2,6-/1,5-Naphthoquinodimethane bridged porphyrin dimer diradicaloids

Hejian Zhang, Jinseok Kim, Hoa Phan, Tun Seng Herng, Tullimilli Y. Gopalakrishna, Wangdong Zeng, Jun DIng, Dongho Kim, Jishan Wu

Research output: Contribution to journalArticlepeer-review

2 Citations (Scopus)

Abstract

2,6-Naphthoquinodimethane (2,6-NQDM)- and 1,5-naphthoquinodimethane (1,5-NQDM)-bridged porphyrin dimers, 2,6-P2 and 1,5-P2, were synthesized as relatively stable compounds. Both exhibit open-shell singlet ground state according to variable-temperature (VT) NMR and magnetic measurements, as well as restricted active space spin-flip (RAS-SF) calculations. The 1,5-P2 isomer has a larger diradical character (y0 = 0.772, based on the RAS-SF calculations) and smaller singlet-triplet energy gap (ΔES-T = -2.6 kcal/mol, based on SQUID measurements) compared to the 2,6-P2 isomer (y0 = 0.501, ΔES-T = -3.1 kcal/mol). In addition, 2,6-P2 shows intense one-photon absorption (OPA) (λmax = 976 nm, = 72200 M-1 cm-1) and a large two-photon absorption (TPA) cross-section (σmax(2) = 3500 GM at 1400 nm) in the near-infrared region, while 1,5-P2 with larger diradical character displays red-shifted but weaker OPA (λmax = 1147 nm, = 18030 M-1 cm-1) and a smaller TPA cross-section (σmax(2) = 1750 GM at 1600 nm). Both compounds show four reversible redox waves and 1,5-P2 has a smaller electrochemical energy gap (1.06 eV vs.1.16 eV for 2,6-P2). Therefore, the bridge structure has a significant impact on the diradical character, electronic properties, and magnetic behaviors of the obtained porphyrin-based diradicaloids.

Original languageEnglish
Pages (from-to)220-229
Number of pages10
JournalJournal of Porphyrins and Phthalocyanines
Volume24
Issue number1-3
DOIs
Publication statusPublished - 2020 Jan 1

Bibliographical note

Funding Information:
We acknowledge financial support from MOE Tier 3 programme (MOE2014-T3-1-004) and NRF Investigatorship (NRF-NRFI05-2019-0005). The work at Yonsei University was supported by Strategic Research (NRF2016R1E1A1A01943379) through the National Research Foundation of Korea (NRF) funded by the Ministry of Science.

All Science Journal Classification (ASJC) codes

  • Chemistry(all)

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