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Light Harvesting and Directional Energy Transfer in Long‐Lived Homo‐ and Heterotrimetallic Complexes of Fe II , Ru II , and Os II
Author(s) -
Maity Dinesh,
Bhaumik Chanchal,
Mardanya Sourav,
Karmakar Srikanta,
Baitalik Sujoy
Publication year - 2014
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.201402591
Subject(s) - excited state , luminescence , chemistry , crystallography , metal , terpyridine , ligand (biochemistry) , photochemistry , bipyridine , phenanthroline , redox , pyridine , imidazole , stereochemistry , crystal structure , materials science , inorganic chemistry , medicinal chemistry , atomic physics , physics , biochemistry , receptor , optoelectronics , organic chemistry
A new family of trimetallic complexes of the form [(bpy) 2 M(phen‐Hbzim‐tpy)M′(tpy‐Hbzim‐phen)M(bpy) 2 ] 6+ (M=Ru II , Os; M′=Fe II , Ru II , Os; bpy=2,2′‐bipyridine) derived from heteroditopic phenanthroline–terpyridine bridge 2‐{4‐[2,6‐di(pyridin‐2‐yl) pyridine‐4‐yl]phenyl}‐1 H‐ imidazole[4,5‐ f ][1,10]phenanthroline (phen‐Hbzim‐tpy) were prepared and fully characterized. Zn 2+ was used to prepare mixed‐metal trimetallic complexes in situ by coordinating with the free tpy site of the monometallic precursors. The complexes show intense absorptions throughout the UV/Vis region and also exhibit luminescence at room temperature. The redox behavior of the compounds is characterized by several metal‐centered reversible oxidation and ligand‐centered reduction processes. Steady‐state and time‐resolved luminescence data show that the potentially luminescent Ru II ‐ and Os II ‐based triplet metal‐to‐ligand charge‐transfer ( 3 MLCT) excited states in the triads are quantitatively quenched, most likely by intercomponent energy transfer to the lower lying 3 MLCT (for Ru and Os) or triplet metal ‐ centered ( 3 MC) excited states of the Fe II subunit (nonluminescent). Interestingly, iron did not adversely affect the photophysics of the respective systems. This suggests that the multicomponent molecular‐wire‐like complexes investigated here can behave as efficient light‐harvesting antennas, because all the light absorbed by the various subunits is efficiently channeled to the subunit(s) in which the lowest‐energy excited states are located.