping dynamics calculations were performed to study the photophysical behavior of cytosine and guanine embedded in DNA using a quantum mechanical/molecular mechanics (QM/MM) approach. It was found that the decay rates of photo excited cytosine and guanine were affected in a completely different way by the hydrogen bonding to the DNA environment. In case of cytosine, the geometrical restrictions exerted by the hydrogen bonds did not influence the relaxation time of cytosine significantly due to the generally small cytosine ring puckering required to access the crossing region between excited and ground state. On the contrary, the presence of hydrogen bonds significantly altered the photodynamics of guanine. The analysis of the dynamics indicates that the major contribution to the lifetime changes comes from the interstrand hydrogen bonds. These bonds considerably restricted the out-of-plane motions of the NH(2) group of guanine which are necessary for the ultrafast decay to the ground state. As a result, only a negligible amount of trajectories decayed into the ground state for guanine embedded in DNA within the simulation time of 0.5 ps, while for comparison, the isolated guanine relaxed to the ground state with a lifetime of about 0.22 ps. These examples show that, in addition to phenomena related to electronic interactions between nucleobases, there also exist relatively simple mechanisms in DNA by which the lifetime of a nucleobase is significantly enhanced as compared to the gas phase.     

Synthesis and characterization of a new fluorene ligand and its complexes with cobalt(II), copper(II), and ruthenium(II)

A new fluorene ligand, benzo[15-crown-5]-5H-pyrido[3′,2′:4,5]cylopenta[1,2-b]pyridin-5-ylidenehydrazone (bph), has been synthesized from the reaction of 4,5-diazafluoren-9-one with 4′-formylbenzo-15-crown-5. The Co(II), Cu(II), and Ru(II) complexes of the ligand were prepared and characterized. The metal-to-ligand ratio of the Co(II) and Cu(II) complexes was found to be 2:1 and that of the Ru(II) complex was found to be 1:1. The ligand and complexes have been characterized by FTIR, UV–visible, ¹H NMR and fluorescence spectra, as well as elemental analyses and mass spectra.     

Derivatization and in situ metallation of phthalocyanines using click chemistry

Dialkyl (3,4-dicyanophenyl)propargylmalonates were prepared by the reaction of propargyl bromide and the potassium salt of dialkyl-3,4-dicyanophenylmalonates. A cyclotetramerization reaction was achieved in pentanol in the presence of DBU without protective/deprotective chemistry, affording the peripherally tetrasubstituted alkynyl phthalocyanines. Subsequently, in situ metallation and ‘clicking’ were employed for the first time as an efficient and quantitative route to tetratriazole-functionalized phthalocyanines.