How Rigidity and Conjugation of Bidentate Ligands Affect the Geometry and Photophysics of Iron N-Heterocyclic Complexes: A Comparative StudyVisa övriga samt affilieringar
2024 (Engelska)Ingår i: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 63, nr 10, s. 4461-4473Artikel i tidskrift (Refereegranskat) Published
Abstract [en]
Two iron complexes featuring the bidentate, nonconjugated N-heterocyclic carbene (NHC) 1,1′-methylenebis(3-methylimidazol-2-ylidene) (mbmi) ligand, where the two NHC moieties are separated by a methylene bridge, have been synthesized to exploit the combined influence of geometric and electronic effects on the ground- and excited-state properties of homoleptic FeIII-hexa-NHC [Fe(mbmi)3](PF6)3 and heteroleptic FeII-tetra-NHC [Fe(mbmi)2(bpy)](PF6)2 (bpy = 2,2′-bipyridine) complexes. They are compared to the reported FeIII-hexa-NHC [Fe(btz)3](PF6)3 and FeII-tetra-NHC [Fe(btz)2(bpy)](PF6)2 complexes containing the conjugated, bidentate mesoionic NHC ligand 3,3′-dimethyl-1,1′-bis(p-tolyl)-4,4′-bis(1,2,3-triazol-5-ylidene) (btz). The observed geometries of [Fe(mbmi)3](PF6)3 and [Fe(mbmi)2(bpy)](PF6)2 are evaluated through L–Fe–L bond angles and ligand planarity and compared to those of [Fe(btz)3](PF6)3 and [Fe(btz)2(bpy)](PF6)2. The FeII/FeIII redox couples of [Fe(mbmi)3](PF6)3 (−0.38 V) and [Fe(mbmi)2(bpy)](PF6)2 (−0.057 V, both vs Fc+/0) are less reducing than [Fe(btz)3](PF6)3 and [Fe(btz)2(bpy)](PF6)2. The two complexes show intense absorption bands in the visible region: [Fe(mbmi)3](PF6)3 at 502 nm (ligand-to-metal charge transfer, 2LMCT) and [Fe(mbmi)2(bpy)](PF6)2 at 410 and 616 nm (metal-to-ligand charge transfer, 3MLCT). Lifetimes of 57.3 ps (2LMCT) for [Fe(mbmi)3](PF6)3 and 7.6 ps (3MLCT) for [Fe(mbmi)2(bpy)](PF6)2 were probed and are somewhat shorter than those for [Fe(btz)3](PF6)3 and [Fe(btz)2(bpy)](PF6)2. [Fe(mbmi)3](PF6)3 exhibits photoluminescence at 686 nm (2LMCT) in acetonitrile at room temperature with a quantum yield of (1.2 ± 0.1) × 10–4, compared to (3 ± 0.5) × 10–4 for [Fe(btz)3](PF6)3.
Ort, förlag, år, upplaga, sidor
American Chemical Society (ACS), 2024. Vol. 63, nr 10, s. 4461-4473
Nationell ämneskategori
Oorganisk kemi
Identifikatorer
URN: urn:nbn:se:uu:diva-528546DOI: 10.1021/acs.inorgchem.3c03972ISI: 001178612200001PubMedID: 38421802OAI: oai:DiVA.org:uu-528546DiVA, id: diva2:1860280
Ingår i projekt
Fotokemi av järnkarbenkomplex, Vetenskapsrådet
Forskningsfinansiär
Stiftelsen för strategisk forskning (SSF), EM16-0067Knut och Alice Wallenbergs Stiftelse, 2018.0074Vetenskapsrådet, 2020-05058Vetenskapsrådet, 2021-05313Swedish National Infrastructure for Computing (SNIC)Carl Tryggers stiftelse för vetenskaplig forskning eSSENCE - An eScience CollaborationNational Supercomputer Centre (NSC), SwedenNational Academic Infrastructure for Supercomputing in Sweden (NAISS)Vetenskapsrådet, 2020-03207Energimyndigheten, P48747-1Sten K Johnsons Stiftelse2024-05-232024-05-232024-05-23Bibliografiskt granskad