A novel dinuclear platinum(II) complex featuring a ditopic, bis-tetradentate ligand has been prepared. The ligand offers each metal ion a planar O^N^C^N coordination environment, with the two metal ions bound...

In this work we present synthesis and an in-depth photophysical analysis of a di-Pt(II) complex with a ditopic bis-N^C^N ligand. The complex exhibits a dual luminescent behaviour by emitting simultaneously...

The spin-forbidden nature of phosphorescence in Ir­(III) complexes is relaxed by the metal-induced effect of spin–orbit coupling (SOC). A further increase of the phosphorescence rate could potentially be achieved by introducing additional centers capable of further enhancing the SOC effect, such as metal-coordinated halides. Herein, we present a dinuclear Ir­(III) complex Ir 2 I 2 that contains two Ir­(III)-iodide moieties. The complex shows intense phosphorescence with a quantum yield of ΦPL(300 K) = 90% and a submicrosecond decay time of only τ­(300 K) = 0.34 μs, as measured under ambient temperature for the degassed toluene solution. These values correspond to a top value T1 → S0 phosphorescence rate of k r = 2.65 × 106 s–1. Investigations at cryogenic temperatures allowed us to determine the zero-field splitting (ZFS) of the emitting state T1 ZFS­(III–I) = 170 cm–1 and unusually short individual decay times of T1 substates: τ­(I) = 6.4 μs, τ­(II) = 7.6 μs, and τ­(III) = 0.05 μs. This indicates a strong SOC of state T1 with singlet states. Theoretical investigations suggest that the SOC of state T1 with singlets is also contributed by halides. Strongly contributing to the higher occupied molecular orbitals of the complex (e.g., HOMO, HOMO – 1, and so forth), iodides work as important SOC centers that operate in tandem with metals. The examples of Ir 2 I 2 and of earlier reported analogous complex Ir 2 Cl 2 reveal that the metal-coordinated halides can enhance the SOC of state T1 with singlets and, consequently, the phosphorescence rate. A comparative study of Ir 2 I 2 and Ir 2 Cl 2 shows that the share of halides in total contribution (halides plus metals) to the SOC of state T1 with singlets increases strongly upon exchange of chlorides for iodides. The exchange also led to the decrease in values of ZFS of the T1 state from ZFS­(III–I) = 205 cm–1 for Ir 2 Cl 2 to T1 ZFS­(III–I) = 170 cm–1 for Ir 2 I 2 . This results in a more efficient thermal population of the fastest emitting T1 substate III, thus further enhancing the room-temperature phosphorescence rate.

A complex in which two Pt(ii) ions are cyclometallated to bis-dithienylpyrimidine displays intense luminescence in the NIR region, both in solution and in an OLED.

Novel 7-N-(beta-alanyl)aminophenoxazin-3-one salts 27a-d have been synthesized and tested as chromogenic substrates for beta-alanyl aminopeptidase, which is present in Pseudomonas aeruginosa, the most common respiratory pathogen in patients with cystic fibrosis. The biological results show that 7-N-(beta-alanyl)amino-1-pentylphenoxazin-3-one trifluoroacetate salt 27a is a chromogenic substrate for this bacterium, with a low degree of diffusion in nutrient media for growing bacterial cultures and a bright red colour, making it easily distinguishable from the agar background.

A dinuclear iridium­(III) complex IrIr shows dual emission consisting of near infrared (NIR) phosphorescence (λmax = 714 nm, CH2Cl2, T = 300 K) and green fluorescence (λmax = 537 nm). The NIR emission stems from a triplet state (T1) localized on the ditopic bridging ligand (3LC). Because of the dinuclear molecular structure, the phosphorescence efficiency (ΦPL = 3.5%) is high compared to those of other known red/NIR-emitting iridium complexes. The weak fluorescence stems from the lowest excited singlet state (S1) of 1LC character. The occurrence of fluorescence is ascribed to relatively slow intersystem crossing (ISC) from state S1 (1LC) to the triplet manifold. The measured ISC rate corresponds to a time constant τISC of 2.1 ps, which is an order of magnitude longer than those usually found for iridium complexes. This slow ISC rate can be explained in terms of the LC character and large energy separation (0.57 eV) of the respective singlet and triplet excited states. IrIr is internalized by live HeLa cells as evidenced by confocal luminescence microscopy.

Herein, we report a profound investigation of the photophysical properties of three mononuclear Ir(III) complexes fac-Ir(dppm) 3 phenyl)pyrimidine), Ir(dppm) 2 (acac) (acacacetylacetonate), and Ir(ppy) 2 (acac) (Hppy-phenylpyridine). The heteroleptic Ir(dppm) 2 (acac) is found to emit with efficiency above 80% and feature a remarkably high rate of emission. As measured under ambient temperature, Ir(dppm) 2 (acac) emits with the unusually short (sub-μs) radiative decay time of τ r = τ em /Φ PL = 1/k r = 0.91 μs in degassed toluene and τ r = 0.73 μs in a doped polystyrene film under nitrogen. Investigations at cryogenic temperatures in glassy toluene showed that the emission stems from the T 1 state and thus represents T 1 → S 0 phosphorescence with individual decay times of the T 1 substates of T 1,I = 66 μs, T 1,II = 7.3 μs, T 1,III = 0.19 μs, and energy gaps between the substates of ΔE(T 1,II −T 1,I ) = 14 cm −1 and ΔE(T 1,III −T 1,I ) = 210 cm −1 . Analysis of the electronic structure of Ir(dppm) 2 (acac) showed that such a high rate of phosphorescence may stem from the two dppm ligands, with extended π-conjugation system and π-deficient character due to the pyrimidine ring, being serially aligned along one axis. Such alignment, along with the quasi-symmetric character of Jahn− Teller distortions in the T 1 state, affords a large chromophore, comprising four (het)aryl rings of the two dppm ligands. This affords an exceptionally large oscillator strength of the MLCT-character singlet state spin-orbit coupled with the T 1 state and thus brings about enhancement of the phosphorescence rate. These findings reveal molecular design principles paving the way to new phosphors of enhanced emission rates.

We present an in-depth investigation of the influence of chloro-to-iodo exchange on the thermally activated delayed fluorescence (TADF) of a dinuclear platinum(II) complex featuring monodentate halide ancillary ligands. The complexes...