Redox Active Multi-nuclear Metal Complexes Bridged by  -Conjugated Systems

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

2. Contents Introduction Pt catecholate compounds My work

3. Near Infrared Absorbing Compounds Organometallic compounds which absorb IR or NIR light efficiently become dyes for Optical data storage devices Laser filter Photodynamic therapy Ex) A mechanism of optical data storage devices NIR Dye Layer Substrate Substrate Substrate Photo diode Laser Beam Signal out Reading date by a difference inlight reflex. If NIR absorption of molecules can be switched by external stimulus, the compounds become switchable electrochromic dyes.

4. Redox Process Donor molecules Acceptor molecules n type semiconductor p type semiconductor Electron transfer e- Donor molecules Acceptor molecules Oxidized Reduced There’re organic molecules which can act as electron donors and acceptors. Electron can be transferred from the donor molecules to the acceptor molecules. At that time, the donor molecules are oxidized and the acceptor molecules are reduced, respectively.

5. Redox Process of Metal Catecholate Complex M= metal, L= substituent

6. Trinuclear Metal-Catecholate Complexes When molecules having three catecholate units bridged by -conjugated linkers are oxidized, three catecholate units are not changed to semi-quinonate units at once. The catecholate units oxidized one by one. Co-existing of the catecholate and seim-quinonate units are called as mix-valued state. At mix-valued state, IVCT (Inter valence charge transfer) transitions are observed.

7. Catecholate Complexes IVCT transition (Intervalence Charge Transfer) IVCT transition sometimes appears at 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

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 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. Pt Complexes • G. A. Abakumov, et al, Inorg. Chim. Acta1979, 32, L57-L59.

10. Cyclic Voltamonmetry The method to observe 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

11. Pt Complexes 1E1/2 1E1/2 2E1/2 2E1/2 3E1/2 3E1/2 [a] All redox potentials are given against ferrocene/ferrocenium redox couple as internal standard. [b] ΔE1 = 2E1/2 − 1E1/2. [c] ΔE2 = 3Epa − 2E1/2

12. Pt Complexes 6-aromatic 4-anti-aromatic 12 -anti-aromatic 10 -aromatic

13. Chemical Oxidation

14. Pt Complexes

15. 1H NMR of Dication dication neutral

16. My Work Investigation of the properties of cation species generated by chemical oxidation of di-nuclear platinium catecholate complexes having [8]annulene and [4]annulene.

17. My Work CVof [8]annulene [a] All redox potentials are given against Ag/AgNO3 redox couple as internal standard. [b] DE1 = 2E1/2 − 1E1/2. [c] DE2 = 3Epa − 2E1/2.

18. My Work UV-vis-NIR spectrum of [8]annulene by chemical oxidation monocation dication Absorbance/a.u. Wavelength (nm)

19. Summary ・Organometallic compounds which absorb IR or NIR light efficiently and have multiple redox centers become switchable electrochromic dyes . ・In the case of metal catecholate complex, the catecholate unitsare oxidized while the metal center was not oxidized. ・Compounds having three catecholate units are not oxidized to semi-quinonate units at once. The catecholate units oxidized one by one. ・ The behaviors of DBA-platinum complexes are different from those of triphenylene-platinum complex. This is because of different electronic properties of p-conjugated linkers. ・My work is to investigate the properties of cation species by oxidation of di-nuclear platinum catecholate complexes having [8]annulene and [4]annulene.