High Open-Circuit Voltage Organic Solar Cells with 19.2% Efficiency Enabled by Synergistic Side-Chain Engineering

Restricted by the energy-gap law, state-of-the-art organic solar cells (OSCs) exhibit relatively low open-circuit voltage (VOC) because of large nonradiative energy losses (ΔEnonrad). Moreover, the trade-off between VOC and external quantum efficiency (EQE) of OSCs is more distinctive; the power conversion efficiencies (PCEs) of OSCs are still <15% with VOCs of >1.0 V. Herein, the electronic properties and aggregation behaviors of non-fullerene acceptors (NFAs) are carefully considered and then a new NFA (Z19) is delicately designed by simultaneously introducing alkoxy and phenyl-substituted alkyl chains to the conjugated backbone. Z19 exhibits a hypochromatic-shifted absorption spectrum, high-lying lowest unoccupied molecular orbital energy level and ordered 2D packing mode. The D18:Z19-based blend film exhibits favorable phase separation with face-on dominated molecular orientation, facilitating charge transport properties. Consequently, D18:Z19 binary devices afford an exciting PCE of 19.2% with a high VOC of 1.002 V, surpassing Y6-2O-based devices. The former is the highest PCE reported to date for OSCs with VOCs of >1.0 V. Moreover, the ΔEnonrad of Z19- (0.200 eV) and Y6-2O-based (0.155 eV) devices are lower than that of Y6-based (0.239 eV) devices. Indications are that the design of such NFA, considering the energy-gap law, could promote a new breakthrough in OSCs.

Sequentially Processed Bulk-Heterojunction-Buried Structure for Efficient Organic Solar Cells with 500 nm Thickness

Large-area printing fabrication is a distinctive feature of organic solar cells (OSCs). However, the advance of upscalable fabrication is challenged by the thickness of organic active layers considering the importance of both exciton dissociation and charge collection. In this work, a bulk-heterojunction-buried (buried-BHJ) structure is introduced by sequential deposition to realize efficient exciton dissociation and charge collection, thereby contributing to efficient OSCs with 500 nm thick active layers. The buried-BHJ distributes donor and acceptor phases in the vertical direction as charge transport channels, while numerous BHJ interfaces are buried in each phase to facilitate exciton dissociation simultaneously. It is found that buried-BHJ configurations possess efficient exciton dissociation and rapid charge transport, resulting in reduced recombination losses. In comparison with traditional structures, the buried-BHJ structure displays a decent tolerance to film thickness. In particular, a power conversion efficiency of 16.0% is achieved with active layers at a thickness of 500 nm. To the best of the authors' knowledge, this represents the champion efficiency of thick film OSCs.

Precise Methylation Yields Acceptor with Hydrogen-Bonding Network for High-Efficiency and Thermally Stable Polymer Solar Cells

Utilizing intermolecular hydrogen-bonding interactions stands for an effective approach in advancing the efficiency and stability of small-molecule acceptors (SMAs) for polymer solar cells. Herein, we synthesized three SMAs (Qo1, Qo2, and Qo3) using indeno[1,2-b]quinoxalin-11-one (Qox) as the electron-deficient group, with the incorporation of a methylation strategy. Through crystallographic analysis, it is observed that two Qox-based methylated acceptors (Qo2 and Qo3) exhibit multiple hydrogen bond-assisted 3D network transport structures, in contrast to the 2D transport structure observed in gem-dichlorinated counterpart (Qo4). Notably, Qo2 exhibits multiple and stronger hydrogen-bonding interactions compared with Qo3. Consequently, PM6 : Qo2 device realizes the highest power conversion efficiency (PCE) of 18.4 %, surpassing the efficiencies of devices based on Qo1 (15.8 %), Qo3 (16.7 %), and Qo4 (2.4 %). This remarkable PCE in PM6 : Qo2 device can be primarily ascribed to the enhanced donor-acceptor miscibility, more favorable medium structure, and more efficient charge transfer and collection behavior. Moreover, the PM6 : Qo2 device demonstrates exceptional thermal stability, retaining 82.8 % of its initial PCE after undergoing annealing at 65 °C for 250 hours. Our research showcases that precise methylation, particularly targeting the formation of intermolecular hydrogen-bonding interactions to tune crystal packing patterns, represents a promising strategy in the molecular design of efficient and stable SMAs.

High-Efficiency Binary and Ternary Organic Solar Cells Based on Novel Nonfused-Ring Electron Acceptors

In this study, three nonfused-ring electron acceptors (2TT, 2TT-C6-F, and 2TT-C11-F) with the same steric hindrance groups (2,4,6-tripropylbenzene) are designed and synthesized and the impact of electron-withdrawing and lateral alkyl side chains on the performance of binary and ternary organic solar cells (OSCs) is explored. For the binary OSCs, 2TT-C11-F with IC-2F terminal groups and lateral undecyl side chains display a red shifted absorption spectrum and suitable energy levels, and the corresponding blend film exhibits appropriate phase separation and crystallinity. Thus, binary OSCs based on 2TT-C11-F achieve an impressive power conversion efficiency of 13.03%, much higher than the efficiencies of those based on 2TT (9.68%) and 2TT-C6-F (12.11%). In the ternary OSCs, 2TT with CC terminal groups and lateral hexyl side chains exhibit complementary absorption and cascade energy levels with a host binary system (D18:BTP-eC9-4F). Hence, the ternary OSCs based on 2TT achieve a remarkable efficiency of 19.39%, ranking among the highest reported values. The research yields comprehensive 2TT-series nonfused-ring electron acceptors, demonstrating their great potential for the fabrication of high-performance binary and ternary OSCs.

Atomically precise photothermal nanomachines

Interfacing molecular machines to inorganic nanoparticles can, in principle, lead to hybrid nanomachines with extended functions. Here we demonstrate a ligand engineering approach to develop atomically precise hybrid nanomachines by interfacing gold nanoclusters with tetraphenylethylene molecular rotors. When gold nanoclusters are irradiated with near-infrared light, the rotation of surface-decorated tetraphenylethylene moieties actively dissipates the absorbed energy to sustain the photothermal nanomachine with an intact structure and steady efficiency. Solid-state nuclear magnetic resonance and femtosecond transient absorption spectroscopy reveal that the photogenerated hot electrons are rapidly cooled down within picoseconds via electron-phonon coupling in the nanomachine. We find that the nanomachine remains structurally and functionally intact in mammalian cells and in vivo. A single dose of near-infrared irradiation can effectively ablate tumours without recurrence in tumour-bearing mice, which shows promise in the development of nanomachine-based theranostics.

Halogenated Nonfused Ring Electron Acceptor for Organic Solar Cells with a Record Efficiency of over 17

Three nonfused ring electron acceptors (NFREAs), namely, 3TT-C2-F, 3TT-C2-Cl, and 3TT-C2, are purposefully designed and synthesized with the concept of halogenation. The incorporation of F or/and Cl atoms into the molecular structure (3TT-C2-F and 3TT-C2-Cl) enhances the π-π stacking, improves electron mobility, and regulates the nanofiber morphology of blend films, thus facilitating the exciton dissociation and charge transport. In particular, blend films based on D18:3TT-C2-F demonstrate a high charge mobility, an extended exciton diffusion distance, and a well-formed nanofiber network. These factors contribute to devices with a remarkable power conversion efficiency of 17.19%, surpassing that of 3TT-C2-Cl (16.17%) and 3TT-C2 (15.42%). To the best of knowledge, this represents the highest efficiency achieved in NFREA-based devices up to now. These results highlight the potential of halogenation in NFREAs as a promising approach to enhance the performance of organic solar cells.

High-Pressure Fabrication of Binary Organic Solar Cells with High Molecular Weight D18 Yields Record 19.65 % Efficiency

In this work, inspired by the principles of a pressure cooker, we utilized a high-pressure method to address the processing challenges associated with high molecular weight polymers. Through this approach, we successfully dissolved high molecular weight D18 in chloroform at 100 °C within a pressure-tight vial. The increased steam pressure raised the boiling point and dissolving capacity of chloroform, enabling the creation of a hybrid film with superior properties, including more ordered molecular arrangement, increased crystallinity, extended exciton diffusion length, and improved phase morphology. Organic solar cells (OSCs) based on D18 : L8-BO prepared using this high-pressure method achieved an outstanding power conversion efficiency of 19.65 %, setting a new record for binary devices to date. Furthermore, this high-pressure method was successfully applied to fabricate OSCs based on other common systems, leading to significant enhancements in device performance. In summary, this research introduces a universal method for processing high molecular weight D18 materials, ultimately resulting in the highest performance reported for binary organic solar cells.

Nickel(II) Phototheranostics: A Case Study in Photoactivated H2O2-Enhanced Immunotherapy

Phototheranostics have emerged as a promising subset of cancer theranostics owing to their potential to provide precise photoinduced diagnoses and therapeutic outcomes. However, the design of phototheranostics remains challenging due to the nature of tumors and their microenvironment, including limitations to the oxygen supply, high rates of recurrence and metastasis, and the immunosuppressive state of cancer cells. Here we report a dual-functional oxygen-independent phototheranostic agent, Ni-2, rationally designed to provide a near-infrared (NIR) photoactivated thermal- and hydroxyl radical (•OH)-enhanced photoimmunotherapeutic anticancer response. Under 880 nm laser irradiation, Ni-2 exhibited high photostability and excellent photoacoustic and photothermal effects with a photothermal conversion efficacy of 58.0%, as well as novel photoredox features that allowed the catalytic conversion of H2O2 to •OH upon photooxidation of Ni(II) to Ni(III). As a multifunctional photoagent, Ni-2 was found not only to inhibit tumor growth in a CT26 tumor-bearing mouse model but also to activate an immune response via a combination of photothermal- and H2O2-induced effects. When combined with an antiprogrammed death-ligand 1 (aPD-L1), Ni-2 treatment allowed for the suppression of distant tumor growth and cancer metastasis. Collectively, the present results provide support for the proposition that Ni-2 or its analogues could emerge as useful tools for photoimmunotherapy. They also highlight the potential of appropriately designed 3d transition metal complexes as "all- in-one" phototheranostics.

Improving the Performance of Layer-by-Layer Organic Solar Cells by n-Doping of the Acceptor Layer

Molecular dopants can effectively improve the performance of organic solar cells (OSCs). Here, PM6/BTP-eC9-4Cl-based OSCs are fabricated by a layer-by-layer (LbL) deposition method, and the electron acceptor BTP-eC9-4Cl layer is properly doped by n-type dopant benzyl viologen (BV) or [4-(1,3-dimethyl-2,3-dihydro-1H-benzoimidazol-2-yl)phenyl]dimethyl-amine (N-DMBI-H). The power conversion efficiency (PCE) of OSCs increases from 16.80 to 17.61 or 17.84% when the acceptor layer is doped by BV (0.01 wt %) or N-DMBI-H (0.01 wt %), respectively. At the optimal doping concentration, the device exhibits more balanced charge transport, fewer bimolecular recombinations, faster charge separation and transfer, and better stability. This doping strategy has good universality; when the acceptor layer L8-BO of LbL OSCs is doped by 0.01 wt % BV or 0.01 wt % N-DMBI-H, the PCE increases from 17.49 to 18.35 or 18.25%, respectively. All in all, our studies have demonstrated that the doping strategy is effective in enhancing the performance of OSCs.

Organic Solar Cells with Over 19% Efficiency Enabled by a 2D-Conjugated Non-Fullerene Acceptor Featuring Favorable Electronic and Aggregation Structures

The π-expansion of non-fullerene acceptors is a promising method for boosting the organic photovoltaic performance by allowing the fine-tuning of electronic structures and molecular packing. In this work, highly efficient organic solar cells (OSCs) are fabricated using a 2D π-expansion strategy to design new non-fullerene acceptors. Compared with the quinoxaline-fused cores of AQx-16, the π-expanded phenazine-fused cores of AQx-18 induce more ordered and compact packing between adjacent molecules, affording an optimized morphology with rational phase separation in the blend film. This facilitates efficient exciton dissociation and inhibited charge recombination. Consequently, a power conversion efficiency (PCE) of 18.2% with simultaneously increasing Voc , Jsc , and fill factor is achieved in the AQx-18-based binary OSCs. Significantly, AQx-18-based ternary devices fabricated via a two-in-one alloy acceptor strategy exhibit a superior PCE of 19.1%, one of the highest values ever reported for OSCs, along with a high Voc of 0.928 V. These results indicate the importance of the 2D π-expansion strategy for the delicate regulation of the electronic structures and crystalline behaviors of the non-fullerene acceptors to achieve superior photovoltaic performance, aimed at significantly promoting further development of OSCs.

Intramolecular and Intermolecular Interaction Switching in the Aggregates of Perylene Diimide Trimer: Effect of Hydrophobicity

The research on perylene diimide (PDI) aggregates effectively promotes their applications in organic photovoltaic solar cells and fluorescent sensors. In this paper, a PDI fabricated with three peripheral PDI units (N, N’-bis(6-undecyl) perylene-3,4,9,10-bis(dicarboximide)) is investigated. The trimer shows different absorption and fluorescence properties due to hydrophobicity when dissolved in the mixed solvent of tetrahydrofuran (THF) and water. Through comprehensive analysis of the fluorescence lifetime and transient absorption spectroscopic results, we concluded that the trimer underwent different excited state kinetic pathways with different concentrations of water in THF. When dissolved in pure THF solvent, both the intramolecular charge-transfer and excimer states are formed. When the water concentration increases from 0 to 50% (v/v), the formation time of the excimer state and its structural relaxation time are prolonged, illustrating the arising of the intermolecular excimer state. It is interesting to determine that the probability of the intramolecular charge-transfer pathway will first decrease and then increase as the speed of intermolecular excimer formation slows down. The two inflection points appear when the water concentration is above 10% and 40%. The results not only highlight the importance of hydrophobicity on the aggregate properties of PDI multimers but also guide the further design of PDI-based organic photovoltaic solar cells.

Charge Transport Dynamics of Quasi-Type II Perovskite Janus Nanocrystals in High-Performance Photoconductors

CsPbBr₃-Pb₄S₃Br₂ Janus nanocrystals (NCs) are the only nanomaterial where the epitaxial structure of perovskite and chalcogenide materials has been realized at the nanoscale, but their exciton dynamics mechanism has not yet been thoroughly investigated or applied in photodetection applications. This work reports an attractive device performance of perovskite photoconductors based on epitaxial CsPbBr₃-Pb₄S₃Br₂ Janus NCs, as well as the carrier relaxation and transfer mechanism of the heterojunction. By a combination of transient optical absorption and quantum dynamics simulation, it is demonstrated that the photogenerated holes on CsPbBr₃ can be successfully extracted by Pb₄S₃Br₂, while the hole transfer proceeds about three times faster than energy loss and remains "hot" for about 300 fs. This feature has favorable effects on long-range charge separation and transport; therefore, the Janus NCs photoconductors exhibit an exceptional responsivity of 34.0 A W^-1 and specific detectivity of 1.26 × 10¹⁴ Jones.

High-Performance Nonfused Ring Electron Acceptors with V-Shaped Side Chains

Motivated by simplifying the synthesis of nonfullerene acceptor and establishing the relation between molecular structure and photovoltaic performance, two isomeric nonfused ring electron acceptors (o-TT-Cl and m-TT-Cl), whose properties can be adjusted by changing the side chains, are designed and synthesized with several high-yield steps. o-TT-Cl with V-shaped side chain induces a dominated J-aggregation and displays much better solubility and more ordered packing than m-TT-Cl with linear side chain. Thus, the o-TT-Cl-based blend film generates better phase morphology and charge transport than m-TT-Cl-based one. Finally, the power conversion efficiency of o-TT-Cl-based devices is 12.84%, which is much higher than that of m-TT-Cl-based ones (6.54%). This work highlights the importance of side chains engineering on improving photovoltaic performance of nonfused ring electron acceptors.

Ultrafast Carrier Dynamics of Non-fullerene Acceptors with Different Planarity: Impact of Steric Hindrance

Most high-performance non-fullerene acceptors are of the acceptor-donor-acceptor (A-D-A)-type structure. Under photoexcitation, the intramolecular charge transfer effect on the A-D-A framework results in a large dipole moment change, facilitating the efficient generation of charge carriers. Achieving more efficient intramolecular charge transfer by adjusting the molecular structure is one of the current research ideas. Recently, we found that the power conversion efficiency can be improved from 4.41 to 13.13% by tuning the planarity of the non-fused ring electron acceptor backbone through steric hindrance of lateral substituents. We found that the planar backbone can effectively improve the intramolecular charge transfer, which has a great influence on the power conversion efficiency of the device. Our results demonstrate that charge transfer dynamics can be controlled by optimizing steric hindrance, which plays a crucial role in the photovoltaic performance of organic solar cells.

Molecular-Shape-Controlled Nonfused Ring Electron Acceptors for High-Performance Organic Solar Cells with Tunable Phase Morphology

Two nonfused ring electron acceptors (NFREAs), BTh-OC8-2F and DTh-OC8-2F, with different molecular shapes are designed and synthesized. Both acceptors can form planar molecular shapes by the assistance of S···O intramolecular interactions. Differently, BTh-OC8-2F, with a linear molecular backbone and two trans-arranged side chains at the core unit, exhibits much stronger crystallinity than DTh-OC8-2, with a C-shape molecular shape and two cis-arranged steric side chains at the core unit. Thus, the DTh-OC8-2F based blend film displays a better nanoscale phase separation, more suppressed charge recombination, more efficient exciton dissociation, and lower nonradiative energy loss. Organic solar cells based on DTh-OC8-2F can deliver a power conversion efficiency of 14.13%, which is much higher than BTh-OC8-2F based ones (11.95%) and is also one of the highest values reported for organic solar cells based on NFREAs.

Designing High-Performance Nonfused Ring Electron Acceptors via Synergistically Adjusting Side Chains and Electron-Withdrawing End-Groups

Three nonfused ring electron acceptors, Hexyl-0F, Isopropyl-0F, and Isopropyl-2F, are designed and synthesized. Unlike Hexyl-0F, Isopropyl-0F with two sterically hindered 2,4,6-triisopropyl-phenyl groups is highly soluble, which provides a good opportunity for solution processability. Compared with Isopropyl-0F, Isopropyl-2F with fluorinated end-groups exhibits red-shifted absorption. Due to these synergistic adjustment, Isopropyl-2F-based devices displayed a high power conversion efficiency of 12.55%, higher than that of Isopropyl-0F (9.49%). The result demonstrates that the introduction of large steric substituents in the π-bridge units and electron-withdrawing end-groups plays a positive role in the construction of high-efficiency nonfused ring electron acceptors.

Nonaromatic Organonickel(II) Phototheranostics

Earth-abundant metal-based theranostics, agents that integrate diagnostic and therapeutic functions within the same molecule, may hold the key to the development of low-cost personalized medicines. Here, we report a set of O-linked nonaromatic benzitripyrrin (C^N^N^N) macrocyclic organonickel(II) complexes, Ni-1-4, containing strong σ-donating M-C bonds. Complexes Ni-1-4 are characterized by a square-planar coordination geometry as inferred from the structural studies of Ni-1. They integrate photothermal therapy, photothermal imaging, and photoacoustic imaging (PAI) within one system. This makes them attractive as potential phototheranostics. Relative to traditional Ni(II) porphyrins, such as F₂₀TPP (tetrapentafluorophenylporphyrin), the lowest energy absorption of Ni-1 is shifted into the near infrared region, presumably as a consequence of Ni-C bonding. Ultrafast transient absorption spectroscopy combined with theoretical calculations revealed that, upon photoexcitation, a higher population of ligand-centered and ³MLCT states is seen in Ni-1 relative to NiTPBP (TPBP = 6,11,16,21-tetraphenylbenziporphyrin). Encapsulating Ni-1 in 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N-[methoxy(polyethylene glycol)-2000] (DSPE-PEG₂₀₀₀) afforded nanoparticles, Ni-1@DSPE, displaying red-shifted absorption features, as well as good photothermal conversion efficiency (∼45%) in aqueous media. Proof-of-principle experiments involving thrombus treatment were carried out both in vitro and in vivo. It was found that Ni-1@DSPE in combination with 785 nm photo-irradiation for 3 min (0.3 W/cm²) proved successful in removing blood clots from a mouse thrombus model as monitored by photoacoustic imaging (PAI). The present work highlights the promise of organonickel(II) complexes as potential theranostics and the benefits that can accrue from manipulating the excited-state features of early transition-metal complexes via, for example, interrupting π-conjugation pathways.

Chlorination Enabling a Low-Cost Benzodithiophene-Based Wide-Bandgap Donor Polymer with an Efficiency of over 17

Three regioregular benzodithiophene-based donor-donor (D-D)-type polymers (PBDTT, PBDTT1Cl, and PBDTT2Cl) are designed, synthesized, and used as donor materials in organic solar cells (OSCs). Because of the weak intramolecular charge-transfer effect, these polymers exhibit large optical bandgaps (>2.0 eV). Among these three polymers, PBDTT1Cl exhibits more ordered and closer molecular stacking, and its devices demonstrate higher and more balanced charge mobilities and a longer charge-separated state lifetime. As a result of these comprehensive benefits, PBDTT1Cl-based OSCs give a very impressive power conversion efficiency (PCE) of 17.10% with a low nonradiative energy loss (0.19 eV). Moreover, PBDTT1Cl also possesses a low figure-of-merit value and good universality to match with different acceptors. This work provides a simply and efficient strategy to design low-cost high-performance polymer donor materials.

Control of the Surface Disorder by Ion-Exchange to Achieve High Open-Circuit Voltage in HC(NH2 )2 PbI3 Perovskite Solar Cell

The ionic nature of organic trihalide perovskite leads to structural irregularity and energy disorder at the perovskite surface, which seriously affects the photovoltaic performance of perovskite solar cells. Here, the origin of the perovskite surface disorder is analyzed, and a facial ion-exchange strategy is designed to regulate the surface chemical environment. By the reconstruction of terminal irregular Pb-I bonds and random cations, the repaired surface is characteristic of the reduced band tail states, consequent to the suppression of the uplift of quasi-Fermi level splitting and photocarrier scattering. The optimized device gets a high open-circuit voltage and operational stability. These findings fully elaborate the underlying mechanism concerning perovskite surface problem, giving guidance on tailoring the energy disorder.

Metal Modulation: An Easy-to-Implement Tactic for Tuning Lanthanide Phototheranostics

Phototheranostics constitute an emerging cancer treatment wherein the core diagnostic and therapeutic functions are integrated into a single photosensitizer (PS). Achieving the full potential of this modality requires being able to tune the photosensitizing properties of the PS in question. Structural modification of the organic framework represents a time-honored strategy for tuning the photophysical features of a given PS system. Here we report an easy-to-implement metal selection approach that allows for fine-tuning of excited-state energy dissipation and phototheranostics functions as exemplified by a set of lanthanide (Ln = Gd, Yb, Er) carbazole-containing porphyrinoid complexes. Femto- and nanosecond time-resolved spectroscopic studies, in conjunction with density functional theory calculations, revealed that the energy dissipation pathways for this set of PSs are highly dependent on the energy gap between the lowest triplet excited state of the ligand and the excited states of the coordinated Ln ions. The Yb complex displayed a balance of deactivation mechanisms that made it attractive as a potential combined photoacoustic imaging and photothermal/photodynamic therapy agent. It was encapsulated into mesoporous silica nanoparticles (MSN) to provide a biocompatible construct, YbL@MSN, which displays a high photothermal conversion efficiency (η = 45%) and a decent singlet oxygen quantum yield (Φ_Δ = 31%). Mouse model studies revealed that YbL@MSN allows for both photoacoustic imaging and synergistic photothermal- and photodynamic-therapy-based tumor reduction in vivo. Our results lead us to suggest that metal selection represents a promising approach to fine-tuning the excited state properties and functional features of phototheranostics.

Regulating the Packing of Non-Fullerene Acceptors via Multiple Noncovalent Interactions for Enhancing the Performance of Organic Solar Cells

Three noncovalently fused-ring electron acceptors (FOC6-IC, FOC6-FIC, and FOC2C6-2FIC) are synthesized. Single crystals of FOC6-IC and FOC2C6-2FIC are prepared, and structure analyses reveal that the molecular backbone can be planarized via the formation of the intramolecular noncovalent interactions. These acceptor molecules can be packed closely in the solid state via π-π stacking and static interactions between the central phenylene unit and the terminal group with a distance of 3.3-3.4 Å. Besides, multiple intermolecular noncovalent interactions can be observed in the single crystal structure of the fluorinated acceptor FOC2C6-2FIC, which help increase the crystallinity of acceptors and the charge mobility of the blends. Photovoltaic devices based on FOC2C6-2FIC give a power conversion efficiency of 12.36%, higher than 12.08% for FOC6-FIC and 10.80% for FOC6-IC.

Unusual near infrared (NIR) fluorescent palladium(ii) macrocyclic complexes containing M-C bonds with bioimaging capability

Near infrared (NIR) luminescent metal complexes are promising probes in bioimaging and biosensing, however they generally suffer from oxygen interference arising from heavy metal effects. We designed new tetradentate macrocyclic benzitripyrrin (C^N^N^N) ligands by combination of M-C bond formation and reducing the π-conjugation to achieve NIR fluorescent Pd complexes (700-1000 nm) with quantum yields up to 14%. To understand the origin of NIR fluorescence, detailed analyses by density functional theory/time-dependent density functional theory (DFT/TDDFT) calculations together with femtosecond and nanosecond transient absorption spectroscopies suggest that M-C bond formation indeed leads to destabilization of the d-d excited state and less effective quenching of emission; and importantly, small spin-orbital coupling (SOC) and the large singlet-triplet energy gap are the primary causes of the non-population of triplet states. Comparison of PdII and PtII analogues shows that the non-radiative channel of the out-plane vibration of the tripyrrin plane effectively quenches the fluorescence of the PtII complex but not the PdII congener. We also demonstrate the proof-of-concept applications of PdII complexes (Pd-1 and Pd-3) encapsulated in silica nanoparticles, in both in vitro and in vivo bioimaging experiments without oxygen interference. Moreover, pH-induced reversible switching of NIR fluorescence was achieved even intracellularly using the Pd complex (Pd-2), which shows the potential to further develop perspective stimuli-responsive NIR materials.

Statin-induced apoptosis of vascular endothelial cells is blocked by dexamethasone

Statins block de novo synthesis of cholesterol by inhibiting the enzyme, HMG CoA reductase. The product of this reaction, mevalonic acid, is also a precursor of isoprenoids, molecules required for the activation of signalling G-proteins, such as Ras. Signal transduction pathways involving Ras are important for cell survival and this may be why statins induce apoptotic death of several cell types. Given that statins are used to treat vascular disease, it is surprising that no studies have been conducted on vascular endothelial cells. For this reason, we have tested the effect of fluvastatin (FS) on the endothelial cell line EA.hy 926. Here we show that FS, at concentrations from 1 to 2 microM, blocks growth and induces apoptosis of the endothelial cell line, EA.hy 926. As considerable redundancy exists in cell signalling pathways for cell survival, toxicity of FS under more physiological conditions might be prevented by pathways that do not require Ras, such as those activated by adrenal or sex steroids. To test this hypothesis, first RT-PCR analysis was performed for nuclear receptor mRNA expression. This revealed the presence of mRNA for the androgen receptor (AR) and glucocorticoid receptor (GR). The effect of the AR agonist, dihydrotestosterone (DHT), and the GR agonist, dexamethasone (Dex), was then tested. Whilst DHT (100 nM) had no effect on FS-induced cell death, Dex (1 microM) blocked FS-induced apoptosis. Cell cycle analysis revealed that 24 h exposure to FS prevented cells from leaving G(1) and 24-48 h later a marked sub-G(1) peak was observed. Dex was able to reduce the sub-G(1) peak, but it failed to reduce accumulation of cells in G(1). Further studies revealed that, in addition to blocking FS-induced apoptosis, Dex was able to block apoptosis of EA.hy 926 cells induced by serum deprivation, tumour necrosis factor-alpha, oxidants, DNA damage and mitochondrial disruption. This study strongly suggests that glucocorticoids have a role to play in preventing vascular injury and they may provide a reason why statins are apparently not toxic to vascular endothelial cells in vivo.

[Reversed-phase high performance liquid chromatographic determination of propofol in human plasma]

An RP-HPLC method is described for the assay of propofol (2,6-diisopropylphenol), a new anesthesia drug, in human plasma. Protein in sample was precipitated with methanol, followed by extraction of propofol with cyclohexane. Both propofol and the internal standard thymol were derivatized with Gibbs' reagent and then chromatographed on an ODS column (Ultrasphere, 250 mm x 4.6 mm i.d.) with a mobile phase of acetonitrile-water-trifluoroacetic acid (80:20:0.1) and UV detection at 276 nm. The detectable limit of propofol was 24.8 microg/L (S/N>2) and calibration curves were linear between 50 to 1500 microg/L (r=0.9991). The average coefficient of variation was 6.1%.