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Synthesis, Electrochemistry, Photophysics, and Photochemistry of a Discrete Tetranuclear Copper(I) Sulfido Cluster

Lam CH, Tang WK, Yam VW

Inorg Chem, 2023 Feb 06;62(5):1942-1949.
PMID: 35925781 DOI: 10.1021/acs.inorgchem.2c01707

A tetranuclear copper(I) complex, [Cu4{μ-(Ph2P)2NH}4(μ4-S)](PF6)2 (1), was synthesized. It was found to display intense and long-lived phosphorescence in the solid and solution states. The lowest-energy excited state was assigned as ligand-to-metal charge transfer (LMCT) [S2- → Cu4] mixed with some metal-centered (ds/dp) character. In addition, the phosphorescent state of this complex was found to be quenched by pyridinium acceptors via an oxidative electron-transfer quenching process. An excited-state reduction potential of -1.74 V versus saturated salt calomel electrode was estimated through oxidative quenching studies with a series of structurally related pyridinium acceptors, indicative of its strong reducing power in the excited state. From the transient absorption difference spectrum of the tetranuclear copper(I) sulfido complex and 4-(methoxycarbonyl)-N-methylpyridinium hexafluorophosphate, in addition to the characteristic absorption of the pyridinyl radical at ca. 395 nm, two absorption bands at ca. 500 and 660 nm were also observed. The former was assigned as an LMCT absorption [S2- → Cu4] and the latter as an intervalence charge-transfer transition, associated with the mixed-valence species CuI/CuI/CuI/CuII.
Fulltext Highly effective ashless and non-corrosive dimercaptobenzothiadiazole as multifunctional lubricant additives in naphthenic base oil

Ong CL, Lai YC, Heidelberg T, Tang WK, Lee VS, Khaligh NG, et al.

RSC Adv, 2023 Oct 18;13(44):30733-30742.
PMID: 37869389 DOI: 10.1039/d3ra05692a

The conventional medium chain chlorinated paraffin (MCCP) and zinc dialkyl dithiophosphate (ZDDP) additives have greatly enhanced the extreme pressure (EP) and anti-wear (AW) performance of the metalworking fluids. However, chlorine- and zinc-containing additives are restricted in use due to eco-toxicity issue. Herein, ashless and non-corrosive dimercaptobenzothiadiazole derivatives, namely bis-2,5-benzylsulfanyl-[1,3,4]thiadiazole (BBST) and bis-2,5-octylsulfanyl-[1,3,4]thiadiazole (BOST) consist of three sulfur atoms have been synthesized and evaluated. The performance of BBST shows a weld load (PD) of 3089 N and AW value of 5 mm2, which represents an improvement of 3.1 and 7.4 folds over naphthenic base oil (NBO). In addition, BBST also outperformed BOST, MCCP, and ZDDP in terms of its weld load and AW properties. Based on XPS analysis and molecular electrostatic potential maps (MEPS), BBST exhibits superior tribology performance due to the interaction between the sulfur (S), nitrogen (N), and π-electrons of the benzene ring with the metal surface. The formation of FeS, Fe2O3 and Fe⋯N coordinate bonds contributes to the creation of an excellent tribofilm.
Fulltext Surface or Internal Hydration - Does It Really Matter?

van der Linde C, Ončák M, Cunningham EM, Tang WK, Siu CK, Beyer MK

J Am Soc Mass Spectrom, 2023 Mar 01;34(3):337-354.
PMID: 36744598 DOI: 10.1021/jasms.2c00290

The precise location of an ion or electron, whether it is internally solvated or residing on the surface of a water cluster, remains an intriguing question. Subtle differences in the hydrogen bonding network may lead to a preference for one or the other. Here we discuss spectroscopic probes of the structure of gas-phase hydrated ions in combination with quantum chemistry, as well as H/D exchange as a means of structure elucidation. With the help of nanocalorimetry, we look for thermochemical signatures of surface vs internal solvation. Examples of strongly size-dependent reactivity are reviewed which illustrate the influence of surface vs internal solvation on unimolecular rearrangements of the cluster, as well as on the rate and product distribution of ion-molecule reactions.
Fulltext Enhancing operational stability of OLEDs based on subatomic modified thermally activated delayed fluorescence compounds

Jung S, Cheung WL, Li SJ, Wang M, Li W, Wang C, et al.

Nat Commun, 2023 Oct 14;14(1):6481.
PMID: 37838720 DOI: 10.1038/s41467-023-42019-6

The realization of operationally stable blue organic light-emitting diodes is a challenging issue across the field. While device optimization has been a focus to effectively prolong device lifetime, strategies based on molecular engineering of chemical structures, particularly at the subatomic level, remains little. Herein, we explore the effect of targeted deuteration on donor and/or acceptor units of thermally activated delayed fluorescence emitters and investigate the structure-property relationship between intrinsic molecular stability, based on isotopic effect, and device operational stability. We show that the deuteration of the acceptor unit is critical to enhance the photostability of thermally activated delayed fluorescence compounds and hence device lifetime in addition to that of the donor units, which is commonly neglected due to the limited availability and synthetic complexity of deuterated acceptors. Based on these isotopic analogues, we observe a gradual increase in the device operational stability and achieve the long-lifetime time to 90% of the initial luminance of 23.4 h at the luminance of 1000 cd m-2 for thermally activated delayed fluorescence-sensitized organic light-emitting diodes. We anticipate our strategic deuteration approach provides insights and demonstrates the importance on structural modification materials at a subatomic level towards prolonging the device operational stability.
Author Correction: Enhancing operational stability of OLEDs based on subatomic modified thermally activated delayed fluorescence compounds

Jung S, Cheung WL, Li SJ, Wang M, Li W, Wang C, et al.

Nat Commun, 2023 Oct 26;14(1):6821.
PMID: 37884574 DOI: 10.1038/s41467-023-42698-1
Quinoline, Indole, and Isogranatanine Alkaloids from Malayan Leuconotis eugeniifolia

Tan YS, Ng MP, Tan CH, Tang WK, Sim KS, Yong KT, et al.

J Nat Prod, 2024 Feb 23;87(2):286-296.
PMID: 38284153 DOI: 10.1021/acs.jnatprod.3c00960

Nine new alkaloids, eugeniinalines A-H (1-8) and (+)-eburnamenine N-oxide (9), comprising one quinoline, six indole, and two isogranatanine alkaloids, were isolated from the stem-bark extract of the Malayan Leuconotis eugeniifolia. The structures and absolute configurations of these alkaloids were established based on the analysis of the spectroscopic data, GIAO NMR calculations, DP4+ probability analysis, TDDFT-ECD method, and X-ray diffraction analysis. Eugeniinaline A (1) represents a new pentacyclic quinoline alkaloid with a 6/6/5/6/7 ring system. Eugeniinaline G (7) and its seco-derivative, eugeniinaline H (8), were the first isogranatanine alkaloids isolated as natural products. The known alkaloids leucolusine (10) and melokhanine A (11) were found to be the same compound, based on comparison of the spectroscopic data of both compounds, with the absolute configuration of (7R, 20R, 21S). Eugeniinalines A and G (1 and 7) showed cytotoxic activity against the HT-29 cancer cell line with IC50 values of 7.1 and 7.2 μM, respectively.
Fulltext Prescription Patterns for Bipolar Disorder in Asian Countries: Findings from Research on Asian Prescription Pattern-Bipolar Disorder

Lin SK, Yang SY, Park SC, Jang OJ, Zhu X, Xiang YT, et al.

Clin Psychopharmacol Neurosci, 2022 Feb 28;20(1):61-69.
PMID: 35078949 DOI: 10.9758/cpn.2022.20.1.61

Objective: Pharmacotherapy including mood stabilizers and antipsychotics are frequently used in bipolar disorder (BD); however, the lack of consensus regarding the definition of polypharmacy hinders conducting comparative studies across different settings and countries. Research on Asian Prescription Pattern (REAP) is the largest and the longest lasting international collaborative research in psychiatry in Asia. The objective of REAP BD was to investigate the prescription patterns of psychotropic medications across Asian countries. The rates of polypharmacy and psychotropic drug load were also analyzed.
Methods: The data collection was web-based. Prescription patterns were categorized as (1) mood stabilizer monotherapy: one mood stabilizer; (2) antipsychotic monotherapy: one antipsychotic; (3) simple polypharmacy: one mood stabilizer and one antipsychotic; and (4) complex polypharmacy: ≥ 2 mood stabilizers or/and antipsychotics. The psychotropic drug load in each patient was calculated using the defined daily dose method.
Results: Among 2003 patients with BD (52.1% female, 42.4 years) from 12 countries, 1,619 (80.8%) patients received mood stabilizers, 1,644 (82.14%) received antipsychotics, and 424 (21.2%) received antidepressants, with 14.7% mood stabilizer monotherapy, 13.4% antipsychotic monotherapy, 48.9% simple polypharmacy, 20.3% complex polypharmacy, and 2.6% other therapy. The average psychotropic drug load was 2.05 ± 1.40. Results varied widely between countries.
Conclusion: Over 70% of psychotropic regimens involved polypharmacy, which accords with the high prevalence of polypharmacy in BD under a permissive criterion (2 or more core psychotropic drugs) worldwide. Notably, ≥ 80% of our sample received antipsychotics, which may indicate an increasing trend in antipsychotic use for BD treatment.
Fulltext Clinical use of mood stabilizers beyond treatment for bipolar disorder: The REAP-MS study

Chen CK, Yang SY, Park SC, Jang OJ, Zhu X, Xiang YT, et al.

Asian J Psychiatr, 2023 Jul;85:103613.
PMID: 37163943 DOI: 10.1016/j.ajp.2023.103613

OBJECTIVE: Mood stabilizers are psychotropic drugs mainly used to treat bipolar disorder in the acute phase or for maintenance therapy to prevent relapse. In clinical practice, mood stabilizers are commonly prescribed for conditions other than bipolar disorder. This study investigated the distribution of mood stabilizer prescriptions for different psychiatric diagnoses and studied differences in the drugs, dosage, and plasma concentration in 10 Asian countries including Taiwan, South Korea, Malaysia, China, Thailand, India, Pakistan, Singapore, Indonesia, and Myanmar.
METHODS: Patients prescribed mood stabilizers (lithium, carbamazepine, valproic acid, or lamotrigine) for a psychiatric condition other than bipolar disorder (codes F31.0-F31.9 in the International Classification of Diseases, 10th Edition, Clinical Modification) were recruited through convenience sampling. A website-based data entry system was used for data collection.
RESULTS: In total, 1557 psychiatric patients were enrolled. Schizophrenia, schizotypal, delusional, and other non-mood psychotic disorders (F20-F29, 55.8 %) was the most common diagnosis, followed by non-bipolar mood disorders (F30, F31- F39, 25.3 %), organic mental disorder (F00-F09, 8.8 %), mental retardation (F70-F79, 5.8 %) and anxiety, dissociative, stress-related, somatoform and other nonpsychotic mental disorders (F40-F48, 4.4 %). The most frequently targeted symptoms (>20 %) were irritability (48 %), impulsivity (32.4 %), aggression (29.2 %), anger (20.8 %), and psychosis (24.1 %). Valproic acid was the most frequently used medication.
CONCLUSIONS: Clinicians typically prescribe mood stabilizers as empirically supported treatment to manage mood symptoms in patients with diagnoses other than bipolar disorders, though there is on official indication for these disorders. The costs and benefits of this add-on symptomatic treatment warrant further investigation.