First charge-transfer complexes between tetrathiafulvalene and 1,2,5-chalcogenadiazole derivatives : design, synthesis, crystal structures, electronic and electrical properties

The authors are grateful to the Royal Society (RS International Joint Project 2010/R3), Deutsche Forschungsgemeinschaft (project 436 RUS 113/967/0-1 R), the Russian Foundation for Basic Research (project 10-03-00735), the Presidium of the Russian Academy of Sciences (projects 7.17, 8.14 and P-8), and to the Siberian Branch of the Russian Academy of Sciences (project 105) for funding.The first charge-transfer complexes of tetrathiafulvalene (1) with 1,2,5-chalcogenadiazole derivatives, i.e. with [1,2,5]thiadiazolo[3,4-c][1,2,5]thiadiazole (2) and 3,4-dicyano-1,2,5-telluradiazole (3), were designed, prepared in the form of air and thermally stable single crystals and structurally defined by X-ray diffraction as 1-2 and 1.3(2), respectively. Starting compound 2 (effective electron acceptor with potentially broad application in the field) was synthesized by a new efficient one-pot method from 3,4-diamino-1,2,5-oxadiazole and disulfur dichloride. The electronic structure of complexes 1.2 and 1.3(2) and thermodynamics of their formation were studied by means of DFT and QTAIM calculations and UV-Vis spectroscopy. The electrical properties of single crystals of the complexes were investigated revealing semiconductor properties with an activation energy of 0.34 eV for 1.2 and 0.40 eV for 1.3(2). Polycrystalline films of the complexes displayed photoconductive effects with increased conductivity under white-light illumination.PostprintPeer reviewe

First charge-transfer complexes between tetrathiafulvalene and 1,2,5-chalcogenadiazole derivatives:design, synthesis, crystal structures, electronic and electrical properties

The first charge-transfer complexes of tetrathiafulvalene (1) with 1,2,5-chalcogenadiazole derivatives, i.e. with [1,2,5]thiadiazolo[3,4-c][1,2,5]thiadiazole (2) and 3,4-dicyano-1,2,5-telluradiazole (3), were designed, prepared in the form of air and thermally stable single crystals and structurally defined by X-ray diffraction as 1-2 and 1.3(2), respectively. Starting compound 2 (effective electron acceptor with potentially broad application in the field) was synthesized by a new efficient one-pot method from 3,4-diamino-1,2,5-oxadiazole and disulfur dichloride. The electronic structure of complexes 1.2 and 1.3(2) and thermodynamics of their formation were studied by means of DFT and QTAIM calculations and UV-Vis spectroscopy. The electrical properties of single crystals of the complexes were investigated revealing semiconductor properties with an activation energy of 0.34 eV for 1.2 and 0.40 eV for 1.3(2). Polycrystalline films of the complexes displayed photoconductive effects with increased conductivity under white-light illumination.</p

Epigenetic Silencing of MicroRNA miR-107 Regulates Cyclin-Dependent Kinase 6 Expression in Pancreatic Cancer

Aberrant expression of microRNAs (miRNAs) has emerged as an important hallmark of cancer. However, the putative mechanisms regulating miRNAs per se are only partially known. It is well established that many tumor suppressor genes in human cancers are silenced by chromatin alterations, including promoter methylation and histone deacetylation. We postulated that miRNAs undergo similar epigenetic inactivation in pancreatic cancer. Two human pancreatic cancer cell lines – MiaPACA-2 and PANC-1 – were treated with the demethylating agent, 5-aza-2′-deoxycytidine (5-Aza-dC) or the histone deacetylase inhibitor, trichostatin A, as well as the combination of the two. Expression of miRNAs in control and treated cell lines was assessed using a custom microarray platform. Fourteen miRNAs were upregulated two-fold or greater in each of the cell lines following exposure to both chromatin-modifying agents, including 5 that were in common (miR-107, miR-103, miR-29a, miR-29b, and miR-320) to both MiaPACA-2 and PANC-1. The differential overexpression of miR-107 in the treated cancer cell lines was confirmed by Northern blot assays. Methylation-specific PCR assays for assessment of CpG island methylation status in the 5′ promoter region of the miR-107 primary transcript demonstrated complete loss of methylation upon exposure to 5-Aza-dC. Enforced expression of miR-107 in MiaPACA-2 and PANC-1 cells downregulated in vitro growth, and this was associated with repression of the putative miR-107 target, cyclin-dependent kinase 6, thereby providing a functional basis for the epigenetic inactivation of this miRNA in pancreatic cancer

First charge-transfer complexes between tetrathiafulvalene and 1,2,5-chalcogenadiazole derivatives:design, synthesis, crystal structures, electronic and electrical properties

The first charge-transfer complexes of tetrathiafulvalene (1) with 1,2,5-chalcogenadiazole derivatives, i.e. with [1,2,5]thiadiazolo[3,4-c][1,2,5]thiadiazole (2) and 3,4-dicyano-1,2,5-telluradiazole (3), were designed, prepared in the form of air and thermally stable single crystals and structurally defined by X-ray diffraction as 1-2 and 1.3(2), respectively. Starting compound 2 (effective electron acceptor with potentially broad application in the field) was synthesized by a new efficient one-pot method from 3,4-diamino-1,2,5-oxadiazole and disulfur dichloride. The electronic structure of complexes 1.2 and 1.3(2) and thermodynamics of their formation were studied by means of DFT and QTAIM calculations and UV-Vis spectroscopy. The electrical properties of single crystals of the complexes were investigated revealing semiconductor properties with an activation energy of 0.34 eV for 1.2 and 0.40 eV for 1.3(2). Polycrystalline films of the complexes displayed photoconductive effects with increased conductivity under white-light illumination.</p