Hexabenzo[4.4.4]propellane:  A Helical Molecular Platform for the Construction of Electroactive Materials

Abstract

Helical hexabenzo[4.4.4]propellane (a relative of hexaphenylethane) and its derivatives are synthesized and their structures are established by X-ray crystallography. Isolation and X-ray crystallographic characterization of a robust trication-radical salt of hexamethoxypropellane derivative confirms that its framework is stable toward oxidative (aliphatic) C-C bond cleavage. It is also demonstrated that propellane can be easily brominated at the 4,4'-positions of the biphenyl linkages for its usage as a molecular platform for the preparation of electroactive materials.

The Synthesis of Organic Molecules of Intrinsic Microporosity Designed to Frustrate Efficient Molecular Packing

“…An investigation to determine the suitability of various rigid structural building units as peripheral arms for OMIM construction was performed by combining catechol derivatives of benzenopentacene ( 6 ) spirobifluorene ( 7 ), propellane ( 8 ), and hexaphenylbenzene ( 9 ) with cores 1 and 2 . Benzenopentacene containing OMIM‐6 and OMIM‐16, were found to possess apparent SA BET in the range 10–15 % lower than their more symmetrical isomeric triptycene‐based counterparts OMIM‐5 and OMIM‐14.…”

“…An investigation to determine the suitability of various rigid structuralb uildingu nits as peripheral arms for OMIM construction was performed by combining catechold erivatives of benzenopentacene (6) [20b] spirobifluorene (7), [28] propellane (8), [29] Chem. Eur.J.2016Eur.J.…”

“…Catechol (3)-and naphthalene( 4)-based arms were selected as base-line controls to examinet he effect of increasing arm length and addings ubstituents. Triptycene (5 and 6) [26,27] and bulkier arm groups,b ased on spirobifluorene (7), [28] propellane (8), [29] and hexaphenylbenzene ( 9), [30] were selected owing to their high internal free volume [26b] andp rovenporosity-enhancing properties in PIMs and other microporous polymers.…”

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

“…Hexabenzo[4.4.4]propellane A [ 24 ], which was first reported in 1971, is a multiply clamped HPE in which the central Csp 3 –Csp 3 bond [bond length: 1.563(2) Å] is not greatly expanded [ 25 ]. In this nonspiro-type clamped HPE, the steric repulsion among the six benzene rings is effectively reduced by adopting a twisted conformation with a torsion angle ( α ) of about 60° around the central C–C bond ( Figure 1 ).…”

2,7-Dibromo-10′H-spiro[fluorene-9,9′-phenanthren]-10′-one

“…They are also of interest as building blocks for the preparation of microporous materials (Taylor et al 2016) and for their electro-chemical properties (Debroy et al 2007). Synthetic methods and physical properties of brominated 10 0 H-spiro[fluorene-9,9 0 -phenanthren]-10 0 -one compounds have been reported (Suzuki et al, 1962;Borowitz et al, 1971).…”