Tobe Lab. M1 Eri Ryomura

1. Redox Active Multi-nuclear Metal Complexes Bridged by -Conjugated Systems Tobe Lab. M1 Eri Ryomura

2. Contents ・Introduction i) Mixed valence states ii) Pt catecholate complexes ・[12]annulene Platinum Complex ・My Work ・Future Work

3. Mixed valence states When the valence state of more than two same kind of atoms within a single molecule is same, a charge transfer dose not occur. On the other hand, the charge transfer occurs when the valence state is different. 2e- 2e- PtⅣ PtⅡ PtⅡ PtⅣ In this event, total charge of compounds do not change.

4. Redox Process of Metal Catecholate Complex M= metal, L= substituent Metal catecholate complexes showed stepwise one-electron oxidations in an electrochemical measurement, forming a semi-quinonate unit followed by the formation of a quinone unit.

5. Trinuclear Metal-Catecholate Complexes When the molecules having three catecholate units bridged by -conjugated linkers are oxidized, three catecholate units are not changed to semi-quinonate units at once because of electronic interaction between each other. Therefore the catecholate units are oxidized one by one. Co-existing of the catecholate and semi-quinonate units corresponds typical example of mix-valued state. At the mix-valued state, IVCT (Inter valence charge transfer) transitions are often observed.

6. Catecholate Complexes IVCT transition (Intervalence Charge Transfer) The IVCT transition sometimes appears at a NIR region for the mixed valence compounds. In the case of trinuclear complex, this transition corresponds to the electron transfer from the catecholate unit to semi-quinonate unit. e- Redox process of metal catecholate complex

7. Pt Complexes 0.870 V 0.266 V The platinum catecholate complexes showed two-step one-electron oxidation waves. 1 mMin CH2Cl2at r.t., 0.1 M TBAP,Scan rate = 0.1 V/s

8. Aromaticity・Hückel’s rule Aromaticity Cyclic compounds with delocalized -electrons have lower molecular orbital energy than those having localized -electrons. Ring current is generated by delocalized cyclic p-electrons which change a magnetic environment of the ring by external magnetic field. Hückel ’s rule -2e- 4np (Non - or anti-aromatic molecules) (4n+2)p・・・Aromatic molecules -2e- (4n+2)p (Aromatic molecules) 4np・・・Non - or anti-aromatic molecules

9. NICS value Absolute values of magnetic shielding effect calculated at center of a ring. Negative NICS value : aromatic Positive NICS value : antiaromatic Zero NICS value : nonaromatic Ex) ・aromatic ・antiaromatic ・nonaromatic -11.5 -13.9 28.8 17.2 3.1

10. Contents ・Introduction i) Mixed valence states ii) Pt catecholate complexes ・[12]annulene Platinum Complex ・My Work ・Future Work

11. Mixed valence states When the valence state of more than two same kind of atoms within a single molecule is same, a charge transfer dose not occur. On the other hand, the charge transfer occurs when the valence state is different. 2e- 2e- PtⅣ PtⅡ PtⅡ PtⅣ In this event, total charge of compounds do not change. The compounds with mixed valence states show characteristic properties.

12. Redox Process of Metal Catecholate Complex M= metal, L= substituent Metal catecholate complexes showed stepwise one-electron oxidations in an electrochemical measurement, forming a semi-quinonate unit followed by the formation of a quinone unit.

13. Trinuclear Metal-Catecholate Complexes When the molecules having three catecholate units bridged by -conjugated linkers are oxidized, three catecholate units are not changed to semi-quinonate units at once because of electronic interaction between each other. Therefore the catecholate units are oxidized one by one. Co-existing of the catecholate and semi-quinonate units corresponds typical example of mix-valued state. At the mix-valued state, IVCT (Inter valence charge transfer) transitions are often observed.

14. Catecholate Complexes IVCT transition (Intervalence Charge Transfer) The IVCT transition sometimes appears at a NIR region for the mixed valence compounds. In the case of trinuclear complex, this transition corresponds to the electron transfer from the catecholate unit to semi-quinonate unit. e- Redox process of metal catecholate complex

15. Pt Complexes 0.870 V 0.266 V The platinum catecholate complexes showed two-step one-electron oxidation waves. 1 mMin CH2Cl2at r.t., 0.1 M TBAP,Scan rate = 0.1 V/s

16. Aromaticity・Hückel’s rule Aromaticity Cyclic compounds with delocalized -electrons have lower molecular orbital energy than those having localized -electrons. Ring current is generated by delocalized cyclic p-electrons which change a magnetic environment of the ring by external magnetic field. Hückel ’s rule -2e- 4np (Non - or anti-aromatic molecules) (4n+2)p・・・Aromatic molecules -2e- (4n+2)p (Aromatic molecules) 4np・・・Non - or anti-aromatic molecules

17. NICS value Absolute values of magnetic shielding effect calculated at center of a ring. Negative NICS value : aromatic Positive NICS value : antiaromatic Zero NICS value : nonaromatic Ex) ・aromatic ・antiaromatic ・nonaromatic -11.5 -13.9 28.8 17.2 3.1

18. Trinuclear DBA Platinum Complex In my laboratory, [12]annulene derivative having three platinum catecholate units was synthesized. Moreover, electrochemical behavior and, optical and magnetic properties of this complex were investigated. 12 -anti-aromatic 10 -aromatic

19. Cyclic Voltamonmetry The method to measure the modulation of current flow by redox reactions on electrodes. W: Working electrode R: Reference electrode A: Auxiliary electrode Fe(CN)63- / Fe(CN)64- cyclic voltammogram

20. DBA platinum catecholate complex -0.24 V -0.48 V 0.45 V ΔE2= 0.70 V ΔE1= 0.23 V Potential V vsFc/Fc+

21. Spectroelectrochemical Study

22. Dicationof [12]annulene platinum catecholate 1H NMR dication neutral NICSvalues neutral monocation dication

23. My Work Investigation of the properties of cation species generated by chemical oxidation of di-nuclear platinum catecholate complexes having [8]annulene. [12]annulene planar [8]annulene tub

24. Theoretical Caluculations Optimization was performed at B3LYP/ 6-31G(d) for C, H, O, P,LANL2DZ for Pt by Gaussian09

25. Theoretical Caluculations Geometry Differential charge densities neutral→monocation monocation→dication

26. Theoretical Calculations neutral monocation dication (singlet)

27. Cyclic Voltamonmetry Potential V vs. Fc-Fc+ Conditions:1 mMin CH2Cl2at r.t., 0.1 M Bu4NClO4,Scan rate = 0.1 V/s c.f. ΔE= 0.73 V

28. UV-vis-NIR Spectra Absorbance/a.u.

29. ESR (Electron Spin Resonance) spectrum When electronic spin is in given magnetic field, the energy level of electronic spin splits into two levels. This is so-called Zeeman effect. When external energy which compensates the energy difference between two levels is applied, electron resonance will be occurred. By detecting this energy absorption, ESR spectrum can be obtained. microwave absorption line shape of ESR spectrum first derivation external magnetic field external magnetic field =0

30. ESR spectrum • B3LYP/6-31g(d)/LanL2DZ. Measured in CH2Cl2 at 298 K Measured in THF at 298 K • G. A. Abakumov, et al., Inorg. Chim. Acta1979, 32, L57-L59.

31. 1H NMR of dication signal of H1 no signal

32. 1H NMR of dication

33. 1H NMR Spectra 8.11 ppm 7.52 ppm 1.8 ppm dication neutral 6.54 ppm 6.22 ppm

34. Summary ・ Platinum catecholate complexes showed stepwise one-electron oxidations in an electrochemical measurement, forming a semi-quinonateunit followed by the formation of a quinone unit. When compounds having some catecholate units, these show mixed valence state. ・ Dication of [12]annulene derivative having three platinum catecholate units is stable because of the formation of an aromatic 10-electron system at the 12-membered ring. And, this shows aromaticity. ・Dication of [8]annulene derivative is electrochemically stable. ・ Absence of the 1H NMR signals of aromatic protons at r.t. is due to the occupation of thermally excited triplet state. ・ NMR spectrum and NICS values ofdicationindicated increased diatropicity due to the formation of an aromatic 6p or 14p electronic system.

35. Future Work