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A novel lysosome-targeted photosensitizer/photoredox catalyst based on cyclometalated Ir(III) complex IrL has been designed and synthesized, which exhibited excellent phosphorescence properties and the ability to generate single oxygen (1O2) and photocatalytically oxidize 1,4-dihydronicotinamide adenine dinucleotide (NADH) under light irradiation. Most importantly, the aforementioned activities are significantly enhanced due to protonation under acidic conditions, which makes them highly attractive in light-activated tumor therapy, especially for acidic lysosomes and tumor microenvironments. The photocytotoxicity of IrL and the mechanism of cell death have been investigated. Additionally, the tumor-killing ability of IrL under light irradiation was evaluated using a 4T1 tumor-bearing mouse model. This work provides a strategy for the development of lysosome-targeted photosensitizers/photoredox catalysts to overcome hypoxic tumors. [ABSTRACT FROM AUTHOR]

A series of luminescent Cu4I4 clusters with stair-step, cubane, and octahedral geometries supported by a novel type of cyclic As,N-ligand, pyridyl-containing 10-phenoxarsines, were synthesized and characterized by NMR spectroscopy, mass spectrometry, elemental analysis, and single-crystal X-ray diffraction analysis. An unusual arrangement of As,N-bidentate and μ2-iodo ligands was found in the octahedral cluster. The structural diversity of the Cu(I) complexes is reflected in their photophysical properties: the phosphorescence spectra of the compounds display emission in a broad spectral range of 495–597 nm. The complex with the Cu4I4L2 stoichiometry bearing a stair-step Cu4I4 core demonstrates temperature-dependent dual emission. The luminescence properties of all complexes were rationalized by DFT calculations. [ABSTRACT FROM AUTHOR]

We report three Pt(II) diimine complexes containing ancillary ligands of phenylpyridine furnished with anionic closo-monocarborane clusters [CB11H12]−. Three neutral complexes exhibit intensive phosphorescence in the solid state and complex 1 was used to detect acetonitrile vapor in a quartz plate. [ABSTRACT FROM AUTHOR]

We report three Pt(II) diimine complexes containing ancillary ligands of phenylpyridine furnished with anionic closo-monocarborane clusters [CB11H12]−. Three neutral complexes exhibit intensive phosphorescence in the solid state and complex 1 was used to detect acetonitrile vapor in a quartz plate. [ABSTRACT FROM AUTHOR]

A series of phosphorescent platinum(II) complexes containing various phenyldiazine-type bidentate N^C ligands have been successfully synthesized and characterized. Structural modifications have been made to bidentate cyclometalating ligands regarding the nature of the diazine ring (pyrimidine, pyrazine and quinazoline), the substituent groups at the C4 position of the pyrimidine ring (OCH3, CF3) and the EDGs at the para position of the Pt atom (OCH3, Ph, NPh2, carbazol). In addition, the electronic properties of the azaheterocyclic ancillary ligand have been modulated in this series of complexes (pyridine, 4-methoxy-pyridine or pyrimidine). X-ray diffraction studies have been performed on three complexes, revealing Pt(II) ions in a distorted square-planar geometrical environment with no Pt(II)⋯Pt(II) interactions but with moderate π–π interactions in the solid-state structure. Electrochemical and computational studies suggest a ligand-centered reduction on the diazine ligands with, in some cases, additional contribution from the azaheterocyclic ancillary ligand, whereas oxidation occurs on the Pt-phenyl ring substituent moieties. All complexes exhibit phosphorescence emission ranging from green to red/near-infrared, both in solution and in the solid state. Complexes bearing a 2-(3-methoxyphenyl)pyrimidine ligand show the best PLQY of the series, up to 52% in a CH2Cl2 solution and 20% in the solid state. Furthermore, the solid state PLQY of one of the near-infrared emitting phenylquinazoline complex has been found to be 6%. [ABSTRACT FROM AUTHOR]

Presented herein are two fully characterized gold tetrathiocyanocorroles representing a potentially significant new class of NIR-emissive 5d-metallocorroles. The four SCN groups on the bipyrrole unit of the corrole exert a powerful electron-withdrawing effect, upshifting both the oxidation and reduction potentials by roughly half a volt relative to their unsubstituted counterparts. That said, the upshift of the LUMO is somewhat higher than that of the HOMO so these complexes also exhibit a smaller HOMO–LUMO gap, as evinced in both electrochemical measurements and Q band energies (∼595 nm relative to ∼571 nm for their SCN-free counterparts). The new compounds exhibit NIR phosphorescence under ambient conditions with emission maxima around 900 nm (compared with 790 nm for simple Au triarylcorroles), phosphorescence quantum yields around 0.3%, phosphorescence lifetimes around 10 μs, and singlet oxygen sensitization with a quantum yield of around 50 ± 5% in solution, together signifying wide-ranging potential applications as triplet photosensitizers in oxygen sensing and photodynamic therapy. [ABSTRACT FROM AUTHOR]

Long triplet lifetimes of excited photosensitizers are essential for efficient energy transfer reactions in water, given that the concentrations of dissolved oxygen and suitable acceptors in aqueous media are typically much lower than in organic solvents. Herein, we report the design, synthesis and photochemical characterization of two structurally related water-soluble ruthenium complex-based dyads decorated with a covalently attached pyrene chromophore. The triplet energy of the latter is slightly below that of the metal complex enabling a so-called triplet reservoir and excited-state lifetime extensions of up to two orders of magnitude. The diimine co-ligands, which can be modified easily, have a major impact on both the ultrafast intramolecular energy transfer (iEnT) kinetics upon excitation with visible light and the lifetime of the resulting long-lived pyrene triplet. The phenanthroline-containing dyad shows fast triplet pyrene formation (25 ps) and an exceptionally long triplet lifetime beyond 50 microseconds in neat water. The iEnT process via the Dexter mechanism is slower by a factor of two when bipyridine co-ligands are employed, which is rationalized by a poor orbital overlap. Both dyads are very efficient sensitizers for the formation of singlet oxygen in air-saturated water as well as for the bimolecular generation of anthracene triplets that are key intermediates in upconversion mechanisms. This is demonstrated by the 5-hydroxymethylfurfural oxidation, which yields completely different main products depending on the pH value of the aqueous solution, as an initial application-related experiment and by time-resolved spectroscopy. Our findings are important in the greater contexts of photocatalysis and energy conversion in the "green" solvent water. [ABSTRACT FROM AUTHOR]

The poor excited-state properties of bis-terpyridine Ru(II) complexes have significantly limited the applications of these complexes as sensitizers in photocatalysis and triplet–triplet annihilation upconversion. In the present work, two novel ruthenium bis-terpyridine complexes (Ru-1 and Ru-2) conjugated with visible-light-harvesting bodipy chromophores were synthesized. These complexes showed strong absorption of visible light, the bodipy-localized intraligand triplet state (3IL) was efficiently populated, and the phosphorescence of bodipy at room temperature in both complexes was observed. The luminescence lifetimes of these complexes were significantly prolonged, with that of the heteroleptic complex Ru-2 prolonged to 37.9 μs and that of the homoleptic bis-terpyridine complex Ru-1 unprecedentedly prolonged to 356 μs, which was hundreds of times longer than the current longest emissive state achieved in ruthenium terpyridine complexes. The ultra-long triplet lifetimes and strong visible-light absorbing ability made them new candidates of triplet sensitizers, and were first applied to TTA-UC for terpyridine Ru(II) complexes with a Ru-1/Py system showing a ΦUC of 2.93% in dilute solutions at concentrations as low as 1.0 μM. [ABSTRACT FROM AUTHOR]

Fluorescent/phosphorescent dual-emissive polymers or hybrids consisting of both fluorophore and phosphor have been used as self-calibrating probes and imaging reagents for cellular molecular oxygen. Oxygen selectively quenches the phosphorescence and the fluorescence serves as an internal reference. The phosphorescence/fluorescence ratio is used as a quantitative indicator of oxygen content. In wavelength- ratiometric probes, the fluorophore and phosphor are designed to emit at different wavelengths. It is easy to achieve spectral separation, but the phosphorescence/fluorescence ratio fluctuates due to the difference in the absorption and scattering of light at different wavelengths by biological samples. Herein we reported a lifetime-ratiometric luminescent polymeric probe where the fluorophore and phosphor emitted at the same wavelength. Spectral separation was achieved based on the difference in their excited-state lifetimes via time-resolved luminescence analysis and imaging. The probe exhibited a phosphorescence lifetime of about 931 ns with a phosphorescence/fluorescence ratio of 4.49 in deaerated aqueous buffer. The lifetime was shortened to 251 ns and the ratio decreased to 1.08 in oxygen saturated solution because of phosphorescence quenching. The utilization of the probe for quantitative oxygen sensing and mapping in living HeLa cells was demonstrated using calibration curves obtained from fixed cells. [ABSTRACT FROM AUTHOR]

Dinuclear gold(I) compounds are of great interest due to their aurophilic interactions that influence their photophysical properties. Herein, we showcase that gold–gold interactions can be influenced by tuning the electronic properties of the ligands. Therefore, various para substituted (R) N,N′-bis(2,6-dimethylphenyl)formamidinate ligands (pRXylForm; Xyl = 2,6-dimethylphenyl and Form = formamidinate) were treated with Au(tht)Cl (tht = tetrahydrothiophene) to give via salt metathesis the corresponding gold(I) compounds [pRXylForm2Au2] (R = –OMe, –Me, –Ph, –H, –SMe, and –CO2Me). All complexes showed intense luminescence properties at low temperatures. Alignment with the Hammett parameter σp revealed the trends in the 1H and 13C NMR spectra. These results showed the influence of the donor–acceptor abilities of different substituents on the ligand system which were confirmed with calculated orbital energies. Photophysical investigations showed their lifetimes in the millisecond range indicating phosphorescence processes and revealed a redshift with the decreasing donor ability of the substituents in the solid state. [ABSTRACT FROM AUTHOR]

Application of NIR (near-infrared) emitting transition metal complexes in biomedicine is a rapidly developing area of research. Emission of this class of compounds in the "optical transparency windows" of biological tissues and the intrinsic sensitivity of their phosphorescence to oxygen resulted in the preparation of several commercial oxygen sensors capable of deep (up to whole-body) and quantitative mapping of oxygen gradients suitable for in vivo experimental studies. In addition to this achievement, the last decade has also witnessed the increased growth of successful alternative applications of NIR phosphors that include (i) site-specific in vitro and in vivo visualization of sophisticated biological models ranging from 3D cell cultures to intact animals; (ii) sensing of various biologically relevant analytes, such as pH, reactive oxygen and nitrogen species, RedOx agents, etc.; (iii) and several therapeutic applications such as photodynamic (PDT), photothermal (PTT), and photoactivated cancer (PACT) therapies as well as their combinations with other therapeutic and imaging modalities to yield new variants of combined therapies and theranostics. Nevertheless, emerging applications of these compounds in experimental biomedicine and their implementation as therapeutic agents practically applicable in PDT, PTT, and PACT face challenges related to a critically important improvement of their photophysical and physico-chemical characteristics. This review outlines the current state of the art and achievements of the last decade and stresses the most promising trends, major development prospects, and challenges in the design of NIR phosphors suitable for biomedical applications. [ABSTRACT FROM AUTHOR]

Two series of cyclometalated PtII and IrIII complexes with general formulas [Pt(pbt){PPh2(R)-κP,O}] (2a–2c) and [Ir(pbt)2{PPh2(R)-κP,O}] (3a–3c), where Hpbt is 2-phenylbenzothiazol and PPh2(R) is a diphenylphosphino donor functionalized deprotonated acid (R = o-C6H4CO2a, o-C6H4SO3b, CH2CH2CO2c) are presented. The structures of 1, 2a–2c, 3a and 3b were confirmed by single X-ray diffraction analyses, and the intermolecular interactions in 2a were studied using Hirshfeld surface analysis and non-covalent interaction (NCI) methods on its X-ray structure. Their photophysical properties were investigated by absorption and emission analyses [CH2Cl2, solid (298, 77 K) and doped polystyrene (PS) films], supported by TD-DFT calculations on 1, 2a–2c and 3a. The PtII complexes exhibit bright phosphorescence in the region 525–542 nm, ascribed to a mixed 3IL/3MLCT excited state with a predominant 3IL contribution. The IrIII derivatives (3a–3c) show orange photoluminescence (535–584 nm, 298 K), blue shifted at 77 K (527–560 nm), originated from the admixture of 3IL/3MLCT/3LLCT excited states. Interestingly, the photoluminescence quantum yields of the Pt complexes 2a–2c (φ = 46.5–66.5%) in PS films are remarkably higher than those of the corresponding iridium complexes (φ = 17.3–32%) and the precursor 1 (φ = 17%). The calculated 3MC-3IL/3MLCT energy gap for 2a and 3a accounts for the higher quantum yield of the Pt in relation to the Ir complex. [ABSTRACT FROM AUTHOR]

The reaction between allenylpyridine (L1) and (Me2S)AuCl resulted in the quantitative formation of the (Indolizy)gold chloride complex 1 (Indolizy = indolizin-2-ylidene). The reaction of 1 with carbazole in the presence of KOtBu affords the corresponding (Indolizy)Au(Cz) complex 2. Both compounds show high air- and temperature stability. The crystal structure of 2 confirmed the linear co-planar geometry. Complex 1 shows an intense low energy absorption of mixed character in the UV-vis spectrum, ascribed to intraligand and (M + Hal)L charge transfer processes, and exhibits bright yellow phosphorescence with an excited state lifetime of 62.8 μs in the crystal and a luminescence quantum yield up to 65%. On the other hand, the carbazolate complex 2 in a polystyrene matrix shows bright red delayed fluorescence at 617 nm with a sub-microsecond excited state lifetime and a quantum yield of 21.6%. [ABSTRACT FROM AUTHOR]

Room-temperature phosphorescent (RTP) materials can be used in anti-counterfeiting, organic light-emitting diodes and displays. However, designing RTP materials with a long luminescence lifetime and high solid-state emission efficiency is still a challenge. Due to the strong quantum confinement effect and the hydrogen bond network structure formed by polyamino sites, 0D RTP materials usually have a higher fluorescence quantum yield and longer phosphorescence lifetime. Here, we synthesized four manganese-based metal halides of different dimensions with a long lifetime and high luminous efficiency by changing organic cations: {[H2DAP]MnCl4}n (1, DAP = 1,3-propanediamine, 2D), {[(H2MELA)2MnCl5]Cl}n (2, MELA = melamine, 1D), [H2TAP]2MnCl6 (3, TAP = 2,4,6-triaminopyrimidine, 0D) and [H2MXD]2MnCl6 (4, MXD = m-xylylenediamine, 0D). [H2MXD]2MnCl6 (4) has a long lifetime (11 ms) and the maximum photoluminescence quantum yield (31.05%). Our work provides a new procedure for the development of RTP materials with high quantum yields. [ABSTRACT FROM AUTHOR]

A series of chiral platina[5]helicenes displaying dual luminescence, i.e., fluorescence between 450 and 600 nm and red/NIR phosphorescence between 700 and 900 nm, has been synthesised, characterised and studied by first-principle calculations. This unusual behavior has been attributed to limited electronic interactions between the d orbitals of the metal and the π-orbitals of the organic ligand on the excited-state. Accordingly, the electron richness of the donor group on the helical ligand does not affect the energy of the phosphorescence process but does play a role on its efficiency. Interestingly, near-infrared circularly polarized luminescence can be obtained for the three complexes with dissymmetry factors up to 3 × 10−3 at 750 nm. [ABSTRACT FROM AUTHOR]

Green to blue-green-emitting cationic iridium complexes free of sp2 C–F bonds, namely [Ir(CF3-dPhTAZ)2(bpy)]PF6 (1), [Ir(CF3-dPhTAZ)2(dmebpy)]PF6 (2) and [Ir(CF3-dPhTAZ)2(phpyim)]PF6 (3), have been designed and synthesized with 3,4-diphenyl-5-(trifluoromethyl)-4H-1,2,4-triazole (CF3-dPhTAZ) as the cyclometalating ligand (C^N) and 2,2′-bipyridine (bpy), 4,4′-dimethyl-2,2′-bipyridine (dmebpy) or 2-(1-phenyl-1H-imidazol-2-yl)pyridine (phpyim) as the ancillary ligand (N^N). In CH3CN solution, complexes 1–3 afford green to blue-green emission centered at 521, 508 and 498 nm, respectively. The electron-withdrawing CF3 group attached at the triazole ring in CF3-dPhTAZ largely blue-shifts (by over 20 nm) the emission of the complex through stabilizing the highest occupied molecular orbital. In doped films, the complexes afford sky-blue emission with near-unity phosphorescent efficiencies. In neat films, the complexes show largely suppressed phosphorescence concentration-quenching, with phosphorescent efficiencies of up to 0.66. Theoretical calculations reveal that the emission of the complexes can arise from either charge-transfer (Ir → C^N/C^N → N^N) or C^N/N^N-centered 3π–π* states, depending on the local environment of the complexes. Solid-state light-emitting electrochemical cells (LECs) based on the complexes afford green to blue-green electroluminescence centered at 525, 517 and 509 nm, respectively, with high current efficiencies of up to 35.1 cd A−1. The work reveals that CF3-dPhTAZ is a promising C^N ligand free of sp2 C–F bonds for constructing efficient cationic iridium complexes with blue-shifted emission. [ABSTRACT FROM AUTHOR]

Several first-row transition metal complexes of the 1,9-bis(2′,4′,6′-triphenylphenyl)-5-mesityl dipyrrinato ligand and its tetrahalogenated analogues have been synthesized and their luminescence spectra obtained. The protonated ligands, as well as the Li(I), Mn(II), Cu(I), Cu(II), and Zn(II) chelates show appreciable luminescence, despite the paramagnetism of the Mn(II) and Cu(II) ions. Fluorescence quantum yields (ΦF) as high as 0.67 were observed for the zinc complex. Luminescence was partially quenched by the introduction of heavy halogens to the backbone of the ligand, as well as by the introduction of paramagnetic metal ions. Room-temperature, solution state phosphorescence was observed from the halogenated dipyrrinato lithium salts, as well as from the non-halogenated Mn(II) complex. [ABSTRACT FROM AUTHOR]

Four new cyclometalated Pt(II) complexes bearing acyclic diaminocarbene (ADC) ligands, [Pt(C^N)Cl{C(NHXyl)(NHR)}] [C^N = 2,6-difluorophenylpyridine (dfppy), phenylquinoline (pq); R = Pr 3a, 4a, CH2Ph 3b, 4b], were prepared by the nucleophilic attack on the isocyanide [Pt(C^N)Cl(CNXyl)] (C^N = dfppy 1, pq 2) by the corresponding amine RNH2 (R = Pr, CH2Ph). Complexes 3 show in their 1H NMR spectra in CDCl3 a notable concentration dependence, with a clear variation of the δH (NHXyl) signal, suggesting an assembling process implying donor–acceptor NHXyl⋯Cl bonding, also supported by 1D-PGSE (Pulse Field Gradient Spin Echo) and 2D-DOSY (Diffusion Ordered Spectroscopy) NMR experiments in solution and X-ray diffraction studies. The intermolecular interactions in compounds 3a and 3b were studied by using Hirshfeld surface analysis and Non-Covalent Interaction (NCI) methods on their X-ray structures. Their photophysical properties were investigated by absorption and emission spectroscopies and also by TD-DFT calculations performed on 3a and 4b. These complexes show green (3) or orange (4) phosphorescence, attributed to a mixed 3IL/3MLCT excited state. The carbene ligand does not affect the emission maxima but it produces an increase of the quantum yields in relation to the isocyanide in the precursors. In fluid solutions, the emission is not concentration-dependent, but the complexes may show aggregation induced emission as detailed for complexes 3a and 4a. In addition, cytotoxicity studies in the human cell lines A549 (lung carcinoma) and HeLa (cervix carcinoma) showed good activity for these complexes and 3a, 3b and 4a exhibit a strong effect on DNA electrophoretic mobility. To the best of our knowledge, compounds 3 and 4 represent the first examples of cycloplatinated complexes bearing acyclic diamino carbenes with antiproliferative properties. [ABSTRACT FROM AUTHOR]

The synthesis of four novel gold(I)-phosphane complexes coordinated to 9-phenanthrene chromophore has been carried out through the reaction of 9-phenanthreneboronic acid and the corresponding AuClPR3 (PR3 = PPh3 for triphenylphosphane (1a); 1,4-bis(diphenylphosphanyl)butane or dppb (2b); bis(diphenylphosphanyl)acetylene or dppa (2c); (AuCl)2(diphos) (diphos = bis(diphenylphosphanyl)methane or dppm (3)) sources. The X-ray crystal structures of compounds 1a and 2b show the existence of MOF-like intermolecular assemblies that contain empty inner cavities in the absence of aurophilic contacts. In contrast, the formation of a tetranuclear complex with intramolecular aurophilic interactions was evidenced for 3. Photophysical characterization indicates dual emission in all gold(I) complexes when oxygen is removed from the sample, while only fluorescence emission is recorded for the uncoordinated ligand. The introduction of the compounds within PMMA and Zeonex was assayed, and luminescent films containing gold(I) complexes where phosphorescence is the sole pathway for emission are obtained, instead of the dual emission (with significant fluorescence contribution) recorded in solution. [ABSTRACT FROM AUTHOR]

The reaction of [Re(CO)3(THF)(μ-Br)]2 or [Re(CO)5X] (X = Cl, Br, I) with the diaryl-2-azabutadienes [(RS)2C＝C(H)–N＝CAr2] containing two thioether arms at the 4,4-position forms the luminescent S,N-chelate complexes fac-[(OC)3ReX{(RS)2C＝C(H)–N＝CAr2}] (1a–h). The halide abstraction by silver triflate converts [(OC)3ReCl{(PhS)2C＝C(H)–N＝CPh2}] (1c) to [(OC)3Re(OS(＝O)2CF3){(PhS)2C＝C(H)–N＝CPh2}] (1j) bearing a covalently bound triflate ligand. The cyclic voltammograms reveal reversible S^N ligand-centred reduction and irreversible oxidation waves for all complexes. The crystal structures of nine octahedral complexes have been determined along with that of (NaphtylS)2C＝C(H)–N＝CPh2 (L6). A rich system of weak non-covalent intermolecular secondary interactions through CH⋯X(Cl, Br)Re, CH⋯O, CO⋯π(Ph), CH⋯πCO, CH⋯O and CH⋯S contacts has been evidenced. The photophysical properties have been investigated by steady-state and time-resolved absorption (fs transient absorption, fs-TAS) and emission (ns-TCSPC and ps-Streak camera) spectroscopy in 2-MeTHF solution at 298 and 77 K. The emission bands are composed of either singlet (450 < λmax < 535 nm) and/or triplet emissions (at 77 K only, λmax < 640 nm, or appearing as a tail at λ > 600 nm), which decay in a multiexponential manner for the fluorescence (short ps (i.e.

Precise control over the production of carbon monoxide (CO) is essential to exploit the therapeutic potential of this molecule. The development of photoactive CO-releasing molecules (PhotoCORMs) is therefore a promising route for future clinical applications. Herein, a tricarbonyl-rhenium(I) complex (1-TPP), which incorporates a phosphine moiety as ancilliary ligand for boosting the photochemical reactivity, and a pyridyltriazole bidentate ligand with appended 2-phenylbenzoxazole moiety for the purpose of photoluminescence, was synthesized and characterized from a chemical and crystallographic point of view. Upon irradiation in the near-UV range, complex 1-TPP underwent fast photoreaction, which was monitored through changes of the UV-vis absorption and phosphorescence spectra. The photoproducts (i.e. the dicarbonyl solvento complex 2 and one CO molecule) were identified using FTIR, 1H NMR and HRMS. The results were interpreted on the basis of DFT/TD-DFT calculations. The effective photochemical release of CO associated with clear optical variations (the emitted light passed from green to orange-red) could make 1-TPP the prototype of new photochemically-active agents, potentially useful for integration in photoCORM materials. [ABSTRACT FROM AUTHOR]

Re(I) complexes bearing thermally reversible photochromic naphthopyran axial ligands undergo highly efficient, reversible phosphorescence quenching actuated by either visible or UV irradiation. The photoinduced quenching of the triplet metal-to-ligand charge-transfer (3MLCT) emission is interpreted based on changes in the relative energies of the excited states. [ABSTRACT FROM AUTHOR]

Bromination of the luminescent borane, anti-B18H22, via electrophilic substitution using AlCl3 and Br2, yields the monosubstituted derivative 4-Br-anti-B18H21 as an air-stable crystalline solid. In contrast to the unsubstituted parent compound, 4-Br-anti-B18H21 possesses dual emission upon excitation with UV light and exhibits fluorescence at 410 nm and phosphorescence at 503 nm, with Φtotal = 0.07 in oxygen-free cyclohexane. Increased oxygen content in cyclohexane solution quenches the phosphorescence signal. The fluorescent signal intensity remains unaffected by oxygen, suggesting that this molecule could be used as a ratiometric oxygen probe. [ABSTRACT FROM AUTHOR]

The gold(I) complexes [μ-LiPr(AuX)2] {X = Cl (1D), Br (2D), and I (3D); LiPr = 1,2-bis[bis(2-isopropylphenyl)phosphino]benzene} were synthesised to investigate the photoluminescence properties of dinuclear Au complexes comprising weak Au(I)–Au(I) bonds. Single crystals of the tetrahydrofuran (THF) adducts 1DOR, 2DOR, and 3DOR were obtained by recrystallisation of 1D, 2D, and 3D from a mixed solution of THF and n-hexane. These THF adducts afford orange emission, with peak wavelengths ranging from 597 to 630 nm, in the crystalline state at 293 K. Recrystallisation of 3D from a mixed solution of acetone and n-hexane afforded single crystals of the acetone adduct 3DGR, which exhibits blue-green emission at 293 K. No crystals of the acetone adduct were obtained from 1D and 2D. The emission spectra and lifetimes of 1DOR, 2DOR, 3DOR, and 3DGR measured in the temperature range 77–293 K indicate that emission from these complexes in the solid state is due to phosphorescence. Notably, although the molecular structure of 3D in the 3DOR crystal is near-similar to that of 3DGR, the phosphorescence spectrum of 3DOR differs markedly from that of 3DGR, with peak wavelengths at 597 and 506 nm, respectively. Theoretical studies revealed that (1) phosphorescence occurs via the electronic transition from the excited triplet state, which is mainly composed of halogen-to-metal–metal charge transfer and metal-centered transitions and (2) the T1-optimised structure of 3D in the 3DGR crystals differs markedly from that in 3DOR, and the differences in the phosphorescence colour observed between 3DGR and 3DOR are ascribed to the differences in their stabilised structures in the excited triplet state. [ABSTRACT FROM AUTHOR]

Presented here is a new class of supramolecular cyclometalated Ir(III) complexes. The 2 : 1 assemblies include two phosphorescent cyclometalated Ir(III) centers spanned by a BODIPY bridge with pyridine substituents at the β-pyrrole positions. The three complexes, which vary with respect to the cyclometalating ligand on iridium, are prepared via a simple one-pot procedure, with the target complexes isolated in 31–75% yield. The photophysics of these new compounds are described in detail. All complexes are strongly photoluminescent, with fluorescence from BODIPY being the dominant emission pathway. One member of the series has a near-unity photoluminescence quantum yield, significantly enhanced relative to the free BODIPY. The cyclometalating ligand on iridium controls the energy of the Ir-centered triplet excited state, but in all cases energy transfer from the Ir centers to the BODIPY quenches almost all phosphorescence. This work outlines a new, simple synthetic method for accessing supramolecular complexes. [ABSTRACT FROM AUTHOR]

Two new aggregation-induced emission (AIE)-active cyclemetalated cationic Ir(III) complexes have been rationally designed and synthesized by introducing O–H substituents into Schiff base ligands. π-Hydrogen bonding is successfully exploited for the first time to realize the mechanochromic luminescence (MCL) property by the synergistic effect of O–H and F substituents in complex 1. An X-ray crystal structure analysis of the two complexes suggests that the intramolecular hydrogen bonding effectively restricted the molecular motions, thus causing typical AIE characteristics. More importantly, a loosely packed structure constructed from intermolecular hydrogen bonding interactions (O–H⋯π and C–H⋯F) is obtained, and it is susceptible to mechanical stimulation. Powder X-ray diffraction (PXRD) studies also prove that the MCL behavior of complex 1 is caused by the reversible phase transition from crystalline to amorphous state under grinding and solvent recrystallization, leading to a change in emission colors. A re-writable phosphorescence data recording device was fabricated using complex 1 as the active material. Our molecular design strategies provide a new avenue for achieving efficient phosphorescence materials with AIE and MCL properties. [ABSTRACT FROM AUTHOR]

We report a series of room temperature phosphorescent compounds 1–6 composed of triarylborane (TAB) and cyclometallated iridium complexes. The optical characteristics such as energy of transition and luminescence quantum yield of these compounds can be conveniently fine-tuned by judiciously varying the cyclometallating ligand and the spacer between boron and iridium centers. Compounds 1–6 exhibit bright phosphorescence with the emission color ranging from green to red under a N2 atmosphere. A maximum quantum yield of 0.95 was observed for complex 2. Complexes 1–6 exhibit a rare type of dual emission from singlet and triplet excited states under ambient conditions. The experimental observations are well supported by the theoretical calculations. [ABSTRACT FROM AUTHOR]

Under solvothermal conditions, a robust Pb2+-based coordination polymer (CP), [Pb(TDC)]n (1), where H2TDC is thiophenedicarboxylic acid, has been achieved. Structural analysis reveals that 1 crystallizes in the monoclinic space group C2/c, where the Pb2+ ions show quadrangular prism coordination geometry. CP 1 represents a 3D coordination network based on a TDC2− ligand as bridges and quadrangular prismatic PbO8 units as nodes, among which the PbO8 units are extended through edge-sharing to form a 2D layer in the bc plane. Interestingly, CP 1 emitted intense and long-lived orange phosphorescence in the solid state at room temperature, with a quantum yield of 6.7% and a phosphorescence lifetime of 1.78 ms. A fine structure is clearly observed in the phosphorescence emission spectra at temperatures below 55 K. The emission mainly arose from the electron transition within the π-type orbitals of the TDC2− ligand. This study gives a fresh impetus to achieve CP-based long-lived phosphorescent materials under ambient conditions. [ABSTRACT FROM AUTHOR]

To tune the lanthanide luminescence in related molecular structures, we synthesized and characterized a series of lanthanide complexes with imidazole-based ligands: two tripodal ligands, tris{[2-{(1-methylimidazol-2-yl)methylidene}amino]ethyl}amine (Me3L), and tris{[2-{(imidazol-4-yl)methylidene}amino]ethyl}amine (H3L), and the dipodal ligand bis{[2-{(imidazol-4-yl)methylidene}amino]ethyl}amine (H2L). The general formulas are [Ln(Me3L)(H2O)2](NO3)3·3H2O (Ln = 3+ lanthanide ion: Sm (1), Eu (2), Gd (3), Tb (4), and Dy (5)), [Ln(H3L)(NO3)](NO3)2·MeOH (Ln3+= Sm (6), Eu (7), Gd (8), Tb (9), and Dy (10)), and [Ln(H2L)(NO3)2(MeOH)](NO3)·MeOH (Ln3+= Sm (11), Eu (12), Gd (13), Tb (14), and Dy (15)). Each lanthanide ion is 9-coordinate in the complexes with the Me3L and H3L ligands and 10-coordinate in the complexes with the H2L ligand, in which counter anion and solvent molecules are also coordinated. The complexes show a screw arrangement of ligands around the lanthanide ions, and their enantiomorphs form racemate crystals. Luminescence studies have been carried out on the solid and solution-state samples. The triplet energy levels of Me3L, H3L, and H2L are 21 000, 22 700, and 23 000 cm−1, respectively, which were determined from the phosphorescence spectra of their Gd3+complexes. The Me3L ligand is an effective sensitizer for Sm3+and Eu3+ions. Efficient luminescence of Sm3+, Eu3+, Tb3+, and Dy3+ions was observed in complexes with the H3L and H2L ligands. Ligand modification by changing imidazole groups alters their triplet energy, and results in different sensitizing ability towards lanthanide ions. [ABSTRACT FROM AUTHOR]