Energy‐Transfer Mechanisms in Ir^III–Eu^III Bimetallic Complexes

Abstract

The bridging ligands in d–f bimetallic complexes play an important role in the excitation energy transfer (EET) process. To elaborate on the effect of the ligand on the EET process, a series of bridging ligands (μ‐L), 1‐(1′,10′‐phenanthrolin‐2′‐yl)‐4,4,4‐trifluorobutane‐1,3‐dione (phen3f), 1‐(1′,10′‐phenanthrolin‐2′‐yl)‐4,4,5,5,5‐pentafluoropentane‐1,3‐dione (phen5f), 1‐(2,2′‐bipyridine‐6‐yl)‐4,4,4‐trifluorobutane‐1,3‐dione (bpy3f), and 1‐(2,2′‐bipyridine‐6‐yl)‐4,4,5,5,5‐pentafluoropentane‐1,3‐dione (bpy5f), and their corresponding iridium complexes, [(dfppy)2Ir(μ‐L)] (dfppy=2‐(4′,6′‐difluorophenyl)pyridinato‐N,C2′), as well as their corresponding heteroleptic IrIII–EuIII complexes [{(dfppy)2Ir(μ‐L)}3EuCl]Cl2 were synthesized and characterized. Photophysical and kinetic results revealed that the alternation of the bridge ligand resulted in a systemic difference in the lowest triplet‐state energy (T1) of the iridium complexes, the EET efficiency from iridium complexes to the EuIII ion, and a significant difference in the total luminescence quantum yields. Based on the nanosecond time‐resolved phosphorescence spectra, a model for the energy‐transfer mechanism was proposed for d–f bimetallic complexes, which indicated that the nonradiative relaxation of the excited energy of EuIII, especially energy dissipation by means of the T1 state, was the main reason for the discrepancy in the quantum yields of the four IrIII–EuIII complexes.

A Family of Highly Emissive Lanthanide Complexes Constructed with 6-(Diphenylphosphoryl)picolinate

“…For Eu­(DPPOP) 3 , the five distinct peaks at 580, 592, 615, 650, and 692 nm correspond to the transitions of 5 D 0 to 7 F J ( J = 0–4), with the electric-dipole transition band at 615 nm being the strongest. In the range of 500–570 nm, three weak emissions at 526, 537, and 558 nm can also be observed (Figure S19), which originate from the transitions of 5 D 1 to 7 F J ( J = 0–2) . The emission spectrum of the Tb­(III) complex shows characteristic peaks at 489, 544, 582, 620, 647, 668, and 678 nm, which are assigned to the transitions of 5 D 4 to 7 F J ( J = 6–0), with the emission at 544 nm being the strongest.…”

Heterobimetallic iridiumIII–europiumIII complex: the role of donor energy on sensitising the EuIII ion

“…In this context, systems based on Ir III complexes coordinated to Eu III ions are the most investigated aiming for synergic results for a good luminophore. [18][19][20] In an Ir III -Eu III heterobimetallic complex, the Ir III complex itself acts as a sensitising ligand, and the fundamental idea is that the triplet excited overpopulated state, resulting from the high spin-orbit coupling (SOC) of the Ir III ion (x = 4430 cm À1 ), 21 transfers its energy to Eu III ion. 22 As in monocentered Eu IIIcomplexes, in heterobimetallic Ir III -Eu III complexes, the sensitisation efficiency depends on the energy difference between D and A; however, for d-f systems, this energy gap still needs to be further studied.…”

“…In this context, systems based on Ir III complexes coordinated to Eu III ions are the most investigated aiming for synergic results for a good luminophore. 18–20…”

Photoluminescence and energy transfer mechanism of Ir<sup>Ⅲ</sup>-Ln<sup>Ⅲ</sup> heteronuclear complexes

“…Ward 课题组 [20] 一直致力于 d-f 双金属体系的结 构与传能关系研究. 2010 年他们报道了一种通过 2,2′-联吡啶衍生物 10a (图 7)作为桥连配体的 Ir III -Eu III 及 Ir III -Nd III /Yb III 双金属体系, 同时采用具有非共轭桥连 配体的 10b (图 7)作为对比, 结果发现, 10b 虽然能降 低金属间的距离, 但由于共轭体系被破坏, 而无法实 图 5 8d 在乙醇(1 × 10 4 mol/L)中的时间分辨光谱(a)和三重态能级传能示意图(b) [18] 图 6 化合物 9a 和 9b 的分子结构 [19] 现双金属之间的有效传能. 这一工作从结构上提出 了传能的条件.…”

“…图 4 化合物 7a~d 及 8d 的分子结构[18] http://engine.scichina.com/doi/10.1360/N032013-00044 中国科学: 化学 2014 年 第 44 卷 第 2 期…”