3 research outputs found
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><sub>p</sub> = 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><sub>1/2</sub> = −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 <sup>1</sup>H, <sup>13</sup>C, and <sup>77</sup>Se 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 tetrakisÂ(triphenylphosphine)Âpalladium 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-bisÂ(thiophen-2-yl)Âdisilene
(<b>1</b>) and 1,2-bisÂ(2,2′-bithiophen-5-yl)Âdisilene
(<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 Siî—»Si double bond and thiophene units. Notably, the
Ï€-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-bisÂ(bithienyl)Âdisilene 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-bisÂ(thiophen-2-yl)Âdisilene
(<b>1</b>) and 1,2-bisÂ(2,2′-bithiophen-5-yl)Âdisilene
(<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 Siî—»Si double bond and thiophene units. Notably, the
Ï€-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-bisÂ(bithienyl)Âdisilene skeleton. The structural
features and electronic properties of <b>1</b> and <b>2</b> have been thoroughly characterized both experimentally and computationally