Synthesis and characterization of novel N-carbazole end-capped oligothiophene-fluorenes

A series of novel N-carbazole end-capped oligothiophene-fluorenes was synthesized using Ullmann coupling, bromination, and Suzuki coupling reactions. The optical, thermal, and electrochemical properties of these materials can be tuned by varying the conjugation length of the oligothiophene segment. The terminal carbazole and central fluorene moieties of the resulting materials are beneficial for their morphology, conjugation length, and solubility.     

Insight into crucial inhibitor–enzyme interaction of arylamides as novel direct inhibitors of the enoyl ACP reductase (InhA) from Mycobacterium tuberculosis: computer-aided molecular design

Abstract  

The enoyl ACP reductase enzyme (InhA) involved in the type II fatty acid biosynthesis pathway of Mycobacterium tuberculosis is an attractive target enzyme for antitubercular drug development. Arylamide derivatives are a novel class of InhA inhibitors used to overcome the drug-resistance problem of isoniazid, the frontline drug for tuberculosis treatment. Their remarkable property of inhibiting the InhA enzyme directly without requiring any coenzyme, makes them especially appropriate for the design of new antibacterials. In order to find a sound binding conformation for the different arylamide analogs, molecular docking experiments were performed with subsequent QSAR investigations. The X-ray conformation of one arylamide within its cocrystallized complex with InhA was used as a starting conformation for the docking experiments. The results thus obtained are perfectly consistent (rmsd = 0.73 ?) with the results from X-ray analysis. A thorough investigation of the arylamide binding modes with InhA provided ample information about structural requirements for appropriate inhibitor–enzyme interactions. Three different QSAR models were established using two three-dimensional (CoMFA and CoMSIA) and one two-dimensional (HQSAR) techniques. With statistically ensured models, the QSAR results obtained had high correlation coefficients between molecular structure properties of 28 arylamide derivatives and their biological activity. Molecular fragment contributions to the biological activity of arylamides could be obtained from the HQSAR model. Finally, a graphic interpretation designed in different contour maps provided coincident information about the ligand–receptor interaction thus offering guidelines for syntheses of novel analogs with enhanced biological activity.     

Synthesis, optical, electrochemical, and thermal properties of conjugated α-fluorenyl oligothiophenes

A series of new α-fluorenyl oligothiophenes up to the pentamer have been synthesized using Suzuki cross-coupling and bromination reactions. The optical, electrochemical, and thermal properties of these materials can be tuned by varying the number of thiophene rings. The longer oligomers (n ? 4) were stable, crystalline, and unreactive to electrochemical oxidative dimerization.     

Synthesis and characterization of N-carbazole end-capped oligofluorene-thiophenes

A series of novel N-carbazole end-capped oligofluorene-thiophenes with one, two, three, and four thiophene rings were synthesized using either palladium catalyzed cross-coupling reaction or nickel-catalyzed reductive dimerization. All the oligomers have been characterized by ¹H, ¹³C NMR, FTIR, UV-vis, PL spectroscopy and mass spectrometry. It has been demonstrated that the optical, thermal, and electrochemical properties of these materials can be tuned by varying the conjugation length of the oligothiophene segment. The terminal carbazole and fluorene moieties of the resulting materials are beneficial for their morphology, conjugation length, and solubility. These bright fluorescent, thermally and electrochemically stable compounds have potential applications as light-emitting and hole-transporting layers in organic light-emitting devices.     

Synthesis, optical, electrochemical, and thermal properties of α,α′-bis(9,9-bis-n-hexylfluorenyl)-substituted oligothiophenes

A series of new α,α′-bis(9,9-bis-n-hexylfluorenyl)-substituted oligothiophenes with 2-, 4-, and 6-thiophene rings have been synthesized via a nickel-catalyzed reductive dimerization and their optical, electrochemical, and thermal properties investigated. The fluorene substituents have shown electronic interactions with the oligothiophene chains, enhanced the solubility of these materials and stabilized the radical cation and dication by blocking the reactive α-positions of the thiophene moieties. The absorption, fluorescence, electrochemical, and thermal properties of these materials can be tuned by varying the conjugation length of the oligothiophene segment.