Three NIR-emitting neutral Ir(III) complexes [Ir(iqbt)2 (dpm)] (1), [Ir(iqbt)2 (tta)] (2), and [Ir(iqbt)2 (dtdk)] (3) based on the 1-(benzo[b]thiophen-2-yl)-isoquinolinate (iqtb) were synthesized and characterized (dpm=2,2,6,6-tetramethyl-3,5-heptanedionate; tta=2-thienoyltrifluoroacetonate; dtdk=1,3-di(thiophen-2-yl)propane-1,3-dionate). The compounds emit between λ=680 and 850 nm with high luminescence quantum yields (up to 16 %). By combining electrochemistry, photophysical measurements, and computational modelling, the relationship between the structure, energy levels, and properties were investigated. NIR-emitting, solution-processed phosphorescent organic light-emitting devices (PHOLEDs) were fabricated using the complexes. The devices show remarkable external quantum efficiencies (above 3 % with 1) with negligible efficiency roll-off values, exceeding the highest reported values for solution-processible NIR emitters.

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Immunoassay is probably the primary in vitro technique employed in medical diagnostics. Its different setups include often the well-known and sensitive analytical method based on electrochemiluminescence (ECL), and approaches relying on nanotechnology have the potentiality to further enhance ECL signal response and detection capability. With this intent, we studied the ECL behavior of dye-doped silica–poly­(ethylene glycol) core–shell nanoparticles (DDSNPs) doped with neutral Ru­(II) complexes in a very large doping range. We found that nanoparticles maintain comparable morphology and dimensions as the amount of Ru­(II) neutral complexes that are covalently linked to their silica matrix increases; meanwhile, ECL shows an enhanced response. The 9-fold ECL signal amplification obtained when compared with [Ru­(bpy)3]2+-doped silica nanoparticles is due to the synergy between the behavior of neutral Ru­(II) complex and the DDSNP architecture: these results pave the way for the development of more efficient probes in ECL technology.

Iridium complexes bearing cyclometalated (C^N) ligands are the current emitters of choice for efficient phosphorescent organic light emitting diodes (OLEDs). Homoleptic iridium complexes Ir(C^N) and the analogous heteroleptic ones carrying a β-diketonate ancillary ligand (C^N)Ir(O^O) often exhibit similar photophysical properties and device performances; the choice among them usually depends both on the yield/ease of the respective synthetic preparations as well as on the device fabrication methods (i.e. vacuum-deposition or solution-process). In our recent study we found a significant spectral red shift on going from the homoleptic to the β-diketonate Ir(iii) derivatives. The NIR emitting complex Ir(iqbt)dpm (λ = 710 nm) has almost 20 nm red shifted emission compared to the homologue Ir(iqbt) making only the former a real NIR emitter. For comparison, we studied the Pt(iqbt)dpm complex as the suitable example to investigate metal ligand interactions. Noteworthily the Pt(iqbt)dpm emission perfectly overlaps that of the Ir(iqbt)dpm. In this paper we provide an in-depth investigation of these systems by electrochemical and spectroscopic analyses and corroborate the results with DFT and TDDFT calculations to investigate whether the Pt(ii) complex can be used as a model system to predict how far the emission can be pushed in a Ir(iii) heteroleptic derivative bearing the same C^N ligand.