Precise ligand engineering of Ir(III)-based photosensitizer with aggregation-induced emission for image-guided photodynamic therapy.

Photodynamic therapy (PDT), which relies on the production of reactive oxygen species (ROS) induced by a photosensitizer to kill cancer cells, has become a non-invasive approach to combat cancer. However, the conventional aggregation-caused quenching effect, as well as the low ROS generation ability of photosensitizers, restrict their biological applications. In this work, a new Ir(III) complex with a dendritic ligand has been strategically designed and synthesized by ingenious modification of the ancillary ligand of a reported Ir(III) complex (Ir-1). The extended π-conjugation and multiple aromatic donor moieties endow the resulting complex Ir-2 with obvious aggregation-induced emission (AIE) activity and bathochromic emission. In in vitro experiments, importantly, Ir-2 nanoparticles exhibit the excellent photoinduced ROS generation capabilities of O2 •- and 1 O2 , as well as excellent biocompatibility and the lipid droplets (LDs) targeting feature. This study would provide useful guidance to design efficient Ir(III)-based photosensitizers used in biological applications in the future.

Exploiting the Twisted Intramolecular Charge Transfer Effect to Construct a Wash-Free Solvatochromic Fluorescent Lipid Droplet Probe for Fatty Liver Disease Diagnosis.

The prominent pathological feature of fatty liver disease lesions is excessive fat accumulation in lipid droplets in hepatocytes. Thus, developing fluorescent lipid droplet-specific probes with high permeability and a high imaging contrast provides a robust tool for diagnosing fatty liver diseases. Herein, we rationally developed a novel donor-acceptor lipophilic fluorescent probe ANI with high photostability for wash-free visualization of lipid droplets and fatty liver disease characteristics. ANI showed a typical twisted intramolecular charge transfer effect with very faint fluorescence in high-polar solvents, but dramatically boosted emissions in low-polar environments. The solvatochromic probe can selectively light up lipid droplets with a high contrast in a wash-free manner. Further use of ANI to reveal the excessive accumulation of lipid droplets with a significantly large size in the liver tissues from the fatty liver disease model mice was successfully demonstrated. The remarkable imaging performances rendered ANI an alternative tool for accurately evaluating fatty liver disease in intraoperative diagnosis.

Rational Design of Ir(III) Phosphors to Strategically Manage Charge Recombination for High-Performance White Organic Light-Emitting Diodes.

Constructing high-quality white organic light-emitting diodes (WOLEDs) remains a big challenge because of high demands on the electroluminescence (EL) performance including high efficiency, excellent spectral stability, and low roll-off simultaneously. To achieve effective energy transfer and trap-assisted recombination in the emissive layer, herein, four Ir(III) phosphors, namely, mOMe-Ir-PI (1), pOMe-Ir-PI (2), mOMe-Ir-PB (3), and pOMe-Ir-PB (4), were strategically designed via simple regulation of the substituent moiety and π conjugation of the chelated ligands. Their photophysical and EL properties were systematically investigated. When these phosphors are employed as doped emitters, the monochromic green organic light-emitting diodes not only exhibit a superior performance with the characteristics of 50.2 cd A-1, 39.2 lm W-1, and 15.1%, but also maintain a negligible roll-off ratio of 0.2% at 1000 cd m-2, which are better than those of commercial green Ir(ppy)2acac and Ir(ppy)3 in the same device configuration. Inspired by these outstanding performances, we successfully fabricated the warm WOLED utilizing 2 as a green component, affording a peak efficiency of 42.0 cd A-1, 29.3 lm W-1, and 18.6% and retaining at 39.9 cd A-1, 23.7 lm W-1, and 17.4% even at 1000 cd m-2. The results herein demonstrate the superiority of the molecular design and propose a simple method toward the development of promising Ir(III) phosphors for high-efficiency WOLEDs.

Copper-Based Metal-Organic Framework with a Tetraphenylethylene-Tetrazole Linker for Visible-Light-Driven CO2 Photoconversion.

The design of efficient and inexpensive photocatalysts for CO2 photoreduction under visible light is of great significance for the sustainable development of the entire society. Herein, a copper-based metal-organic framework (MOF) (CUST-804) using a bulky tetraphenylethylene-tetrazole linker is synthesized and successfully used as a photocatalyst for CO2 reduction. The structural characterizations, as well as the photophysical properties, are investigated systematically. In the heterogeneous catalytic system, CUST-804 exhibits a robust CO production activity up to 2.71 mmol g-1 h-1 with excellent recyclability along with a selectivity of 82.8%, which is comparable with those of the reported copper-based MOF system. Theoretical calculations demonstrated that, among three kinds of coordinated model, only the 5-coordinated Cu site is active for CO2 reduction, in which the *COOH intermediate is stabilized and CO is readily desorbed. The results obtained herein can provide fresh insights into the realization of efficient copper-functionalized crystalline photocatalysts for CO2 reduction.

Novel Ir(III) Complexes with NHC-Based Ancillary Ligands for Efficient Nondoped OLEDs.

Nondoped organic light-emitting diodes (OLEDs) are of paramount importance for display and lighting applications owing to their advantages of facile fabrication and outstanding stability. However, nondoped OLEDs achieving extraordinary electroluminescence (EL) performance and low turn-on voltage (Von) remain sparse. Here, three Ir(III) complexes featuring N-heterocyclic carbene (NHC) auxiliary ligands functionalized with electron-deficient aromatic sulfonyl or phosphine oxide groups are reported as promising emitters for nondoped OLEDs. All Ir(III) complexes exhibit green emission with relatively high neat film efficiency. Although the photoluminescence spectra of three complexes reveal similarities, there are distinct differences in the nondoped EL performance. The nondoped device N3 based on tBu-Ir-ISO displays the most eminent EL performances and presents a low Von of 2.1 V, a power efficiency of 30.7 lm W-1, and a maximum current efficiency of 27.0 cd A-1, which can be attributed to steric hindrance and balanced carrier-transporting ability induced by electron-deficient substituents. Moreover, doped devices D1-D3 also realize excellent EL performance. It is believed that the strategy reported herein is a simple and efficient way of constructing excellent Ir(III) complexes for nondoped phosphorescent OLEDs.

A thiol-functionalized zirconium metal-organic cage for the effective removal of Hg2+ from aqueous solution.

The mercury ions in waste water have threatened public health and environmental protection. In this sense, novel materials with outstanding performances for removal of Hg2+ are imperative. Herein, we demonstrate a thiol-functionalized zirconium metal-organic cage (MOC-(SH)2) with excellent dispersion displays ideal properties for Hg2+ capture. MOC-(SH)2 exhibits the ability of removing Hg2+ in aqueous solutions with a capacity of 335.9 mgHg2+/gMOC-(SH)2, which surpasses that of classical Zr-based metal-organic framework Uio-66-(SH)2 by 1.89 folds. The higher loading capacity of MOC-(SH)2 is probably owing to the excellent dispersion of the discrete cage, which makes the accessibility of binding sites (thiol) easier. Additionally, 99.6% of Hg2+ can be effectively captured by MOC-(SH)2 with the concentration decreased from 5 to 0.02 ppm reaching the permissible limit for Hg2+, outperforming the performance of Uio-66-(SH)2. The excellent absorption property of MOC-(SH)2 is also achieved in terms of superior selectivity under the presence of competitive metal ions. Meanwhile, the regenerated MOC-(SH)2 can be reused without apparent loss of Hg2+ loading capacity. UV-vis absorption spectra, IR spectra and emission spectra further verified the strong chemical affinity between Hg2+ and the thiol of MOC-(SH)2. The study lays the groundwork for using Zr-MOCs in the removal of toxic metal ions and environmental sustainability.

New Wine in Old Bottles: Prolonging Room-Temperature Phosphorescence of Crown Ethers by Supramolecular Interactions.

Supramolecular macrocyclic hosts have long been used in smart materials. However, their triplet emission and regulation at crystal level is rarely studied. Herein, ultralong and universal room-temperature phosphorescence (RTP) is reported for traditional crown ethers. A supramolecular strategy involving chain length adjustment and morphological locking through complexation with K+ was explored as a general method to tune the phosphorescence lifetime in the solid state. A maximum 10-fold increase of lifetime after complex formation accompanied with by invisible to visible phosphorescence was achieved. A deep encryption based on this activated RTP strategy was also facilely fabricated. This work thus opens a new world for supramolecular macrocycles and their intrinsic guest responsiveness offers a new avenue for versatile smart luminescent materials.

Organometallic Ir(III) Phosphors Decorated by Carbazole/Diphenylphosphoryl Units for Efficient Solution-Processable OLEDs with Low Efficiency Roll-Offs.

Recently, solution-processable PhOLEDs have been attracting great interest for their low cost and high productivity relative to the vacuum-deposited devices. Similar to vacuum-deposited OLEDs, however, they usually suffer from serious efficiency roll-offs, especially in high brightness. Finding a feasible way and/or designing novel materials to increase efficiencies and reduce roll-offs simultaneously are highly desired. Herein, a new family of solution-processable cyclometalated iridium(III) phosphors with carbazole (Cz) and/or diphenylphosphoryl (Ph2PO) units functionalized main ligands has been designed. Owing to Cz and Ph2PO moieties possessing bulky steric effects, they can suppress the intermolecular strong packing and then decrease TTA effects and emission quenching. Meanwhile, the resulting OLEDs based on the designed phosphors exhibit considerable efficiencies and relatively small efficiency roll-offs. The device based on 4 containing both Cz and Ph2PO units realized a maximum current efficiency of 21.3 cd A-1, accompanied by a small roll-off. By optimization of the configuration of OLEDs, the device performance can be further enhanced, demonstrating their potential for high-performance solution-processable PhOLEDs.

Molecular Engineering of Phenylbenzimidazole-Based Orange Ir(III) Phosphors toward High-Performance White OLEDs.

To develop B-O complementary-color white organic light-emitting diodes (WOLEDs) exhibiting high efficiency and low roll-off as well as color stability simultaneously, we have designed two orange iridium(III) complexes by simply controlling the position of the methoxyl group on the cyclometalated ligand. The obtained emitters mOMe-Ir-BQ and pOMe-Ir-BQ show good photophysical and electrochemical stabilities with a broadened full width at half-maximum close to 100 nm. The corresponding devices realize highly efficient electrophosphorescence with a maximum current efficiency (CE) and power efficiency (PE) of 24.4 cd A-1 and 15.3 lm W-1 at a high doping concentration of 15 wt %. Furthermore, the complementary-color all-phosphor WOLEDs based on these phosphors exhibit good performance with a maximum CE of 31.8 cd A-1, PE of 25.0 lm W-1, and external quantum efficiency of 15.5%. Particularly, the efficiency of this device is still as high as 29.3 cd A-1 and 14.2% at the practical brightness level of 1000 cd m-2, giving a small roll-off. Meanwhile, extremely high color stability is achieved by these devices with insignificant chromaticity variation.

Achieving High Performances of Nondoped OLEDs Using Carbazole and Diphenylphosphoryl-Functionalized Ir(III) Complexes as Active Components.

Nondoped electroluminescent devices offer advantages over their doped counterparts such as good reproducibility, reduced phase separation between host and guest materials, and potential of lower-cost devices. However, low luminance efficiencies and significant roll-off values are longstanding issues for nondoped devices, and a rational design strategy for the preparation of efficient phosphors is highly desired. In this work, cyclometalated Ir(III) complexes 3CzIr(mtpy), 4CzIr(mtpy), 3POIr(mtpy), and 4POIr(mtpy) bearing carbazole (Cz) or diphenylphosphoryl (Ph2PO) groups substituted at different positions of 1,2-diphenyl-H-benzimidazole (HPBI) were designed and synthesized. Owing to the steric effects induced by these groups, a significant intermolecular interaction was avoided, thereby reducing self-quenching and triplet-triplet annihilation (TTA) at high brightness. Simultaneously, attached functional moieties manipulate the charge-carrier character and enhance the EL performance of the complexes. Device N3-10, based on 3POIr(mtpy), successfully realized excellent performance and improved efficiency stability, rendering a turn-on voltage of 2.5 V, a maximum current efficiency of 29.7 cd A-1, and a maximum power efficiency of 31.1 lm W-1, which are all almost 3-fold higher than that of the control device N-10 based on parent complex. Inspiringly, all of the devices showed reduced efficiency roll-off as luminance increased. To the best of our knowledge, these are good results for green-emitting PHOLEDs using vacuum evaporation techniques, and they provide fundamental insights into the future realization of efficient phosphorescent Ir(III) complexes and corresponding nondoped devices.

Correction: Theoretical study and design of multifunctional phosphorescent platinum(ii) complexes containing triarylboron moieties for efficient OLED emitters.

Correction for 'Theoretical study and design of multifunctional phosphorescent platinum(ii) complexes containing triarylboron moieties for efficient OLED emitters' by Yong Wu et al., Phys. Chem. Chem. Phys., 2015, DOI: .

Theoretical study and design of multifunctional phosphorescent platinum(II) complexes containing triarylboron moieties for efficient OLED emitters.

The geometries, electronic structures, photophysical properties and spin-orbit coupling (SOC) effects in the radiative process for the recently synthesized complexes (Bppy)Pt(acac) (1) and (BNppy)Pt(acac) (2) as well as the designed complexes 3-6 were investigated by DFT and TD-DFT calculations, to reveal the influences of the functional ligands on charge injection ability and phosphorescence efficiency of emitters. It is found that compared with electron acceptor complex 1, complexes 2-6 have lower ionization potentials and comparable high electronic affinities, which are suited for bipolar luminescent materials. The results also demonstrated that Bppy complexes 1, 5 and 6 have more (3)MLCT compositions in T1 emitting states compared with BNppy complexes 2-4, which results in strong SOC and fast kr. Thus, the phosphorescence efficiency of 1 is higher than that of 2. In addition, 5 and 6 have the balanced charge transport and better hole injection ability when the hole-transporting ligand is incorporated to 1. Therefore, 5 and 6 can server as promising candidates for efficient multifunctional phosphorescent OLED emitters owing to their ambipolar characters, balanced charge carrier injection/transport features and high phosphorescence quantum efficiency.

Deep-red Emitting Ir(III) Complexes as Type-I Photosensitizers for Lipid Droplets Targeted Photodynamic Therapy.

Photodynamic therapy (PDT) relying on photosensitizer-induced production of reactive oxygen species (ROS) for killing cancer cells has emerged as a non-invasive anti-cancer strategy. Compared with oxygen-dependent type-II photosensitizers (PSs) for PDT, the development of intrinsic oxygen-independent type-I ones is highly desired but remains a challenge. In this work, two netural Ir(III) complexes that can produce type-I reactive oxygen species, namely MPhBI-Ir-BIQ (Ir-1) and NPhBI-Ir-BIQ (Ir-2), were synthesized. Bright deep-red emitting nanoparticles with moderate particle size are beneficial for imaging-guided PDT. In in vitro experiments, importantly, the excellent biocompatibility, the targeting of lipid droplets (LDs), and the type-I ⋅OH and O2 ⋅- generation promoted effective photodynamic activity. This work will guide the building of type-I Ir(III) complexes PSs and can provide advantages for potential clinical applications under hypoxic conditions.

AIE-active Ir(III) complexes as type-I dominant photosensitizers for efficient photodynamic therapy.

The ability of a photosensitizer (PS) to generate reactive oxygen species (ROS) including type I oxygen free radicals and type II 1O2 is pivotal for photodynamic therapy. Luminescent Ir(III) complexes are effective PSs with high 1O2 generation ability owing to their high intersystem crossing ability and effective energy transfer to 3O2. However, so far, reports on type I ROS based on ˙OH generation induced by Ir(III) PS are still rare. In this work, four novel aggregation-induced emission (AIE)-active Ir(III) PSs, namely MFIriqa, MFIrqa, SFIriqa, and SFIrqa have been designed and synthesized, which show highly efficient emission in the aggregated state. Cell imaging experiment results indicate that all four Ir(III) PSs can effectively improve the signal-to-noise ratio of imaging by reducing the interference from the background due to their fascinating AIE properties. Importantly, in vitro, Ir(III) PSs MFIrqa, SFIriqa, and SFIrqa nanoparticles show obvious photodynamic activity toward cancer cells upon irradiation accompanied by type I ˙OH generation, which may be attributed to the unique excited-state characteristics of Ir(III) complexes. This work will provide guidance for the construction of a type I photosensitizer based on the AIE-active Ir(III) complex, which offers great advantages for potential clinical applications under hypoxic conditions.

Chiral self-sorting and guest recognition of porous aromatic cages.

The synthesis of ultra-stable chiral porous organic cages (POCs) and their controllable chiral self-sorting at the molecular and supramolecular level remains challening. Herein, we report the design and synthesis of a serial of axially chiral porous aromatic cages (PAC 1-S and 1-R) with high chemical stability. The theoretical and experimental studies on the chiral self-sorting reveal that the exclusive self-recognition on cage formation is an enthalpy-driven process while the chiral narcissistic and self-sorting on supramolecular assembly of racemic cages can be precisely regulated by π-π and C-H…π interactions from different solvents. Regarding the chemical stability, the crystallinity of PAC 1 is maintained in aqueous solvents, such as boiling water, high-concentrated acid and alkali; mixtures of solvents, such as 1 M H2SO4/MeOH/H2O solution, are also tolerated. Investigations on the chiral sensing performance show that PAC 1 enables enantioselective recognition of axially chiral biaryl molecules.

An unprecedented fully reduced {MoV 60} polyoxometalate: from an all-inorganic molecular light-absorber model to improved photoelectronic performance.

Fully reduced polyoxometalates are predicted to give rise to a broad and strong absorption spectrum, suitable energy levels, and unparalleled electronic and optical properties. However, they are not available to date. Here, an unprecedented fully reduced polyoxomolybdate cluster, namely Na8[MoV 60O140(OH)28]·19H2O {MoV 60}, was successfully designed and obtained under hydrothermal conditions, which is rare and is the largest fully reduced polyoxometalate reported so far. The MoV 60 molecule describes one Keggin {ε-Mo12} encapsulated in an unprecedented {Mo24} cage, giving rise to a double truncated tetrahedron quasi-nesting architecture, which is further face-capped by another four {Mo6} tripods. Its crystalline stability in air, solvent tolerance, and photosensitivity were all shown. As a cheap and robust molecular light-absorber model possessing wide light absorption, MoV 60 was applied to build a co-sensitized solar cell photoelectronic device along with N719 dyes and the optimal power conversion efficiency was 28% higher than that of single-dye sensitization. These results show that MoV 60 polyoxometalate could serve as an ideal model for the design and synthesis of all-inorganic molecular light-absorbers for other light-driven processes in the future.

Molecular engineering to achieve AIE-active photosensitizers with NIR emission and rapid ROS generation efficiency.

Near-infrared (NIR) photosensitizers with rapid reactive oxygen species (ROS) production ability are in great demand owing to their promising performance toward boosting photodynamic therapy (PDT) and deep-tissue imaging, but molecular design guidelines for efficient photosensitizers are rarely elucidated. Herein, three AIEgens named DBP, TBP, and TBP-SO3 are designed and synthesized by precise donor-acceptor (D-A) molecular engineering to deeply understand the structure-property-application relationships. All the compounds exhibit AIE characteristics with strong long-wavelength emission in the aggregated state and are capable of efficiently producing ROS under white light irradiation. By controlling the ability of the D-A units, TBP-SO3 realizes NIR emission and more rapid ROS generation ability due to the promoted intersystem crossing processes compared with those of DBP and TBP. In addition, NIR-emitting TBP-SO3 is capable of specific endoplasmic reticulum targeting and excellent PDT treatment ability of cancer cells and bacteria. This successful example of molecular engineering paves a valuable way for developing advanced PSs with AIE properties, efficient ROS generation ability, and intense emission for fluorescence imaging PDT.

Self-cleaning wearable masks for respiratory infectious pathogen inactivation by type I and type II AIE photosensitizer.

Although face masks as personal protective equipment (PPE) are recommended to control respiratory diseases with the on-going COVID-19 pandemic, improper handling and disinfection increase the risk of cross-contamination and compromise the effectiveness of PPE. Here, we prepared a self-cleaning mask based on a highly efficient aggregation-induced emission photosensitizer (TTCP-PF6) that can destroy pathogens by generating Type I and Type II reactive oxygen species (ROS). The respiratory pathogens, including influenza A virus H1N1 strain and Streptococcus pneumoniae (S. pneumoniae) can be inactivated within 10 min of ultra-low power (20 W/m2) white light or simulated sunlight irradiation. This TTCP-PF6-based self-cleaning strategy can also be used against other airborne pathogens, providing a strategy for dealing with different microbes.

Dynamic Interface with Enhanced Visible-Light Absorption and Electron Transfer for Direct Photoreduction of Flue Gas to Syngas.

The direct usage of CO2 in the flue gas to produce fuels or chemicals is of great significance from energy-saving and low-cost perspectives, yet it is still underexplored. Herein, we report the photoreduction of CO2 from the simulated industrial exhaust by synergistic catalysis of TEOA and a metal-free composite (COF1-g-C3N4) fabricated via covalently grafting COF1 with g-C3N4. The hydrogen bond interaction between TEOA and hydrazine units on COF1 is detected in diluted CO2, which leads to significantly enhanced light absorption in the whole visible-light region. Also, the photo-induced electrons undergo fast transfer from COF1 to g-C3N4. This kind of dynamic interface with enhanced light absorption and electron transfer effects promotes the photosynthetic yield of syngas to 165.6 µmol·g-1·h-1 with the use of simulated exhaust gas as a raw material directly. The photosynthetic yield of syngas ranks among the highest of known metal-free catalysts in diluted CO2. This work provides a general rule for designing efficient catalysts via a controlled catalytic interface and new insights into the role of TEOA in photochemical CO2 reduction.

Boosting the photodynamic therapy of near-infrared AIE-active photosensitizers by precise manipulation of the molecular structure and aggregate-state packing.

Organic functional materials have emerged as a promising class of emissive materials with potential application in cancer phototheranostics, whose molecular structures and solid-state packing in the microenvironment play an important role in reactive oxygen species (ROS) generation and the photodynamic therapy (PDT) effect. Clarifying the guidelines to precisely modulate PDT performance from molecular and aggregate levels is desired but remains challenging. In this work, two compounds, TCP-PF6 and TTCP-PF6, with similar skeletons are strategically synthesized, in which a thiophene segment is ingeniously introduced into the molecular backbone of TCP-PF6 to adjust the intrinsic molecular characteristics and packing in the aggregate state. The experimental and theoretical results demonstrate that TTCP-PF6 can form tight packing mode in comparison with TCP-PF6, resulting in efficient cell imaging and enhanced ROS generation ability in vitro and in vivo. The promising features make TTCP-PF6 a superior photosensitizer for PDT treatment against cancer cells by targeting mitochondria. These findings can provide a feasible molecular design for modulating the biological activity and developing photosensitizers with high ROS generation and PDT effect.