Metal Complexes Supported on Solid Matrices for Visible‐Light‐Driven Molecular Transformations

Mori, Kohsuke; Yamashita, Hiromi

doi:10.1002/chem.201600441

Cited by 46 publications

(20 citation statements)

References 149 publications

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“…Luminescent materials based on transition metal complexes possess a wide range of potential applications in fields such as photocatalysis, , sensing, and optoelectronic devices. , Phosphorescent metal complexes are of particular interest in the field of OLED (Organic Light Emitting Diode) applications, due to the ability of these materials to harvest all generated excitons in electroluminescent devices by means of efficient spin-orbit coupling (SOC) associated with the heavy metal centers . Typical phosphorescent emitters are based on metal cations such as Ir(III), Ru(II), and Pt(II). , While the d 6 metal centers like Ir(III) and Ru(II) often adopt a octahedral coordination environment, metals with a d 8 electron configuration, such as Pt(II), Pd(II), and Au(III), often display square-planar geometries with open coordination vacancies in the axial positions. , These open axial flanks can lead to metal-metal (M···M) and/or π-π stacking interactions in the aggregated state with red-shifted emission from the MMLCT (metal-metal-to-ligand charge transfer, eventually with excimeric M···M shortening) or LC (ligand-centered) character …”

Section: Introductionmentioning

confidence: 99%

Photophysics and Excited State Dynamics of Cyclometalated [M(Phbpy)(CN)] (M = Ni, Pd, Pt) Complexes: A Theoretical and Experimental Study

et al. 2021

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Cyclometalated complexes [M(Phbpy)(CN)] (HPhbpy = 6-phenyl-2,2′-bipyridine) of the group 10 metals (Ni, Pd, and Pt) bearing a carbanionic –C∧N∧N pincer ligand were synthesized and studied in a combined experimental and computational DFT approach. All three complexes were crystallographically characterized showing closely packed dimers with head-to-tail stacking and short metal-metal contacts in the solid state. The computational models for geometries, excited states, and electronic transitions addressed both monomeric (Ni-mono, Pd-mono, and Pt-mono) and dimeric (Ni-dim, Pd-dim, and Pt-dim) entities. Photophysical properties and excited state dynamics of all title complexes were investigated in solution and in the solid at 298 and 77 K. [Ni(Phbpy)(CN)] and [Pd(Phbpy)(CN)] are virtually nonemissive in solution at 298 K, whereas [Pt(Phbpy)(CN)] shows phosphorescence in CH2Cl2 (DCM) solution (λ em = 562 nm) stemming from a mixed 3MLCT/ILCT (metal-to-ligand charge transfer/intraligand charge transfer) state. At 77 K in a glassy frozen DCM:MeOH matrix, [Pd(Phbpy)(CN)] shows a remarkable emission (λ em = 571 nm) with a photoluminescence quantum yield reaching almost unity, whereas [Ni(Phbpy)(CN)] is again nonemissive. Calculations on the monomeric models M-mono show that low-lying metal-centered states (MC, i.e., d-d* configuration) with dissociative character quench the photoluminescence. In the solid state, the complexes [M(Phbpy)(CN)] show defined photoluminescence bands (λ em = 561 nm for Pd and 701 nm for Pt). Calculations on the dimeric models M-dim shows that the axial M···M interactions alter the photophysical properties of Pd-dim and Pt-dim toward MMLCT (metal-metal-to-ligand charge transfer) excited states with Pd-dim showing temperature-dependent emission lifetimes, suggesting thermally activated delayed fluorescence, whereas Pt-dim displayed phosphorescence with excimeric character. The metal-metal interactions were analyzed in detail with the quantum theory of atoms in molecules approach.

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Section: Introductionmentioning

confidence: 99%

Photophysics and Excited State Dynamics of Cyclometalated [M(Phbpy)(CN)] (M = Ni, Pd, Pt) Complexes: A Theoretical and Experimental Study

et al. 2021

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“…Luminescent transition metal complexes have gained enormous importance in the last 20 years with potential applications in fields such as photocatalysis [ 1 , 2 ], sensing [ 3 , 4 , 5 , 6 ], and optoelectronic devices [ 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 ]. Phosphorescent metal complexes are of particular interest in the field of OLED (organic light emitting diode) applications, as these materials are able to harvest all generated excitons in the operating electroluminescent devices [ 11 ].…”

Section: Introductionmentioning

confidence: 99%

Photoluminescence of Ni(II), Pd(II), and Pt(II) Complexes [M(Me2dpb)Cl] Obtained from C‒H Activation of 1,5-Di(2-pyridyl)-2,4-dimethylbenzene (Me2dpbH)

et al. 2021

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The three complexes [M(Me2dpb)Cl] (M = Ni, Pd, Pt) containing the tridentate N,C,N-cyclometalating 3,5-dimethyl-1,5-dipyridyl-phenide ligand (Me2dpb−) were synthesised using a base-assisted C‒H activation method. Oxidation potentials from cyclic voltammetry increased along the series Pt < Ni < Pd from 0.15 to 0.74 V. DFT calculations confirmed the essentially ligand-centred π*-type character of the lowest unoccupied molecular orbital (LUMO) for all three complexes in agreement with the invariant reduction processes. For the highest occupied molecular orbitals (HOMO), contributions from metal dyz, phenyl C4, C2, C1, and C6, and Cl pz orbitals were found. As expected, the dz2 (HOMO-1 for Ni) is stabilised for the Pd and Pt derivatives, while the antibonding dx2−y2 orbital is de-stabilised for Pt and Pd compared with Ni. The long-wavelength UV-vis absorption band energies increase along the series Ni < Pt < Pd. The lowest-energy TD-DFT-calculated state for the Ni complex has a pronounced dz2-type contribution to the overall metal-to-ligand charge transfer (MLCT) character. For Pt and Pd, the dz2 orbital is energetically not available and a strongly mixed Cl-to-π*/phenyl-to-π*/M(dyz)-to-π* (XLCT/ILCT/MLCT) character is found. The complex [Pd(Me2dpb)Cl] showed a structured emission band in a frozen glassy matrix at 77 K, peaking at 468 nm with a quantum yield of almost unity as observed for the previously reported Pt derivative. No emission was observed from the Ni complex at 77 or 298 K. The TD-DFT-calculated states using the TPSSh functional were in excellent agreement with the observed absorption energies and also clearly assessed the nature of the so-called “dark”, i.e., d‒d*, excited configurations to lie low for the Ni complex (≥3.18 eV), promoting rapid radiationless relaxation. For the Pd(II) and Pt(II) derivatives, the “dark” states are markedly higher in energy with ≥4.41 eV (Pd) and ≥4.86 eV (Pt), which is in perfect agreement with the similar photophysical behaviour of the two complexes at low temperatures.

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“…To counter such sustainability issues, our group and others have developed recyclable photocatalytic systems, such as heterogenized solid PCs (Mori et al, 2010;Mori and Yamashita, 2016;Tambosco et al, 2018;Choi et al, 2020;Gisbertz and Pieber, 2020;Soria-Castro et al, 2020;Materna and Hammarström, 2021). In particular, we investigated the straightforward non-covalent immobilization of PCs on silica particles which resulted in an improved reactivity and stability (Tambosco et al, 2018), and provided additional physical properties such as magnetism (Terra et al, 2020) or plasmonic resonance (Gellé et al, 2021).…”

Section: Introductionmentioning

confidence: 99%

Performances of Homogeneous and Heterogenized Methylene Blue on Silica Under Red Light in Batch and Continuous Flow Photochemical Reactors

et al. 2021

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Methylene blue was efficiently immobilized on silica micro- and nanoparticles by electrostatic interactions and the performances of the heterogenized photocatalysts were compared against the homogeneous conditions using the photooxidation of citronellol as a model reaction under red light, in a batch and a continuous flow photochemical reactor. In batch, the heterogeneous photocatalyst outperforms the homogeneous one, presumably due to kinetic and stability effects. The two catalytic systems are also compared in a flow reactor displaying improved mass transfer properties. We demonstrate that this results in a dramatic enhancement in photocatalyst stability, reactivity and productivity. This study highlights the importance of photocatalyst stability under homogeneous versus heterogenized conditions and in batch versus flow photochemistry.

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Metal Complexes Supported on Solid Matrices for Visible‐Light‐Driven Molecular Transformations

Cited by 46 publications

References 149 publications

Photophysics and Excited State Dynamics of Cyclometalated [M(Phbpy)(CN)] (M = Ni, Pd, Pt) Complexes: A Theoretical and Experimental Study

Photophysics and Excited State Dynamics of Cyclometalated [M(Phbpy)(CN)] (M = Ni, Pd, Pt) Complexes: A Theoretical and Experimental Study

Photoluminescence of Ni(II), Pd(II), and Pt(II) Complexes [M(Me2dpb)Cl] Obtained from C‒H Activation of 1,5-Di(2-pyridyl)-2,4-dimethylbenzene (Me2dpbH)

Performances of Homogeneous and Heterogenized Methylene Blue on Silica Under Red Light in Batch and Continuous Flow Photochemical Reactors

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