Role of Triple Bond in 1,2-Diphenylacetylene Crystal:  A Combined Experimental and Theoretical Study

Abstract

We have performed a combined experimental and theoretical study of the molecular system of 1,2-diphenylacetylene. The occurrence of two different geometries of the molecule in the crystal structure, one being planar and the other tilted by approximately 6 degrees , has been investigated in relation to the nature of the acetylenic linker. The experimental charge density analysis shows that the acetylenic linker exhibits a noncylindrical density reminiscent of the strong conjugation present in the molecule. The pi-orbitals of the acetylenic linker derived from density functional theory (DFT) calculations are found to sustain a variety of conjugation lengths between the phenyl rings, thereby giving flexibility to the molecule to arrange itself in various packing conformations in the crystal. It is interesting that the energy involved for such distortions is only kBT, allowing several polymorphic forms of the crystal structure as reported in the literature. The distortions entertained by the molecule and the corresponding changes in the charge density distribution and energy are all relevant to molecular electronics.

Attempted covalent imitation of a supramolecular synthon moiety embedded in a crystalline hydrogen-bonded aggregate structure

“…The bond distances within this molecular unit agree well with those found in the crystal structure of tolane [25]. The hydroxy groups of the 1,3-bis(hydroxymethyl)-phenyl element are located on one side of the ring plane, but are oriented in opposite directions.…”

Synthesis of an [(NHC)2Pd(SiMe3)2] Complex and Catalytic cis‐Bis(silyl)ations of Alkynes with Unactivated Disilanes

“…Single crystals of 6 were obtained from a saturated toluene solution upon cooling to −30 °C and the result of X‐ray analysis is depicted in Figure 2, featuring a Y‐shaped structure. There is a clear and expected elongation of the CC bond and a shortening of the CCC bond when compared to free diphenylacetylene 22. To the best of our knowledge, this is the first example of an NHC/Pd 0 complex bearing an η 2 ‐bound alkyne.…”

ChemInform Abstract: Synthesis of an [(NHC)2Pd(SiMe3)2] Complex and Catalytic cis‐Bis(silyl)ations of Alkynes with Unactivated Disilanes.

“…The stoichiometric reaction of 4 with diphenylacetylene at room temperature yielded the corresponding cis-bis(silyl)ated product 5 (Scheme 4) within 30 hours in quantitative yield (see the Supporting Information). [22] To the best of our knowledge,this is the first example of an NHC/Pd 0 complex bearing an h 2 -bound . Compound 6 was fully characterized by NMR spectroscopy and elemental analysis.S ingle crystals of 6 were obtained from asaturated toluene solution upon cooling to À30 8 8Ca nd the result of X-ray analysis is depicted in Figure 2, featuring aY -shaped structure.T here is ac lear and expected elongation of the CCb ond and as hortening of the CCÀCb ond when compared to free diphenylacetylene.…”

“…Compound 6 was fully characterized by NMR spectroscopy and elemental analysis.S ingle crystals of 6 were obtained from asaturated toluene solution upon cooling to À30 8 8Ca nd the result of X-ray analysis is depicted in Figure 2, featuring aY -shaped structure.T here is ac lear and expected elongation of the CCb ond and as hortening of the CCÀCb ond when compared to free diphenylacetylene. [22] To the best of our knowledge,this is the first example of an NHC/Pd 0 complex bearing an h 2 -bound . .…”