A density functional theory investigation of charge mobility in titanyl-phthalocyanines and their tailored peripherally substituted complexes

TL;DR

This study uses density functional theory to analyze charge mobility in titanyl-phthalocyanines and their derivatives, revealing how specific substitutions influence electron transfer properties relevant for electronic devices.

Contribution

The paper provides a detailed computational analysis of how peripheral substitutions affect charge mobility and reorganization energies in titanyl-phthalocyanines, advancing understanding of their electronic properties.

Findings

Chlorine substitution yields highest electron hopping rate.

Weak electron-donating groups increase electron transport.

Chlorine-substituted Ti(II)Pc has lowest reorganization energy (0.09 eV).

Abstract

Titanyl-phthalocyanines catalytic ability towards oxygen reduction is demonstrated in experimental literature. Our recent theoretical simulations revealed electronic structure origin of catalytic ability in peripherally and axially substituted triplet and singlet titanyl-phthalocyanines. However, the origin of high electron transfer ability to spontaneously reduce peroxide in chlorine substituted singlet complex and triplet state Ti(II)Pc complexes remain elusive. Thus, we performed density functional theory calculations to study Ti(IV)Pc and their tailored peripheral substituted complexes as representative compounds of titanyl-phthalocyanines for charge mobilities, reorganization energies and electronic couplings. In addition, oxo(phthalocyaninato)titanium(IV) (TiOPc) convex and concave compounds were investigated to benchmark the method. Based on the results, Reorganization energies of triplet state Ti(II)Pc and their tailored peripheral substituted complexes are compared with Ti(IV)Pc singlet complexes in order to understand the charge mobility. Chlorine substituted complex demonstrates higher electron hopping rate due to higher electronic coupling in comparison to other halogens. Similarly, weak electron-donating methyl group increases the electron transport rate. Moreover, halogen substituted Ti(II)Pc complexes elucidate lower reorganization energies. The lowest reorganization energy is predicted for chlorine substituted Ti(II)Pc complex, which is 0.09 eV. Therefore, higher electronic coupling and lower reorganization energies can be considered as the origin of higher electron transfer ability of these complexes. Furthermore, increase electron hopping rate due to weak electron-donating substituents provide a method to produce efficient n-channel organic field-effect transistors with higher electron mobility.