Introduction of a triphenylamine substituent on pyridyl rings as a springboard for a new appealing brightly luminescent 1,3-di-(2-pyridyl)benzene platinum(ii) complex family

Abstract

The preparation and characterization of three new complexes, namely [Pt(1,3-bis(4-triphenylamine-pyridin-2-yl)-4,6-difluoro-benzene)Cl] ([PtL1Cl]), [Pt(1,3-bis(4-triphenylamine-pyridin-2-yl)-5-triphenylamine-benzene)Cl] ([PtL2Cl]), and [Pt(1,3-bis(4-triphenylamine-pyridin-2-yl)-5-mesityl-benzene)Cl] ([PtL3Cl]), is reported. All of them are highly luminescent in dilute deaerated dichloromethane solution (Φlum...

Introduction of a mesityl substituent on pyridyl rings as a facile strategy for improving the performance of luminescent 1,3-bis-(2-pyridyl)benzene platinum(ii) complexes: a springboard for blue OLEDs

“…Complex [Pt(bis(4-Mes-py)-4,6-dFb)Cl] is highly luminescent in dilute deaerated dichloromethane solution (5 × 10 −6 M), with an absolute luminescence quantum yield ( Φ lum ) of 0.97, superior to that recently reported by our group for the parent [Pt(bis(4-TPA-py)-4,6-dFb)Cl] complex ( Φ lum = 0.90) 50 or for [Pt(bis(4-H-py)-4,6-dFb)Cl] ( Φ lum = 0.85). 49 As expected from the behaviour of similar platinum compounds, 50 the luminescence of the novel complex is efficiently quenched by oxygen, being its quantum yield of 0.18 in air-equilibrated dichloromethane solution. In addition, there is quenching of the luminescence quantum yield upon increasing the complex concentration at 2 × 10 −4 M in deaerated dichloromethane solution ( Φ lum = 0.62).…”

“…However, an underlying excimer emission cannot be ruled out, as previously reported for related platinum( ii ) complexes. 50 In any case, the presence of the band at 680 nm puts evidence that the introduction of the bulky mesityl groups on the pyridine rings does not block completely the formation of excimers/aggregates.…”

“…The absorption spectra of the novel complex display an intense absorption band at 250–330 nm ( ε 263 = 2.3 × 10 4 L mol −1 cm −1 ) attributed to singlet intraligand transitions ( 1 IL) of the cyclometalated N^C^N ligand and a less intense band at 350–420 nm ( ε 376 = 7.8 × 10 3 L mol −1 cm −1 ) assigned to singlet charge-transfer transitions involving the metal and the cyclometalated ligand ( 1 MLCT). 50,56,58 At wavelengths above 420 nm, weak absorption bands with peaks at 438 and 467 nm ( ε 438 = 1.4 × 10 2 M −1 cm −1 , ε 467 = 1.2 × 10 2 M −1 cm −1 ) can be observed (inset Fig. 3(A)).…”

“…Moreover, the λ max of the complex is similar to that of the parent complex without the mesityl substituents [Pt(bis(4-H-py)-4,6-dFb)Cl] ( λ max = 472 nm), 56 longer than that of the complex with NMe 2 groups in position 4 on the pyridines ( [Pt(bis(4-NMe 2 -py)-4,6-dFb)Cl] , λ max = 453 nm) 59 as expected since the introduction of electron-donor groups on the pyridines leads to a blue shift of the emission, 59,60 but much shorter than that of the complex with triphenylamino groups ( [Pt(bis(4-TPA-py)-4,6-dFb)Cl] , λ max = 562 nm). 50 Therefore, the introduction of the very bulky mesityl groups on the pyridine rings of the cyclometalated ligand does not affect the emission color of the platinum complex, in sharp contrast with the introduction of triphenylamine substituents. When the concentration of the monomer is increased up to 1 × 10 −3 M, a new broad structureless band centered at 680 nm is detected (Fig.…”

“…67 Similarly, we recently reported that the luminescence quantum yield of the parent [Pt(bis(4-TPA-py)-4,6-dFb)Cl] complex decreases on going from CH 2 Cl 2 solution ( Φ lum = 0.90) to the polymethylmetacrylate (PMMA) film ( Φ lum = 0.56) and drops drastically as the neat film ( Φ lum = 0.05); although a significant quantum yield was obtained in the PMMA film, the higher presence of excimers and aggregates in the neat film caused strong quenching of the quantum yield. 50 We were curious to see the effect of the substitution of the triphenylamine substituents by the mesityl groups on the luminescence properties in the solid state. Therefore, we prepared a thin film in PMMA (1 wt%) and a neat film of the [Pt(bis(4-Mes-py)-4,6-dFb)Cl] complex, characterized by high solubility in dichloromethane (see the preparation and characterization of the films in the ESI†).…”