9,10-Dihydrophenanthrene with Two Spiro(dibenzocycloheptatriene) Units: A Highly Strained Caged Hydrocarbon Exhibiting Reversible Electrochromic Behavior

Abstract

The title dispiro hydrocarbon 1 was designed as a new electrochromic material. This multiply clamped hexaphenylethane-type electron donor was prepared from 2,2′-diiodobiphenyl via biphenyl-2,2′-diylbis(dibenzotropylium) 22+ salt. X-ray analysis of 1 revealed a highly strained structure as reflected by an elongated “ethane” bond [bond length: 1.6665(17) Å] and nearly eclipsed conformation. The weakened bond was cleaved upon two-electron oxidation to regenerate the deeply colored dication 22+. The reversible interconversion between 1 and 22+ is accompanied not only by a drastic color change but also by C–C bond formation/cleavage. Thus, the voltammogram showed a pair of well-separated redox waves, which is characteristic of “dynamic redox (dyrex)” behavior. The tetrahydro derivative of 1 with two units of spiro(dibenzocycloheptadiene), which suffers from more severe steric congestion, was also prepared. The crystallographically determined bond length for the central C–C bond [1.705(4) Å] is greatest among the values reported for 9,9,10,10-tetraaryl-9,10-dihydrophenanthrene derivatives.

Flexible C−C Bonds: Reversible Expansion, Contraction, Formation, and Scission of Extremely Elongated Single Bonds

“…Especially in 1c/2c,w e found the largest difference in potential of about 1.1 eV before and after photocyclization. This change can be explained as follows:( i) the through-bond interaction that causes an increasing in the HOMO level would be maximized by expansion of the C À Cs ingle bond [40,41] and (ii)t he coefficients in HOMO are located on the DBCHT unit and the elongated s-bond in 1,w hereas the coefficients are located on the acenaphthene,pyracene,ordihydropyracylene skeleton in 2 based on DFT calculations ( Figures S10 and S13). On the other hand, two-electron reduction peaks were found in the far cathodic region due to cleavage of the elongated C À Cb ond to give 3 2+ or 4 2+ (dyrex behavior).…”

High‐Fidelity Dimerization of Xanthenyl Radicals and Dynamic Qualities of a Congested Ethane: Diethyl Dixanthenyl‐9,9′‐Dicarboxylate

“…Further computational details are available in Section 5 of the Supporting Information. It has also been previously suggested that cofacial xanthenyl π‐systems provide a stabilizing influence via through‐bond and through‐space interactions [39,40] . Dispersion interactions between xanthenyl moieties in 1 2 were calculated as described by Johnson and co‐workers [41] as implemented in Multiwfn v3.8 [42] .…”

Multi‐Redox Active Carbons and Hydrocarbons: Control of their Redox Properties and Potential Applications

“…describe the fabrication of various functional C x H y molecules that exhibit interesting redox behaviors, even though electrochromic devices have not been reported [108–110] . For example, they used two spiro(dibenzocycloheptatriene) units to synthesize 9,10‐dihydrophenanthrene and observed a color change (from colorless to red) associated with C−C bond cleavage after two‐electron oxidation [110] . At a negative potential, its dication could be reduced back to the neutral spiro‐compound.…”