Radical and Diradical Formation in Naphthalene Diimides through Simple Chemical Oxidation

Sangsu Lee; Fang Miao; Hoa Phan; Tun Seng Herng; Jun Ding; Jishan Wu; Dongho Kim

doi:10.1002/cphc.201700015

Radical and Diradical Formation in Naphthalene Diimides through Simple Chemical Oxidation

Chemphyschem. 2017 Mar 17;18(6):591-595. doi: 10.1002/cphc.201700015. Epub 2017 Feb 1.

Authors

Sangsu Lee¹, Fang Miao², Hoa Phan², Tun Seng Herng³, Jun Ding³, Jishan Wu², Dongho Kim¹

Affiliations

¹ Department of Chemistry and Spectroscopy, Laboratory for Functional π-Electronic Systems, Yonsei University, Seoul, 03722, Korea.
² Department of Chemistry, National University of Singapore, 3 Science Drive 3, 117543, Singapore, Singapore.
³ Department of Materials Science & Engineering, National University of Singapore, 119260, Singapore, Singapore.

PMID: 28078728
DOI: 10.1002/cphc.201700015

Abstract

We successfully synthesized, for the first time, a naphthalene diimide (NDI) radical and diradical by simple chemical oxidation using lead(IV) dioxide. The formation of the (di)radical is confirmed by UV/Vis/NIR absorption, ¹ H NMR, and electron paramagnetic resonance (EPR) measurements. In particular, temperature-dependent EPR, SQUID (superconducting quantum interference device) measurements, and quantum calculations demonstrated that the generated NDI diradical has a singlet diradical character of y=0.69 in the ground state. Subsequent characterization of this (di)radical revealed its stabilities, large two-photon absorption cross-section, and short excited-state lifetime.

Keywords: naphthalene diimide; oxidation; radicals; sextet rule; singlet diradicals.