Is Iron the New Ruthenium?

Abstract

Ruthenium complexes with polypyridine ligands are very popularc hoices for applications in photophysics and photochemistry,f or example, in lighting, sensing, solar cells, and photoredox catalysis. There is al ong-standing interest in replacing ruthenium with iron because ruthenium is rare and expensive, whereas iron is comparatively abundant and cheap.H owever,i ti sv ery difficult to obtain iron complexes with an electronic structure similart ot hat of ruthenium(II) polypyridines. The latter typicallyh ave al onglived excited state with pronounced charge-transferc haracter between the ruthenium metal and ligands. These metalto-ligand charge-transfer( MLCT) excited states can be luminescent, with typical lifetimesi nt he range of 100 to 1000 ns, and the electrochemical properties are drastically altered during this time. These properties make ruthenium(II) polypyridine complexes so well suited for the abovementioned applications. In iron(II) complexes, the MLCT states [a] Prof.

Recombination and regeneration dynamics in FeNHC(ii)-sensitized solar cells

“…100 fs) deactivation of the MLCT manifold to metal-centered (MC) states. [6][7][8][9] Thus, the too short lived the excited state impedes injection into the SC conduction band. One of the most successful strategies employed to delay the deactivation is to increase the ligand field strength.…”

Excited-State Relaxation in Luminescent Molybdenum(0) Complexes with Isocyanide Chelate Ligands

“…The molecular and the electronic structures of these compounds are reminiscent of Fe II and Ru II polypyridine complexes, which have been investigated extensively in the past. Until now, no convincing case of steady-state MLCT luminescence from a Fe II complex has been reported despite significant advances in extending their 3 MLCT lifetimes in recent years [18][19][20][21][22][23]; hence, our Cr 0 complex currently seems to be the only example of a first-row d 6 -metal complex showing MLCT luminescence in solution at room temperature under steady-state photo-irradiation [24]. The Mo 0 diisocyanide complexes are not only emissive, but they can furthermore be employed in photoredox catalysis of thermodynamically challenging reductions, which cannot be performed with more widely known photoreductants such as fac-[Ir(ppy)3] (ppy = 2-phenylpyridine) [25].…”

Excited‐State Kinetics of an Air‐Stable Cyclometalated Iron(II) Complex

“…An overview of the conceptual approaches to increaset he 3 MLCTl ifetimeo fF e II complexesw as recently given by Wenger. [7] Optimized octahedral symmetry in combination with p-accepting ligandst ol ower the t 2g -levels, or ap ush-pull ligandc ombinationt os tabilizeM LCT states while destabilizing the MC states, are successful concepts established by McCusker [8] and Heinze [9] for [Fe(N^N^N) 2 ] 2 + chromophores. Exchange of pyridyl units by N-heterocyclic carbene( NHC) ligands by Wärnmark, Gros, and Bauer lead to [Fe(C NHC^N^CNHC ) 2 ] 2 + and relatedc omplexes.…”