Iron(ii) coordination complexes with panchromatic absorption and nanosecond charge-transfer excited state lifetimes

Braun, Jason D.; Lozada, Issiah B.; Kolodziej, Charles; Burda, Clemens; Newman, Kelly M. E.; Lierop, J. van; Davis, Rebecca L.; Herbert, David E.

doi:10.1038/s41557-019-0357-z

Cited by 131 publications

(218 citation statements)

References 52 publications

Supporting

Mentioning

207

Contrasting

Order By: Relevance

“…Cyclometallating ligands have been proposed to have very beneficial properties due to their strong σ-donating character [63][64][65][66][67]. Recently, the first synthesis of an air-stable cyclometallated iron complex has been presented along with investigations of the excited state properties of the compound and a 0.8 ps MLCT lifetime was found (a 5.5-fold increase compared to the 140 fs in the parent [Fe(tpy) 2 ] 2+ ) [68]. Furthermore, the use of ligands with an amido motif that lead to strong mixing of filled ligand and metal orbitals, combined with a phenanthridine moiety that has low-lying π* orbitals, produced Fe(II) complexes with MLCT-type excited state lifetimes exceeding 2 ns and broad absorption in the visible spectrum [68].…”

Section: Discussionmentioning

confidence: 99%

“…Recently, the first synthesis of an air-stable cyclometallated iron complex has been presented along with investigations of the excited state properties of the compound and a 0.8 ps MLCT lifetime was found (a 5.5-fold increase compared to the 140 fs in the parent [Fe(tpy) 2 ] 2+ ) [68]. Furthermore, the use of ligands with an amido motif that lead to strong mixing of filled ligand and metal orbitals, combined with a phenanthridine moiety that has low-lying π* orbitals, produced Fe(II) complexes with MLCT-type excited state lifetimes exceeding 2 ns and broad absorption in the visible spectrum [68]. Considering the progress made and the challenges lying ahead, the photochemistry of iron-based coordination compounds remains an interesting and vibrant field of research.…”

Section: Discussionmentioning

confidence: 99%

See 1 more Smart Citation

Design and Synthesis of Photoactive Iron N-Heterocyclic Carbene Complexes

Kaufhold

Wärnmark

2020

Catalysts

View full text Add to dashboard Cite

The use of iron in photoactive metal complexes has been investigated for decades. In this respect, the charge transfer (CT) states are of particular interest, since they are usually responsible for the photofunctionality of such compounds. However, only recently breakthroughs have been made in extending CT excited state lifetimes that are notoriously short-lived in classical polypyridine iron coordination compounds. This success is in large parts owed to the use of strongly σ-donating N-heterocyclic carbene (NHC) ligands that help manipulating the photophysical and photochemical properties of iron complexes. In this review we aim to map out the basic design principles for the generation of photofunctional iron NHC complexes, summarize the progress made so far and recapitulate on the synthetic methods used. Further, we want to highlight the challenges still existing and give inspiration for future generations of photoactive iron complexes.

show abstract

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Design and Synthesis of Photoactive Iron N-Heterocyclic Carbene Complexes

Kaufhold

Wärnmark

2020

Catalysts

View full text Add to dashboard Cite

show abstract

“…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].…”

Section: Introductionmentioning

confidence: 99%

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

Herr

Wenger

2020

Inorganics

View full text Add to dashboard Cite

Diisocyanide ligands with a m-terphenyl backbone provide access to Mo 0 complexes exhibiting the same type of metal-to-ligand charge transfer (MLCT) luminescence as the well-known class of isoelectronic Ru II polypyridines. The luminescence quantum yields and lifetimes of the homoleptic tris(diisocyanide) Mo 0 complexes depend strongly on whether methyl-or tert-butyl substituents are placed in α-position to the isocyanide groups. The bulkier tert-butyl substituents lead to a molecular structure in which the three individual diisocyanides ligated to one Mo 0 center are interlocked more strongly into one another than the ligands with the sterically less demanding methyl substituents. This rigidification limits the distortion of the complex in the emissive excited-state, causing a decrease of the nonradiative relaxation rate by one order of magnitude. Compared to Ru II polypyridines, the molecular distortions in the luminescent 3 MLCT state relative to the electronic ground state seem to be smaller in the Mo 0 complexes, presumably due to delocalization of the MLCT-excited electron over greater portions of the ligands. Temperature-dependent studies indicate that thermally activated nonradiative relaxation via metal-centered excited states is more significant in these homoleptic Mo 0 tris(diisocyanide) complexes than in [Ru(2,2 -bipyridine) 3 ] 2+ . complexes with monodentate arylisocyanide ligands are very strong photoreductants, capable, for example, of reducing anthracene to its radical anion form. Many different kinds of metal complexes with isocyanide ligands have been explored over the past few decades [11][12][13][14][15], but metals with the d 6 or d 10 electron configurations are unique in their ability to show luminescence from a 3 MLCT excited state.Whilst structurally more flexible, multidentate isocyanide chelate ligands had been known for some time [16], we found that chelating diisocyanide ligands based on a m-terphenyl backbone permit the synthesis of homoleptic tris(diisocyanide) complexes of Cr 0 and Mo 0 that luminesce from 3 MLCT excited states (Figure 1) [17]. 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]. Thus, the Mo 0 diisocyanide complexes represent Earth-abundant alternatives to precious-...

show abstract

“…0.08 to 4.80 10 5 m À1 cm À1 )s een for 5 over the 250-800 nm spectral region were found to be comparable or better than those of other known chromophores exhibiting panchromatic absorption. [18] We thus suggest that calix [16]phyrin 5 may have ar ole to play as an initial light capture chromophore.…”

Section: Optical Properties Uv/vis/nir Absorption and Emission Studiesmentioning

confidence: 82%

Excitonically Coupled Cyclic BF₂ Arrays of Calix[8]‐ and Calix[16]phyrin as Near‐IR‐Chromophores

et al. 2020

View full text Add to dashboard Cite

Two giant calix[n]phyrin derivatives namely calix[8]‐ (4) and calix[16]phyrin (5), involving two and four BF2 units, respectively, were prepared through the condensation of the bis‐naphthobipyrrolylmethene‐BF2 complex (3) with pentafluorobenzaldehyde. Calix[n]phyrins 4 and 5 display extremely high extinction coefficients (3.67 and 4.82×105 m−1 cm−1, respectively) in the near‐IR region, which was taken as initial evidence for strong excitonic coupling within these cyclic multi‐chromophoric systems. Detailed insights into the effect of excitonic coupling dynamics on the electronic structure and photophysical properties of the macrocycles came from fluorescence, time‐correlated single‐photon counting (TCSPC) and transient absorption (TA) measurements. Support for these experimental findings came from theoretical studies. Theory and experiment confirmed that the coupling between the excitons depends on the specifics of the calix[n]phyrin structure, not just its size.

show abstract

Iron(ii) coordination complexes with panchromatic absorption and nanosecond charge-transfer excited state lifetimes

Cited by 131 publications

References 52 publications

Design and Synthesis of Photoactive Iron N-Heterocyclic Carbene Complexes

Design and Synthesis of Photoactive Iron N-Heterocyclic Carbene Complexes

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

Excitonically Coupled Cyclic BF₂ Arrays of Calix[8]‐ and Calix[16]phyrin as Near‐IR‐Chromophores

Contact Info

Product

Resources

About

Iron(ii) coordination complexes with panchromatic absorption and nanosecond charge-transfer excited state lifetimes

Cited by 131 publications

References 52 publications

Design and Synthesis of Photoactive Iron N-Heterocyclic Carbene Complexes

Design and Synthesis of Photoactive Iron N-Heterocyclic Carbene Complexes

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

Excitonically Coupled Cyclic BF2 Arrays of Calix[8]‐ and Calix[16]phyrin as Near‐IR‐Chromophores

Contact Info

Product

Resources

About

Excitonically Coupled Cyclic BF₂ Arrays of Calix[8]‐ and Calix[16]phyrin as Near‐IR‐Chromophores