Nationwide Big Data Analysis of Statin Use and Intracerebral Hemorrhage Risk in Acute Ischemic Stroke Patients in Taiwan.

Background and Objectives: Although statins are recommended for secondary prevention of acute ischemic stroke, some population-based studies and clinical evidence suggest that they might be used with an increased risk of intracranial hemorrhage. In this nested case-control study, we used Taiwan's nationwide universal health insurance database to investigate the possible association between statin therapy prescribed to acute ischemic stroke patients and their risk of subsequent intracerebral hemorrhage and all-cause mortality in Taiwan. Materials and Methods: All data were retrospectively obtained from Taiwan's National Health Insurance Research Database. Acute ischemic stroke patients were divided into a cohort receiving statin pharmacotherapy and a control cohort not receiving statin pharmacotherapy. A 1:1 matching for age, gender, and index day, and propensity score matching was conducted, producing 39,366 cases and 39,366 controls. The primary outcomes were long-term subsequent intracerebral hemorrhage and all-cause mortality. The competing risk between subsequent intracerebral hemorrhage and all-cause mortality was estimated using the Fine and Gray regression hazards model. Results: Patients receiving statin pharmacotherapy after an acute ischemic stroke had a significantly lower risk of subsequent intracerebral hemorrhage (p < 0.0001) and lower all-cause mortality rates (p < 0.0001). Low, moderate, and high dosages of statin were associated with significantly decreased risks for subsequent intracerebral hemorrhage (adjusted sHRs 0.82, 0.74, 0.53) and all-cause mortality (adjusted sHRs 0.75, 0.74, 0.74), respectively. Conclusions: Statin pharmacotherapy was found to safely and effectively reduce the risk of subsequent intracerebral hemorrhage and all-cause mortality in acute ischemic stroke patients in Taiwan.

A causal examination of the correlation between hormonal and reproductive factors and low back pain.

Background: The relationship between hormonal fluctuations in the reproductive system and the occurrence of low back pain (LBP) has been widely observed. However, the causal impact of specific variables that may be indicative of hormonal and reproductive factors, such as age at menopause (ANM), age at menarche (AAM), length of menstrual cycle (LMC), age at first birth (AFB), age at last live birth (ALB) and age first had sexual intercourse (AFS) on low back pain remains unclear. Methods: This study employed Bidirectional Mendelian randomization (MR) using publicly available summary statistics from Genome Wide Association Studies (GWAS) and FinnGen Consortium to investigate the causal links between hormonal and reproductive factors on LBP. Various MR methodologies, including inverse-variance weighted (IVW), MR-Egger regression, and weighted median, were utilized. Sensitivity analysis was conducted to ensure the robustness and validity of the findings. Subsequently, Multivariate Mendelian randomization (MVMR) was employed to assess the direct causal impact of reproductive and hormone factors on the risk of LBP. Results: After implementing the Bonferroni correction and conducting rigorous quality control, the results from MR indicated a noteworthy association between a decreased risk of LBP and AAM (OR=0.784, 95% CI: 0.689-0.891; p=3.53E-04), AFB (OR=0.558, 95% CI: 0.436-0.715; p=8.97E-06), ALB (OR=0.396, 95% CI: 0.226-0.692; p=0.002), and AFS (OR=0.602, 95% CI: 0.518-0.700; p=3.47E-10). Moreover, in the reverse MR analysis, we observed no significant causal effects of LBP on ANM, AAM, LMC and AFS. MVMR analysis demonstrated the continued significance of the causal effect of AFB on LBP after adjusting for BMI. Conclusion: Our study explored the causal relationship between ANM, AAM, LMC, AFB, AFS, ALB and the prevalence of LBP. We found that early menarche, early age at first birth, early age at last live birth and early age first had sexual intercourse may decrease the risk of LBP. These insights enhance our understanding of LBP risk factors, offering valuable guidance for screening, prevention, and treatment strategies for at-risk women.

Genetically proxied PCSK9 inhibition is associated with reduced psoriatic arthritis risk.

BACKGROUND: Lipid pathways play a crucial role in psoriatic arthritis development, and some lipid-lowering drugs are believed to have therapeutic benefits due to their anti-inflammatory properties. Traditional observational studies face issues with confounding factors, complicating the interpretation of causality. This study seeks to determine the genetic link between these medications and the risk of psoriatic arthritis. METHODS: This drug target study utilized the Mendelian randomization strategy. We harnessed high-quality data from population-level genome-wide association studies sourced from the UK Biobank and FinnGen databases. The inverse variance-weighted method, complemented by robust pleiotropy methods, was employed. We examined the causal relationships between three lipid-lowering agents and psoriatic arthritis to unveil the underlying mechanisms. RESULTS: A significant association was observed between genetically represented proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibition and a decreased risk of psoriatic arthritis (odds ratio [OR]: 0.51; 95% CI 0.14-0.88; P < 0.01). This association was further corroborated in an independent dataset (OR 0.60; 95% CI 0.25-0.94; P = 0.03). Sensitivity analyses affirmed the absence of statistical evidence for pleiotropic or genetic confounding biases. However, no substantial associations were identified for either 3-hydroxy-3-methylglutaryl-CoA reductase inhibitors or Niemann-Pick C1-like 1 inhibitors. CONCLUSIONS: This Mendelian randomization analysis underscores the pivotal role of PCSK9 in the etiology of psoriatic arthritis. Inhibition of PCSK9 is associated with reduced psoriatic arthritis risk, highlighting the potential therapeutic benefits of existing PCSK9 inhibitors.

An innovative approach to assess spinal canal expansion following French-door cervical laminoplasty by intraoperative ultrasonography.

OBJECTIVE: To investigate the feasibility and effectiveness of applying intraoperative ultrasound (IOUS) to evaluate spinal canal expansion in patients undergoing French-door cervical laminoplasty (FDCL). MATERIALS AND METHODS: Twenty-five patients who underwent FDCL for multilevel degenerative cervical myelopathy were prospectively recruited. Formulae describing the relationship between laminoplasty opening angle (LOA) and laminoplasty opening size, the increase in sagittal canal diameter and the spinal canal area were deduced with trigonometric functions. The LOA was measured with IOUS imaging during surgery, and other spinal canal parameters were assessed. Actual spinal canal enlargement was verified on postoperative CT images. Linear correlation analysis and Bland‒Altman analysis were used to evaluate correlation and agreement between the intraoperative and postoperative measurements. RESULTS: The LOA at C5 measured with IOUS was 27.54 ± 3.12°, and it was 27.23 ± 3.02° on postoperative CT imaging. Linear correlation analysis revealed a significant correlation between IOUS and postoperative CT measurements (r = 0.88; p < 0.01). Bland-Altman plots showed good agreement between these two methods, with a mean difference of 0.30°. For other spinal canal expansion parameter measurements, correlation analysis showed a moderate to a high degree of correlation (p < 0.01), and Bland-Altman analysis indicated good agreement. CONCLUSION: In conclusion, during the French-door cervical laminoplasty procedure, application of IOUS can accurately evaluate spinal canal expansion. This innovative method may be helpful in improving surgical accuracy by enabling the operator to measure and determine canal enlargement during surgery, leading to ideal clinical outcomes and fewer postoperative complications. CLINICAL RELEVANCE STATEMENT: The use of intraoperative ultrasonography to assess spinal canal expansion following French-door cervical laminoplasty may improve outcomes for patients undergoing this procedure by providing more accurate measurements of spinal canal expansion. KEY POINTS: • Spinal canal expansion after French-door cervical laminoplasty substantially influences operative prognosis; insufficient or excessive lamina opening may result in unexpected outcomes. • Prediction of spinal canal expansion during surgery was previously impracticable, but based on this study, intraoperative ultrasonography offers an innovative approach and strongly agrees with postoperative CT measurement. • Since this is the first research to offer real-time canal expansion guidance for cervical laminoplasty, it may improve the accuracy of the operation and produce ideal clinical outcomes with fewer postoperative complications.

Effect of mechanical stimulation on tissue heterotopic ossification: an in vivo experimental study.

Background: Heterotopic ossification of tendons and ligaments (HOTL) is a common clinical condition characterized by the absence of discernible features and a lack of effective treatment. In vitro experiments have demonstrated that mechanical stimulation can induce cell differentiation toward osteogenesis, thereby promoting heterotopic ossification. Currently, there are few experimental designs aimed at inducing ligament stretching in mice, and the mechanism of heterotopic ossification may not entirely mirror that observed in clinical cases. Therefore, there is an urgent imperative to develop a novel and feasible animal model. Methods: In this study, all the Enpp1 gene deficiency mice (a mouse model with heterotopic ossification of multiple ligaments) were divided into three groups: the control group, the spinal brake group, and the hyperactive group (treadmill training group). An external spinal fixation device was designed to restrict mice's spinal flexion and extension at 6 weeks of age. The brace was adjusted weekly according to the changes in the size of the mice. Additionally, treadmill training was used to increase activity in the spinal ligaments and Achilles tendons of the mice. Micro-CT scanning and HE staining were performed at 12, 20, and 28 W to evaluate the degree of ossification in the spinal ligament and Achilles tendon. What's more, As one of the mechanical stimulation transduction signals, YAP plays a crucial role in promoting osteogenic differentiation of cells. Immunofluorescence was utilized to assess YAP expression levels for the purpose of determining the extent of mechanical stimulation in tissues. Results: Our findings showed that a few ossification lesions were detected behind the vertebral space of mice at 8 weeks of age. Spinal immobilization effectively restricts the flexion and extension of cervical and thoracic vertebrae in mice, delaying spinal ligament ossification and reducing chronic secondary spinal cord injury. Running exercises not only enhance the ossification area of the posterior longitudinal ligament (PLL) and Achilles tendons but also exacerbate secondary spinal cord injury. Further immunofluorescence results revealed a notable increase in YAP expression levels in tissues with severe ossification, suggesting that these tissues may be subjected to higher mechanical stimulation. Conclusion: Mechanical stimulation plays a pivotal role in the process of heterotopic ossification in tissues. Our study provided valid animal models to further explore the pathological mechanism of mechanical stimulation in HOTL development.

Quantitative Analysis of Brain Swelling Resolution With Regard to Cranioplasty After Decompressive Craniectomy.

OBJECTIVE: Adequate brain swelling resolution prior to cranioplasty (CP) is an important yet loosely defined issue. Despite efforts to balance timely CP and patient safety, heterogeneous study methodologies have led to conflicting results. This study aims to standardize this issue through quantifying degree of brain swelling resolution using a proposed Visual CP Scale. METHODS: The proposed Visual CP Scale is validated through a 2-pronged approach. The first prong involves a national survey in Taiwan, where neurosurgeons were surveyed to determine what constitutes a patient's readiness for CP. The second prong involves a large retrospective cohort, where the correlations between timing, degree of brain swelling resolution, and post-CP complication rates, are evaluated. RESULTS: In the national Taiwan CP Survey, 124 out of 772 neurosurgeons (17.2%) completed the survey. Respondents who chose higher grades on the Visual CP Scale preferred later CP timings. In the retrospective data, 378 out of 770 (49.1%) patients had pre-CP brain images, allowing for the utilization of the Visual CP Scale. A Visual CP Scale score of greater than or equal to 4 was associated with fewer complications after CP. CONCLUSIONS: The timing of CP should be determined by the degree of brain swelling resolution, not vice versa. The proposed Visual CP Scale offers an objective method for assessing brain swelling resolution, making it an adjuvant tool for clinical decision-making and future research related to CP.

Increased blood flow of spinal cord lesion after decompression improves neurological recovery of degenerative cervical myelopathy: an intraoperative ultrasonography-based prospective cohort study.

INTRODUCTION: Surgical decompression is a highly effective therapy for degenerative cervical myelopathy (DCM), but the mechanisms of neurological recovery following decompression remain unclear. This study aimed to evaluate the spinal cord blood flow status after sufficient decompression by intraoperative contrast-enhanced ultrasonography (CEUS) and to analyze the correlation between neurological recovery and postdecompressive spinal cord blood perfusion in DCM. MATERIALS AND METHODS: Patients with multilevel DCM were treated by ultrasound-guided modified French-door laminoplasty using a self-developed rongeur. Neurological function was evaluated using the modified Japanese Orthopaedic Association (mJOA) score preoperatively and at 12 months postoperatively. Spinal cord compression and cervical canal enlargement before and after surgery were assessed by magnetic resonance imaging and computerized tomography. The decompression status was evaluated in real time by intraoperative ultrasonography, while the spinal cord blood flow after sufficient decompression was assessed by CEUS. Patients were categorized as favourable (≥50%) or unfavourable (<50%) recovery according to the recovery rate of the mJOA score at 12 months postoperatively. RESULTS: Twenty-nine patients were included in the study. The mJOA scores were significantly improved in all patients from 11.2±2.1 preoperatively to 15.0±1.1 at 12 months postoperatively, with an average recovery rate of 64.9±16.2%. Computerized tomography and intraoperative ultrasonography confirmed adequate enlargement of the cervical canal and sufficient decompression of the spinal cord, respectively. CEUS revealed that patients with favourable neurological recovery had a greater increased blood flow signal in the compressive spinal cord segment after decompression. CONCLUSIONS: In DCM, intraoperative CEUS can clearly reflect spinal cord blood flow. Patients with increased blood perfusion of the spinal cord lesion immediately after surgical decompression tended to achieve greater neurological recovery.

High-Speed Shift Register with Dual-Gated Thin-Film Transistors for a 31-Inch 4K AMOLED Display.

In this work, a promising dual-gated thin film transistor (TFT) structure has been proposed and introduced in the shift register (SR)-integrated circuits to reduce the rising time. The threshold voltage can be simultaneously changed by the top gate and the bottom gate in the proposed dual-gated TFTs. When the SR circuits start to export the scan signals in the displays, the driving currents in the SR circuits are increased by switching the working station of driving TFTs from the enhancement characterization to the depletion characterization. Subsequently, the detailed smart spice simulation has been used to study the function of the proposed SR circuits. In the next step, the proposed SR circuits have been fabricated in a G4.5 active-matrix organic light-emitting diode manufacture factory. The simulated and experimental results indicate that the shift register pulses with the full swing amplitude can be obtained in the SR circuits. Moreover, in contrast to the conventional SR circuits employing with the single-gated TFTs, it has been found that the rising time of the output signals can be reduced from 3.75 µs to 1.23 µs in the proposed SR circuits with the dual-gated TFTs, thus exhibiting the significant improvement of the driving force in the proposed SR circuits. Finally, we demonstrated a 31-inch 4K AMOLED display with the proposed SR circuits.

Evaluation of the 10 Years' Association Between DXA Screening and Mortality in Patients Who Received Vertebroplasty in the Taiwan Population.

BACKGROUND: Osteoporotic fractures are a significant cause of morbidity and mortality affecting population worldwide. All guidelines recommended vertebral fracture assessment by dual-energy X-ray absorptiometry (DXA). This study aimed at evaluation of any associated benefits of screening with DXA in patients who had received vertebroplasty in Taiwan. METHODS: Data were obtained from the National Health Insurance Research Database (NHIRD) in Taiwan. We retrospectively compared the data of patients, who were admitted for vertebroplasty, whether they received DXA screening or not. The outcomes of interest were recurrence of spinal fracture and mortality during a follow-up period of 10 years. RESULTS: From this Taiwan national database, the screening rate of osteoporosis in patient who received vertebroplasty was 11.7%. The mean age in the non-DXA screened cohort (n=32,986) was 74.03±12.21 years (71.98% female). In the DXA screened cohort (n=4361), the mean age was 76.43±9.19 years (79.91% female). During the 10-year follow-up period, after matching, non-DXA patients had significantly higher mortality rates than their DXA counterparts, which were 42.37% and 37.73% (p-value < 0.0001), respectively. The re-fracture rates between non-DXA and DXA patients were not significantly different at 17.26% and 16.89% (p-value = 0.1766), respectively. CONCLUSION: The rate of DXA screening before patients receiving vertebroplasty was extremely low, at 11.7%. Our results showed that DXA screening before vertebroplasty in spinal fractures patients had lower mortality. From this national retrospective cohort study, routine screening of osteoporosis in spinal fracture patients can lead to reduction in mortality.

Adjunctive Statin Therapy Reduces Mortality After Acute Hemorrhagic Stroke.

BACKGROUND: Statin treatment improves clinical outcomes in patients with ischemic strokes, although there is no evidence regarding the safety of statin therapy in patients with intracerebral hemorrhage (ICH). This study aimed at evaluating the effects of continuing statin treatment after ICH. METHODS: Data were obtained from the National Health Insurance Research Database in Taiwan. We retrospectively compared the data of patients with and without statin exposure after ICH. The outcomes of interest were recurrence of hemorrhagic stroke and mortality during a follow-up period of 10 years. RESULTS: During the 10-year follow-up period, the mortality rate was 32.73% in the statin group and 42.77% in the non-statin group. Statin therapy in patients with acute ICH with dyslipidemia can decrease mortality. CONCLUSION: Statin therapy reduced the risk of 10-year mortality in patients who experienced acute hemorrhagic stroke.

Patient-specific instrumentation improves functional kinematics of minimally-invasive total knee replacements as revealed by computerized 3D fluoroscopy.

BACKGROUND AND OBJECTIVES: Minimally-invasive total knee arthroplasty (MIS-TKA) has demonstrated very good short-term success, but its mid- to long-term results remain inconclusive. The success may be related to the tradeoff between a small incision and accurate positioning of the implant components. Patient-specific instrumentation (PSI) aims to improve the accuracy in restoring the knee axis and the clinical outcomes for MIS-TKA, but the results are yet to be confirmed by accurate assessment during functional activities. The purpose of the current study was to measure and compare the in vivo three-dimensional (3D) rigid-body and surface kinematics of MIS-TKA implanted with and without PSI during isolated knee active flexion/extension and sit-to-stand using state-of-the-art 3D model-based fluoroscopy technology. METHODS: Ten patients treated for advanced medial knee osteoarthritis by MIS-TKA without PSI (non-PSI group) and nine with PSI (PSI group) participated in the current study. Each subject performed non-weight-bearing knee flexion/extension and sit-to-stand tasks while the motion of the prosthetic knee was under bi-plane fluoroscopy surveillance. The computer models of each of the knee prosthesis components were registered to the measured fluoroscopy images for each time frame via a novel validated 3D fluoroscopy method. Non-parametric 1-tailed Mann-Whitney tests were performed to detect the differences in the joint and surface kinematic variables every 10° of knee flexion between the non-PSI and PSI groups. The 1-tailed significance level was at α = 0.05. RESULTS: The PSI group showed clear, coupled flexion/internal rotation during activities, while the non-PSI group remained roughly at an externally rotated position with slight internal rotations. The coupled rotation in the PSI group was accompanied by an anterior displacement of the medial contact and a posterior displacement of the lateral contact, which was different from the screw-home mechanism. Neither of the two groups showed the normal roll-back phenomenon, i.e., posterior translation of the femur relative to the tibia during knee flexion. CONCLUSIONS: With the state-of-the-art 3D fluoroscopy method, differences in both the rigid-body and surface kinematics of the prosthetic knees between MIS-TKA with and without PSI were identified. Patients with PSI demonstrated significant positive effects on the reconstructed rigid-body kinematics of the knee, showing clearer coupled flexion/internal rotations - an important kinematic characteristic in healthy knees - than those without PSI during activities with or without weight-bearing. However, none of them showed normal contact patterns. The current findings will be helpful for surgical instrument design, as well as for surgical decision-making in MIS total knee arthroplasty.

Nonresectable Thoracic Rosai-Dorfman Disease: A Case Report and Review of the Literature.

INTRODUCTION: Rosai-Dorfman disease (RDD) is a rare disease that can be triggered by either viral or bacterial infection. Several parts of the body can be involved, from the central nervous system to the pelvic regions had been reported. At present, there is a serious lack of guidelines as to how to treat cases of RDD involving the spine. Current trends show that surgery remains the first method of choice to cure this disease, but in refractory or recurrent RDD, repeat surgery cannot guarantee total resection. Under such circumstances, adjuvant therapy can be very useful. Here, we share our experience of treating recurrent spinal RDD. CASE DESCRIPTION: Our patient was a 32-year-old male patient with hepatitis B virus infection. He suffered from lower back pain with lower limb weakness after being hit by a metal pipe. Laminectomy of T11-12 was performed to decompress the spinal cord. The final pathological results demonstrated chronic inflammation. After surgery, the lower limbs improved and the patient recovered quite well. However, he returned 3 years later with the same complaints and was diagnosed with RDD. Durectomy was performed and repaired with an artificial dura. Thalidomide therapy was initiated. Currently, 9 years later, the patient has not experienced recurrence or any form of neurological deficit. CONCLUSIONS: RDD is a rare disease and can be misdiagnosed easily. Although it may resolve spontaneously, recurrence is possible. Hence, extensive follow-up is necessary. Surgery remained the first choice of surgery, however, when encountered recurrent or nonresectable RDD, adjuvant therapy such as corticosteroids, thalidomide, and radiotherapy could help. In this article, we shared our experience using thalidomide in treating nonresectable RDD.

Inhibition of astrocytic differentiation of transplanted neural stem cells by chondroitin sulfate methacrylate hydrogels for the repair of injured spinal cord.

Neural stem cell (NSC) transplantation exerts a therapeutic effect on spinal cord injury (SCI) but is limited to an unregulated differentiation pattern by which NSCs preferentially differentiate into astrocytes, with relatively few neurons. It is well established that the increased NSC-derived astrocytes exhibit aberrant axonal sprouting associated with allodynia-like symptoms of the forepaws. Some strategies have been used to overcome this issue, such as regulation of major pathways, ex vivo gene transfer, and genetic overexpression. However, lack of efficiency, viral vector safety issues and the risk of tumorigenesis have hindered the clinical application of these treatments. Here, we show that astrocytic differentiation of NSCs in vitro and in vivo can be inhibited by encapsulation of cells in a three-dimensional chondroitin sulfate methacrylate (CSMA) hydrogel. When CSMA hydrogels were used to transplant NSCs, the combinatory implant promoted functional recovery and attenuated the hypersensitivity responses of the forepaws. Further analysis showed that transplantation of NSCs within CSMA hydrogels reduced injured cavity areas and promoted neurogenesis rather than fibroglial formation after graft implantation. Furthermore, the treatment prevented allodynia-related CGRP/GAP43-positive nociception due to fibers sprouting into inappropriate lamina regions. Taken together, these findings show that CSMA/NSCs combined transplantation helps prevent adverse side effects of NSCs treatment and promotes recovery of SCI.

Interaction of iPSC-derived neural stem cells on poly(L-lactic acid) nanofibrous scaffolds for possible use in neural tissue engineering.

Tissue engineering is a rapidly growing technological area for the regeneration and reconstruction of damage to the central nervous system. By combining seed cells with appropriate biomaterial scaffolds, tissue engineering has the ability to improve nerve regeneration and functional recovery. In the present study, mouse induced pluripotent stem cells (iPSCs) were generated from mouse embryonic fibroblasts (MEFs) with the non-integrating episomal vectors pCEP4-EO2S-ET2K and pCEP4-miR-302-367 cluster, and differentiated into neural stem cells (NSCs) as transplanting cells. Electrospinning was then used to fabricate randomly oriented poly(L-lactic acid) (PLLA) nanofibers and aligned PLLA nanofibers and assessed their cytocompatibility and neurite guidance effect with iPSC-derived NSCs (iNSCs). The results demonstrated that non-integrated iPSCs were effectively generated and differentiated into iNSCs. PLLA nanofiber scaffolds were able to promote the adhesion, growth, survival and proliferation of the iNSCs. Furthermore, comp-ared with randomly oriented PLLA nanofibers, the aligned PLLA nanofibers greatly directed neurite outgrowth from the iNSCs and significantly promoted neurite growth along the nanofibrous alignment. Overall, these findings indicate the feasibility of using PLLA nanofiber scaffolds in combination with iNSCs in vitro and support their potential for use in nerve tissue engineering.

Charge-transfer and isomerization reactions of trans-4-(N-arylamino)stilbenes.

We studied the excited-state dynamics of trans-4-(N-arylamino)stilbenes with aryl = phenyl (p1H), 4-methoxyphenyl (p1OM), or 4-cyanophenyl (p1CN) in solvents of varied polarity and viscosity by using femtosecond transient absorption and time-correlated single photon counting techniques. In nonpolar solvents the decay is triexponential, in which the rapid component corresponds to vibrational cooling combined with solvation, the intermediate temporal component 41-120 ps to trans-cis isomerization, and the long one ∼1 ns to fluorescence decay of the S1 state. The S1 state has a delocalized geometry and charge-transfer characteristics, corresponding to a planar intramolecular charge transfer (PICT) state. In polar solvents, an excited-state absorption band appears near 520 and 480 nm for p1OM and p1CN, respectively but not for p1H. This band has a rise lifetime of 4.3/7.5, 16.3/9.4, and 29.5/16 ps for p1CN/p1OM in acetonitrile (ACN), dimethylformamide (DMF), and dimethyl sulfoxide (DMSO), respectively and matches the decay of the 600 nm PICT band. This band is thus assigned to the absorption of a singlet twisted intramolecular charge transfer state (TICT). The conversion rate decreases as the solvent viscosity is increased and is consistent with a large structural variation amplitude. Theoretical calculations using density functional theory (DFT), method PEB0, were employed to obtain the optimized structures and energies of those states. The PICT state possesses delocalized π electrons along the molecule. The TICT for p1CN is formed by twisting about the aminostilbene-benzonitrile C-N bond by ∼90°, but it is about the stilbene-aniline C-N bond for p1OM. We observed faster conversion rates for p1CN in alcoholic solvents, in which the lifetimes for both the PICT and TICT states are shortened to 20-99 ps and 120-660 ps, respectively, as a result of solvent-solute H-bonding interactions. In p1OM, the TICT state has an elongated C[double bond, length as m-dash]C bond in the stilbene moiety, which might facilitate the trans-cis isomerization reaction and thus account for the relatively short lifetime of 58-420 ps in polar solvents.

Conformational control of oligo(p-phenyleneethynylene)s with intrinsic substituent electronic effects: origin of the twist in pentiptycene-containing systems.

Dependence of the backbone planarity of oligo(p-phenyleneethynylene)s (OPEs) on the intrinsic electronic character of substituents and on the nature of the solvent has been experimentally demonstrated with a series of center-symmetrical five-ring systems, pentiptycene-pentiptycene-arene-pentiptycene-pentiptycene, differing in the substituents on the central arene. In frozen 2-methyltetrahydrofuran (MTHF), the adjacent pentiptycene units prefer to be in a mutually twisted orientation when the substituents are electron-withdrawing (F and amido), resulting in a TPPT or TTTT conformation, whereas a planarized PPPP backbone is favored in the case of electron-donating substituents (alkyl and alkoxy). The propensity to adopt the PPPP form is generally enhanced by replacing MTHF with either methylcyclohexane or mixed ethanol/methanol as solvent. These observations reveal that the twist between adjacent pentiptycene units in OPEs is a consequence of the electronic rather than steric effects of iptycenyl substituents. The electronic effect of iptycenyl substituents is manifested in decreased phenylene π polarizability as the net effect of both electron-donating hyperconjugation and an electron-withdrawing inductive effect. Variable-temperature electronic absorption and emission spectroscopies are the critical tools for this work. Our findings provide important guidelines for conformational and electronic engineering of OPEs and for the design of novel iptycene-based organic electronic materials.

Multisite constrained model of trans-4-(N,N-dimethylamino)-4'-nitrostilbene for structural elucidation of radiative and nonradiative excited states.

A constrained model compound of trans-4-(N,N-dimethylamino)-4'-nitrostilbene (DNS), namely, compound DNS-B3 that is limited to torsions about the phenyl-nitro C-N bond and the central C═C bond, was prepared to investigate the structural nature of the radiative and nonradiative states of electronically excited DNS. The great similarities in solvent-dependent electronic spectra, fluorescence decay times, and quantum yields for fluorescence (Φf) and trans → cis photoisomerization (Φtc) between DNS and DNS-B3 indicate that the fluorescence is from a planar charge-transfer state and torsion of the nitro group is sufficient to account for the nonradiative decay of DNS. This conclusion is supported by TDDFT calculations on DNS-B3 in dichloromethane. The structure at the conical intersection for internal conversion is associated with not only a twisting but also a pyramidalization of the nitro group. The mechanism of the NO2 torsion is discussed in terms of the effects of solvent polarity, the substituents, and the volume demand. The differences and analogies of the NO2- vs amino-twisted intramolecular charge-transfer (TICT) state of trans-aminostilbenes are also discussed.

o-Amino conjugation effect on the photochemistry of trans-aminostilbenes.

The excited-state behavior of a series of trans-2-(N-arylamino)stilbenes (aryl = phenyl (o1H), 4-methylphenyl (o1Me), 4-methoxyphenyl (o1OM), and 4-cyanophenyl (o1CN)) and trans-2-(N,N-diphenylamino)stilbene (o2) in both nonpolar and polar solvents is reported and compared to that of the parent trans-2-aminostilbene and the corresponding meta- and para-isomers (m1R and p1R, where R = H, Me, OM, and CN, and m2 and p2). Two types of torsional motions, the D-A torsion that results in a nonfluorescent twisted intramolecular charge transfer (TICT) state and the C═C torsion that leads to the cis isomers, account for the radiationless decays of o1R and o2. The relative efficiencies of these torsions can be readily evaluated from their quantum yields for fluorescence (Φ(f)) and trans → cis isomerization (Φ(tc)). The propensities of the D-A torsion are similar for the ortho and meta isomers, which is 1OM > 1Me and negligible for 1H, 1CN, and 2. The activation parameters determined from temperature-dependent fluorescence lifetimes suggest that the C═C torsion occurs mainly via the triplet state for the ortho systems, a behavior again similar to that of the meta isomers. Whereas the intersystem crossing in o1R, m1R, and m2 is essentially a nonactivated process, it encounters a barrier of 2.7-3.8 kcal mol(-1) in o2. As a result of the barriers that decelerate the radiationless decays and the slow fluorescence rate for o2 in acetonitrile, the observed long fluorescence lifetime 24.5 ns at room temperature reaches a new record for unconstrained trans-stilbenes.

Isotruxene-derived cone-shaped organic dyes for dye-sensitized solar cells.

The synthesis, electronic properties, and performance in dye-sensitized solar cells (DSSCs) of four cone-shaped organic dyes (ITD, ITD-Th, ITD-Hx, and ITD-OM) containing the isotruxene π-scaffold are reported. Selective substitution of the unsymmetrical isotruxene core with two diarylamino donors and one cyanocarboxylic acid acceptor was achieved by using a prefunctionalized dibromoisotruxene building block. The ortho-para-branched isotruxene core allows strong electronic couplings among the donors and the acceptor, leading to red-shifted absorption profiles with significant charge-transfer character. All four isotruxene dyes display reversible anodic waves in cyclic voltammagrams with both HOMO and LUMO potentials suitable for application in DSSCs. The DSSCs fabricated with these cone-shaped organic dyes exhibited high open-circuit voltages (0.67-0.76 V) and fill factors (0.67-0.72) with a power conversion efficiency (η) up to 5.45%, which is 80% of the ruthenium dye N719-based standard cell fabricated and measured under the same conditions.