Comparison of biportal endoscopic technique and uniportal endoscopic technique in Unilateral Laminectomy for Bilateral Decomprssion (ULBD) for lumbar spinal stenosis.

OBJECTIVE: Unilateral laminotomy for bilateral decompression (ULBD) has been adopted widely to treat lumbar spinal stenosis (LSS). The objective of the study is to investigate clinical and radiological outcomes of the biportal endoscopic ULBD (BE-ULBD) and uniportal endoscopic ULBD (UE-ULBD). METHODS: We collected retrospectively 65 patients' data who met the inclusion criteria (July 2019-June 2021). 33 patients underwent BE-ULBD surgery, and 32 patients underwent the UE-ULBD surgery, and were followed up for at least 1 year. The following preoperative and postoperative outcomes were compared between groups: the visual analog scale (VAS) for pain, the Oswestry disability index (ODI) for nerve function, and modified Macnab criteria for satisfaction, the cross-sectional area of the dural sac (DSCSA), the mean angle of facetectomy. RESULTS: Age, BMI, gender, levels of involvement and duration of symptoms were not significantly different at baseline in this study. Clinical data showed that postoperative ODI, VAS scores and Modified Macnab Criteria were not statistically different between the two groups. The BE-ULBD group had a shorter operation time than the UE-ULBD group (P < 0.001). Patients in the BE-ULBD group had a larger postoperative expansion of DSCSA expansion postoperatively (85.58 ± 3.16 mm2 VS 71.43 ± 3.35 mm2, P < 0.001) and a larger contralateral facetectomy angle (63.95 ± 3.34° vs 57.80 ± 3.43°, P < 0.001) compared with patients in the UE-ULBD group. There were no statistical differences in the incidence of postoperative complications between the two groups. CONCLUSION: Both the BE-ULBD and the UE-ULBD yielded clinical improvement in terms of pain and stenosis symptoms. The BE-ULBD technique has the advantages of the shorter operation time, larger DSCSA expansion and larger contralateral facetectomy angle.

[Clinical Effect of Unilateral Biportal Endoscopic Lumbar Interbody Fusion and Minimally Invasive Transforaminal Lumbar Interbody Fusion on Single-segment Lumbar Stenosis with Instability].

Objective To compare the early clinical effects of unilateral biportal endoscopic lumbar interbody fusion (ULIF) and minimally invasive transforaminal lumbar interbody fusion (MIS-TLIF)on single-segment lumbar stenosis with instability. Methods The patients who had single-segment lumbar spinal stenosis with instability and were treated in our hospital from August 2020 to May 2021 were selected.According to the operation methods,they were classified into ULIF group and MIS-TLIF group.The operation duration,hospital stay after operation,perioperative blood loss (drainage volume 48 h after operation,total blood loss),creatine kinase,inflammatory cytokines (C-reactive protein,interleukin-6),D-dimer,and the incidence of lower-extremity venous thrombosis were compared between the two groups.The visual analogue scale and Oswestry disability index were used to evaluate the functional recovery of the two groups in 1 week,1 month,and 3 months after operation. Results The ULIF group had longer operation duration (P<0.001) and shorter hospital stay after operation (P=0.022)than the MIS-TLIF group.The drainage volume 48 h after operation and total blood loss in ULIF group were lower than those in MIS-TLIF group (all P<0.001).The levels of creatine kinase (all P<0.001),C-reactive protein (P<0.001,P=0.002),and interleukin-6 (P=0.003,P<0.001) in ULIF group were lower than those in MIS-TLIF group on the 1st and 3rd day after operation.However,the D-dimer in ULIF group was insignificantly different from that in MIS-TLIF group on the 1st and 3rd day after operation (P=0.117,P=0.683).Lower-extremity venous thrombosis occurred in neither group.The score of visual analogue scale showed no significant difference between the two groups 1 week,1 month,and 3 months after operation (P=0.447,P=0.578,P=0.538),so did the Oswestry disability index (P=0.832,P=0.797,P=0.619). Conclusion ULIF shows similar clinical effect on single-segment lumbar stenosis with instability to MIS-TLIF,which features less bleeding,mild inflammation,mild muscle injury,but long operation duration.

Ni-Co bimetallic catalysts on coconut shell activated carbon prepared using solid-phase method for highly efficient dry reforming of methane.

Ni-Co bimetallic catalysts supported on coconut shell activated carbon are synthesized using solid-phase method and investigated for dry reforming of methane, to explore the impact of Ni:Co ratio on the catalyst activity and stability. The catalyst performances are evaluated under the temperature varying from 600 to 900 °C and gas hourly space velocity (GHSV) of 7200 mL/h·g-cat. The characterization results show that metal nanoparticles are produced on the support, and the bimetallic catalyst with an explicit Ni:Co ratio (2:1) is the most beneficial for metal particle dispersion and acquires the minimum particle size of 4.41 nm. The bimetallic catalysts with an explicit Ni:Co ratio of 1:2 and 1:1 exhibit a synergistic effect towards the conversions of CH4 and CO2, respectively. The experimental results reveal that the highest CH4 and CO2 conversions rise to 94.0% and 97.5% within 12 h at 900 °C on average, respectively, assisted with the two bimetallic catalysts. The intensity of disordered carbon and thermal stability are enhanced with the extension of reforming process, contributing to a long-term catalytic stability. Besides, no obvious carbon deposition is detected, leading to a highly catalytic stability for the bimetallic catalysts.

Extracellular vesicles derived from astrocytes facilitated neurite elongation by activating the Hippo pathway.

Spinal cord injury (SCI) often causes severe neurological dysfunction, and facilitating neurite elongation is particularly important in its treatment. Astrocytes (AS) play an important role in the central nervous system (CNS), and their high plasticity and versatility provide a feasible entry point for relevant research. Our purpose was to explore whether extracellular vesicles (EVs) from astrocytes (AS-EVs) and lipopolysaccharide (LPS)-preactivated astrocytes (LPAS-EVs) facilitate neurite elongation, to explore the underlying mechanism, and to verify whether these EVs promote locomotor recovery in rats. We used LPS to preactivate astrocytes and cocultured them with PC12 cells to observe neurite changes, then extracted and identified AS-EVs and LPAS-EVs and the role and mechanism of these EVs in facilitating neurite elongation was examined in vivo and vitro. We demonstrated that AS-EVs and LPAS-EVs facilitated the elongation of neurites and the recovery of rats with SCI. LPAS-EVs had a stronger effect than AS-EVs, by activating the Hippo pathway, promoting monopole spindle binding protein 1 (MOB1) expression, and reducing Yes-associated protein (YAP) levels. The data also suggest a feedback regulation between MOB1 and p-YAP/YAP. In sum, AS-EVs and LPAS-EVs can play an active role in facilitating neurite elongation by activating the Hippo pathway. These findings provide a new strategy for treating SCI and other CNS-related injuries.

Supramolecular Crystal Networks Constructed from Cucurbit[8]uril with Two Naphthyl Groups.

Naphthyl groups are widely used as building blocks for the self-assembly of supramolecular crystal networks. Host-guest complexation of cucurbit[8]uril (Q[8]) with two guests NapA and Nap1 in both aqueous solution and solid state has been fully investigated. Experimental data indicated that double guests resided within the cavity of Q[8], generating highly stable homoternary complexes NapA2@Q[8] and Nap12@Q[8]. Meanwhile, the strong hydrogen-bonding and π···π interaction play critical roles in the formation of 1D supramolecular chain, as well as 2D and 3D networks in solid state.

a-PET and Weakened Triplet-Triplet Annihilation Self-Quenching Effects in Benzo-21-Crown-7-Functionalized Diiodo-BODIPY.

Weakening the triplet-triplet annihilation (TTA) self-quenching effect induced by sensitizers remains a tremendous challenge due to the very few investigations carried out on them. Herein, benzo-21-crown-7 (B21C7)-functionalized 2,6-diiodo-1,3,5,7-tetramethyl-8-phenyl-4,4-difluoroboradiazaindacene (DIBDP) was synthesized to investigate the influences of huge bulks and electron-rich cavities of B21C7 moieties on the fluorescence emission and triplet-state lifetimes of DIBDP moieties. Density functional theory (DFT)/time-dependent DFT (TDDFT) computable results preliminarily predicted that B21C7 moieties had influences on the fluorescence emissions of DIBDP moieties but not on their localization of triplet states of B21C7-functionalized DIBDP (B21C7-DIBDP). The UV-vis absorption spectra, fluorescence emission spectra, and cyclic voltammograms verified that there was an electron-transfer process from the B21C7 moiety to the DIBDP moiety in B21C7-DIBDP. However, the calculated results of ΔG CS and E CS values and nanosecond time-resolved transient absorption spectra demonstrated that the electron-transfer process from the B21C7 moiety to the DIBDP moiety in B21C7-DIBDP had direct influences on the fluorescence emission of DIBDP moieties but not on the triplet states of DIBDP moieties. The experimental values of triplet-state lifetimes of B21C7-DIBDP were obviously longer than those of DIBDP at a high concentration (1.0 × 10-5 M); however, the fitted values of intrinsic triplet-state lifetimes of B21C7-DIBDP were slightly greater than those of DIBDP in the same solvent. These results demonstrated that the steric hindrance of B21C7 moieties could weaken the TTA self-quenching effect of DIBDP moieties at a high concentration and the a-PET effect induced a proportion of the produced singlet states of DIBDP moieties and could not emit fluorescence in the form of radiation transition but they could be transformed into triplet states through intersystem crossing (ISC) processes due to the iodine atoms in the DIBDP moiety. The stronger a-PET effects in polar solvents induced smaller fluorescence quantum yields so that more singlet states of DIBDP moieties were transformed into triplet states to weaken the TTA self-quenching effects.

Highly stable halide perovskite with Na incorporation for efficient photocatalytic degradation of organic dyes in water solution.

To overcome water instability and low photocatalytic activity of lead-free halide perovskite for the degradation of organic dyes, we report a novel photocatalyst of lead-free halide perovskite with Na incorporation and employ it for the photocatalytic degradation of organic dyes in water solution under visible light irradiation. The main purpose of this work is to confirm the feasibility of lead-free halide perovskite with Na incorporation for improving the photocatalytic efficiency and recyclability in water solution and further to explore the mechanism behind the enhancement of photocatalytic performance after Na incorporation. The results show that Cs2Ag0.60Na0.40InCl6 can increase the dye degradation rate by at least 50% than the lead-free halide perovskite (Cs2AgInCl6) and the photocatalyst of Ag substituted by Na (Cs2NaInCl6). The degradation efficiency of rhodamine 6G catalyzed by Cs2Ag0.60Na0.40InCl6 reaches 94.94% over 60 min, which is 72% higher than that catalyzed by Cs2NaInCl6 and 27% higher than that catalyzed by Cs2AgInCl6. What's more, the degradation efficiency of methyl orange catalyzed by Cs2Ag0.60Na0.40InCl6 is 90.39% within 150 min, which is 66% higher than that catalyzed by Cs2NaInCl6 and 54% higher than that catalyzed by Cs2AgInCl6. Moreover, the photocatalyst of Cs2Ag0.60Na0.40InCl6 exhibits a desirable recyclability by water exposure, retaining the degradation efficiency over 90% after five cycles. The strengthened photocatalytic performance in the presence of Cs2Ag0.60Na0.40InCl6 is ascribed to an increase of radiative recombination rate and an improvement of average lifetime to 204 ns since an appropriate Na incorporation at the atomic ratio of Na/Ag=4:6 breaks the original crystal lattice and meanwhile increases the electron and hole overlap. The work proves a great potential of halide perovskite with Na incorporation for the highly efficient photocatalytic degradation of organic dyes in water solution.

Weakened Triplet-Triplet Annihilation of Diiodo-BODIPY Moieties without Influence on Their Intrinsic Triplet Lifetimes in Diiodo-BODIPY-Functionalized Pillar[5]arenes.

The triplet-triplet annihilation (TTA) effect of sensitizers themselves can lead to the additional quenching of lifetimes of triplet states; therefore, how to weaken the TTA effect of sensitizers is an urgent issue to be resolved for their further applications. Besides, it remains a tremendous challenge for constructing supramolecular systems of photosensitizers based on photosensitizer-functionalized pillararenes because there have been very few investigations on them. Thus, 2,6-diiodo-1,3,5,7-tetramethyl-8-phenyl-4,4-difluoroboradiazaindacene (DIBDP) and ethoxy pillar[5]arene (EtP5) were utilized to synthesize a DIBDP-functionalized pillar[5]arene (EtP5-DIBDP), a cyano-containing DIBDP (G) used as a guest molecule was also prepared, and they were used to investigate the electron-transfer mechanism between EtP5 and DIBDP moieties and weaken the TTA effect of DIBDP moieties. The theoretical computational results of frontier molecular orbitals and isosurfaces of spin density preliminarily predicted that the cavities of the EtP5 moiety had influence on the fluorescence emission of DIBDP units but not on their triplet states in EtP5-DIBDP. The fluorescence emission intensities in a variety of solvents with different polarities and electrochemical studies revealed that there was electron transfer from EtP5 to the DIBDP units, and the electron-transfer process had influence on the fluorescence emission but not on the triplet states of DIBDP moieties in EtP5-DIBDP, which verified the results of density functional theory calculations. The triplet state lifetimes of EtP5-DIBDP were longer than those of DIBDP and G and the photooxidation abilities of EtP5-DIBDP were better than those of DIBDP and G at a high concentration (1.0 × 10-5 M) in various solvents; in contrast, the intrinsic triplet state lifetimes and singlet oxygen quantum yields (ΦΔ) of DIBDP, G, and EtP5-DIBDP were very similar. This was because the steric hindrance of EtP5 moieties could weaken the TTA effect of DIBDP moieties without influencing their intrinsic triplet state lifetimes in EtP5-DIBDP.

Proanthocyanidin promotes functional recovery of spinal cord injury via inhibiting ferroptosis.

Improving the microenvironment of lesioned spinal cord to minimize the secondary injury is one important strategy to treat spinal cord injury (SCI). The ensuing hemorrhage after SCI has tight connection with ferroptosis. This study investigated the effects of proanthocyanidins (PACs) on SCI repair and the underlying mechanisms. Adult female mice were divided into four groups, including sham, SCI, PACs5 and PACs10 (i.p. 5 and 10 mg/kg PACs after SCI respectively). The impacts of SCI and PACs treatment on redox parameters (iron contents, TBARS, GSH, and GPX activities) and ferroptosis essential factors such as ACSL4, LPCAT3, Alox15B, Nrf2, HO-1, GPX4 were investigated. The results demonstrated that PACs treatment significantly decreased the levels of iron, TBARS, ACSL4, and Alox15B, while increased the levels of GSH, GPX4, Nrf2, and HO-1 in traumatic spinal cords. Above all, PACs improved the locomotive function of SCI mice. These results suggest that PACs might be potential therapeutics for SCI repair by inhibiting ferroptosis in SCI.

Highly Emissive Self-Assembled BODIPY-Platinum Supramolecular Triangles.

Light-emitting supramolecular coordination complexes (SCCs) have been widely studied for applications in the chemical and biological sciences. Herein, we report the coordination-driven self-assembly of two highly emissive platinum(II) supramolecular triangles (1 and 2) containing BODIPY-based bridging ligands. The metallacycles exhibit favorable anticancer activities against HeLa cells (IC50 of 6.41 and 2.11 µM). The characteristic ∼570 nm fluorescence of the boron dipyrromethene (BODIPY) moieties in the metallacycles permits their intracellular visualization using confocal microscopy. Additionally, the BODIPY fluorophore is an excellent photodynamic agent, making the metallacycles as ideal therapeutics for photodynamic therapy (PDT) and chemotherapy. In vitro studies demonstrate that the combination indexes against HeLa cells are 0.56 and 0.48 for 1 and 2, respectively, confirming their synergistic anticancer effect. More importantly, these SCCs also exhibit superior anticancer efficacy toward cisplatin-resistant A2780cis cell line by combining PDT and chemotherapy, showing promise in overcoming drug resistance. This study exploits a multicomponent approach to self-assembled metallacages that enables design of effective theranostic agents wherein the platinum acceptors are toxic chemotherapeutics and the BODIPY donors are imaging probes and photosensitizers. Since each piece may be independently tuned, i.e., Pt(II) polypyridyl fragment swapped for Pt(II) phosphine, the activity may be optimized without a total redesign of the system.

An AIEE fluorescent supramolecular cross-linked polymer network based on pillar[5]arene host-guest recognition: construction and application in explosive detection.

Here a novel fluorescent supramolecular cross-linked polymer network with aggregation induced enhanced emission (AIEE) properties was constructed via pillar[5]arene-based host-guest recognition. Furthermore, the supramolecular polymer network can be used for explosive detection in both solution and thin films.

Acid/Base-Controllable FRET and Self-Assembling Systems Fabricated by Rhodamine B Functionalized Pillar[5]arene-Based Host-Guest Recognition Motifs.

A novel supramolecular Föster resonance energy transfer (FRET) system was fabricated by utilizing rhodamine B (RB) functionalized pillar[5]arene (EtP5-RB) and cyano-modified boron dipyrromethene (BDP-CN) based on their host-guest recognition at 5.0 × 10-5 M, which could be turned "on" and "off" by adding trifluoroacetic acid (TFA) and triethylamine (TEA), respectively. At a higher concentration (1.0 × 10-4 M) in acetone, EtP5-RB self-assembled into vesicles while EtP5-RBH self-assembled into nanoribbons. After the addition of BDP-CN, both EtP5-RB⊃BDP-CN and EtP5-RBH⊃BDP-CN self-assembled into nanoparticles, which caused the fluorescence of the host-guest complexes to be quenched.

Effect of Calcium-sensing Receptor on the Apoptosis of Rat Spinal Cord Neurons in Anoxia/Reoxygenation Injury and Its Significance.

Objective To investigate the effect and significance of calcium-sensing receptor (CaSR) on the apoptosis of rat spinal cord neurons in anoxia/reoxygenation(A/R) injury. Methods The spinal cells were in ischemia and hypoxia environment for 1 h and in normal environment for 24 h to establish a model of A/R. After spinal A/R model was established,the spinal cells were divided into four groups randomly:the control group,A/R group,A/R+GdCl3 group,and A/R+NPS-2390 group. The expression of CaSR in each group was detected by immunofluorescence and Western blotting. The concentration of intracellular calcium was measured by laser confocal scanning microscopy. The expressions of Caspase-3,Bax,and Bcl-2 were detected by using Western blotting. The apoptotic rate of spinal cells was detected by Tunel assay. Results Compared to the control group, there was a significant increase in the level of CaSR (t=5.462, P=0.006), the concentration of intracellular calcium (t=8.573, P=0.001), the apoptotic rate (t=4.899, P=0.008), Caspase-3 (t=5.118, P=0.007), and Bax (t=10.930,P=0.001) in A/R group. Compared to the A/R group, there was a significant increase in the level of CaSR (t=4.975, P=0.008),the concentration of intracellular calcium (t=4.899, P=0.008), the apoptotic rate (t=7.746, P=0.002), Caspase-3 (t=4.776, P=0.009), and Bax (t=5.281, P=0.006) in A/R+GdCl3 group. Compared to the A/R group, there was a significant decrease in the level of CaSR (t=3.674,P=0.021), the concentration of intracellular calcium (t=3.846, P=0.018), the apoptotic rate (t=4.281,P=0.013), Caspase-3 (t=3.521, P=0.024), and Bax(t=3.473, P=0.026) in A/R+NPS-2390 group. However, compared to the control group, there was a significant decrease in the level of Bcl-2 (t=6.242,P=0.003) in A/R group. Compared to the A/R group, there was a significant decrease in the level of Bcl-2(t=3.028, P=0.004) in A/R+GdCl3 group. Compared to the A/R group, there was a significant increase in the level of Bcl-2 (t=2.840, P=0.047) in A/R+NPS-2390 group.Conclusion During the process of A/R injury in rat spinal cord neurons,the expression of calcium sensing receptor increases,along with increase in intracellular calcium and spinal neuron apoptosis.

Correlation Between Expression of High Temperature Requirement Serine Protease A1 (HtrA1) in Nucleus Pulposus and T2 Value of Magnetic Resonance Imaging.

BACKGROUND Degrading enzymes play an important role in the process of disc degeneration. The objective of this study was to investigate the correlation between the expression of high temperature requirement serine protease A1 (HtrA1) in the nucleus pulposus and the T2 value of the nucleus pulposus region in magnetic resonance imaging (MRI). MATERIAL AND METHODS Thirty-six patients who had undergone surgical excision of the nucleus pulposus were examined by MRI before surgery. Pfirrmann grading of the target intervertebral disc was performed according to the sagittal T2-weighted imaging, and the T2 value of the target nucleus pulposus was measured according to the median sagittal T2 mapping. The correlation between the Pfirrmann grade and the T2 value was analyzed. The expression of HtrA1 in the nucleus pulposus was analyzed by RT-PCR and Western blot. The correlation between the expression of HtrA1 and the T2 value was analyzed. RESULTS The T2 value of the nucleus pulposus region was 33.11-167.91 ms, with an average of 86.64±38.73 ms. According to Spearman correlation analysis, there was a rank correlation between T2 value and Pfirrmann grade (P<0.0001), and the correlation coefficient (rs)=-0.93617. There was a linear correlation between the mRNA level of HtrA1 and T2 value in nucleus pulposus tissues (a=3.88, b=-0.019, F=112.63, P<0.0001), normalized regression coefficient=-0.88. There was a linear correlation between the expression level of HtrA1 protein and the T2 value in the nucleus pulposus tissues (a=3.30, b=-0.016, F=93.15, P<0.0001) and normalized regression coefficient=-0.86. CONCLUSIONS The expression of HtrA1 was strongly related to the T2 value, suggesting that HtrA1 plays an important role in the pathological process of intervertebral disc degeneration.

CaSR and calpain contribute to the ischemia reperfusion injury of spinal cord.

Spinal cord ischemia reperfusion injury (SCIRI) can cause spinal cord dysfunction and even devastating paraplegia. Calcium-sensing receptor (CaSR) and calpain are two calcium related molecules which have been reported to be involved in the ischemia reperfusion injury of cardiomyocytes and the subsequent apoptosis. Here, we studied the expression of CaSR and calpain in spinal cord neurons and tissues, followed by the further investigation of the role of CaSR/calpain axis in the cellular apoptosis process during SCIRI. The results of in vitro and in vivo studies showed that the expression of CaSR and calpain in spinal cord neurons increased during SCIRI. Moreover, the CaSR agonist GdCl3 and antagonist NPS-2390 enhanced or decreased the expression of CaSR and calpain respectively. The expressions of CaSR and calpain were also consistent with the cellular apoptosis in spinal cord. Taken together, CaSR-calpain contributes to the SCIRI apoptosis, and CaSR antagonist might be a helpful drug for alleviating SCIRI.

Correlation between the Expression of High Temperature Requirement Serine Protease A1 in Nucleus Pulposus Tissue and the Degree of Intervertebral Disc Degeneration.

Objective To investigate the correlation between the expression level of high temperature requirement serine protease A1 (HtrA1) in nucleus pulposus and the degree of intervertebral disc degeneration (Pfirrmann grade).Methods Thirty-six patients who underwent excision of nucleus pulposus were examined by magnetic resonance imaging (MRI) before operation,and the Pfirrmann grading of all patients was performed according to the sagittal T2 weighted MRI.The expression of HtrA1 in nucleus pulposus tissue was detected by reverse transcription polymerase chain reaction and Western blot.The correlation between the expression level of HtrA1 in nucleus pulposus tissue and Pfirrmann grade was analyzed.Results MRI in all 36 patients showed that there were 3 cases of Pfirrmann grade Ⅰ,10 cases of grade Ⅱ,11 cases of grade Ⅲ,7 cases of grade Ⅲ,and 5 cases of grade Ⅴ.The mRNA and protein expressions of HtrA1 in nucleus pulposus tissue increased with the increase of Pfirrmann grade.There were significant differences in the expression level of HtrA1 among different Pfirrmann grade groups (P<0.05) except for the difference between grade Ⅲ and Ⅴ (P>0.05).Spearman rank correlation analysis revealed that there was a rank correlation between expression level of HtrA1 and Pfirrmann grade (P<0.000 1).Conclusion The mRNA and protein expressions of HtrA1 in nucleus pulposus tissue increase with the increase of Pfirrmann grade,indicating HtrA1 is correlated with the degree of intervertebral disc degeneration.

Zinc(II) tetraphenyltetrabenzoporphyrin complex as triplet photosensitizer for triplet-triplet annihilation upconversion.

Zn(II) tetraphenyltetrabenzoporphyrin (TPTBP) and the free base H2TPTBP were used as triplet photosensitizers for triplet-triplet annihilation (TTA) upconversion, to replace the long-established precious metal complex triplet photosensitizers such as those containing Pd(II)-Pt(II) atoms.

Observation of the long-lived triplet excited state of perylenebisimide (PBI) in C

Perylenebisimide (PBI) was used to prepare C^N cyclometalated Ir(III) complexes that show strong absorption of visible light and it is the first time the long-lived triplet excited state of PBI chromophore was observed in a transition metal complex (τT = 22.3 µs). Previously, the lifetime of the triplet state of PBI in transition metal complexes was usually shorter than 1.0 µs. Long-lived triplet excited states are useful for applications in photocatalysis or other photophysical processes concerning triplet-triplet-energy-transfer. PBI and amino-PBI were used for preparation of cyclometalated Ir(III) complexes (Ir-2 and Ir-3), in which the PBI chromophore was connected to the coordination center via C≡C π-conjugation bond. The new complexes show strong absorption in visible region (ε = 34,200 M(-1) cm(-1) at 541 nm for Ir-2, and ε = 19,000 at 669 nm for Ir-3), compared to the model complex Ir(ppy)(bpy)[PF6] Ir-1 (ε < 5000 M(-1) cm(-1) in the region beyond 400 nm). The nanosecond time-resolved transient absorption and DFT calculations indicated that PBI-localized long-lived (3)IL states were populated for Ir-2 and Ir-3 upon photoexcitation. The complexes were used as triplet photosensitizers for (1)O2-mediated photooxidation of 1,5-dihydronaphthalene to produce juglone, an important intermediate for preparation of anti-cancer compounds. (1)O2 quantum yields (Φ(Δ)) up to 91% were observed for the new Ir(III) complexes and the overall photosensitizing ability is much higher than the conventional Ir(III) complex Ir-1, which shows the typical weak visible light absorption in visible region. Our results are useful for preparation of transition metal complexes that show strong absorption of visible light and long-lived triplet excited state and for the application of these complexes in photocatalysis.

Triplet photosensitizers: from molecular design to applications.

Triplet photosensitizers (PSs) are compounds that can be efficiently excited to the triplet excited state which subsequently act as catalysts in photochemical reactions. The name is originally derived from compounds that were used to transfer the triplet energy to other compounds that have only a small intrinsic triplet state yield. Triplet PSs are not only used for triplet energy transfer, but also for photocatalytic organic reactions, photodynamic therapy (PDT), photoinduced hydrogen production from water and triplet-triplet annihilation (TTA) upconversion. A good PS should exhibit strong absorption of the excitation light, a high yield of intersystem crossing (ISC) for efficient production of the triplet state, and a long triplet lifetime to allow for the reaction with a reactant molecule. Most transition metal complexes show efficient ISC, but small molar absorption coefficients in the visible spectral region and short-lived triplet excited states, which make them unsuitable as triplet PSs. One obstacle to the development of new triplet PSs is the difficulty in predicting the ISC of chromophores, especially of organic compounds without any heavy atoms. This review article summarizes some molecular design rationales for triplet PSs, based on the molecular structural factors that facilitate ISC. The design of transition metal complexes with large molar absorption coefficients in the visible spectral region and long-lived triplet excited states is presented. A new method of using a spin converter to construct heavy atom-free organic triplet PSs is discussed, with which ISC becomes predictable, C60 being an example. To enhance the performance of triplet PSs, energy funneling based triplet PSs are proposed, which show broadband absorption in the visible region. Applications of triplet PSs in photocatalytic organic reactions, hydrogen production, triplet-triplet annihilation upconversion and luminescent oxygen sensing are briefly introduced.

Green light-excitable naphthalenediimide acetylide-containing cyclometalated Ir(III) complex with long-lived triplet excited states as triplet photosensitizers for triplet-triplet annihilation upconversion.

Naphthalenediimide (NDI) was connected to the ligand of a cyclometalated Ir(III) complex (Ir-1) via a C≡C triple bond to enhance the absorption in the visible region and to access long-lived triplet excited states. Ir(ppy)2(bpy)[PF6] (Ir-2, ppy = 2-phenylpyridine and bpy = 2,2'-bipyridine) was used as a model complex. The photophysical properties of the complexes were studied with steady state and time-resolved spectroscopy. Ir-1 shows strong absorption in the visible region (ε = 11,000 M(-1) cm(-1) at 542 nm) and in comparison Ir-2 shows typically weak absorption in the visible region (ε < 3000 M(-1) cm(-1) above 400 nm). Room temperature near IR emission at 732 nm (Φ(P) = 0.1%) was observed for Ir-1, which is attributed to the NDI localized emissive triplet excited state, by transient absorption spectra and DFT calculations on the spin density surface. The lifetime of the NDI-localized triplet excited state is up to 130.0 µs, which is rarely reported for Ir(III) complexes. In comparison, Ir-2 shows phosphorescence at 578 nm and the triplet state lifetime is a typical value of 0.3 µs. The complexes were used as triplet photosensitizers for triplet-triplet annihilation (TTA) upconversion and an upconversion quantum yield of 6.7% was observed with Ir-1. No upconversion was observed with Ir-2 as the triplet photosensitizer at the same experimental conditions.