Luminescent complexes made from chelating isocyanide ligands and earth-abundant metals

Büldt, Laura A.; Wenger, Oliver S.

doi:10.1039/c7dt03620e

Cited by 31 publications

(18 citation statements)

References 48 publications

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“…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-metal based luminophores and photoredox catalysts, and in our view, there is interesting fundamental photophysics and photochemistry to be explored in this field [26]. Recently we reported that the [Mo(L tBu )3] complex exhibits much more favorable photophysical properties than the closely related [Mo(L Me )3] compound, and we demonstrated that [Mo(L tBu )3] is more widely applicable in photoredox catalysis due to greater photo-robustness [27].…”

Section: Introductionmentioning

confidence: 99%

“…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-metal based luminophores and photoredox catalysts, and in our view, there is interesting fundamental photophysics and photochemistry to be explored in this field [26].Inorganics 2020, 8, x FOR PEER REVIEW 2 of 11…”

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confidence: 99%

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

Herr

Wenger

2020

Inorganics

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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-...

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Section: Introductionmentioning

confidence: 99%

“…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-metal based luminophores and photoredox catalysts, and in our view, there is interesting fundamental photophysics and photochemistry to be explored in this field [26].Inorganics 2020, 8, x FOR PEER REVIEW 2 of 11…”

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confidence: 99%

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

Herr

Wenger

2020

Inorganics

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“…MLCT excited state,63 a design principle that was inspired by the well-known [Cu(dpp)2] + complex(Figure 6a).42 Nevertheless, these Ni(0) complexes are only luminescent well below room temperature(Table 3).…”

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Photoactive Complexes with Earth-Abundant Metals

2018

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In this invited Perspective recent developments and possible future directions of research on photoactive coordination compounds made from non-precious transition metal elements will be discussed. The focus is on conceptually new, structurally well-characterized complexes with excited-state lifetimes between 10 ps and 1 ms in fluid solution for possible applications in photosensitizing, light-harvesting, luminescence, and catalysis. The key metal elements considered herein are Cr, Mn, Fe, Co, Ni, Cu, Zn, Zr, Mo, W, and Ce in various oxidation states equipped with diverse ligands, giving access to long-lived excited states via a range of fundamentally different types of electronic transitions. Research performed in this area over the past five years demonstrated that a much broader spectrum of metal complexes than what was long believed relevant exhibits useful photophysics and photochemistry.

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“…The next publication on luminescent Ni(0) complexes appeared in 2017 after a break of 14 years, when we reported on two homoleptic complexes with bidentate isocyanide ligands (Scheme 3a/b) [28]. We had previously discovered that such chelating isocyanides provide access to relatively robust d 6 metal complexes made from Cr(0) and Mo(0) that are luminescent analogues of well-known Ru(II) polypyridyl and cyclometalated Ir(III) complexes [34][35][36][37][38]. The molecular design of the Ni(0) complexes in Scheme 3a/b was inspired by the structure of the Cu(dpp)2 + parent complex (dpp = 2,9-diphenyl-1,10-phenanthroline), in which the phenyl-substituents in -position to the ligating N-atoms are used to impede planarization in the MLCT state, thereby enhancing the luminescence properties [1,5].…”

Section: From Early Structural Studies To Emissive Complexesmentioning

confidence: 99%

Luminescent Ni(0) complexes

Malzkuhn

Wenger

2018

Coordination Chemistry Reviews

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With its 3d 10 valence electron configuration Ni(0) is isoelectronic with Cu(I). While many Cu(I) complexes emitting from metal-to-ligand charge transfer (MLCT) excited states have been explored, the number of luminescent Ni (0) complexes known to date is very limited. Ni(0) is typically stabilized by carbonyls, phosphines or isocyanides due to the -acceptor properties of these ligands, and photoluminescence has been reported in a few selected cases that are reviewed herein. Recent studies indicate that chelating isocyanide ligands are promising for obtaining Ni (0) complexes with long-lived 3 MLCT states, and this could be interesting for a similar range of applications as with photoactive Cu(I) complexes, including for example luminescent devices, solar cells, and organic photoredox reactions.Keywords metal-to-ligand charge transfer; isocyanide, phosphine; N-heterocyclic carbene; -acceptor; earth-abundant metal element Abbreviations

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Luminescent complexes made from chelating isocyanide ligands and earth-abundant metals

Cited by 31 publications

References 48 publications

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

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

Photoactive Complexes with Earth-Abundant Metals

Luminescent Ni(0) complexes

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