From Ligand to Phosphor: Rapid, Machine‐Assisted Synthesis of Substituted Iridium(III) Pyrazolate Complexes with Tuneable Luminescence

Abstract

A first-generation machine-assisted approach towards the preparation of hybrid ligand/metal materials has been developed. A comparison of synthetic approaches demonstrates that incorporation of both flow chemistry and microwave heating can be successfully applied to the rapid synthesis of a range of new phenyl-1H-pyrazoles (ppz) substituted with electron-withdrawing groups (-F, -CF , -OCF , and -SF ). These, in turn, can be translated into heteroleptic complexes, [Ir(ppz) (bipy)]BF (bipy=2,2'-bipyridine). Microwave-assisted synthesis for the Ir complexes allows isolation of spectroscopically pure species in less than 1 h of reaction time starting from IrCl . All of the new complexes have been characterised photophysically (including nanosecond time-resolved transient absorption spectroscopy), electrochemically, and by TD-DFT studies. The complexes exhibit ligand-dependent, tuneable, green-yellow luminescence (500-560 nm), with quantum yields in the range 5-15 %.

Ligand‐Tuneable, Red‐Emitting Iridium(III) Complexes for Efficient Triplet–Triplet Annihilation Upconversion Performance

“…Each feature, including the ground‐state bleaching and recovery, and the phosphorescence, exhibit similar TA lifetimes (Figure , right), which suggests that each peak relates to the same photoexcitation, ISC process and deactivation. This is attributed to the formation of the lowest triplet state, through prompt S 1 /T 1 ISC, and compares relatively well with the observed lifetime from time‐resolved emission measurements . Figure displays a comparison of TA spectra for the complexes [Ir(L1) 2 (bpy)]PF 6 , [Ir(L5) 2 (bpy)]PF 6 and [Ir(L6) 2 (bpy)]PF 6 .…”

Comparison of the Thermal Stabilities of Diazonium Salts and Their Corresponding Triazenes

“…Diazonium salt 1a , derived from anthranilic acid, was not prepared because it is known to be a contact explosive. − The triazene compound series was prepared using a telescoped continuous flow process optimized to generate and consume the diazonium salt in situ while avoiding precipitation of the intermediate diazonium salt (see Figure ). − …”

“…[29][30][31][32][33][34][35] The triazene compound series was prepared using a telescoped continuous flow process optimized to generate and consume the diazonium salt in situ while avoiding precipitation of the intermediate diazonium salt (Figure 3). [36][37][38] The degradation temperature of each compound has been assessed using Differential Scanning Calorimetry (DSC). DSC is a thermo-analytical technique in which a sample and a reference (typically an empty sample holder) are heated or cooled at constant rate.…”

Theoretical insight on electronic structure and photophysical properties of a series of cyclometalated iridium(III) complexes bearing the substituted phenylpyrazole with different electron-donating or electron-accepting groups

“…L.M. Groves et al have studied a series of Ir(III) complexes based on phenylpyrazole (ppz) derivatives with electron-withdrawing groups (-F, -CF 3 , -OCF 3 , and -SF 5 ), which revealed a broad, featureless emission peak that ranged between 510 and 560 nm [20]. Z.G.…”