Electrocatalytic hydrogen evolution mediated by an organotelluroxane macrocycle stabilized through secondary interactions.

A discrete liphophilic organotelluroxane macrocycle has been found to catalyse the hydrogen evolution reaction (HER) by proton reduction efficiently. The macrocycle is synthesized via chloride abstraction from bis(p-methoxyphenyl) tellurium dichloride (p-MeOC6H5)2TeCl2 (1) by silver salts AgMX4 (MX4 = BF4-, and ClO4-) resulting in in situ generated di-cationic tetraorganoditelluroxane units; two such units are held together by two weak anions µ2-MX4, bridging to form 12-membered di-cationic macrocycles [((p-MeO-C6H4)2Te)2(µ-O)(µ2-F2BF2)2]2+ (2) and [((p-MeO-C6H4)2Te)2(µ-O)(µ2-O2ClO2)2]2+ (3) stabilized via Te-(µ2-BF4/ClO4), with secondary interactions. The charge is balanced by the presence of two more anions, one above and another below the plane of the macrocycle. Similar reaction at higher temperatures leads to the formation of telluronium salts R3TeX [X = BF4- (4), ClO4- (5)] as a major product. The BF4- anion containing macrocycle and telluronium salt were monitored using 19F NMR. HRMS confirmed the structural stability of all the compounds in the solution state. The organotelluroxane macrocycle 2 has been found to act as an efficient electrocatalyst for proton reduction in an organic medium in the presence of p-toluene sulfonic acid as a protic source.

Tunable bandgaps in self-assembled transition metal-incorporated heterometallic M2Sb4 (M = V, Mn, Co, Ni, and Cu) oxo clusters.

This paper investigates the reactivity and optical properties of transition metal-incorporated organoantimony(V) clusters prepared by a solvothermal route. The detailed structural characterization of novel heterometallic M2Sb4 oxo clusters is reported herein. Single crystal X-ray diffraction revealed the formation of hexanuclear organoantimony(V) based oxo clusters [(p-ClC6H4Sb)4V2(O)2(µ3-O)2(µ2-O)2(t-BuPO3)4(µ2-OCH3)4] (1), [M2(p-iPr-C6H4Sb)4(µ3-O)2(µ2-O)2(µ2-OCH3)4(t-BuPO3)4(py)2]·xCH3OH, where M = Mn, x = 2 (2), Co, x = 1 (3), Ni, x = 2 (4) and Cu, x = 2 (5). The magnetic behaviour of the clusters was probed by magnetic susceptibility measurements. Optical absorption studies showed that bandgap reduction can be achieved by incorporating an appropriate transition metal into the homometallic Sb6 oxo cluster.

Discrete Molecular Aggregates Based on ZnII and SbIII/V Ions Displaying Efficient Antibacterial and Antioxidant Properties.

The reactions of [Zn3Cl2(3,5-Me2PzH)4(t-BuPO3)2] with organostibonic acid in varying reaction conditions have been investigated. Single-crystal X-ray diffraction studies reveal the formation of [Zn2(p-ClC6H4Sb)2(O)2(OCH3)2(t-BuPO3)3(py)2] (1), [Zn2(p-ClC6H4SbV)4(SbIII)2(O)8(t-BuPO3H)4(t-BuPO3)2(py)2Cl2] (2), and [Zn2(RSb)4(O)4(OCH3)4(t-BuPO3)4(py)2], where R = p-ClC6H4 (3) and R = p-iPrC6H4 (4), respectively. Interestingly, in the synthesis of 2, complete dearylation of organoantimony moieties followed by C-F bond formation, a reduction from Sb (V) to Sb (III), and Sb···Cl weak intermolecular interactions have been observed. ESI-MS studies suggested that clusters 1-4 maintained their structural integrity in the solution state also. Solution NMR studies (1H, 31P, and 13C) support well the observed solid-state structures. 1-4 were tested for antibacterial activity using a microdilution assay. 1 and 4 showed the best activity with lower MIC values (0.78-6.25 µg/mL) against all the tested pathogens. The total antioxidant activity of 1-4 was evaluated through the phosphomolybdenum assay, which showed a total antioxidant activity ranging from 28.96 to 86.46 mg AAE/g compound with the ascorbic acid standard.

Stibonic acids and related stibonate-phosphonate clusters: Synthesis, characterization and bioactivity evaluation.

The reaction of 4-(azobenzene)phenylstibonic acid with t-butylphosphonic acid led to the isolation of the tetranuclear oxo-hydroxo antimony cluster of formulae [(4-azobenzene-C6H4Sb)4(OH)4(tBuPO3)6] (C1). The reaction of (p-t-butyl phenyl stibonic acid with phenyl phosphonic acid resulted in the isolation of complex with formulae [(p-t-BuC6H4Sb)4(O)2(PhPO3)4(PhPO3H)4] (C2). Based upon the initial results from docking studies, parent stibonic acids, t-butyl-phenylstibonic acid, p-isopropylphenylstibonic acid, 4-azobenzenephenylstibonic acid, and the derived tetranuclear organoantimonate-phosphonate clusters were screened against different cancer cell lines, various Gram-positive and Gram-Negative bacteria and mycobacteria for possible bioactivity profile.

In Situ Assembled Polynuclear Zinc Oxo Clusters Using Modified Schiff Bases as Ligands.

A series of different cores and nuclearity zinc metal clusters 1-5 have been synthesized using Zn(ClO4)2·6H2O, Schiff-base primary ligands, and dibenzoyl methane (DBM) or monoethanolamine (MEA) as co-ligand in a room-temperature reaction. The structure of the complexes is characterized using single-crystal X-ray diffraction. Among them, (1) [Zn(L1)(DBM)] is mononuclear; (2) [Zn4(L2)2(DBM)4], (3) [Zn4(L2)4(H2O)2(ClO4)2]·2CH2Cl2, and (4) [Zn4(L3)2(DBM)4] have a cubane core; and (5) [Zn4(L4)4(MEA)2(ClO4)2] has a ladderlike core structure. Compounds 1-5 have also been characterized using UV-vis absorption and emission spectroscopies. For an in-depth understanding of the absorption spectra of 1 and 3, density functional theory (DFT) calculations have been performed, which suggest that the transitions correspond to the π → π* intraligand charge transfer (ILCT) transitions.

Retrospective analysis (2009-2017) of factors associated with progression and regression of non-alcoholic fatty liver disease (Hepatic steatosis) in patients with type 2 diabetes seen at a tertiary diabetes centre in Southern India.

AIM: To identify the profiles and factors associated with progression/regression of ultrasound-derived hepatic steatosis with type 2 diabetes mellitus seen at a tertiary diabetes center in southern India. METHODS: Participants were individuals with type 2 diabetes mellitus with at least two consecutive ultrasound measurements available. Hepatic steatosis was assessed using high-resolution B-mode ultrasonography. Admittedly ultrasonography has lower sensitivity and specificity, however, it is the only modality available in a routine clinical setting to screen for hepatic steatosis. Progression or regression of hepatic steatosis was assessed after a mean follow-up of 3.0 ± 2.1 years and correlated with clinical and biochemical parameters. RESULTS: A total of 1835 participants with type 2 diabetes mellitus were studied, of whom 88.6% had some form of hepatic steatosis at baseline which included mild steatosis (grade 1) in 982 (53.5%), moderate steatosis (grade 2) in 628 (34.2%) and severe steatosis (grade 3) in 15 (0.8%). Hepatic steatosis progression, regression or no change in grade of hepatic steatosis were seen in 21.5%, 26.6% and 51.9% of participants. Increase in body weight, body mass index, glycated haemoglobin, serum triglycerides and gamma glutamyl transferase were the factors associated with progression of hepatic steatosis, whereas regression showed reduction in body weight, body mass index, fasting plasma glucose and glycated haemoglobin. CONCLUSION: Among South Indian type 2 diabetes patients with hepatic steatosis, severity of steatosis progressed in 1/3rd while it regressed in 1/4th. These retrospective data need proper ascertainment in controlled studies.

Profiles of Intraday Glucose in Type 2 Diabetes and Their Association with Complications: An Analysis of Continuous Glucose Monitoring Data.

Aims: To identify profiles of type 2 diabetes from continuous glucose monitoring (CGM) data using ambulatory glucose profile (AGP) indicators and examine the association with prevalent complications. Methods: Two weeks of CGM data, collected between 2015 and 2019, from 5901 adult type 2 diabetes patients were retrieved from a clinical database in Chennai, India. Non-negative matrix factorization was used to identify profiles as per AGP indicators. The association of profiles with existing complications was examined using multinomial and logistic regressions adjusted for glycated hemoglobin (HbA1c; %), sex, age at onset, and duration of diabetes. Results: Three profiles of glycemic variability (GV) were identified based on CGM data-Profile 1 ["TIR Profile"] (n = 2271), Profile 2 ["Hypo"] (n = 1471), and Profile 3 ["Hyper"] (n = 2159). Compared with time in range (TIR) profile, those belonging to Hyper had higher mean fasting plasma glucose (202.9 vs. 167.1, mg/dL), 2-h postprandial plasma glucose (302.1 vs. 255.6, mg/dL), and HbA1c (9.7 vs. 8.6; %). Both "Hypo profile" and "Hyper profile" had higher odds of nonproliferative diabetic retinopathy ("Hypo": 1.44, 1.20-1.73; "Hyper": 1.33, 1.11-1.58), macroalbuminuria ("Hypo": 1.58, 1.25-1.98; "Hyper": 1.37, 1.10-1.71), and diabetic kidney disease (DKD; "Hypo": 1.65, 1.18-2.31; "Hyper": 1.88, 1.37-2.58), compared with "TIR profile." Those in "Hypo profile" (vs. "TIR profile") had higher odds of proliferative diabetic retinopathy (PDR; 2.84, 1.65-2.88). Conclusions: We have identified three profiles of GV from CGM data. While both "Hypo profile" and "Hyper profile" had higher odds of prevalent DKD compared with "TIR profile," "Hypo profile" had higher odds of PDR. Our study emphasizes the clinical importance of recognizing and treating hypoglycemia (which is often unrecognized without CGM) in patients with type 2 Diabetes Mellitus.

Accuracy of 1-Hour Plasma Glucose During the Oral Glucose Tolerance Test in Diagnosis of Type 2 Diabetes in Adults: A Meta-analysis.

OBJECTIVE: One-hour plasma glucose (1-h PG) during the oral glucose tolerance test (OGTT) is an accurate predictor of type 2 diabetes. We performed a meta-analysis to determine the optimum cutoff of 1-h PG for detection of type 2 diabetes using 2-h PG as the gold standard. RESEARCH DESIGN AND METHODS: We included 15 studies with 35,551 participants from multiple ethnic groups (53.8% Caucasian) and 2,705 newly detected cases of diabetes based on 2-h PG during OGTT. We excluded cases identified only by elevated fasting plasma glucose and/or HbA1c. We determined the optimal 1-h PG threshold and its accuracy at this cutoff for detection of diabetes (2-h PG ≥11.1 mmol/L) using a mixed linear effects regression model with different weights to sensitivity/specificity (2/3, 1/2, and 1/3). RESULTS: Three cutoffs of 1-h PG, at 10.6 mmol/L, 11.6 mmol/L, and 12.5 mmol/L, had sensitivities of 0.95, 0.92, and 0.87 and specificities of 0.86, 0.91, and 0.94 at weights 2/3, 1/2, and 1/3, respectively. The cutoff of 11.6 mmol/L (95% CI 10.6, 12.6) had a sensitivity of 0.92 (0.87, 0.95), specificity of 0.91 (0.88, 0.93), area under the curve 0.939 (95% confidence region for sensitivity at a given specificity: 0.904, 0.946), and a positive predictive value of 45%. CONCLUSIONS: The 1-h PG of ≥11.6 mmol/L during OGTT has a good sensitivity and specificity for detecting type 2 diabetes. Prescreening with a diabetes-specific risk calculator to identify high-risk individuals is suggested to decrease the proportion of false-positive cases. Studies including other ethnic groups and assessing complication risk are warranted.

Novel subgroups of type 2 diabetes and their association with microvascular outcomes in an Asian Indian population: a data-driven cluster analysis: the INSPIRED study.

INTRODUCTION: Type 2 diabetes is characterized by considerable heterogeneity in its etiopathogenesis and clinical presentation. We aimed to identify clusters of type 2 diabetes in Asian Indians and to look at the clinical implications and outcomes of this clustering. RESEARCH DESIGN AND METHODS: From a network of 50 diabetes centers across nine states of India, we selected 19 084 individuals with type 2 diabetes (aged 10-97 years) with diabetes duration of less than 5 years at the time of first clinic visit and performed k-means clustering using the following variables: age at diagnosis, body mass index, waist circumference, glycated hemoglobin, serum triglycerides, serum high-density lipoprotein cholesterol and C peptide (fasting and stimulated). This was then validated in a national epidemiological data set of representative individuals from 15 states across India. RESULTS: We identified four clusters of patients, differing in phenotypic characteristics as well as disease outcomes: cluster 1 (Severe Insulin Deficient Diabetes, SIDD), cluster 2 (Insulin Resistant Obese Diabetes, IROD), cluster 3 (Combined Insulin Resistant and Deficient Diabetes, CIRDD) and cluster 4 (Mild Age-Related Diabetes, MARD). While SIDD and MARD are similar to clusters reported in other populations, IROD and CIRDD are novel clusters. Cox proportional hazards showed that SIDD had the highest hazards for developing retinopathy, followed by CIRDD, while CIRDD had the highest hazards for kidney disease. CONCLUSIONS: Compared with previously reported clustering, we show two novel subgroups of type 2 diabetes in the Asian Indian population with important implications for prognosis and management. The coexistence of insulin deficiency and insulin resistance seems to be peculiar to the Asian Indian population and is associated with an increased risk of microvascular complications.

Assembling Homometallic Sb6 and Heterometallic Ti4Sb2 Oxo Clusters.

Isolation and structural characterization of novel organoantimony(V)-based oxo clusters are reported. (RSb)4(OH)4(t-BuPO3)6 and (RSb)2(O)(t-BuPO3H)6 independently in the presence of pyridine under solvothermal conditions afford the hexanuclear organoantimonate clusters [(RSb)6(µ3-O)2(µ2-O)6(t-BuPO3)4], where R = p-i-PrC6H4 (1), p-ClC6H4 (2). Further, reaction of organostibonate phosphonate with Ti(OiPr)4 in the presence of pyridine under solvothermal conditions afforded the mixed-metal titanium stibonate hexanuclear clusters [(RSb)2Ti4(µ3-O)2(µ2-O)2(t-BuPO3)4(µ-OCH3)4(OCH3)4], where R = p-i-PrC6H4 (3), p-ClC6H4 (4). Band gap measurements were performed on 1-4. They reveal a remarkable reduction in the band gap on moving from the heavier main-group-based oxo cages (1 and 2) to the titanium-incorporated oxo cages (3 and 4).

Bismuth and Titanium Phosphinates: Isolation of Tetra-, Hexa- and Octanuclear Clusters.

The reaction of organobismuth precursors with trityl-H-phosphinic acid in varying reaction conditions afforded colorless crystals, whose single crystal X-ray characterization revealed the formation of monomer {(Ph3Bi)[(Ph3C)(H)PO2]2}·3/2(CH3CN)2.1/2H2O (1) and butterfly shaped tetranuclear cluster Bi4(µ3-O)2[(Ph3C)(H)(PO2)]8·2CH2Cl2·1/2CH3CN.2H2O (2). The reaction of titanium isopropoxide with two different phosphinic acids trityl-H-phosphinic acid and cycP(O)(OH) led to isolation of cubane type octahedral complex {Ti8(µ2-O)8(µ2-OH)4[(Ph3C)(H)PO2]12}[3C7H8] (3) and hexanuclear complex Ti6(µ2-cycPO2)9(µ2-O)6(µ2-OH)3·4CH3CN·4H2O (4) respectively.

Effect of coordination geometry on the magnetic properties of a series of Ln2 and Ln4 hydroxo clusters.

A series of three isostructural tetranuclear complexes with the general molecular formula [Ln4(µ3-OH)4(L)4(µ2-piv)4(MeOH)4] (Ln = Gd 1, Dy 2 and Ho 3; LH = [1,3-bis(o-methoxyphenyl)-propane-1,3-dione]) were isolated and unambiguously characterized by single crystal XRD. Under similar reaction conditions, simply changing the co-ligand from pivalate to 2,6-bis(hydroxymethyl)-p-cresol (LH'3) led to the isolation of dinuclear Ln(iii) complexes with the general molecular formula [Ln2(L)4(µ2-LH'2)2]·4DMF (Ln = Gd 4, Dy 5 and Ho 6). Direct current magnetic susceptibility data studies on the polycrystalline sample of 1-6 and the results reveal the existence of weak antiferromagnetic exchange interactions between the lanthanide ions in 1 which is evident from the spin Hamiltonian (SH) parameters (J1 = -0.055 cm-1 and g = 2.01) extracted by fitting χMT(T). On the other hand, though complex 4 exhibits weak antiferromagnetic coupling (J1 = -0.048 cm-1 and g = 1.99) between the Gd(iii) ions, the χMT(T) data of complexes 5 and 6 unambiguously disclose the presence of ferromagnetic interactions between Dy(iii) and Tb(iii) ions at lower temperature. Magnetization relaxation dynamics studies performed on 2 show frequency dependent out-of-phase susceptibility signals in the presence of an optimum external magnetic field of 0.5 kOe. In contrast, complex 5 shows slow magnetization relaxation with an effective energy barrier (Ueff) of 38.17 cm-1 with a pre-exponential factor (τ0) of 1.85 × 10-6 s. The magnetocaloric effect (MCE) of complexes 1 and 4 was extracted from the detailed magnetization measurement and the change in the magnetic entropy (-ΔSm) of 1 and 4 was found to be 25.57 J kg-1 K-1 and 12.93 J kg-1 K-1, respectively, at 3.0 K for ΔH = 70 kOe.

In situ generated polysiloxanes stabilizing µ3-oxo bridged Sb3 triangles.

The reaction of RSbO3H2 with t-butylsilanetriol has led to the isolation of organoantimony(v) based molecular triangles stabilized by siloxane frameworks. Depending on the reaction conditions employed or the substituents present on the antimony atom, either a combination of a disiloxane and a tetrasiloxane framework or a trisiloxane framework was generated in situ leading to the stabilization of the Sb3 triangle.

Monoorganoantimony(v) phosphonates and phosphoselininates.

Molecular oxo-hydroxo clusters have been synthesized by reactions of arylstibonic acids with organophosphonic acid and phenylseleninic acid. Single crystal X-ray structural elucidation revealed the formation of [(p-i-PrC6H4Sb)4(OH)4(t-BuPO3)6] (1), [(p-t-BuC6H4Sb)4(O)2(PhPO3)4(PhPO3H)4] (2), [(p-i-PrC6H4Sb)4(O)3(OH)(PhSeO2)2(t-BuPO3)4(t-BuPO3H2)2] (3), [(p-MeC6H4Sb)4(O)3(OH)(PhSeO2)2(t-BuPO3)4(t-BuPO3H2)2] (4) and [(p-t-BuC6H4Sb)2(O) (PhSeO2)2(t-BuPO3H)4] (5) respectively. Mass spectral studies reveal that the clusters maintain their structural integrity in solution as well. Solution NMR studies ((1)H, (31)P and (77)Se) show spectral patterns which correlate well with the observed solid state structures of 1-5.

Te4Se2O6 macrocycle stabilizing triangular planar and tetrahedral anions.

The anion exchange reactions of Cl-macrocycle 1a [(p-MeO-C6H4)2Te)2(µ-O)(µ-PhSeO2)(µ4-Cl)]2 with AgNO3, AgClO4 and AgBF4 yielded colourless solids whose single crystal X-ray diffraction studies revealed the formation of 12-membered macrocycles [(p-MeO-C6H4)2Te)2(µ-O)(µ-PhSeO2)(µ-X)]2 [X = NO3 (2), ClO4 (3), BF4 (4)]. ESI-MS studies revealed that macrocycles 2­4 retain their integrity in solution. The solution (125)Te NMR spectrum of 4 shows the appearance of a triplet ((1)JTe···F = 568 Hz) that can be assigned to coupling between (125)Te nuclei and two fluorine atoms in BF4(−) ions.

Assembling anionic Sb(V)/(III) containing polyoxostibonates stabilized by triphenyltellurium cations.

Reactions of diphenyltellurium oxide with organostibonic acid and polymeric triphenylantimony oxide have been investigated independently. Single crystal X-ray diffraction studies have revealed the formation of novel and rare mixed valent Sb(v)/(iii) containing polyoxostibonates {(C6H5)3Te}2{Na2(H2O)2(p-Br-C6H4Sb(V))10(Sb(III))4[(C6H5)2Te]4(O)30(OH)4} and {(C6H5)3Te}4{[(C6H5)2Sb(V)]4(Sb(III))4(O)12(OH)4} . Solution (125)Te NMR supports the solid state structures presented. Interestingly, during the assembly of these POMs several processes happen simultaneously. Rarely observed reduction from Sb(v) to Sb(iii), complete dearylation of organoantimony precursors and complexation ability of a tetraorganoditelluroxane moiety stabilizing large and novel POM structures (as in ) along with the formation of triphenyltellurium cations which not only provide charge balance but also stabilize the POM framework (as in ) by weak interactions are reported.

Hexa- and trinuclear organoantimony oxo clusters stabilized by organosilanols.

Reactions of Ph2SbCl3 with RSi(OH)3 [where R = tert-Bu, cyclo-C6H11] and Ph2Si(OH)2 in toluene in the presence of triethylamine as a base were performed. Single-crystal X-ray structural elucidation of the products revealed the formation of hexanuclear antimony(V) and mixed-valent antimony (III/V) oxo-hydroxo clusters built up of an incomplete cubane subunit. Interestingly, in all the reactions, at least one Sb-C bond cleavage has been observed, leading to the formation of novel cluster assemblies [(Ph2Sb)4(PhSb)2(C4H9SiO3)2(O)6(OH)2] (1), [(Ph2Sb)4(PhSb)2(C6H11SiO3)2(O)6(OH)2] (2), [(Ph2Sb)(PhSb)2(Ph2SiO2)2(O)3(OH)2](-)Et3NH(+) (3), and [(Ph2Sb)4(Sb)2(Ph2SiO2)2(O)6(OH)2] (4), respectively.

New structural form of a tetranuclear lanthanide hydroxo cluster: Dy4 analogue display slow magnetic relaxation.

A series of tetranuclear lanthanide (Ln = Tb, Dy, Ho) hydroxo clusters has been synthesized by reaction of LnCl3·6H2O (Ln = Tb (1), Dy (2), Ho (3)) with o-vanilin based schiff base ligand 2-(2,3 dihydroxpropyl imino methyl) 6-methoxy phenol (H3L) in methanol and in the presence of triethylamine as base. The solid state structures of all the products were established by single crystal X-ray diffraction technique. Magnetism studies reveal that Dy4 analogue exhibits slow magnetic relaxation at low temperatures.

Tetranuclear stiboxanes (RSb)4O6, exhibiting an adamantane-type structure.

Depolymerization reactions of organostibonic acids with protic ligands have been investigated. Reaction of arylstibonic acids with 8-hydroxyquinoline (8-HQ), or {2-[1H-pyrazol-5(3)-yl]naphthalene-1-ol} (H(2)naphpz) in a 1 : 1 stoichiometry in refluxing toluene affords adamantane-like L(4)(RSb)(4)O(6) clusters [(p-XC(6)H(4)Sb)(4)(O)(6)(Q)(4)] (where X = Cl (1), Br (2), QH = 8-hydroxyquinoline), [(p-ClC(6)H(4)Sb)(4)(O)(6)(Hnaphpz)(4)]·H(2)naphpz (3) and [(p-Br-C(6)H(4)Sb)(4)(O)(6)(Hnaphpz)(4)](2)·H(2)naphpz (4). Further a tetrameric organoantimony oxo cluster, L(4)(RSb)(4)O(4) [(p-ClC(6)H(4)Sb)(4)(O)(4)(naphpz)(4)] (5) has also been isolated as a side product in the reaction of arylstibonic acid with naphthylphenolic pyrazole. Interestingly 1-4 structurally resemble the dimeric form of the antimony oxide Sb(2)O(3) and its mineral senarmontite.