2011. 06. 29. Tobe Laboratory Kitabayashi Kenichi

1. Synthesis and Physical Properties of Zethrene Derivatives with Singlet Diradical Character 2011. 06. 29. Tobe Laboratory KitabayashiKenichi

2. Contents 1. Introduction - singlet diradical - two-photon absorption 2. Background -singlet diradicals synthesized so far 3. Zethrene - singlet diradical character of zethrene - previous research in our group 4. My project 5. Summary

3. Singlet Diradical Singlet diradicals are compounds having characteristic electron structure, that is, two electrons on the radical centers are weakly coupled. diradical character y y = 0 0 < y < 1 y = 1 closed shell singlet diradical open shell 閉殻 一重項ジラジカル 開殻 cyclopentane-1,3-diyl ethylene p-quinodimethane

4. Two-Photon Absorption Singlet open-shell molecule with intermediate diradical exhibits enhanced g value. second excited singlet state hn’ first excited singlet state hn hn’ singlet ground state Nakano, M. et al. Phys. Rev. A1997, 55, 1503. Spatially-selective excitation • : second hyperpolarizabilities • 第二超分極率 two-photon absorption

5. Singlet Diradicals Synthesized So Far p-quinodimethane poly-p-xylylene unstable 1.381 Å Thiele‘s hydrocarbon 1.449 Å 1.346 Å 1.415 Å 1.448 Å Chichibabin‘s hydrocarbon 1.429 Å 1.420Å 1.372 Å Montgomery, L. K. et al. J. Am. Chem. Soc.1986, 108, 6004.

6. Singlet Diradicals Synthesized So Far y = 0.76 Kubo, T. et al. Angew. Chem. Int. Ed.2005, 44, 6564. top view y = 0.81 side view 3.137Å Kubo, T. et al. J. Am. Chem. Soc. 2010, 132, 11021. crystal structure

7. Singlet Diradical Character of Zethrene Zethreneis predicted to exhibit moderate singlet diradical character (y = 0.41)by computational studies. Nakano, M. et al. Comp. Lett.2007, 3, 333. zethrene (dibenzo[de,mn]tetracene) 7 14 7 7 14 14 HOMO −4.56 eV spin density LUMO −2.34 eV (B3LYP/6-31G*) Tobe, Y. et al. Pure Appl. Chem.2010, 82, 871. It is predicted theoretically that large spin density and frontier orbital coefficients of zethreneare located at the 7,14-positions.

8. Stepwise Synthesis of Zethrene by Clar zethrene Clar, E. et al. Chem. Ber. 1955, 88, 1520. Low accessibility and high sensitivity to air and light. Physical properties of zethrene are almost unknown.

9. Previous ResearchSynthesis and Physical Properties of Bis(phenylethynyl)zethrene e / mo l L-1 cm-1 cross coupling transannularcyclization Tobe, Y. et al. Org. Lett.2009,11, 4104. UV / vis CV FL wavelength / nm 3b voltage / V 578 (22400)541 (17200) 619 (0.05) – -1.85 +0.12 +0.61 UV lmax/ nm (e / mol L-1 cm-1) FL lmax/ nm (F) Ered2 / V Ered1 / V Eox1 / V Eox2 / V

10. Previous ResearchTPA Cross-Section of Zethrene Derivatives zethrene diphenylzethrene bis(phenylethnyl)zethrene rubrene 3b Wu, Y. T. et al. Angew. Chem. Int. Ed.2010, 49, 7059. zethrene diphenylzethrene rubrene 3b 509GM (604 nm) 1138 GM (604 nm) 492 GM (650 nm) 67GM (612 nm) TPA cross−section diradical character 0.407 0.324 0.432 ̶ GM = 10−50 cm4 s photon−1 molecule−1 TPA cross−section : 二光子吸収断面積

11. My Project Zethrenedimer (Candidate forTetraradical) 5 4 Interaction betweendiradicals tert-butyl groups aresubstituted to hydrogen for clarity. Bertrand, G. et al.Angew. Chem. Int. Ed.2004, 43, 4876.

12. My Project Synthetic Plan for Zethrenedimer4 In progress

13. Summary • Recently, p conjugated compounds with a large diradical character have been studied experimentally and theoretically. •Our group developed convenient synthetic method of stable zethrene derivatives • TPA cross-section of 3b is much larger than that of rubrene most probably due to the diradical character of 3b. • Synthesis of zethrenedimer4 including two diradicals is in progress.