Cyclometallated platinum(ii) complexes of 1,3-di(2-pyridyl)benzenes: tuning excimer emission from red to near-infrared for NIR-OLEDs
作者:Ester Rossi、Lisa Murphy、Phillipa L. Brothwood、Alessia Colombo、Claudia Dragonetti、Dominique Roberto、Renato Ugo、Massimo Cocchi、J. A. Gareth Williams
DOI:10.1039/c1jm12716k
日期:——
The Pt(II) complex N^C2^N-1,3-di(2-pyridyl)benzene platinum chloride (PtL1Cl) is known to display efficient triplet luminescence in the green region of the spectrum, and to form an unusually emissive excimer that emits around 690 nm. In this contribution, the introduction of trifluoromethyl groups into either the 4- or 5-position of the pyridyl rings of the ligand is shown to lead to a red-shift in the excimer band, moving it into the near infra-red (NIR) region. The new ligands, synthesised by either Suzuki or Stille cross-coupling methods, are 1,3-bis(4-(trifluoromethyl)pyridin-2-yl)benzene HL27, 1,3-bis(4-(trifluoromethyl)pyridin-2-yl)-4,6-difluorobenzene HL28, and 1,3-bis(5-(trifluoromethyl)pyridin-2-yl)-4,6-difluorobenzene HL29, from which the corresponding Pt(II) complexes PtLnCl have been prepared. The monomer and excimer emission energies in solution are compared with those of PtL1Cl and PtL22Cl HL22 = 1,3-di(2-pyridyl)-4,6-difluorobenzene}. The order for the monomer can be rationalised in terms of the stabilising effects of the F atoms and the CF3 groups on the HOMO and LUMO respectively. The order of excimer emission proves to be subtly different, but the most red-shifted complex in both cases is PtL27Cl. The electroluminescence of neat films of the complexes as emitting layers in OLEDs displays uniquely excimer-like emission, extending well into the technologically important NIR region.
已知Pt(II)配合物N^C2^N-1,3-二(2-吡啶基)苯铂氯化物(PtL1Cl)在绿色光谱区域展现出有效的三重态发光,并形成一种异常发光的激基复合物,其发射波长约为690 nm。本文研究表明,向配体的吡啶环的4-或5-位引入三氟甲基基团,会导致激基复合物的发光带红移至近红外(NIR)区域。通过Suzuki或Stille交叉偶联方法合成的新配体是1,3-双(4-(三氟甲基)吡啶-2-基)苯HL27、1,3-双(4-(三氟甲基)吡啶-2-基)-4,6-二氟苯HL28和1,3-双(5-(三氟甲基)吡啶-2-基)-4,6-二氟苯HL29,从中制备了相应的Pt(II)配合物PtLnCl。溶液中单体和激基复合物的发光能量与PtL1Cl和PtL22ClHL22 = 1,3-二(2-吡啶基)-4,6-二氟苯}进行了比较。单体发光的顺序可以从F原子和CF3基团分别对HOMO和LUMO的稳定作用来理解。激基复合物发光的顺序是微妙的,但两种情况下红移最多的都是PtL27Cl。将这些配合物纯薄膜作为OLED的发光层,展现出独特的激基复合物发射,发射光谱良好地延伸到技术上重要的近红外区域。