Regulation of Charge Delocalization in a Heteronuclear Fe 2 Ru System by a Stepwise Photochromic Process

• Published in: Chemistry : a European journal 2015-02, Vol.21 (8), p.3318-3326
• Main Authors: Xu, Guang‐Tao, Li, Bin, Wang, Jin‐Yun, Zhang, Dao‐Bin, Chen, Zhong‐Ning
• Format: Article
• Language: English
• ISSN: 0947-6539; 1521-3765
• DOI: 10.1002/chem.201405464

Heteronuclear complexes FeCp 2 DTECCRu(dppe) 2 Cl ( 1 o ; dppe=1,2‐bis(diphenylphosphino)ethane, Cp=cyclopentadienyl, DTE=dithienylethene) and FeCp 2 DTECCRu(dppe) 2 CCDTEFeCp 2 ( 2 oo ), with redox‐active ferrocenyl and ruthenium centers separated by a photochromic DTE moiety, were prepared to achieve photoswitchable charge delocalization and Fe⋅⋅⋅Ru electronic communication. Upon UV‐light irradiation of 2 oo , the Fe⋅⋅⋅Ru heterometallic electronic interaction is increasingly facilitated with stepwise photocyclization, 2 oo → 2 co → 2 cc ; this is ascribed to the gradual increase in π‐conjugated systems. The near‐infrared absorptions in mixed‐valence species [ 2 oo ] + /[ 2 co ] + /[ 2 cc ] + are gradually intensified following the conversion of [ 2 oo ] + →[ 2 co ] + →[ 2 cc ] + , which demonstrates that the extent of charge delocalization shows progressive enhancement with stepwise photocyclization. As revealed by electrochemical, spectroscopic, and theoretical studies, complex 2 exhibits nine switchable states through stepwise photochromic and reversible redox processes.