Two-photon luminescence from polar bis-terpyridyl-stilbene derivatives of Ir(iii) and Ru(ii)

Abstract

Four structurally related iridium(III) and ruthenium(II) complexes bearing two polar terpyridyl-stilbene derived chromophores 4-(4-{2-[4-(methoxy)phenyl]ethenyl}phenyl)-2,2'-6',2''-terpyridine (ttpyeneanisole) and 4-(4-{2-[phenyl]ethenyl}phenyl)-2,2'-6',2''-terpyridine (tpystilbene) have been synthesised and characterised in the solid state and in solution. In the solid state, the dihedral angle subtending the pyridyl and tolyl groups of 27.1° in the Ir(III) complex [Ir(ttpyeneanisole)(2)]·3PF(6) is more acute than in the Ru(II) derivative [Ru(tpystilbene)(2)]·2PF(6) (35.5°), indicating the presence of a greater degree of π-delocalisation across the terpyridine unit in the former compound. Their luminescence properties in fluid solution have been investigated following both resonant and non-resonant excitation. We have shown that each of the complexes undergoes two-photon excitation when excited in the near infrared (740 to 820 nm), with two-photon absorption cross sections in the range 11-67 × 10(-50) cm(4) s photon(-1). The larger cross sections for the Ir(III) complexes reflect the differences observed in the solid state. This work therefore demonstrates that such complexes are promising as luminescent markers for 3D imaging and illustrates that simple functionalisation of the chromophores and the choice of metal can lead to marked enhancements in the two-photon cross sections (σ(2)) compared to those of simpler heteroleptic polypyridyl based derivatives.

Solvent dependent photosensitized singlet oxygen production from an Ir(iii) complex: pointing to problems in studies of singlet-oxygen-mediated cell death

“…The data obtained yielded Ir(ppy) 2 (phen) + absorption cross sections that were, within the margins of our errors, independent of the solvent used:  800 = 1.9 ± 0.5 GM in H 2 O,  800 = 2.1 ± 0.5 GM in D 2 O,  800 = 2.8 ± 0.7 GM in octan-1-ol, and  800 = 2.4 ± 0.6 GM in CH 2 Cl 2 (1 GM = 10 -50 cm 4 s photon -1 ). Although these absorption cross sections are ~ 10 times smaller than cross sections that have previously been reported for similar Ir(III) complexes, 53,54 it is important to note that we did not record the full two-photon spectrum and, as such, may not be recording data at the absorption band maximum. Nevertheless, for the purpose of our present study, and as outlined below, we do not expect an appreciable solvent-dependent shift in the two-photon spectrum.…”

Theranostic Iridium(III) Complexes as One‐ and Two‐Photon Phosphorescent Trackers to Monitor Autophagic Lysosomes

“…[8] Meanwhile, cyclometalated iridium(III) complexes have gained increasing attention in bioimaging and biosensing due to their rich photophysical properties, e.g., high quantum yields, large Stokes shifts, long-lived phosphorescence, and good photostability. [10] TPA materials that can be excited by near-infrared light (700-1100 nm) have several advantages over conventional one-photon excited staining agents when applied in biosensing and bioimaging, such as decreased photobleaching effects, minimal photodamage of cellular structures, low background interference, and long penetration depth (> 500 mm). [10] TPA materials that can be excited by near-infrared light (700-1100 nm) have several advantages over conventional one-photon excited staining agents when applied in biosensing and bioimaging, such as decreased photobleaching effects, minimal photodamage of cellular structures, low background interference, and long penetration depth (> 500 mm).…”

“…The TPA cross-sections of LysoIr1 and LysoIr2 at different pH were determined by investigating their two-photon excited fluorescence (TPEF) using rhodamine 6G as the reference. [10] The two-photon action cross-section (Fd), the product of the TPA cross-section and fluorescence/phosphorescence quantum yield, can provide direct measure of TPEF brightness and is a more important feature to evaluate the efficiency of twophoton luminophores. These values are among the largest TPA cross-sections reported for iridium complexes.…”

A novel multifunctional cyclometallated iridium(III) complex with interesting second-order nonlinear optical properties and two-photon absorption activity

“…Beeby and co-workers reported a series of iridium(III) acetylacetonate complexes, bearing two cyclometallated substituted 2-phenylpyridines, characterized by fair values of TPA cross sections (approximatively 20 GM) [10]. Another report concerning iridium complexes of a terpyridyl-stilbene system demonstrated TPA cross-sections in the range of 10-70 GM [11].…”

“…Whereas cyclometallated Ir(III) complexes have been intensively studied for their interesting luminescent properties, to our knowledge, only a few reports appeared in the literature on their second-order NLO properties [6,7] or two-photon absorption (TPA) activity [8][9][10][11]. Yet, two-photon absorbing materials having large two-photon absorption cross-section (σ), especially in the near-infrared (NIR) region, are required for photodynamic therapy, bio-imaging, upconversion lasing and drug delivery [9] whereas the design of novel second-order NLO active compounds is crucial for many applications in the fields of optical communication and data processing [2].…”