Solid-State Order and Charge Mobility in [5]- to [12]Cycloparaphenylenes

Abstract

We report a computational study of mesoscale morphology and charge-transport properties of radially π-conjugated cycloparaphenylenes ([n]CPPs) of various ring sizes (n = 5−12, where n is the number of repeating phenyl units). These molecules are considered structural constituents of fullerenes and carbon nanotubes.[n]CPP molecules are nested in a unique fashion in the solid state. Molecular dynamics simulations show that while intramolecular structural stability (order) increases with system size, intermolecular structural stability decreases. Density functional calculations reveal that reorganization energy, an important parameter in charge transfer, decreases as n is increased. Intermolecular charge-transfer electronic couplings in the solid state are relatively weak (due to curved π-conjugation and loose intermolecular contacts) and are on the same order of magnitude (∼10 meV) for each system. Intrinsic charge-carrier mobilities were simulated from kinetic Monte Carlo simulations; hole mobilities increased with system size and scaled as ∼n 4 . We predict that disordered [n]CPPs exhibit hole mobilities as high as 2 cm 2 /(V•s). Our computations show a strong correlation between reorganization energy and hole mobility (μ ∼ λ −4 ). Quantum mechanical calculations were performed on cofacially stacked molecular pairs for varying phenyl units and reveal that orbital delocalization is responsible for both decreasing reorganization energies and electronic couplings as n is increased.

The Supramolecular Chemistry of Strained Carbon Nanohoops

“…c) Simulated hole mobilities of [n]CPPs.d )Solid-state packing of [n]CPPs in different crystallographic directions.c)a nd d) reproduced from Ref. [139] with permission from the American ChemicalS ociety,copyright (2019).…”

“…c) and d) reproduced from Ref. with permission from the American Chemical Society, copyright (2019).…”

[4]Cyclo‐N‐ethyl‐2,7‐carbazole: Synthesis, Structural, Electronic and Charge Transport Properties

“…[11] In 2019, theoreticalc alculations have predicted the strongp otentialo fC PPs and donor-acceptor CPPs as high mobilitym aterials. [12,13] However,a nd despite the fantastic development of organic electronics technology in the last twenty years, [14] only very few exampleso fn anorings incorporation in organic electronic devices have been reported so far. [15,16] Bridging the gap between organic electronics and nanorings appears hence as an appealing challenge.…”

Nanohoop Rotaxanes from Active Metal Template Syntheses and Their Potential in Sensing Applications

“…Specifically, our laboratory and others have synthesized molecules referred to as carbon nanohoops because of their structural relationship to carbon nanotubes (Figure a) . These shape‐persistent macrocycles can be prepared with varying size and atomic composition (Figure b), which has unveiled their numerous size‐dependent optoelectronic behavior and promising materials applications . In particular, owing to the tunable and bright fluorescence, biocompatibility, and metal binding capabilities,,, we have a growing interest in the development of these π‐rich macrocycles for biological applications.…”