Non-benzenoid high-spin polycyclic hydrocarbons generated by atom manipulation

TL;DR

This study demonstrates the on-surface synthesis of a non-benzenoid triradical with a high-spin ground state, using atom manipulation techniques and advanced microscopy to characterize its electronic and magnetic properties at the single-molecule level.

Contribution

It introduces a novel synthetic approach to create non-benzenoid high-spin polycyclic hydrocarbons and characterizes their magnetic states using microscopy and spectroscopy.

Findings

Successfully synthesized a non-benzenoid triradical with a quartet ground state.

Confirmed the open-shell electronic structure through microscopy and spectroscopy.

Isolated reactive intermediates with different spin states for potential magnetic applications.

Abstract

We report the on-surface synthesis of a non-benzenoid triradical through dehydrogenation of truxene (C27H18) on coinage metal and insulator surfaces. Voltage pulses applied via the tip of a combined scanning tunneling microscope/atomic force microscope were used to cleave individual C-H bonds in truxene. The resultant final product truxene-5,10,15-triyl (1) was characterized at the single-molecule scale using a combination of atomic force microscopy, scanning tunneling microscopy and scanning tunneling spectroscopy. Our analyses show that 1 retains its open-shell quartet ground state, predicted by density functional theory, on a two monolayer-thick NaCl layer on a Cu(111) surface. We image the frontier orbital densities of 1 and confirm that they correspond to spin-split singly occupied molecular orbitals. Through our synthetic strategy, we also isolate two reactive intermediates toward the synthesis of 1 - derivatives of fluorenyl radical and indeno[1,2-a]fluorene, with predicted spin-doublet and spin-triplet ground states, respectively. Our results should have bearings on the synthesis of non-benzenoid high-spin polycyclic frameworks with magnetism beyond Lieb's theorem.