Ion‐Pairing Assemblies Based on Pentacyano‐Substituted Cyclopentadienide as a π‐Electronic Anion

Abstract

Pentacyanocyclopentadienide (PCCp(-) ), a stable π-electronic anion, provided various ion-pairing assemblies in combination with various cations. PCCp(-) -based assemblies exist as single crystals and mesophases owing to interionic interactions with π-electronic and aliphatic cations with a variety of geometries, substituents, and electronic structures. Single-crystal X-ray analysis revealed that PCCp(-) formed cation-dependent arrangements with contributions from charge-by-charge and charge-segregated assembly modes for ion pairs with π-electronic and aliphatic cations, respectively. Furthermore, some aliphatic cations gave dimension-controlled organized structures with PCCp(-) , as observed in the mesophases, for which synchrotron XRD analysis suggested the formation of charge-segregated modes. Noncontact evaluation of conductivity for (C12 H25 )3 MeN(+) ⋅PCCp(-) films revealed potential hole-transporting properties, yielding a local-scale hole mobility of 0.4 cm(2) V(-1) s(-1) at semiconductor-insulator interfaces.

First decade of π-electronic ion-pairing assemblies

“…34,35 Based on the ion-exchange strategy, a Na + salt of PCCp − and Cl − salts of desired cations were mixed under appropriate conditions, affording the corresponding ion pairs of PCCp − . 36 Cations with bulky geometries afforded chargesegregated assemblies. For example, the ion pairs of PCCp − with a triethylammonium cation by Wood and Wright et al 37 and with butyltrimethylammonium (C 4 H 9 IJCH 3 ) 3 N + ) and TPA + provided charge-segregated assemblies based on the stacking columnar structures of PCCp − in the crystal state (Fig.…”

“…15b). 36 Charge-segregated dimension-controlled assemblies are fascinating, because the alignment of identically charged π-electronic ions shows effective charge-carrier transport properties. Accordingly, ion pairs consisting of PCCp − with aliphatic cations such as dimethyldioctadecylammonium ((C 18 H 37 ) 2 IJCH 3 ) 2 N + ) and tridodecylmethylammonium ((C 12 -H 25 ) 3 CH 3 N + ) (Fig.…”

Substitution‐Pattern‐ and Counteranion‐Depending Ion‐Pairing Assemblies Based on Electron‐Deficient Porphyrin–AuIII Complexes

“…PCCp − is a stable six π‐electron aromatic anionic species with a planar geometry and is an important building block for the alignment of π‐electronic charged species . A charge‐by‐charge assembly was observed in the single crystal of 2 + ‐PCCp − , which was prepared by vapor diffusion of THF/ n ‐hexane (Figure a).…”

Ion‐Free and Ion‐Pairing Assemblies of Anion‐Responsive π‐Electronic Systems Possessing Directly Linked Alkyl Chains

“…These ion‐pairing materials exhibited charge‐carrier transport properties within their molecular assembly. Further investigations on these assemblies based on designed non‐complexed ions and genuine π‐electronic ions and their unique properties are currently underway.…”