Position Of Thiophene Ring Research Articles

Synthesis, optical properties and self-organization of blue-emitting butterfly-shaped dithienobenzosiloles

Ten novel butterfly-shaped dithienobenzosilole-based luminogens, which are peripherally installed with a variety of substituents including hydrogen, phenyl and substituted phenyl groups, have been readily prepared via an iodine-induced intramolecular electrophilic double-cyclisation reaction and subsequent deiodination or coupling reactions. The optical and electrochemical properties of these compounds were systematically investigated to clarify the relationships between their structures and properties, supported by theoretical calculations. These compounds exhibit deep-blue to sky-blue emissions and high photoluminescence quantum yields up to 0.84 in solution and solid states which are regulated by the functional blades and their steric hindrance on the α– and β–positions of thiophene rings. Their high thermal- and photo- stabilities have been revealed and mainly attributed to the dithienobenzosilole core.

Enhancement of near-infrared luminescence of ytterbium in triple-stranded binuclear helicates.

A bis-β-diketone, bis(4,4,4-trifluoro-1,3-dioxobutyl)(2,2'-bithienyl) (BTT), which can be looked upon as coupling of two mono-β-diketones (2-thenoyltrifluoroacetone, TTA) at the 5,5'-position of thiophene ring, has been designed for exploring the advantages of binuclear helical structure in sensitizing the lanthanide NIR luminescence. The Yb(iii) ion was selected as the luminescent center, and its corresponding mono-β-diketone complex Yb(TTA)3(DMSO) () and bis-β-diketone complex Yb2(BTT)3(DMSO)4 () were synthesized and isolated. X-ray crystallographical analysis reveals that the bis-β-diketone complex Yb2(BTT)3(DMSO)4 adopts a triple-stranded dinuclear structure, in which the two Yb(iii) ions are helically wrapped by three ligands, and each Yb(iii) ion is eight-coordinated by six oxygen atoms from three ligands and two oxygen atoms from the coordinated DMSO molecules. Whereas, the mono-β-diketone complex Yb(TTA)3(DMSO) is a mononuclear structure, the central Yb(iii) ion is coordinated by seven oxygen atoms from three ligands and a DMSO molecule. The photophysical properties related to the electronic transition are characterized by the absorbance spectra, the emission spectra, the emission quantum yields, the emission lifetimes, and the radiative (kr) and nonradiative rate constants (knr). The luminescence quantum yield experiment reveals that the dinuclear complex has about 10 times luminescence enhancement compared with the mononuclear complex. This enhancement mainly benefits from its helical structure, which effectively depresses the nonradiative transition caused by high-energy oscillators in ligands, and the part-encapsulated structure decreases the probability of solvents entering the metal centers.

Planar supramolecular systems based on geometrical isomers of crown-containing oligothiophenes

The properties of ultrathin films of two geometric isomers of oligothiophene derivatives containing two crowned styryl fragments in 2- (I) or 3- (II) positions of thiophene rings (Fig. 1) are studied in this work. The ability of these compounds to form stable monolayers at the air/water interface is shown. The structural organization of crown-substituted oligothiophenes in monolayers is determined by the π-π-stacking interaction of hydrophobic styrylthiophene fragments and interaction of hydrophilic macrocycles with the water subphase. Analysis of ultrathin film physicochemical characteristics has shown that the difference in the structure of oligothiophene molecules leads to the formation of distinct monolayer architectures with various electrochemical and optical characteristics. Two types of aggregates (H and J) are generated in monolayers formed from different geometrical isomers at the air/water interface. The effect of barium cation presence in the subphase on the oligomer aggregation in monolayer is discussed. The phase diagrams characterizing the behavior from two-dimensional mixtures of studied crown-substituted oligothiophenes and amphiphilic spreader are plotted basing on compression isotherms accompanied by absorbance and fluorescence spectra of monolayers of different composition. The ability to fine tune the emitted radiation parameters is demonstrated. The obtained results show the efficiency of application of geometrical isomers for investigation of the fundamental “structure-property” ratio of planar supramolecular systems, which is important for organic optics and electronics.

Synthesis by oxidative polymerization of optically active, regioregular polythiophene from quinquethiophene monomer bearing chiral and n-dodecyl groups as substituents

AbstractThe synthesis and characterization of an optically active quinquethiophene monomer 3,3””-didodecyl-4’,3”’-di[(S)-(+)-2-methylbutyl]- 2,2’:5’,2”:5”,2”’:5”’,2””-quinquethiophene [(S)-(+)-DDDMBQT], bearing at the C-β positions of thiophene rings both linear C12 alkyl chain and chiral, enantiomerically pure, alkyl group is described. The polymerization of [(S)-(+)-DDDMBQT] by oxidative mechanism has been optimized in terms of yield of soluble polymer with high molecular weight.The obtained polymeric derivative displays enhanced conjugation extension with respect to similar poly(3-alkylthiophene)s reported in the literature and optical activity in the spectral region related to the chromophore absorptions when in the microaggregate state, indicative of the presence of supramolecular chiral conformations.