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Ferromagnetically Coupled Chromium(III) Dimer Shows Luminescence and Sensitizes Photon Upconversion. Chemistry 2024:e202400856. [PMID: 38523568 DOI: 10.1002/chem.202400856] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/29/2024] [Revised: 03/23/2024] [Accepted: 03/25/2024] [Indexed: 03/26/2024]
Abstract
There has been much progress on mononuclear chromium(III) complexes featuring luminescence and photoredox activity, but dinuclear chromium(III) complexes have remained underexplored in these contexts until now. We identified a tridentate chelate ligand able to accommodate both meridional and facial coordination of chromium(III), to either access a mono- or a dinuclear chromium(III) complex depending on reaction conditions. This chelate ligand causes tetragonally distorted primary coordination spheres around chromium(III) in both complexes, entailing comparatively short excited-state lifetimes in the range of 400 to 800 ns in solution at room temperature and making photoluminescence essentially oxygen insensitive. The two chromium(III) ions in the dimer experience ferromagnetic exchange interactions that result in a high spin (S=3) ground state with a coupling constant of +9.3 cm-1. Photoinduced energy transfer from the luminescent ferromagnetically coupled dimer to an anthracene derivative results in sensitized triplet-triplet annihilation upconversion. Based on these proof-of-principle studies, dinuclear chromium(III) complexes seem attractive for the development of fundamentally new types of photophysics and photochemistry enabled by magnetic exchange interactions.
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Electronic Structure and Excited-State Dynamics of the NIR-II Emissive Molybdenum(III) Analogue to the Molecular Ruby. Inorg Chem 2023; 62:15797-15808. [PMID: 37718553 DOI: 10.1021/acs.inorgchem.3c02186] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/19/2023]
Abstract
Photoactive chromium(III) complexes saw a conceptual breakthrough with the discovery of the prototypical molecular ruby mer-[Cr(ddpd)2]3+ (ddpd = N,N'-dimethyl-N,N'-dipyridin-2-ylpyridine-2,6-diamine), which shows intense long-lived near-infrared (NIR) phosphorescence from metal-centered spin-flip states. In contrast to the numerous studies on chromium(III) photophysics, only 10 luminescent molybdenum(III) complexes have been reported so far. Here, we present the synthesis and characterization of mer-MoX3(ddpd) (1, X = Cl; 2, X = Br) and cisfac-[Mo(ddpd)2]3+ (cisfac-[3]3+), an isomeric heavy homologue of the prototypical molecular ruby. For cisfac-[3]3+, we found strong zero-field splitting using magnetic susceptibility measurements and electron paramagnetic resonance spectroscopy. Electronic spectra covering the spin-forbidden transitions show that the spin-flip states in mer-1, mer-2, and cisfac-[3]3+ are much lower in energy than those in comparable chromium(III) compounds. While all three complexes show weak spin-flip phosphorescence in NIR-II, the emission of cisfac-[3]3+ peaking at 1550 nm is particularly low in energy. Femtosecond transient absorption spectroscopy reveals a short excited-state lifetime of 1.4 ns, 6 orders of magnitude shorter than that of mer-[Cr(ddpd)2]3+. Using density functional theory and ab initio multireference calculations, we break down the reasons for this disparity and derive principles for the design of future stable photoactive molybdenum(III) complexes.
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Tantalum ureate complexes for photocatalytic hydroaminoalkylation. Chem Sci 2023; 14:4928-4934. [PMID: 37181785 PMCID: PMC10171191 DOI: 10.1039/d3sc00042g] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2023] [Accepted: 03/13/2023] [Indexed: 05/16/2023] Open
Abstract
Using a tantalum ureate pre-catalyst, photocatalytic hydroaminoalkylation of unactivated alkenes with unprotected amines at room temperature is demonstrated. The combination of Ta(CH2SiMe3)3Cl2 and a ureate ligand with a saturated cyclic backbone resulted in this unique reactivity. Preliminary investigations of the reaction mechanism suggest that both the thermal and photocatalytic hydroaminoalkylation reactions begin with N-H bond activation and subsequent metallaaziridine formation. However, a select tantalum ureate complex, through ligand to metal charge transfer (LMCT), results in photocatalyzed homolytic metal-carbon bond cleavage and subsequent addition to unactivated alkene to afford the desired carbon-carbon bond formation. Origins of ligand effects on promoting homolytic metal-carbon bond cleavage are explored computationally to support enhanced ligand design efforts.
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Complex-as-Ligand Strategy as a Tool for the Design of a Binuclear Nonsymmetrical Chromium(III) Assembly: Near-Infrared Double Emission and Intramolecular Energy Transfer. Inorg Chem 2022; 61:11023-11031. [PMID: 35820089 DOI: 10.1021/acs.inorgchem.2c01940] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
The chromium(III) polypyridyl complexes are appealing for their long-lived near-infrared (NIR) emission reaching the millisecond range and for the strong circularly polarized luminescence of their isolated enantiomers. However, harnessing those properties in functional polynuclear CrIII devices remains mainly inaccessible because of the lack of synthetic methods for their design and functionalization. Even the preparation and investigation of most basic nonsymmetrical CrIII dyads exhibiting directional intramolecular intermetallic energy transfer remain unexplored. Taking advantage of the inertness of heteroleptic chromium(III) polypyridyl building blocks, we herein adapt the "complex-as-ligand" strategy, largely used with precious 4d and 5d metals, for the preparation of a binuclear nonsymmetrical CrIII complex (3d metal). The resulting [(phen)2Cr(L)Cr(tpy)]6+ dyad shows dual long-lived NIR emission and a directional intermetallic energy transfer that is controlled by the specific arrangements of the different coordination spheres. This strategy opens a route for building predetermined polynuclear assemblies with this earth-abundant metal.
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Abstract
Bis-terdentate (N^N^N) ligands coordinated to Cr(III) yield complexes that display near-IR emission under aerated solvent conditions at room temperature.
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Heteroleptic mer-[Cr(N ∩N ∩N)(CN) 3] complexes: synthetic challenge, structural characterization and photophysical properties. Dalton Trans 2022; 51:4297-4309. [PMID: 35195140 PMCID: PMC8922558 DOI: 10.1039/d2dt00126h] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The substitution of three water molecules around trivalent chromium in CrBr3·6H2O with the tridentate 2,2′:6′,2′′-terpyridine (tpy), N,N′-dimethyl-N,N′-di(pyridine-2-yl)pyridine-2,6-diamine (ddpd) or 2,6-di(quinolin-8-yl)pyridine (dqp) ligands gives the heteroleptic mer-[Cr(L)Br3] complexes. Stepwise treatments with Ag(CF3SO3) and KCN under microwave irradiations provide mer-[Cr(L)(CN)3] in moderate yields. According to their X-ray crystal structures, the associated six-coordinate meridional [CrN3C3] chromophores increasingly deviate from a pseudo-octahedral arrangement according to L = ddpd ≈ dpq ≪ tpy; a trend in line with the replacement of six-membered with five-membered chelate rings around CrIII. Room-temperature ligand-centered UV-excitation at 18 170 cm−1 (λexc = 350 nm), followed by energy transfer and intersystem crossing eventually yield microsecond metal-centered Cr(2E → 4A2) phosphorescence in the red to near infrared domain 13 150–12 650 cm−1 (760 ≤ λem ≤ 790 nm). Decreasing the temperature to liquid nitrogen (77 K) extends the emission lifetimes to reach the millisecond regime with a record of 4.02 ms for mer-[Cr(dqp)(CN)3] in frozen acetonitrile. The heteroleptic mer-[Cr(L)(CN)3] (L = tpy, ddpd, dqp) complexes with their C2v-symmetrical [CrC3N3] luminescent chromophores represent the missing links between pseudo-octahedral [CrN6] and [CrC6] units found in their well-known homoleptic parents.![]()
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Abstract
In molecular photochemistry, charge-transfer emission is well understood and widely exploited. In contrast, luminescent metal-centered transitions only came into focus in recent years. This gave rise to strongly phosphorescent CrIII complexes with a d3 electronic configuration featuring luminescent metal-centered excited states which are characterized by the flip of a single spin. These so-called spin-flip emitters possess unique properties and require different design strategies than traditional charge-transfer phosphors. In this review, we give a brief introduction to ligand field theory as a framework to understand this phenomenon and outline prerequisites for efficient spin-flip emission including ligand field strength, symmetry, intersystem crossing and common deactivation pathways using CrIII complexes as instructive examples. The recent progress and associated challenges of tuning the energies of emissive excited states and of emerging applications of the unique photophysical properties of spin-flip emitters are discussed. Finally, we summarize the current state-of-the-art and challenges of spin-flip emitters beyond CrIII with d2, d3, d4 and d8 electronic configuration, where we mainly cover pseudooctahedral molecular complexes of V, Mo, W, Mn, Re and Ni, and highlight possible future research opportunities.
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Abstract
The discovery of the highly NIR-luminescent Molecular Ruby [Cr(ddpd)2]3+ 13+ (ddpd = N,N’-dimethyl-N,N’-dipyridine-2-ylpyridine-2,6-diamine) has been a milestone in the development of earth-abundant luminophors and has led to important new impulses...
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Abstract
Precious and rare elements have traditionally dominated inorganic photophysics and photochemistry, but now we are witnessing a paradigm shift toward cheaper and more abundant metals. Even though emissive complexes based on selected first-row transition metals have long been known, recent conceptual breakthroughs revealed that a much broader range of elements in different oxidation states are useable for this purpose. Coordination compounds of V, Cr, Mn, Fe, Co, Ni, and Cu now show electronically excited states with unexpected reactivity and photoluminescence behavior. Aside from providing a compact survey of the recent conceptual key advances in this dynamic field, our Perspective identifies the main design strategies that enabled the discovery of fundamentally new types of 3d-metal-based luminophores and photosensitizers operating in solution at room temperature.
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Abstract
The combination of π-donating amido with π-accepting pyridine coordination units in a tridentate chelate ligand causes a strong nephelauxetic effect in a homoleptic CrIII complex, which shifts its luminescence to the NIR-II spectral range. Previously explored CrIII polypyridine complexes typically emit between 727 and 778 nm (in the red to NIR-I spectral region), and ligand design strategies have so far concentrated on optimizing the ligand field strength. The present work takes a fundamentally different approach and focusses on increasing metal-ligand bond covalence to shift the ruby-like 2 E emission of CrIII to 1067 nm at 77 K.
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Electronic Structures of Cr(III) and V(II) Polypyridyl Systems: Undertones in an Isoelectronic Analogy. Inorg Chem 2021; 60:12823-12834. [PMID: 34382400 DOI: 10.1021/acs.inorgchem.1c01129] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
A recently reported description of the photophysical properties of V2+ polypyridyl systems has highlighted several distinctions between isoelectronic, d3, Cr3+, and V2+ tris-homoleptic polypyridyl complexes of 2,2'-bipyridine (bpy) and 1,10-phenanthroline (phen). Here, we combine theory and experimental data to elucidate the differences in electronic structures. We provide the first crystallographic structures of the V2+ complexes [V(bpy)3](BPh4)2 (V-1B) and [V(phen)3](OTf)2 (V2) and observe pronounced trigonal distortion relative to analogous Cr3+ complexes. We use electronic absorption spectroscopy in tandem with TD-DFT computations to assign metal-ligand charge transfer (MLCT) properties of V-1B and V2 that are unique from the intraligand transitions, 4(3IL), solely observed in Cr3+ analogues. Our newly developed natural transition spin density (NTρα,β) plots characterize both the Cr3+ and V2+ absorbance properties. A multideterminant approach to DFT assigns the energy of the 2E state of V-1B as stabilized through electron delocalization. We find that the profound differences in excited state lifetimes for Cr3+ and V2+ polypyridyls arise from differences in the characters of their lowest doublet states and pathways for intersystem crossing, both of which stem from trigonal structural distortion and metal-ligand π-covalency.
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Abstract
Gaining chemical control over the thermodynamics and kinetics of photoexcited states is paramount to an efficient and sustainable utilization of photoactive transition metal complexes in a plethora of technologies. In contrast to energies of charge transfer states described by spatially separated orbitals, the energies of spin-flip states cannot straightforwardly be predicted as Pauli repulsion and the nephelauxetic effect play key roles. Guided by multireference quantum chemical calculations, we report a novel highly luminescent spin-flip emitter with a quantum chemically predicted blue-shifted luminescence. The spin-flip emission band of the chromium complex [Cr(bpmp)2]3+ (bpmp = 2,6-bis(2-pyridylmethyl)pyridine) shifted to higher energy from ca. 780 nm observed for known highly emissive chromium(III) complexes to 709 nm. The photoluminescence quantum yields climb to 20%, and very long excited state lifetimes in the millisecond range are achieved at room temperature in acidic D2O solution. Partial ligand deuteration increases the quantum yield to 25%. The high excited state energy of [Cr(bpmp)2]3+ and its facile reduction to [Cr(bpmp)2]2+ result in a high excited state redox potential. The ligand's methylene bridge acts as a Brønsted acid quenching the luminescence at high pH. Combined with a pH-insensitive chromium(III) emitter, ratiometric optical pH sensing is achieved with single wavelength excitation. The photophysical and ground state properties (quantum yield, lifetime, redox potential, and acid/base) of this spin-flip complex incorporating an earth-abundant metal surpass those of the classical precious metal [Ru(α-diimine)3]2+ charge transfer complexes, which are commonly employed in optical sensing and photo(redox) catalysis, underlining the bright future of these molecular ruby analogues.
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Heteroleptic trivalent chromium in coordination chemistry: Novel building blocks for addressing old challenges in multimetallic luminescent complexes. Coord Chem Rev 2021. [DOI: 10.1016/j.ccr.2020.213750] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
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Bright Long‐Lived Circularly Polarized Luminescence in Chiral Chromium(III) Complexes. Angew Chem Int Ed Engl 2021; 60:10095-10102. [DOI: 10.1002/anie.202101158] [Citation(s) in RCA: 31] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2021] [Indexed: 11/11/2022]
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Bright Long‐Lived Circularly Polarized Luminescence in Chiral Chromium(III) Complexes. Angew Chem Int Ed Engl 2021. [DOI: 10.1002/ange.202101158] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
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Beyond Chiral Organic (p-Block) Chromophores for Circularly Polarized Luminescence: The Success of d-Block and f-Block Chiral Complexes. Front Chem 2020; 8:555. [PMID: 32850617 PMCID: PMC7399180 DOI: 10.3389/fchem.2020.00555] [Citation(s) in RCA: 35] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2020] [Accepted: 05/29/2020] [Indexed: 12/16/2022] Open
Abstract
Chiral molecules are essential for the development of advanced technological applications in spintronic and photonic. The best systems should produce large circularly polarized luminescence (CPL) as estimated by their dissymmetry factor (g lum), which can reach the maximum values of -2 ≤ g lum ≤ 2 when either pure right- or left-handed polarized light is emitted after standard excitation. For matching this requirement, theoretical considerations indicate that optical transitions with large magnetic and weak electric transition dipole moments represent the holy grail of CPL. Because of their detrimental strong and allowed electric dipole transitions, popular chiral emissive organic molecules display generally moderate dissymmetry factors (10-5 ≤ g lum ≤ 10-3). However, recent efforts in this field show that g lum can be significantly enhanced when the chiral organic activators are part of chiral supramolecular assemblies or of liquid crystalline materials. At the other extreme, chiral EuIII- and SmIII-based complexes, which possess intra-shell parity-forbidden electric but allowed magnetic dipole transitions, have yielded the largest dissymmetry factor reported so far with g lum ~ 1.38. Consequently, 4f-based metal complexes with strong CPL are currently the best candidates for potential technological applications. They however suffer from the need for highly pure samples and from considerable production costs. In this context, chiral earth-abundant and cheap d-block metal complexes benefit from a renewed interest according that their CPL signal can be optimized despite the larger covalency displayed by d-block cations compared with 4f-block analogs. This essay thus aims at providing a minimum overview of the theoretical aspects rationalizing circularly polarized luminescence and their exploitation for the design of chiral emissive metal complexes with strong CPL. Beyond the corroboration that f-f transitions are ideal candidates for generating large dissymmetry factors, a special attention is focused on the recent attempts to use chiral CrIII-based complexes that reach values of g lum up to 0.2. This could pave the way for replacing high-cost rare earths with cheap transition metals for CPL applications.
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Key Strategy for the Rational Incorporation of Long-Lived NIR Emissive Cr(III) Chromophores into Polymetallic Architectures. Inorg Chem 2020; 59:1424-1435. [PMID: 31909978 DOI: 10.1021/acs.inorgchem.9b03163] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The CrIIIN6 chromophores are particularly appealing for low-energy sensitization via energy transfer processes since they show extremely long excited state lifetimes reaching the millisecond range in the technologically crucial near-infrared domain. However, their properties were barely harnessed in multimetallic structures because of the lack of both monitoring methods and accessible synthetic pathways. We herein report a remedy to monitor and control the formation of CrIII-containing assemblies in solution via the design of a CrIIIN6 inert "complex-as-ligand" that can be included into polymetallic architectures. As a proof of concept, these CrN6 building blocks were reacted in solution with ZnII or FeII to give extended trinuclear linear Cr-M-Cr assemblies, the structure of which could be addressed by NMR spectroscopy despite the presence of two slowly relaxing CrIII paramagnetic centers. In addition to long CrIII excited state lifetimes and weak sensitivity to oxygen quenching, these polymetallic assemblies display controlled CrIII to MII energy transfers, which pave the way for use of the "complex-as-ligand" strategy for introducing photophysically active CrIII probes into light-converting polymetallic devices.
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Luminescent polypyridyl heteroleptic Cr III complexes with high quantum yields and long excited state lifetimes. Dalton Trans 2020; 49:13528-13532. [PMID: 32968750 DOI: 10.1039/d0dt02872j] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Implementing high quantum yields and long-lived excited state lifetimes within heteroleptic luminescent CrIII complexes is a keystone for the design of supramolecular energy-converting devices exploiting this cheap metal. In this contribution, we discuss the stepwise and rational optimization of these two limiting factors within a series of heteroleptic CrIII complexes.
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Iron(II) coordination complexes with panchromatic absorption and nanosecond charge-transfer excited state lifetimes. Nat Chem 2019; 11:1144-1150. [PMID: 31740761 DOI: 10.1038/s41557-019-0357-z] [Citation(s) in RCA: 93] [Impact Index Per Article: 18.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2018] [Accepted: 09/23/2019] [Indexed: 11/09/2022]
Abstract
Replacing current benchmark rare-element photosensitizers with ones based on abundant and low-cost metals such as iron would help facilitate the large-scale implementation of solar energy conversion. To do so, the ability to extend the lifetimes of photogenerated excited states of iron complexes is critical. Here, we present a sensitizer design in which iron(II) centres are supported by frameworks containing benzannulated phenanthridine and quinoline heterocycles paired with amido donors. These complexes exhibit panchromatic absorption and nanosecond charge-transfer excited state lifetimes, enabled by the combination of vacant, energetically accessible heterocycle-based acceptor orbitals and occupied molecular orbitals destabilized by strong mixing between amido nitrogen atoms and iron. This finding shows how ligand design can extend metal-to-ligand charge-transfer-type excited state lifetimes of iron(II) complexes into the nanosecond regime and expand the range of potential applications for iron-based photosensitizers.
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Luminescence and Light-Driven Energy and Electron Transfer from an Exceptionally Long-Lived Excited State of a Non-Innocent Chromium(III) Complex. Angew Chem Int Ed Engl 2019; 58:18075-18085. [PMID: 31600421 PMCID: PMC6916301 DOI: 10.1002/anie.201909325] [Citation(s) in RCA: 64] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2019] [Revised: 10/01/2019] [Indexed: 01/10/2023]
Abstract
Photoactive metal complexes employing Earth-abundant metal ions are a key to sustainable photophysical and photochemical applications. We exploit the effects of an inversion center and ligand non-innocence to tune the luminescence and photochemistry of the excited state of the [CrN6 ] chromophore [Cr(tpe)2 ]3+ with close to octahedral symmetry (tpe=1,1,1-tris(pyrid-2-yl)ethane). [Cr(tpe)2 ]3+ exhibits the longest luminescence lifetime (τ=4500 μs) reported up to date for a molecular polypyridyl chromium(III) complex together with a very high luminescence quantum yield of Φ=8.2 % at room temperature in fluid solution. Furthermore, the tpe ligands in [Cr(tpe)2 ]3+ are redox non-innocent, leading to reversible reductive chemistry. The excited state redox potential and lifetime of [Cr(tpe)2 ]3+ surpass those of the classical photosensitizer [Ru(bpy)3 ]2+ (bpy=2,2'-bipyridine) enabling energy transfer (to oxygen) and photoredox processes (with azulene and tri(n-butyl)amine).
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Luminescence and Light‐Driven Energy and Electron Transfer from an Exceptionally Long‐Lived Excited State of a Non‐Innocent Chromium(III) Complex. Angew Chem Int Ed Engl 2019. [DOI: 10.1002/ange.201909325] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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Long-Lived, Strongly Emissive, and Highly Reducing Excited States in Mo(0) Complexes with Chelating Isocyanides. J Am Chem Soc 2019; 141:14394-14402. [PMID: 31464429 DOI: 10.1021/jacs.9b07373] [Citation(s) in RCA: 59] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Newly discovered tris(diisocyanide)molybdenum(0) complexes are Earth-abundant isoelectronic analogues of the well-known class of [Ru(α-diimine)3]2+ compounds with long-lived 3MLCT (metal-to-ligand charge transfer) excited states that lead to rich photophysics and photochemistry. Depending on ligand design, luminescence quantum yields up to 0.20 and microsecond excited state lifetimes are achieved in solution at room temperature, both significantly better than those for [Ru(2,2'-bipyridine)3]2+. The excited Mo(0) complexes can induce chemical reactions that are thermodynamically too demanding for common precious metal-based photosensitizers, including the widely employed fac-[Ir(2-phenylpyridine)3] complex, as demonstrated on a series of light-driven aryl-aryl coupling reactions. The most robust Mo(0) complex exhibits stable photoluminescence and remains photoactive after continuous irradiation exceeding 2 months. Our comprehensive optical spectroscopic and photochemical study shows that Mo(0) complexes with diisocyanide chelate ligands constitute a new family of luminophores and photosensitizers, which is complementary to precious metal-based 4d6 and 5d6 complexes and represents an alternative to nonemissive Fe(II) compounds. This is relevant in the greater context of sustainable photophysics and photochemistry, as well as for possible applications in lighting, sensing, and catalysis.
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Chiral Molecular Ruby [Cr(dqp)2]3+ with Long-Lived Circularly Polarized Luminescence. J Am Chem Soc 2019; 141:13244-13252. [DOI: 10.1021/jacs.9b06524] [Citation(s) in RCA: 89] [Impact Index Per Article: 17.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
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Abstract
Visible light photoredox catalysis has exploded into the consciousness of the synthetic chemist. We critically review Earth-abundant metal complexes photocatalysts including Cu(i), Zn(ii), Ni(0), V(v), Zr(iv), W(0), W(vi), Mo(0), Cr(iii), Co(iii) and Fe(ii).
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