Phosphorescent Square‐Planar Platinum(II) Complexes of 1,3‐Bis(2‐pyridylimino)isoindoline with a Monodentate Strong‐Field Ligand

Wen, Hu; Wang, Jin Yun; Li, Bin; Zhang, Li Yi; Chen, Chang Neng; Chen, Zhong Ning

doi:10.1002/ejic.201300622

Cited by 8 publications

(7 citation statements)

References 76 publications

(58 reference statements)

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“…In this work, we could not observe phosphorescence; this might be due to the triplet states not being emissive or the ISC process is slow for inefficient SOC, despite the Ln center being close enough (∼1 Å) to chromophore ligands. With reference to Pt or Pd salen counterparts even with the same ligand, which display strong phosphorescence arising from the triplet intraligand transition or 3 MLCT, we tentatively excluded the possibility that the triplet states are not emissive. Thus, we ascribed strong fluorescence to slow ISC due to inefficient SOC.…”

Section: Resultsmentioning

confidence: 97%

Strong Fluorescent Lanthanide Salen Complexes: Photophysical Properties, Excited-State Dynamics, and Bioimaging

et al. 2018

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The synthesis, excited-state dynamics, and biological application of luminescent lanthanide salen complexes (Ln = Lu, Gd, Eu, Yb, salen = N,N′-bis(salicylidene)ethylenediamine-based ligands) with sandwich structures are described. Among them, Lu(III) complexes show unusually strong ligand-centered fluorescence with quantum yields up to 62%, although the metal center is close to a chromophore ligand. The excited-state dynamic studies including ultrafast spectroscopy for Ln-salen complexes revealed that their excited states are solely dependent on the salen ligands and the ISC rates are slow (10 8 −10 9 s −1 ). Importantly, time-dependent density functional theory calculations attribute the low energy transfer efficiency to the weak spin−orbital coupling (SOC) between the singlet and triplet excited states. More importantly, Lu-salen has been applied as a molecular platform to construct fluorescence probes with organelle specificity in living cell imaging, which demonstrates the advantages of the sandwich structures as being capable of preventing intramolecular metal−ligand interactions and behaviors different from those of the previously reported Zn-salens. Most importantly, the preliminary study for in vivo imaging using a mouse model demonstrated the potential application of Ln coordination complexes in therapeutic and diagnostic bioimaging beyond living cells or in vitro.

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Section: Resultsmentioning

confidence: 97%

Strong Fluorescent Lanthanide Salen Complexes: Photophysical Properties, Excited-State Dynamics, and Bioimaging

et al. 2018

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“…This ligand, first reported in 1952, has a highly delocalized electronic structure, akin to porphyrin and terpyridine ligands. Indeed, the electronic and photophysical properties of Pt(II) and Pd(II) BPI complexes with a range of additional ligands have been investigated in great detail. − Goldberg recently reported the oxygen insertion of Pt(II) and Pd(II) methyl complexes with BPI -type ligands to give methylperoxo complexes (see Figure ). Kinetic studies with AIBN as an initiator indicated a radical chain mechanism for the oxygen insertion process.…”

Section: Introductionmentioning

confidence: 99%

Photolytic Activation of Late-Transition-Metal–Carbon Bonds and Their Reactivity toward Oxygen

Lam

Aguirre

et al. 2021

Organometallics

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The photolytic activation of palladium(II) and platinum(II) complexes [M(BPI)(R)] (R = alkyl, aryl) featuring the 1,3-bis(2-pyridylimino)isoindole (BPI) ligand has been investigated in various solvents. In the absence of oxygen, the formation of chloro complexes [M(BPI)Cl] is observed in chlorinated solvents, most likely due to the photolytic degradation of the solvent and formation of HCl. The reactivity of the complexes toward oxygen has been studied both experimentally and computationally. Excitation by UV irradiation (365 nm) of the metal complexes [Pt(BPI)Me] and [Pd(BPI)Me] leads to distortion of the square-planar coordination geometry in the excited triplet state and a change in the electronic structure of the complexes that allows the interaction with oxygen. TD-DFT computational studies suggest that, in the case of palladium, the Pd(III) superoxide intermediate [Pd(BPI)(κ 1 -O 2 )Me] is formed and, in the case of platinum, the Pt(IV) peroxide intermediate [Pt(BPI)(κ 2 -O 2 )Me]. For alkyl complexes where metal−carbon bonds are sufficiently weak, the photoactivation leads to the insertion of oxygen into the metal−carbon bond to generate alkylperoxo complexes: for example [Pd(BPI)OOMe], which has been isolated and structurally characterized. For stronger M−C(aryl) bonds, the reaction of [Pt(BPI)Ph] with O 2 and light results in a Pt(IV) complex, tentatively assigned as the peroxo complex [Pt(BPI)(κ 2 -O 2 )Ph], which in chlorinated solvents reacts further to give [Pt(BPI)Cl 2 Ph], which has been isolated and characterized by scXRD. In addition to the facilitation of oxygen insertion reactions, UV irradiation can also affect the reactivity of other components in the reaction mixture, such as the solvent or other reaction products, which can result in further reactions. Labeling studies using [Pt(BPI)(CD 3 )] in chloroform have shown that photolytic reactions with oxygen involve degradation of the solvent.

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“…Both strategies are understood to impact absorption/emission spectra by influencing the relative energies of the frontier orbitals (HOMO/LUMO), though not always in an obvious manner. For example, despite the prevailing expectation that extending π-conjugation via benzannulation of aromatic molecules or ligands will induce bathochromic (red) shifts in absorption/emission spectra by stabilizing ligand-based π* acceptor orbitals, both red and blue shifts in absorption/emission bands have been recorded for Pt(II) complexes of benzannulated derivatives of 1,3-bis(2-pyridylimino)isoindoline (BPI) ligands (Figure b). − Using a series of benzannulated (BPI)PtCl complexes, Thompson and colleagues detailed a general theoretical framework for understanding and predicting the direction of energy shifts caused by benzannulation. In that paradigm, the site of benzannulation is critical, and the shift in absorption/emission energy can be traced to a selective stabilization or destabilization of the HOMO or the LUMO.…”

Section: Introductionmentioning

confidence: 99%

Luminescent Platinum(II) Complexes of N^N^–^N Amido Ligands with Benzannulated N-Heterocyclic Donor Arms: Quinolines Offer Unexpectedly Deeper Red Phosphorescence than Phenanthridines

et al. 2019

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A platform for investigating the impact of π-extension in benzannulated, anionic pincertype N^N-^N-coordinating amido ligands and their Pt(II) complexes is presented. Based on bis(8-quinolinyl)amine, symmetric and asymmetric proligands bearing quinoline or πextended phenanthridine (3,4-benzoquinoline) units are reported, along with their redemitting, phosphorescent Pt(II) complexes of the form (N^N-^N)PtCl. Comparing the photophysical properties of complexes of (quinolinyl)amido ligands with those of πextended (phenanthridinyl)amido analogs revealed a counter-intuitive impact of siteselective benzannulation. Contrary to conventional assumptions regarding π-extension, and in contrast to isoenergetic lowest energy absorption bands and a red shift in fluorescence from the organic proligands, a blue shift of nearly 40 nm in the emission wavelength is observed for Pt(II) complexes with more extended bis(phenanthridinyl) ligand π-systems. Comparing the ground state and triplet excited state structures optimized from DFT and TD-DFT calculations, we trace this effect to a greater rigidity of the benzannulated complexes, resulting in a higher energy emissive triplet state, rather than to a significant perturbation of orbital energies caused by π-extension.

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Phosphorescent Square‐Planar Platinum(II) Complexes of 1,3‐Bis(2‐pyridylimino)isoindoline with a Monodentate Strong‐Field Ligand

Cited by 8 publications

References 76 publications

Strong Fluorescent Lanthanide Salen Complexes: Photophysical Properties, Excited-State Dynamics, and Bioimaging

Strong Fluorescent Lanthanide Salen Complexes: Photophysical Properties, Excited-State Dynamics, and Bioimaging

Photolytic Activation of Late-Transition-Metal–Carbon Bonds and Their Reactivity toward Oxygen

Luminescent Platinum(II) Complexes of N^N^–^N Amido Ligands with Benzannulated N-Heterocyclic Donor Arms: Quinolines Offer Unexpectedly Deeper Red Phosphorescence than Phenanthridines

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Phosphorescent Square‐Planar Platinum(II) Complexes of 1,3‐Bis(2‐pyridylimino)isoindoline with a Monodentate Strong‐Field Ligand

Cited by 8 publications

References 76 publications

Strong Fluorescent Lanthanide Salen Complexes: Photophysical Properties, Excited-State Dynamics, and Bioimaging

Strong Fluorescent Lanthanide Salen Complexes: Photophysical Properties, Excited-State Dynamics, and Bioimaging

Photolytic Activation of Late-Transition-Metal–Carbon Bonds and Their Reactivity toward Oxygen

Luminescent Platinum(II) Complexes of N^N–^N Amido Ligands with Benzannulated N-Heterocyclic Donor Arms: Quinolines Offer Unexpectedly Deeper Red Phosphorescence than Phenanthridines

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Luminescent Platinum(II) Complexes of N^N^–^N Amido Ligands with Benzannulated N-Heterocyclic Donor Arms: Quinolines Offer Unexpectedly Deeper Red Phosphorescence than Phenanthridines