Effect of arrangement of the styryl fragment on the optical properties and complexation of mono-and bis(styryl)-substituted <Emphasis Type="Italic">N</Emphasis>-methylpyridinium perchlorates containing benzo-15-crown-5 ether moieties

Using ¹H NMR spectroscopy and steady-state and time-resolved electronic spectroscopy, the optical properties of mono-and bis(styryl)pyridinium perchlorates and their complexes with Mg²⁺, Ba²⁺ cations were studied. The stability constants of the complexes were determined using spectrophotometric titration. The formation of inclusion complexes for Mg²⁺ and sandwich type complexes for Ba²⁺ results in fluorescence enhancement and increases the lifetimes of the excited states of the initial bis-styryl ligands. The variation of position of the styryl fragment in the pyridinium aromatic ring gives rise to photochromic crown ethers with different optical and photophysical characteristics and is also an easy route to bis(crown-ethers) of symmetrical and unsymmetrical structure. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2092–2100, November, 2007.     

Interaction of Crown Ether‐Annelated Styryl Dyes with Double‐Stranded DNA

DNA‐binding properties of 15‐crown‐5‐derived mono‐ and bis‐styryl dyes were investigated in the presence of calf thymus DNA. To access the factors that influence the DNA association in the series of these ligands, the structure of the molecules was varied by either changing size of the heterocyclic moiety or altering the position of the styryl substituents. The major binding mode for the monostyryl dyes is intercalation. Notably, binding of the dyes to the nucleic acids leads to a fluorescence enhancement by a factor of up to 54. Therefore, these cationic styryl derivatives may be applied as fluorescent “light‐up” probes for DNA detection.     

Synthesis, complex-formation, and extracting ability of new derivatives of dithia-13(16)-crown-4(5) ethers

Various methods of synthesizing functional derivatives of dithia-13(16)-crown-4(5) ethers are proposed. Complex-formation of the obtained compounds with Ag⁺ and Pb²⁺ ions has been studied using ¹H NMR. A radiometric method was used to investigate the extracting ability of substituted dithia-13(16)-crown-4(5) ethers in relation to Ag⁺ and Cd²⁺ ions from aqueous solution in the presence of anions of various degree of hardness, with determination of the metal content. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 233–243, February, 2006.     

Efficient Solution‐Processed Bulk Heterojunction Solar Cells by Antiparallel Supramolecular Arrangement of Dipolar Donor–Acceptor Dyes

A series of dipolar donor–acceptor (D –A) chromophores with aminothiophene donor and different heterocyclic acceptor units is reported. By modulation of the acceptor strength, absorption bands over the whole visible spectrum are accessible as well as adjustment of the frontier molecular orbital levels. The performance of the chromophores in blends with fullerene acceptors in solution‐processed bulk heterojunction solar cells was studied and related to the molecular properties of the dyes. In particular, the effect of the large ground‐state dipole moments of these dyes was investigated by single crystal X‐ray analysis, which revealed antiparallel dimers, resulting in an annihilation of the dipole moments. This specific feature of supramolecular organization explains the excellent performance of merocyanine dyes in organic solar cells. With blends of HB366 :PC₇₁BM, the most efficient solar cell with a V_OC of 1.0 V, a J_SC of 10.2 mA cm⁻², and a power‐conversion efficiency of 4.5 % was achieved under standard AM1.5, 100 mW cm⁻² conditions. Under reduced lighting conditions, even higher efficiencies up to 5.1 % was obtained.     

Metal-ion induced FRET in macrocyclic dynamic tweezers

We report here about effective FRET process (73–99%) in mono-Mg²⁺ complexes of symmetrical crown ether bis(styryl) dyes. The FRET process has not been observed in the free state and in binuclear complexes. The formation of mononuclear complex provides two styrylic fragments with appropriate positions of absorption and emission bands for FRET. The other important parameter for FRET is the proper geometric orientation of both chromophores, which attain sandwich conformation with close positioning of complexed and free styryl fragments induced by ion-modulated geometry reorganization of the bis-dye.     

Spin-glass, antiferromagnetism and kondo behavior in Ce2Au1−x Co x Si3 alloys

Recently, the solid solution Ce₂Au_{1− x Co} xSi₃ has been shown to exhibit many magnetic anomalies associated with the competition between magnetic ordering and the Kondo effect. Here we report high pressure electrical resistivity of Ce₂AuSi₃, ac susceptibility (X) and magnetoresistance of various alloys of this solid solution in order to gain better knowledge of the magnetism of these alloys. High pressure resistivity behavior is consistent with the proposal that Ce₂AuSi₃ lies at the left-hand side of the maximum in Doniach’s magnetic phase diagram. The ac X data reveal that there are in fact two magnetic transitions, one at 2 K and the other at 3 K for this compound, both of which are spin-glass-like. However, as the Co concentration is increased, antiferromagnetism is stabilized for intermediate compositions before attaining non-magnetism for the Co end member.     

Assignment of the bands in the range of the P=S stretching vibrations in the spectra of amides of thiophosphoric acid

Journal of Applied Spectroscopy -