An Iridium(III) Complex that Exhibits Dual Mechanism Nonlinear Absorption

Abstract

The photophysical properties of the complex (L)Ir(ppy)(2)(+), where ppy = 2-phenylpyridine and L = 4,4'-(2,2'-bipyridine-5,5'-diylbis(ethyne-2,1-diyl))bis(N,N-dihexylaniline), have been investigated under one- and two-photon excitation conditions. In THF solution, the complex exhibits broad ground-state absorption with lambda(max) approximately 500 nm and weak photoluminescence with lambda(max) approximately 730 nm. Excitation of (L)Ir(ppy)(2)(+) at 355 nm produces a long-lived excited state (tau approximately 1 mus) that features a strong excited-state absorption in the near-infrared (lambda(max) approximately 875 nm, Deltaepsilon approximately 6.1 x 10(4) M(-1) cm(-1)). Photoluminescence and transient absorption studies of (L)Ir(ppy)(2)(+) carried out using 5 ns, 1064 nm pulsed excitation demonstrate that the same long-lived and strongly absorbing excited state can be efficiently produced by two-photon absorption. Solutions of the complex in THF display nonlinear absorption of 5 ns, 1064 nm pulses in a process that is believed to involve a combination of two-photon absorption and reverse saturable absorption.

Photophysical Properties of Oligo­(phenylene ethynylene) Iridium(III) Complexes Functionalized with Metal‐Anchoring Groups

“…As for related ligands, we assign the lower-and higher-energy bands to long-and short-axis polarized π→π* transitions, respectively. [37,38,51] The absorption bands of Ir1-Ir4 are broader than those of the bare ligands 1-4 ( Figure 2 ) in the λ = 350-450 nm range. On the basis of previous reports, [28][29][30][31]33,37] we assign the first band to π→π* transitions centred on the ppy and phen ligands.…”

“…[37,38] However, the interplay between the conjugation and different anchoring groups in Ir1-Ir4 makes it difficult to anticipate the nature of the emitting excited state and, thus, their behaviour at illuminated molecular junctions. For the first time, this work brings together electro-and spectrochemical techniques along with theoretical calculations in the study of iridium(III) bis-cyclometallated 2-phenylpyridine complexes with phenylethynyl-substituted diimine ligands.…”

“…6 × 10 8 M -1 s -1 (see Figure 5, b and d) and by low-energy triplet acceptors such as -carotene; as for related Ir III complexes, they are assigned to 3 MLCT excited states. [37,38,55] Additionally, the decay traces of Ir1-Ir4 at λ = 510 nm can be accurately fitted with a first-order exponential function. The lifetimes range from 0.24 to 0.54 μs and are very close to the photoluminescence decay components detected by emission spectroscopy (Table 2).…”

Influence of a Naphthaldiimide Substituent at the Diimine Ligand on the Photophysics and Reverse Saturable Absorption of PtII Diimine Complexes and Cationic IrIII Complexes

“…[32,34] The groups of both Bryce and Schanze reported that incorporation of π-conjugated substituents, such as fluorenyl and 4-ethynyl-N,N-dihexylaniline substituents on the N ∧ N ligand led to a mixture of 3 MLCT (metal-to-ligand charge transfer) and 3 π,π* characters in the lowest triplet excited state (T 1 state) and thus increased the T 1 lifetimes. [17,35] Our group also demonstrated that introducing the benzothiazolylfluorenyl (BTF) substituents to the N ∧ N ligand dramatically increased the T 1 state lifetimes for both Pt II diimine acetylide complexes [23] and heteroleptic Ir III complexes. [18,19,27] However, incorporation of the BTF motif into the C ∧ N ligands in the Ir III complex resulted in a reduced T 1 lifetime.…”

Strong triplet excited-state absorption in a phenanthrolinyl iridium(III) complex with benzothiazolylfluorenyl-substituted ligands

“…Excited-state absorption in platinum(II) complexes has been much studied in recent years, notably in platinum(II) diimines [9][10][11][12][13][14] and terpyridines [14][15][16]. In contrast to the recent interest in platinum complexes, nonlinear absorption in iridium complexes has received comparatively little attention [17,18].…”