Redox‐Active Hydrocarbons: Isolation and Structural Determination of Cationic States toward Advanced Response Systems

Abstract

Organic chemistry has developed rapidly as a carbon‐based science. Particularly, hydrocarbons with aromatic rings have attracted much attention as molecular materials for use in organic electronics. In principle, aromatic species can be constructed if carbon and hydrogen atoms are available. Therefore, revealing the nature of pure hydrocarbons with an (anti)aromatic nature should pave the way for the development of as yet unexplored organic materials. In this Review, we focus on pure hydrocarbons composed of only carbon and hydrogen atoms, and present recent studies on their intrinsic electrochemical and spectroscopic properties and structural characterization of their cationic states. We also address more sophisticated hydrocarbon‐based response systems that are capable of modulating their properties in response to external stimuli such as light, heat, and electric potential.

Automated and Efficient Generation of General Molecular Aggregate Structures

“…For the cationic trimethine cyanine within the cucurbit[8]uril (Figure 2 A), [35] the interaction energies of the aISS structures are almost identical to those from the NCI‐iMTD algorithm. This indicates a similar structure quality and holds also for the electronically difficult cationic, open‐shell octamethylated‐naphthalene complex between naphthalene and anionic antimony hexafluoride (Figure 2 D) [37] and the paramagnetic copper complex (Figure 2 E). [38] Noteworthy is the tremendous difference in computational time.…”

“…To demonstrate the general applicability and efficiency of the aISS algorithm and to validate the resulting structures, we investigated a variety of currently researched dimers and trimers (Figure 2 ). [ 35 , 36 , 37 , 38 , 39 , 40 ]…”

Robust Radical Cations of Hexabenzoperylene Exhibiting High Conductivity and Enabling an Organic Nonvolatile Optoelectronic Memory

“…Such unusual air stability of [HBP-H] •+ might be attributed to two factors. The delocalization of spin density in the π-backbone provides thermodynamic stability, ,, and the twisted π-backbone impedes dimerization enhancing kinetic stability. For comparison, chemical oxidation of 6,13-bis­(triisopropylsilylethynyl)-pentacene (TIPS-PEN), whose first oxidation potential measured in CH 2 Cl 2 is +0.37 V versus Fc + /Fc, , was investigated under the same condition.…”

“…For example, radical cations are formed in a p-type organic field transistor (OFET), as induced by a gate voltage to result in the conduction channel, and radical cations are formed in p-type semiconductors in an organic solar cell as a result of photo-induced charge separation. Stable π-conjugated radical cations are not only of key importance to these devices but also, due to the presence of unpaired spin densities, may offer unique optoelectronic and magnetic properties for unconventional applications, − for example, doublet emission for organic light-emitting diodes with 100% internal quantum efficiency and molecular spintronics. , However, π-conjugated radical cations are typically reactive species that are difficult to isolate . A widely used strategy to enhance the stability of a π-conjugated radical cation is to embed a heterocycle , or a carbocycle that contains seven π-electrons.…”