Room-temperature luminescence from Pd(<scp>ii</scp>) and Pt(<scp>ii</scp>) complexes: from mechanochromic crystals to flexible polymer matrices

Suburu, Matias Ezequiel Gutierrez; Maisuls, Iván; Kösters, Jutta; Strassert, Cristian A.

doi:10.1039/d2dt01693a

Cited by 6 publications

(16 citation statements)

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“…However, in this case, the photophysical properties were not improved by aggregation in the same way as in the previous article. Complexes 81 and 82 were further studied later [ 90 ], both showing very poor emission in fluid solutions due to dissociative MC states thermally accessible at room temperature. At 77 K, in a frozen 1:1 DCM/MeOH glassy matrix, 79 – 82 show a blue-shift in the emission spectra when compared to data gathered at 298 K, as well as unitary Φ L values and a drastic increase in their lifetimes.…”

Section: Orthopalladated Ligandsmentioning

confidence: 99%

Luminescence and Palladium: The Odd Couple

Dalmau

Urriolabeitia

2023

Molecules

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The synthesis, photophysical properties, and applications of highly fluorescent and phosphorescent palladium complexes are reviewed, covering the period 2018–2022. Despite the fact that the Pd atom appears closely related with an efficient quenching of the fluorescence of different molecules, different synthetic strategies have been recently optimized to achieve the preservation and even the amplification of the luminescent properties of several fluorophores after Pd incorporation. Beyond classical methodologies such as orthopalladation or the use of highly emissive ligands as porphyrins and related systems (for instance, biladiene), new concepts such as AIE (Aggregation Induced Emission) in metallacages or in coordination-driven supramolecular compounds (CDS) by restriction of intramolecular motions (RIM), or complexes showing TADF (Thermally Activated Delayed Fluorescence), are here described and analysed. Without pretending to be comprehensive, selected examples of applications in areas such as the fabrication of lighting devices, biological markers, photodynamic therapy, or oxygen sensing are also here reported.

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Section: Orthopalladated Ligandsmentioning

confidence: 99%

Luminescence and Palladium: The Odd Couple

Dalmau

Urriolabeitia

2023

Molecules

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“…The 3-n compounds were obtained as main products by working with 1.2 equivalents of the boronic acid. Based on our previous work, we took advantage of the free phenol moiety to provide diverse alkyl chain lengths employing a straightforward Williamson's ether synthesis, thus yielding compounds 4-n. [21] Finally, a second Suzuki-Miyaura cross-coupling reaction between 4-n and the selected boronic acid provided the intended asymmetric ligands L Fpy -n and L Ph -n (n = 6, 12, and 18). The Pt(II) complexes PtL Fpy -n and PtL Ph -n (n = 6, 12, and 18) were synthesized by well-established cycloplatination conditions employing the corresponding ligand and K 2 PtCl 4 in glacial acetic acid at 130 • C. Detailed experimental procedures, as well as the exact mass (EM) spectrometry data and 2D-NMR spectra including the unambiguous signal assignment for all ligand precursors and their complexes, can be found in the Supporting Information (Figures S1-S114).…”

Section: Synthesis Of the Complexesmentioning

confidence: 99%

“…[28][29][30] All the compounds have significantly higher Φ L at r.t. than previous Pt(II) complexes with tetradentate luminophores reported by our group (Figures S117-S134). [13,21,24] This outcome probably stems from the replacement of the orthogonal-to-plane phenyl ring on the bridging N-atom by a slim alkyl moiety; hence, it reduces the non-radiative deactivation of the excited state via molecular distortion caused by repulsion between the Hatoms of the phenyl group at the bridge and at the pyridine rings of the luminophore. [24] At 77 K, all the complexes have unitary Φ L within the experimental uncertainty, which can be ascribed to the inaccessible thermal population of dissociative metal-centered states (MC, which would provide radiationless deactivation channels by conical intersections with the ground state).…”

Section: Photophysical Characterizationmentioning

confidence: 99%

“…Based on our previous work, we took advantage of the free phenol moiety to provide diverse alkyl chain lengths employing a straightforward Williamson's ether synthesis, thus yielding compounds 4‐n . [ 21 ] Finally, a second Suzuki‐Miyaura cross‐coupling reaction between 4‐n and the selected boronic acid provided the intended asymmetric ligands L Fpy ‐n and L Ph ‐n ( n = 6 , 12 , and 18 ). The Pt(II) complexes PtL Fpy ‐n and PtL Ph ‐n ( n = 6 , 12 , and 18 ) were synthesized by well‐established cycloplatination conditions employing the corresponding ligand and K 2 PtCl 4 in glacial acetic acid at 130°C.…”

Section: Introductionmentioning

confidence: 99%

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On the thermodynamics of aggregation toward phosphorescent metallomesogens: From electronic tuning to supramolecular design

Gutierrez Suburu,

Blanke,

Geerkens

et al. 2024

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Two series with three Pt(II) complexes each (PtLPh‐n, PtLFpy‐n) bearing asymmetric tetradentate ligands as dianionic luminophores with variable alkyl chain lengths were synthesized. Hence, each ligand series is distinguished by one of its cyclometallating rings (phenyl vs. 2,6‐difluoropyrid‐3‐yl). Steady‐state and time‐resolved photoluminescence spectroscopic studies in diluted solutions at room temperature and in glassy matrices at 77 K show that the emissive state is mainly centered on the invariantly electron‐rich cyclometalated side while the second ring regulates the admixture of ligand‐centered and metal‐to‐ligand charge‐transfer character. Hence, the radiative rates can be controlled, as indicated by quantum‐mechanical calculations, which also explain the temperature‐dependent trend in the phosphorescence rate constants. Studies in condensed phases (single‐crystal X‐ray diffractometry, polarized optical microscopy, differential scanning calorimetry, steady‐state and time‐resolved photoluminescence micro(spectro)scopy) showed the development of a smectic A mesophase for the fluorinated species bearing the two longest alkyl chains. Nuclear magnetic resonance‐based studies on the thermodynamics of aggregation in solution confirm the marked enthalpic stabilization of aggregates mediated by the polar 2,6‐difluoropyrid‐3‐yl moiety (and to a lesser extent by dispersive forces between the alkyl chains). On the other hand, the negative entropy of aggregation is dominated by the restriction of degrees of freedom involving the peripheral alkyl moieties upon stacking, which becomes increasingly relevant for longer chains. All these factors control Pt···Pt coupling, a crucial interaction for the design of photofunctional mesogens based on Pt(II) complexes.

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“…Noteworthily, very few examples of Pd II complexes that showed RT aggregation-induced phosphorescent emission have been reported so far (Figures B and S18). ,,− Strassert et al described Pd II complexes featuring tetradentate ligands, while Lu et al reported pincer Pd II allenylidene derivatives . Although the aforementioned reports support the role of self-assembly as an enabler of phosphorescence, the extent to which solid-state phosphorescence can be generated rationally upon chemical structure analysis is compulsive for further investigation.…”

mentioning

confidence: 99%

Phosphorescent Cyclometalated Palladium(II) and Platinum(II) Complexes Derived from Diaminocarbene Precursors

Kashina,

Luzyanin,

Dar’in

et al. 2024

Inorg. Chem.

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Metal-mediated self-assembly of isocyanides and methyl 4-aminopyrimidine-5-carboxylate leads to luminescent Pd II and Pt II complexes featuring C,N-cyclometalated acyclic diaminocarbene (ADC) ligands. The solid-state luminescent properties of these diaminocarbene derivatives are attributed to their triplet-state metal/metal-to-ligand charge-transfer ( 3 MMLCT) nature, which is driven by attractive intermolecular M•••M interactions further reinforced by the intramolecular π−π interactions even in the structure of the Pd compound, which is the first Pd-ADC phosphor reported. C,N-cyclometalated diaminocarbene-based ligands provides access to unique luminescent Pd II derivatives. The emergence of intermolecular interactions is recognized as a driving force toward the phosphorescence of diaminocarbene complexes described in this work, and our future efforts will be dedicated to a better understanding of the relationship between the molecular construction and luminescence properties of metal aminocarbene species. ■ ASSOCIATED CONTENT * sı Supporting InformationThe Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acs.inorgchem.3c03346.Experimental section, spectral, XRD, and experimental data, structural features discussion, and theoretical calculations (PDF)Accession Codes

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Room-temperature luminescence from Pd(ii) and Pt(ii) complexes: from mechanochromic crystals to flexible polymer matrices

Abstract: A series of Pd(ii) and Pt(ii) complexes bearing tetradentate ligands as dianionic luminophores were synthesized and their room-temperature photoluminescence in PMMA films as well as in mechanochromic crystalline phases was correlated with molecular structure.

Cited by 6 publications

References 67 publications

Luminescence and Palladium: The Odd Couple

Luminescence and Palladium: The Odd Couple

On the thermodynamics of aggregation toward phosphorescent metallomesogens: From electronic tuning to supramolecular design

Phosphorescent Cyclometalated Palladium(II) and Platinum(II) Complexes Derived from Diaminocarbene Precursors

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