Design of Luminescent, Heteroleptic, Cyclometalated Pt<sup>II</sup> and Pt<sup>IV</sup> Complexes: Photophysics and Effects of the Cyclometalated Ligands

Giménez, Nora; Lalinde, Elena; Lara, Rebeca

doi:10.1002/chem.201806240

Cited by 24 publications

(17 citation statements)

References 114 publications

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“…The structure of t Bu L Pt(CCC 6 H 4  t Bu) confirmed the replacement of the chlorido ligand by 4-( tert -butyl)phenylacetylido, although the diffraction data indicated the presence of residual cocrystallized t Bu L PtCl in the sample analyzed (around 5%). The PtC bond length in CF3 L Pt(IV)Cl 3 [2.006(6) Å] is slightly longer than the Pt(II)C bonds [ t Bu L PtCl 1.979(13) Å; [ CF3 L Pt(py)]PF 6 1.962(4) Å] and consistent with literature reports on Pt(II) vs Pt(IV). − …”

Section: Results and Discussionsupporting

confidence: 87%

Brightly Luminescent Platinum Complexes of N^∧C^–^∧N Ligands Forming Six-Membered Chelate Rings: Offsetting Deleterious Ring Size Effects Using Site-Selective Benzannulation

et al. 2021

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Brightly emissive platinum(II) complexes (λemission,max = 607–612 nm) of the type R LPtCl are reported, where R L is a cyclometalated N∧C–∧N-coordinating ligand derived from 1,3-di(2-trifluoromethyl-4-phenanthridinyl)benzene ( CF3 LH) or 1,3-di(2-tert-butyl-4-phenanthridinyl)benzene ( t Bu LH). Metathesis of the chlorido ligand can be achieved under mild conditions, enabling isolation of ionic compounds with the formula [ CF3 LPtL′]PF6 where L′ = pyridine or (4-dimethylamino)pyridine (DMAP), as well as the charge-neutral species t Bu LPt(CCC6H4tBu) (CCC6H4tBu = 4-tert-butylphenylacetylido). Compared with N∧N∧N-ligated Pt(II) complexes that form 5-membered chelates, these compounds all contain 6-membered rings. Expanding the chelate ring size from 5 to 6 has been previously demonstrated to enhance emission in some N∧N∧N-coordinated Pt(II) speciesfor example, in complexes of 2,6-di(8-quinolinyl)pyridine vs those of 2,2′:6′,2″-terpyridinebut in related N∧C–∧N-coordinated species, luminescence quantum yields are significantly lower for the 6-membered chelate ring complexes. Here, we demonstrate that site-selective benzannulation of the quinolinyl side-arms can offset the deleterious effect of changing the chelate ring-size and boost photophysical properties such as the quantum yield. Density functional theory (DFT) and time-dependent DFT (TD-DFT) calculations suggest that benzannulation counterintuitively destabilizes the emissive triplet states compared to the smaller π-system, with the “imine-bridged biphenyl” form of the phenanthridinyl arm helping to buffer against larger molecular distortions, enhancing photoluminescence quantum yields up to 0.09 ± 0.02. The spontaneous formation under aerated conditions of a Pt(IV) derivative ( CF3 LPtCl3) is also reported, together with its molecular structure in the solid state.

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Section: Results and Discussionsupporting

confidence: 87%

Brightly Luminescent Platinum Complexes of N^∧C^–^∧N Ligands Forming Six-Membered Chelate Rings: Offsetting Deleterious Ring Size Effects Using Site-Selective Benzannulation

et al. 2021

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“…In accord with Kasha's rule, [37] the chromophoric ligand in the heteroleptic complexes is the one with the lowest p-p*t ransition energy,i .e.,p qi nfac-3ba, thpy in fac-3ca andp iq in fac-3ad, 3bd, 3cd and 3da,a sd educed by comparison with other cyclometalated Pt IV emitters bearing thesel igands. [14,35,38,39] The excitation spectra faithfully reproduce the absorption profiles in all cases ( Figure S18, Supporting Information). An additional band is observeda ta higher energy (400-450 nm) for all the piq derivatives, which can be ascribed to fluorescencef rom a 1 LC(piq)s tate on the basis of its small Stokes shift and very short lifetime (< 0.2 ns), implyingt hat intersystem crossing to and radiatived ecay from the piq-centeredt riplet state are less efficient as compared with the pq-or thpy-centered triplet states, which results in fluorescenceb ecoming competitive.…”

Section: Photophysical Studymentioning

confidence: 64%

Stereoselective Formation of Facial Tris‐Cyclometalated Pt^IV Complexes: Dual Phosphorescence from Heteroleptic Derivatives

López-López

Bautista

González‐Herrero

2020

Chemistry A European J

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A stereoselective synthetic route to homo‐ and heteroleptic facial tris‐cyclometalated PtIV complexes is reported, involving the oxidative addition of 2‐(2‐pyridyl)‐ or 2‐(1‐isoquinolinyl)benzenediazonium salts to cis‐[Pt(C^N)2] precursors, with C^N=cyclometalated 2‐(p‐tolyl)pyridine (tpy), 2‐phenylquinoline (pq), 2‐(2‐thienyl)pyridine or 1‐phenylisoquinoline (piq), to produce labile diazenide intermediates that undergo photochemical or thermal elimination of N2. The method allows the preparation of derivatives bearing cyclometalated ligands of low π–π* transition energies. The new complexes exhibit phosphorescence in fluid solution at room temperature arising from triplet ligand‐centered (3LC) excited states, which, in the cases of the heteroleptic derivatives, involve the ligand with the lowest π–π* gap. The heteroleptic piq derivatives exhibit fluorescence and dual phosphorescence from different ligand‐centered excited states in rigid media, demonstrating the potential of cyclometalated PtIV complexes as multi‐emissive materials.

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“…Transition-metal complexes featuring long-lived emissive triplet excited states are at the core of numerous technological, analytical, biomedical, and synthetic developments, including chemosensing, , cell imaging, photodynamic therapy, photocatalysis, and light-emitting materials. − Over the past decades, most research in this area has focused on luminescent Ir(III) − and Pt(II) − complexes with cyclometalating heteroaromatic ligands because of the high tunability and adaptability of their excited states, whereas Pt(IV) complexes have only started to be systematically explored as strong emitters in recent years. − …”

Section: Introductionmentioning

confidence: 99%

Strongly Luminescent Pt(IV) Complexes with a Mesoionic N-Heterocyclic Carbene Ligand: Tuning Their Photophysical Properties

et al. 2021

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The synthesis, electrochemistry, and photophysical properties of a series of bis-cyclometalated Pt(IV) complexes that combine the mesoionic aryl-NHC ligand 4-butyl-3-methyl-1-phenyl-1H-1,2,3-triazol-5-ylidene (trz) with either 1-phenylpyrazole or 2-arylpyridine (C ∧ N) are reported. The complexes (OC-6-54)-[PtCl 2 (C ∧ N)(trz)] bearing cyclometalating 2-arylpyridines present phosphorescent emissions in the blue to yellow color range, which essentially arise from 3 LC(C ∧ N) states, and reach quantum yields of ca. 0.3 in fluid solutions and almost unity in poly(methyl methacrylate) (PMMA) matrices at 298 K, thus representing a class of strong emitters with tunable properties. A systematic comparison with the homologous C 2 -symmetrical species (OC-6-33)-[PtCl 2 (C ∧ N) 2 ], which contains two equal 2-arylpyridine ligands, shows that the introduction of a trz ligand leads to significantly lower nonradiative decay rates and higher quantum efficiencies. Computational calculations substantiate the effect of the carbene ligand, which raises the energy of dσ* orbitals in these derivatives and results in the higher energies of nonemissive deactivating 3 LMCT states. In contrast, the isomers (OC-6-42)-[PtCl 2 (C ∧ N)(trz)] are not luminescent because they present a 3 LMCT state as the lowest triplet.

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Design of Luminescent, Heteroleptic, Cyclometalated Pt^II and Pt^IV Complexes: Photophysics and Effects of the Cyclometalated Ligands

Cited by 24 publications

References 114 publications

Brightly Luminescent Platinum Complexes of N^∧C^–^∧N Ligands Forming Six-Membered Chelate Rings: Offsetting Deleterious Ring Size Effects Using Site-Selective Benzannulation

Brightly Luminescent Platinum Complexes of N^∧C^–^∧N Ligands Forming Six-Membered Chelate Rings: Offsetting Deleterious Ring Size Effects Using Site-Selective Benzannulation

Stereoselective Formation of Facial Tris‐Cyclometalated Pt^IV Complexes: Dual Phosphorescence from Heteroleptic Derivatives

Strongly Luminescent Pt(IV) Complexes with a Mesoionic N-Heterocyclic Carbene Ligand: Tuning Their Photophysical Properties

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Design of Luminescent, Heteroleptic, Cyclometalated PtII and PtIV Complexes: Photophysics and Effects of the Cyclometalated Ligands

Cited by 24 publications

References 114 publications

Brightly Luminescent Platinum Complexes of N∧C–∧N Ligands Forming Six-Membered Chelate Rings: Offsetting Deleterious Ring Size Effects Using Site-Selective Benzannulation

Brightly Luminescent Platinum Complexes of N∧C–∧N Ligands Forming Six-Membered Chelate Rings: Offsetting Deleterious Ring Size Effects Using Site-Selective Benzannulation

Stereoselective Formation of Facial Tris‐Cyclometalated PtIV Complexes: Dual Phosphorescence from Heteroleptic Derivatives

Strongly Luminescent Pt(IV) Complexes with a Mesoionic N-Heterocyclic Carbene Ligand: Tuning Their Photophysical Properties

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Product

Resources

About

Design of Luminescent, Heteroleptic, Cyclometalated Pt^II and Pt^IV Complexes: Photophysics and Effects of the Cyclometalated Ligands

Brightly Luminescent Platinum Complexes of N^∧C^–^∧N Ligands Forming Six-Membered Chelate Rings: Offsetting Deleterious Ring Size Effects Using Site-Selective Benzannulation

Brightly Luminescent Platinum Complexes of N^∧C^–^∧N Ligands Forming Six-Membered Chelate Rings: Offsetting Deleterious Ring Size Effects Using Site-Selective Benzannulation

Stereoselective Formation of Facial Tris‐Cyclometalated Pt^IV Complexes: Dual Phosphorescence from Heteroleptic Derivatives