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Past one decade has witnessed a tremendous growth in the field of carbenes stabilized low-valent silicon compounds unravelling very exciting properties of these molecules. Herein, we have employed a bicyclic (alkyl)(amino)carbene, (MeBICAAC) to explore the low-valent chemistry of silicon compounds. The reduction of bicyclic (alkyl)(amino)carbene-SiCl4 complex, [(MeBICAAC)SiCl4] (1) with KC8 afforded low-valent Si complexes, including Si(III) radical [(MeBICAAC)SiCl3] (2) and a complex with silicon center in a formal zero-valent state, [(MeBICAAC)2Si] (3). Similarly, the reduction of in-situ generated MeBICAAC adduct of Me2SiCl2 with one equivalent of KC8 led to the formation of [(MeBICAAC)SiMe2Cl] (4) complex having an unpaired electron. These complexes have been characterized by IR, UV-Vis., NMR, HRMS, EPR and their solid-state structures were also elucidated by single crystal X-ray crystallography. Further, DFT calculations revealed the lower energy singlet state for complexes 1, 3 and doublet state for complexes 2, 4.
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Inverse sandwich complexes of Yb and Sm stabilized by a bulky ß-diketiminate (BDI) ligand have been prepared: (BDI)Ln(η6,η6-C6H6)Ln(BDI); Ln=lanthanide. Coordinated benzene ligands can be neutral, di-anionic or, often controversially discussed, even tetra-anionic. The formal charge on benzene is correlated to assignment of the metal oxidation state which generally poses a problem. Herein, we take advantage of the structural similarities found when comparing CaII with YbII, and SrII with SmII complexes. In this work, we found an excellent overlap of the Ca/Yb inverse sandwich structures but a striking difference for the Sr/Sm pair. The much shorter Sm-N and Sm-C6H6 distances are strong evidence for a SmIII-benzene-4-SmIII assignment. This was further supported by NMR spectroscopy, magnetic susceptibility, reactivity and comprehensive computational investigation.
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We report a new class of arylazopyrazolium-based ionic photoswitches (AAPIPs). These AAPIPs with different counter ions have been accessed through a modular synthetic approach in high yields. More importantly, the AAPIPs exhibit excellent reversible photoswitching and exceptional thermal stability in water. The effects of solvents, counter ions, substitutions, concentration, pH, and glutathione (GSH) have been evaluated using spectroscopic investigations. The results revealed that the bistability of studied AAPIPs is robust and near quantitative. The thermal half-life of Z isomers is extremely high in water (up to years), and it can be lowered electronically by the electron-withdrawing groups or highly basic pH.
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Negishi cross-coupling reaction of organozinc compounds as nucleophiles with aryl halides has drawn immense focus for C-C bond formation reactions. In comparison to the well-established library of Pd complexes, the C-C cross-coupling of this particular approach is largely primitive with nickel-complexes. Herein, we describe the syntheses of Ni(II) complexes, [(Me BICAAC)2 NiX2 ] (X=Cl (1), Br (2), and I (3)) by employing the bicyclic (alkyl)(amino)carbene (Me BICAAC) ligand. The reduction of complexes 1-3 using KC8 afforded the two coordinate low valent, Ni(0) complex, [(Me BICAAC)2 Ni(0)] (4). Complexes 1-4 have been characterized by spectroscopic techniques and their solid-state structures were also confirmed by X-ray crystallography. Furthermore, complexes 1-4 have been applied in a direct and convenient method to catalyze the Negishi cross-coupling reaction of various aryl halides with 2,6-difluorophenylzinc bromide or phenylzinc bromide as the coupling partner in the presence of 3â mol % catalyst. Comparatively, among all-pristine complexes, 1 exhibit high catalytic potential to afford value-added C-C coupled products without the use of any additive. The UV-vis studies and HRMS measurements of controlled stochiometric reactions vindicate the involvement of Ni(I)-NI(III) cycle featured with a penta-coordinated Ni(III)-aryl species as the key intermediate for 1 whereas Ni(0)/Ni(II) species are potentially involved in the catalytic cycle of 4.
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A modular approach has been adopted to synthesize a wide range of visible light-driven photoswitchable azoheteroarenes. In this regard, we considered ortho substitution of cyclic amines in the aryl ring and varied substitution patterns. Using detailed spectroscopic studies, we established a relationship between structure and photoswitching ability and also half-lives of the Z-isomers. Through this, we envision tunable and bidirectional longer wavelength photoswitches.
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LuzRESUMEN
BACKGROUND: The prevalence of dry eye disease is increasing globally and requires the attention of healthcare professionals as it worsens patients' quality of life. No published studies on the epidemiology of dry eyes have been found in Dubai. PURPOSE: To describe the epidemiology, prevalence, severity, and associated factors of dry eyes in Dubai, United Arab Emirates, in 2019. METHODS: This was an analytical, cross-sectional, survey-based study. An online survey was distributed by email to Mohammed Bin Rashid University students, staff, and faculty and to the staff at Mediclinic City and Parkview Hospitals in Dubai, United Arab Emirates, from April-June 2019. The survey included demographic questions and the Ocular Surface Disease Index (OSDI). RESULTS: The survey was completed by 452 participants; the majority were females (288/452; 63.7 %). The prevalence of dry eyes in Dubai was estimated to be 62.6 % (283/452), with severely dry eyes being the most prevalent (119/283; 42 %). Females, high daily screen time (> 6 h), and the use of contact lenses were found to be associated with dry eyes (P-value < 0.05, 95 % confidence interval). Age was found to be negatively correlated with prevalence of dry eyes. Exposure to smoking/shisha, history of eye injury/surgery, and nationality were not associated with dry eyes. CONCLUSIONS: This is the first cross-sectional study to investigate the prevalence of dry eyes in Dubai (62.6 %). The majority of participants had severe dry eyes symptoms. Severely dry eyes were more common among females and users of contact lenses.
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Síndromes de Ojo Seco , Calidad de Vida , Estudios Transversales , Síndromes de Ojo Seco/epidemiología , Síndromes de Ojo Seco/etiología , Femenino , Humanos , Masculino , Prevalencia , Factores de Riesgo , Encuestas y CuestionariosRESUMEN
The present work represented first study of the spatio-seasonal distribution of the multi-elements in the suspended particulate matter (SPM) of the tropical Hooghly river estuary (HRE), eastern part of India. The high load of SPM (20-3460 mg/l) might have induced negative impact on the phytoplankton density. The relative abundance of the studied elements exhibited the following decreasing trend (concentration in µg/g and %): Si(26.44 ± 3.75%) > Al(7.94 ± 1.52%) > Fe(6.17 ± 1.9%) > K(3.05 ± 1.5%) > Ca(1.97 ± 1.11%) > Mg(1.57 ± 1.71%) > Na(1.45 ± 8.40%) > Mn(1273 ± 2003) > Zn(178.43 ± 130.95) > V(151.54 ± 27.13) > Cr(147.08 ± 32.21) > Cu(62.06 ± 14.03) > Ni(49.64 ± 12.09) > Pb(21.5 ± 10.45). The accumulation of Ni, Cr, Pb, and Cu is mainly controlled by the formation of Fe hydroxides along with particulate organic carbon (POC) and salinity. The average geo-accumulation index (Igeo) and enrichment factor (EF) endorsed the substantial input of Cr (Igeo = 0.037; EF = 1.61) and Zn (Igeo = 0.123; EF = 2.07) from diffused pollution sources. From ecotoxicological point of view, the quality guidelines (QGs) suggested that Cr and Ni might possess frequent adverse biological effects. However, the mean probable effect level (PEL) quotient values revealed 49% probability of toxicity to the aquatic biota for five toxic elements (Cr, Ni, Cu, Zn, and Pb). The geochemical approaches, pollution indices, and statistical evaluation together revealed low to moderate contamination in the estuary. This baseline data would be beneficial in adopting proper management strategies for sustainable utilization and restoration of the water resources. The authors strongly recommend continuous systematic monitoring and installation of treatment plants for management of this stressed estuary.
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Metales Pesados/análisis , Oligoelementos/análisis , Contaminantes Químicos del Agua/análisis , Monitoreo del Ambiente , Estuarios , Sedimentos Geológicos , India , Material Particulado/análisis , Ríos , Estaciones del AñoRESUMEN
The reactivity of a bicyclic (alkyl)(amino)carbene (BICAAC) towards different boranes has been examined in the present work. The reactions with boranes BX3·SMe2 (X = H, Cl, Br), BF3·OEt2 and BCl3 yield Lewis adducts [BICAAC·BH3] (1), [BICAAC·BHCl2] (2), [BICAAC·BH2Cl] (3), [BICAAC·BF3] (4), [BICAAC·BCl3] (5) and [BICAAC·BBr3] (6) respectively, whereas more hydridic boranes, 9-borabicyclo[3.3.1]nonane (9-BBN) and catecholborane (HBcat), enable the insertion of the carbene carbon into the B-H bond to form [BICAAC(H)-(9-BBN)] (7) and [BICAAC(H)-Bcat] (8). These complexes are the first examples of BICAAC-boron compounds and have been characterized using IR, multinuclear NMR spectroscopy, HRMS spectrometry and single crystal X-ray diffraction. Computational analyses were also performed to gain insight into the mechanism of B-H bond activation and adduct formation. Furthermore, the reactions of the BICAAC with boranes have been compared with the known reactions of CAACs and NHCs.
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This study demonstrates the first synthesis of cyclic (alkyl)(amino)carbene (cAAC) adducts of Hg(ii), [cAACMe·HgBr(µ-Br)]2 (1a) and [cAACcy·HgBr(µ-Br)]2 (1b). Adduct 1b catalyzes intermolecular hydroamination of aromatic alkynes and amines under mild conditions to afford aromatic imines. The quest to prepare an electrophilic Hg(ii) complex resulted in the synthesis of cationic [(cAACcy)2Hg(H2O)]2+2[NO3]- (3) by reacting 1b with AgNO3.
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CONTEXT: Asthma is multifaceted disease where many targets contribute towards its development and progression. Among these, adenosine receptor subtypes play a major role. OBJECTIVE: MCD-KV-10, a novel thiazolo-thiophene was designed and evaluated pre-clinically for its implication in management of asthma. MATERIALS AND METHODS: This compound showed good affinity and selectivity towards A(2A)/A3 adenosine receptor (AR) subtypes. Furthermore, MCD-KV-10 was evaluated for in vitro lipoxygenase inhibition activity; in vivo mast cell stabilization potential and in vivo anti-asthmatic activity was done in ovalbumin-induced airway inflammation model in guinea pigs. RESULTS: The compound showed good (>57%) inhibition of lipoxygenase enzyme and also effectively protected mast cell degranulation (>63%). The compound showed good anti-asthmatic activity as inferred from the in vivo studies. DISCUSSION: These results indicate that MCD-KV-10 has an inhibitory effect on airway inflammation. CONCLUSION: Though, we have identified a potential candidate for management of asthma, further mechanistic studies are needed.
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Antiasmáticos/farmacología , Asma/tratamiento farmacológico , Antagonistas de Receptores Purinérgicos P1/farmacología , Tiazoles/química , Tiofenos/química , Animales , Antiasmáticos/síntesis química , Antiasmáticos/química , Antiasmáticos/uso terapéutico , Asma/inmunología , Asma/metabolismo , Asma/patología , Citocinas/sangre , Cobayas , Histamina/metabolismo , Lipooxigenasas/metabolismo , Pulmón/efectos de los fármacos , Pulmón/inmunología , Pulmón/patología , Masculino , Mastocitos/efectos de los fármacos , Estructura Molecular , Ovalbúmina/inmunología , Antagonistas de Receptores Purinérgicos P1/síntesis química , Antagonistas de Receptores Purinérgicos P1/química , Antagonistas de Receptores Purinérgicos P1/uso terapéutico , Receptor de Adenosina A2A/metabolismo , Receptor de Adenosina A3/metabolismo , Tiazoles/síntesis química , Tiazoles/farmacología , Tiazoles/uso terapéutico , Tiofenos/síntesis química , Tiofenos/farmacología , Tiofenos/uso terapéuticoRESUMEN
Multiple sclerosis (MS) is an autoimmune inflammatory disease of the central nervous system (CNS) where the communication ability of nerve cells in the brain and spinal cord with each other gets impaired. Some current findings suggest the role of glutamate excitotoxicity in the development and progression of MS. An excess release of glutamate leads to the activation of ionotropic and metabotropic receptors, thus resulting in accumulation of toxic cytoplasmic Ca(2+) and cell death. However, it has been observed that gamma-aminobutyric acid-A (GABAA) receptors located in the nerve terminals activate presynaptic Ca(2+)/calmodulin-dependent signaling to inhibit depolarization-evoked Ca(2+) influx and glutamate release from isolated nerve terminals, which suggest a potential implication of GABAA receptor in management of MS. With this proof of concept, we tried to explore the potential of selective GABAA receptor agonists or positive allosteric modulators (diazepam and phenobarbitone sodium) and GABAA level enhancer (sodium valproate) for management of MS by screening them for their activity in experimental autoimmune encephalomyelitis (EAE) model in rats and cuprizone-induced demyelination model in mice. In this study, sodium valproate was found to show the best activity in the animal models whereas phenobarbitone sodium showed moderate activity. However, diazepam was found to be ineffective.
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PURPOSE: To evaluate the efficacy of transpupillary thermotherapy (TTT) in choroidal neovasularisation (CNVM) secondary to age related macular degeneration (AMD). MATERIAL AND METHODS: Retrospective, non-randomized study of 28 eyes of 28 patients with subfoveal CNVM (classic, occult or mixed) secondary to AMD. RESULTS: Fifteen patients (53.57%) maintained their pre-treatment vision, 2 (7.14%) patients showed improvement of more than 2 lines and 11 (39.28%) patients showed deterioration of vision by >2 lines. Angiographic and clinical regression of CNVM was noted in 19 patients (67.8%) on an average follow up of 15.32 +/- 3.31 months. CONCLUSION: TTT leads to stabilisation of vision in 60% of treated eyes with CNVM due to AMD.