4,5-Dicyano-3,6-diethylbenzo-1,2-diselenete, a Highly Stable 1,2-Diselenete: Its Preparation, Structural Characterization, Calculated Molecular Orbitals, and Complexation with Tetrakis(triphenylphosphine)palladium

The first isolable benzo-1,2-diselenete, 4,5-dicyano-3,6-diethylbenzo-1,2-diselenete (<b>4</b>), was prepared by the reaction of 4,5-(<i>o</i>-xylylenediseleno)-3,6-diethylphthalonitrile (<b>3</b>) with aluminum chloride in toluene. X-ray crystallographic analysis demonstrated that <b>4</b> contains a trapezoidal diselenide ring rather than a benzo-1,2-diselenone structure. In crystal form, <b>4</b> undergoes self-assembly and generates structures based on layered molecular sheets since the unit cell contains only one molecule. While the cyclic voltammogram of <b>4</b> exhibited only one irreversible peak (<i>E</i>_p = 1.59 V) during oxidation and two quasireversible couples during reduction, three peaks were observed in the differential pulse voltammogram of the reduction couples (<i>E</i>_1/2 = −1.19, −0.75, and −0.69 V). Although a THF solution of <b>4</b> in the presence of sodium metal was EPR silent, various signals were readily observed in its ¹H, ¹³C, and ⁷⁷Se NMR spectra. Molecular orbital calculations for <b>4</b> demonstrated that the HOMO orbital is primarily localized at the two selenium atoms and four of the benzene carbon atoms while the LUMO orbital is situated solely on the diselenete ring. It appears that the HOMO and LUMO orbitals of <b>4</b> receive significant stabilization from the nitrile groups compared to the level of stabilization in the unsubstituted benzo-1,2-diselenete (<b>BDS</b>). The reaction of <b>4</b> with tetrakis­(triphenylphosphine)­palladium in benzene was found to produce a dinuclear palladium complex (<b>8</b>), and the structure of this complex was determined by X-ray crystallographic analysis. The central four membered ring of <b>8</b> consists of the Pd1, Se2, Pd2, and Se3 atoms and is not planar but rather adopts a folded arrangement

π‑Conjugation between a SiSi Double Bond and Thiophene Rings: Synthesis, Structural Characteristics, and Photophysical Properties of 1,2-Bis(thiophen-2-yl)disilene and 1,2-Bis(2,2′-bithiophen-5-yl)disilene

The two new disilene compounds, 1,2-bis­(thiophen-2-yl)­disilene (<b>1</b>) and 1,2-bis­(2,2′-bithiophen-5-yl)­disilene (<b>2</b>), supported by the fused-ring bulky Eind groups (Eind = 1,1,3,3,5,5,7,7-octaethyl-<i>s</i>-hydrindacen-4-yl) have been obtained as orange and purple crystals, respectively, by the reduction of the corresponding dibromosilanes. Their X-ray structures and spectroscopic properties demonstrate the effective π-conjugation between a SiSi double bond and thiophene units. Notably, the π-extended <b>2</b> exhibits a distinct emission both in solution and in the solid state at room temperature based on the essentially coplanar 1,2-bis­(bithienyl)­disilene skeleton. The structural features and electronic properties of <b>1</b> and <b>2</b> have been thoroughly characterized both experimentally and computationally

π‑Conjugation between a SiSi Double Bond and Thiophene Rings: Synthesis, Structural Characteristics, and Photophysical Properties of 1,2-Bis(thiophen-2-yl)disilene and 1,2-Bis(2,2′-bithiophen-5-yl)disilene

The two new disilene compounds, 1,2-bis­(thiophen-2-yl)­disilene (<b>1</b>) and 1,2-bis­(2,2′-bithiophen-5-yl)­disilene (<b>2</b>), supported by the fused-ring bulky Eind groups (Eind = 1,1,3,3,5,5,7,7-octaethyl-<i>s</i>-hydrindacen-4-yl) have been obtained as orange and purple crystals, respectively, by the reduction of the corresponding dibromosilanes. Their X-ray structures and spectroscopic properties demonstrate the effective π-conjugation between a SiSi double bond and thiophene units. Notably, the π-extended <b>2</b> exhibits a distinct emission both in solution and in the solid state at room temperature based on the essentially coplanar 1,2-bis­(bithienyl)­disilene skeleton. The structural features and electronic properties of <b>1</b> and <b>2</b> have been thoroughly characterized both experimentally and computationally