Molecular Tuning of the Magnetic Response in Organic Semiconductors

TL;DR

This paper demonstrates how the magnetic response of organic semiconductors can be tuned through molecular design, focusing on the g-tensor variability driven by spin-orbit coupling influenced by geometry and composition.

Contribution

It introduces a first-principles theoretical model linking molecular structure to magnetic response, guiding chemical tuning of organic semiconductors for spintronics.

Findings

g-tensor shifts are determined by effective molecular spin-orbit coupling

Variations in SOC explained by molecular geometry and composition

Model provides a guide for chemical synthesis to tune magnetic properties

Abstract

The tunability of high-mobility organic semi-conductors (OSCs) holds great promise for molecular spintronics. In this study, we show this extreme variability - and therefore potential tunability - of the molecular gyromagnetic coupling ("g-") tensor with respect to the geometric and electronic structure in a much studied class of OSCs. Composed of a structural theme of phenyl- and chalcogenophene (group XVI element containing, five-membered) rings and alkyl functional groups, this class forms the basis of several intensely studied high-mobility polymers and molecular OSCs. We show how in this class the g-tensor shifts, $\Delta g$, are determined by the effective molecular spin-orbit coupling (SOC), defined by the overlap of the atomic spin-density and the heavy atoms in the polymers. We explain the dramatic variations in SOC with molecular geometry, chemical composition, functionalization, and charge life-time using a first-principles theoretical model based on atomic spin populations. Our approach gives a guide to tuning the magnetic response of these OSCs by chemical synthesis.