Sensitized Near-Infrared Emission from IrIII-LnIII (Ln = Nd, Yb, Er) Bimetallic Complexes with a (N∧O)(N∧O) Bridging Ligand

Organometallic Ir(III) complexes: post-synthetic modification, photophysical properties and binuclear complex construction

Two methods of post-synthetic modification (Suzuki coupling and CuAAC click-reaction) were applied to Ir(III) complexes [Ir(C^{^}N)₂N^{^}N]⁺ to provide the second highly selective donor site. One family of functionalized complexes was used to demonstrate the potential of post-synthetic modification for controlled construction of d-d and d-f binuclear complexes. The complexes obtained were characterized by CHN elemental analysis, NMR spectroscopy, ESI mass-spectrometry, FTIR spectroscopy and single crystal X-ray diffraction analysis. By means of XPS and NEXAFS spectroscopy the coordination of diimine donor site to the Ln(III) centre has been definitely confirmed. The photophysical properties of mono- and binuclear complexes were carefully investigated, and the evolution of luminescent characteristics during the formation of a system of connected metallocenters is also discussed. TDDFT calculations were used to describe the luminescence mechanism and to confirm the conclusions made on the basis of experimental data.

A Multimodal Ratiometric Luminescent Thermometer Based on a Single-Dysprosium Metal-Organic Framework

The design of high-performance luminescent MOF thermometers with multi-operation modes has been long sought but remains a formidable challenge. In this work, for the first time, we present a multimodal luminescent ratiometric thermometer based on the single-lanthanide metal-organic framework (MOF) DyTPTC-2Me (H₄TPTC-2Me = 2',5'-dimethyl-[1,1':4',1″-terphenyl]-3,3″,5,5″-tetracarboxylic acid). It not only has the characteristic luminescence of Dy³⁺ in which the atomic transitions from the ⁴I_15/2 and ⁴F_9/2 states (thermally coupled energy levels, TCELs) are included but also emits ligand fluorescence due to the efficient energy back-transfer of Dy³⁺ to the ligand, thus allowing accurate non-invasive determination of temperature by different modes. In particular, the TCEL-based emissions of the Dy³⁺ ions give ideal signals for measuring the temperature in the 303-423 K range. The emissions of the ligand and Dy³⁺ (⁴F_9/2 → ⁶H_13/2) are used for temperature sensing in the range of 423 to 503 K. Both two modes feature promising thermometric performance, including high relative sensitivity, high temperature resolution, and excellent repeatability. Their combination is thus beneficial to achieve more accurate temperature detection over a broad temperature range, which can broaden the application scope of the ratiometric luminescent thermometers.

Luminescent Ir(iii)–Ln(iii) coordination polymers showing slow magnetization relaxation

Two structural types of iridium(iii)–lanthanide(iii) coordination polymers, single-chain Ir2Ln and double-chain Ir4Ln2 (Ln = Gd, Dy, Er, and Yb), have been prepared. SMM behaviour and NIR luminescence were observed for the Ir–Er and Ir–Yb systems.

Sensitization of NIR luminescence of Yb3+ by Zn2+ chromophores in heterometallic complexes with a bridging Schiff-base ligand

Herein, complexes [ZnL]₂ (1), {(H₂O)Zn(μ-L)Yb[OCH(CF₃)₂]₃} (2), {[(CF₃)₂HCO]Zn(μ-L)Yb[OCH(CF₃)₂](μ-OH)}₂ (3), and [(H₂O)Ln₂(L)₃] (Ln = Yb (4) and Gd (5)) containing a bridging Schiff-base ligand (H₂L = N,N'-bis(3-methoxy salicylidene)phenylene-1,2-diamine) were synthesized. The compounds 1-4 were structurally characterized. The ytterbium derivatives 2-4 exhibited bright NIR metal-centred photoluminescence (PL) of Yb³⁺ ion under one- (λ_ex = 380 nm) and two-photon (λ_ex = 750 nm) excitation. The superior luminescence properties of complex 2, which was suggested as a marker for NIR bioimaging, were explained via the strong absorption of the 375 nm LMCT state of the ZnL chromophore, efficient energy transfer from ZnL towards Yb³⁺ through a reversible ligand-to-lanthanide electron transfer process, and absence of luminescence quenchers (C-H and O-H groups) in the first coordination sphere of the rare-earth atom.

A highly sensitive near-infrared luminescent metal-organic framework thermometer in the physiological range

A near-infrared luminescent metal-organic framework Nd0.866Yb0.134BTB was developed as a self-calibrated thermometer in the physiological range. Its features include high sensitivity and resolution, and good biocompatibility, making such a material useful for biomedical applications.

Heteronuclear Ir(III)-Ln(III) Luminescent Complexes: Small-Molecule Probes for Dual Modal Imaging and Oxygen Sensing

Luminescent, mixed metal d-f complexes have the potential to be used for dual (magnetic resonance imaging (MRI) and luminescence) in vivo imaging. Here, we present dinuclear and trinuclear d-f complexes, comprising a rigid framework linking a luminescent Ir center to one (Ir·Ln) or two (Ir·Ln2) lanthanide metal centers (where Ln = Eu(III) and Gd(III), respectively). A range of physical, spectroscopic, and imaging-based properties including relaxivity arising from the Gd(III) units and the occurrence of Ir(III) → Eu(III) photoinduced energy-transfer are presented. The rigidity imposed by the ligand facilitates high relaxivities for the Gd(III) complexes, while the luminescence from the Ir(III) and Eu(III) centers provide luminescence imaging capabilities. Dinuclear (Ir·Ln) complexes performed best in cellular studies, exhibiting good solubility in aqueous solutions, low toxicity after 4 and 18 h, respectively, and punctate lysosomal staining. We also demonstrate the first example of oxygen sensing in fixed cells using the dyad Ir·Gd, via two-photon phosphorescence lifetime imaging (PLIM).

Observation of cascade f → d → f energy transfer in sensitizing near-infrared (NIR) lanthanide complexes containing the Ru(ii) polypyridine metalloligand

A possible approach to achieve multiple f → d, d → f and cascade f → d → f energy transfer processes in heteronuclear Ru–Ln and Ln1–Ru–Ln2 complexes.