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Photochromic Organometallics with a Dithienylethene (DTE) Bridge, [YCCDTECCY] (Y={MCp*(dppe)}): Photoswitchable Molecular Wire (M=Fe) versus Dual Photo‐ and Electrochromism (M=Ru)
Author(s) -
Tanaka Yuya,
Ishisaka Takuya,
Inagaki Akiko,
Koike Takashi,
Lapinte Claude,
Akita Munetaka
Publication year - 2010
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200903583
Subject(s) - photochromism , photostationary state , chemistry , ruthenium , triphenylamine , irradiation , conjugated system , comproportionation , photochemistry , crystallography , stereochemistry , photoisomerization , isomerization , electrochemistry , catalysis , organic chemistry , physics , polymer , electrode , nuclear physics
Dinuclear acetylide‐type complexes bridged by a photochromic dithienylethene unit (DTE), [YCCDTECCY] 1 (Y={MCp*(dppe)}; Cp*=pentamethylcyclopentadienyl, M=Fe ( 1 Fe ), Ru ( 1 Ru )), have been prepared, and their wirelike and switching behavior, as well as their oxidation chemistry has been investigated. The DTE complexes 1 exhibit photochromic behavior in a manner similar to organic DTE derivatives; UV irradiation causes ring closure of the open isomer 1O to form the closed isomer 1C and visible‐light irradiation of the resultant 1C causes reverse ring opening to regenerate 1O . But the performance is dependent on the metals. With respect to the interconversion rates and the 1C content at the photostationary state under UV irradiation, the ruthenium complex 1 Ru is superior to the iron analogue 1 Fe . The wirelike performance is associated with the photochromic processes, and the efficient switching performance has been verified for 1 Fe as characterized by the V ab values [ V ab is the electronic coupling derived from intervalence charge‐transfer (IVCT) bands: V ab ( 1 Fe C ; ON)=0.047 eV versus V ab ( 1 Fe O ; OFF)=0 eV], and are also supported by the large switching factor (SF= K C ( C ; ON)/ K C ( O ; OFF)=39; K C =comproportionation constant). SF for 1 Ru is determined to be 4.2. The remarkable switching behavior arises from the different π‐conjugated systems in the two isomeric forms, that is, cross‐conjugated ( 1O ) and fully conjugated π‐systems ( 1C ). It was also found that, in contrast to the reversible redox behavior of the iron complex 1 Fe , the ruthenium complex 1 Ru O undergoes oxidative ring closure to form the dicationic species of the closed isomer 1 Ru C 2+ and, thus, the ruthenium system 1 Ru shows dual photo‐ and electrochromism. The distinct oxidation behavior of 1 Fe and 1 Ru can be ascribed to the spin distribution on the diradical intermediates 1 Fe O 2+ and 1 Ru O 2+ , as supported by DFT calculations.