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A Heteroleptic Ferrous Complex with Mesoionic Bis(1,2,3‐triazol‐5‐ylidene) Ligands: Taming the MLCT Excited State of Iron(II)
Author(s) -
Liu Yizhu,
Kjær Kasper S.,
Fredin Lisa A.,
Chábera Pavel,
Harlang Tobias,
Canton Sophie E.,
Lidin Sven,
Zhang Jianxin,
Lomoth Reiner,
Bergquist KarlErik,
Persson Petter,
Wärnmark Kenneth,
Sundström Villy
Publication year - 2015
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.201405184
Subject(s) - mesoionic , homoleptic , chemistry , photochemistry , excited state , ligand (biochemistry) , bridging ligand , bipyridine , singlet state , ground state , absorption spectroscopy , metal , crystallography , medicinal chemistry , crystal structure , organic chemistry , biochemistry , physics , receptor , quantum mechanics , nuclear physics
Strongly σ‐donating N‐heterocyclic carbenes (NHCs) have revived research interest in the catalytic chemistry of iron, and are now also starting to bring the photochemistry and photophysics of this abundant element into a new era. In this work, a heteroleptic Fe II complex ( 1 ) was synthesized based on sequentially furnishing the Fe II center with the benchmark 2,2′‐bipyridine (bpy) ligand and the more strongly σ‐donating mesoionic ligand, 4,4′‐bis(1,2,3‐triazol‐5‐ylidene) (btz). Complex 1 was comprehensively characterized by electrochemistry, static and ultrafast spectroscopy, and quantum chemical calculations and compared to [Fe(bpy) 3 ](PF 6 ) 2 and (TBA) 2 [Fe(bpy)(CN) 4 ]. Heteroleptic complex 1 extends the absorption spectrum towards longer wavelengths compared to a previously synthesized homoleptic Fe II NHC complex. The combination of the mesoionic nature of btz and the heteroleptic structure effectively destabilizes the metal‐centered (MC) states relative to the triplet metal‐to‐ligand charge transfer ( 3 MLCT) state in 1 , rendering it a lifetime of 13 ps, the longest to date of a photochemically stable Fe II complex. Deactivation of the 3 MLCT state is proposed to proceed via the 3 MC state that strongly couples with the singlet ground state.