Eight-coordinate mono- and dinuclear Dy(III) complexes containing a rigid equatorial plane and an anisobidentate carboxylate ligand in the axial position: synthesis, structure and magnetism.

A rigid pentadentate chelating ligand (H2L) has been utilized to synthesize a series of octacoordinate mononuclear complexes, [Dy(L)(Ph3PO)(OOCR)] (where R = C6H5 (1), C(CH3)3 (2), CF3 (3)) and a dinuclear complex, [Dy2(L)2(Ph3PO)2{(OOC)2C6H4}] (4) based on the highly anisotropic Dy(III) ion. All the complexes were structurally characterized by single-crystal X-ray diffraction studies. The complexes were formed by the coordination action of the dianionic pentadentate ligand [L]2-, one phosphine oxide, and carboxylate ligands. DC and AC magnetic measurements were performed on 1-4. Complexes 1-4 show SMM behaviour, under zero DC field for 1 and 4, and under 500 Oe and 1000 Oe DC fields for 2 and 3 respectively, with thermally activated, Raman, and Raman and quantum tunnelling dominant relaxation mechanisms for 1 and 2, 3 and 4, respectively.

In situ hydrolysis of a carbophosphazene ligand leads to one-dimensional lanthanide coordination polymers. Synthesis, structure and dynamic magnetic studies.

An in situ hydrolysis of the P-Cl bonds of the carbophosphazene [{NC(NMe2)}2{NPCl2}] (LPCl2) in the presence of hydrated lanthanide(III) nitrates in a dichloromethane and methanol (2 : 1) solvent mixture afforded a series of novel 1D coordination polymers: [{Ln(LHPO2)3(NO3)2(CH3OH)(H2O)} (Cl)]n {where Ln(III) = Gd (1), Tb (2), Dy (3), or Er (4) and LHPO2 is the hydrolyzed carbophosphazene (LPCl2) ligand}. X-ray crystallographic analysis revealed that complexes 1-4 are isostructural and crystallized in the monoclinic crystal system having P21/c space group. The coordination polymers are formed because of the involvement of the geminal P(O)(OH) moieties of the carbophosphazene ligand. Each lanthanide(III) ion is 9-coordinate (9O) in a distorted muffin geometry. Magnetic measurements revealed that both DyIII and ErIII analogues exhibit field-induced single-molecule magnet (SMM) behavior at 0.8 kOe and 2.2 k Oe, respectively. At such dc fields, the dynamic magnetic susceptibility displays complex behavior with a triple magnetic relaxation contribution for 3, while two contributions were identified for 4. The observed static and dynamic magnetic behavior for complexes 1-4 were further rationalized with the aid of BS-DFT and CASSCF/SO-RASSI/SINGLE_ANISO calculations.

Self-Assembly Driven Formation of Functional Ultralong "Artificial Fibers" to Mitigate the Neuronal Damage Associated with Alzheimer's Disease.

Fibrillation of amyloid beta (Aß) is the key event in the amyloid neurotoxicity process that induces a chain of toxic events including oxidative stress, caspase activation, poly(ADP-ribose) polymerase cleavage, and mitochondrial dysfunction resulting in neuronal loss and memory decline manifesting as clinical dementia in humans. Herein, we report the development of a novel, biologically active supramolecular probe, INHQ, and achieve functional nanoarchitectures via a self-assembly process such that ultralong fibers are achieved spontaneously. With specifically decorated functional groups on INHQ such as imidazole, hydroxyquinoline, hydrophobic chain, and hydroxyquinoline molecules, these ultralong fibers coassembled efficiently with toxic Aß oligomers and mitigated the amyloid-induced neurotoxicity by blocking the aforementioned biochemical events leading to neuronal damage in mice. These functional ultralong "Artificial Fibers" morphologically resemble the amyloid fibers and provide a higher surface area of interaction that improves its clearance ability against the Aß aggregates. The efficacy of this novel INHQ molecule was ascertained by its high ability to interact with Aß. Moreover, this injectable, ultralong INHQ functional "artificial fiber" translocates through the blood-brain barrier and successfully attenuates the amyloid-triggered neuronal damage and pyknosis in the cerebral cortex of wild-type mouse. Utilizing various spectroscopic techniques, morphology analysis, and in vitro, in silico, and in vivo studies, these ultralong INHQ fibers are proven to hold great promise for treating neurological disorders at all stages with a potential to replace the existing medications, reduce complications in the brain, and eradicate the amyloid-triggered neurotoxicity implicated in numerous disorders in human through a rare synergistic mechanism.

Sustainable hydrogen generation and storage - a review.

In 21st century, the energy demand has grown incredibly due to globalization, human population explosion and growing megacities. This energy demand is being mostly fulfilled by fossil-based sources, which are non-renewable and a major cause of global warming. Energy from these fossil-based sources is cheaper, however challenges exist in terms of climate change. This makes renewable energy sources more promising and viable for the future. Hydrogen is a promising renewable energy carrier for fulfilling the increasing energy demand due to its high energy density, non-toxic and environment friendly characteristics. It is a non-toxic energy carrier as combustion of hydrogen produces water as the byproduct whereas other conventional fuels produce harmful gases and carcinogens. Because of its lighter weight, hydrogen leaks are also easily dispersed in the atmosphere. Hydrogen is one of the most abundant elements on Earth, yet it is not readily available in nature like other fossil fuels. Hence, it is a secondary energy source and hydrogen needs to be produced from water or biomass-based feedstock for it to be considered renewable and sustainable. This paper reviews the renewable hydrogen generation pathways such as water splitting, thermochemical conversion of biomass and biological conversion technologies. Purification and storage technologies of hydrogen is also discussed. The paper also discusses the hydrogen economy and future prospects from an Indian context. Hydrogen purification is necessary because of high purity requirements in particular applications like space, fuel cells etc. Various applications of hydrogen are also addressed and a cost comparison of various hydrogen generation technologies is also analyzed. In conclusion, this study can assist researchers in getting a better grasp of various renewable hydrogen generation pathways, it's purification and storage technologies along with applications of hydrogen in understanding the hydrogen economy and its future prospect.

Synthesis, structures and magnetic studies of hexanuclear lanthanide complexes: SMM behavior of the DyIII analogue and MCE properties of the GdIII analogue.

The synthesis, structure and magnetic properties of homometallic hexanuclear lanthanide complexes [Ln6(HL)4(tfa)4(S)2]·2NO3·x H2O·yMeOH (1, Ln = Gd, S = MeOH, x = 0, y = 0; 2, Ln = Tb, S = H2O, x = 2, y = 2; 3, Ln = Dy, S = MeOH, x = 0, y = 2; 4, Ln = Er, S = MeOH, x = 0, y = 2). [(H4L) = 6-((bis(2-hydroxyethyl)amino)-N'-(2-hydroxybenzylidene)picolinohydrazide) (tfa = trifloroacetylacetone)] are reported. These hexanuclear assemblies are made up of two trinuclear triangular sub-units linked through the oxygen atoms of two phenoxide bridging groups in a corner sharing arrangement. Magnetic studies reveal that 1 displays a magnetocaloric effect with a maximum value of -ΔSm = 21.03 J kg-1 K-1 at T = 3 K and under an applied field change ΔB = 5 T. Complex 3 shows slow relaxation of magnetization even under zero applied field although a clear maximum in the ac susceptibility plots cannot be seen. However, under an optimal applied field of 0.2 T, clear maxima are observed in the out-of-phase (χ''M) component of the ac susceptibility in the temperature range 3.5 K (2 kHz) to 10.5 K (10 kHz). The temperature dependence of the relaxation times could be fitted to the sum of Orbach, Raman and QTM relaxation processes affording the following parameters: τo = 3.4(9) × 10-8 s, Ueff = 94(2) K, BRaman = 16.43(1) K-n s-1, n = 3.2(3) and τQTM = 0.0044(3) s. 4, under an applied magnetic field of 0.2 T, shows slow relaxation of magnetization through a thermally activated Orbach process with Ueff = 18.2(9) K and τo = 3.5(3) × 10-8 s.

Slow magnetic relaxation in a homoaxially phosphine oxide coordinated pentagonal bipyramidal Dy(III) complex.

We report the synthesis of [(L)DyIII(Cy3PO)2]·[BPh4] (1-Dy) (where H2L = 2,6-diacetylpyridine bis-benzoylhydrazone and Cy = cyclohexyl) which crystallized in the triclinic, P1̄ space group. The local geometry around Dy(III) in 1-Dy was found to be pentagonal bipyramidal (pseudo-D5h). The AC magnetic susceptibility measurements performed on 1-Dy and on its diluted 1-Y(Dy) samples showed a typical single-molecule magnet signature revealed by the appearance of AC-frequency dependent out-of-phase susceptibility signals in the absence of a static magnetic field. The out-of-phase AC susceptibility signals were well resolved on the application of a small magnetic field (HDC = 500 Oe) and yielded an energy barrier for magnetization flipping of Ueff/kB = 50 K for the diluted derivative. The magnetic studies on 1-Dy and 1-Y(Dy) and data analysis further confirm that Raman and QTM under-barrier magnetic relaxations play a crucial role in lowering Ueff despite the almost axial nature of the Dy(III) ion in 1-Dy. We have rationalized these observations through detailed ab initio calculations performed on the X-ray crystal structure of 1-Dy.

Oxidative stress-A key determinant of complications and negative outcome in hepatitis E virus infected pregnancies: A comprehensive account involving cases from northeast India.

Regulated oxidative stress (OS) is important during pregnancy. Sporadic studies suggest the significance of deregulated OS in hepatitis E virus (HEV) infected pregnancy, but with limited reactive oxygen species (ROS) or antioxidant markers. The present novel study, therefore, aimed to evaluate the significance of ROS-antioxidant imbalance and resulting altered OS in HEV infected pregnancy complications like preterm delivery (PTD) and outcome. Difference in serum levels of ROS and antioxidant panel of markers were evaluated by ELISA for HEV immunoglobulin M RNA positive genotype 1 cases (including acute [acute viral hepatitis, AVH] and fulminant [fulminant hepatic failure, FHF] cases) and healthy term delivery subjects, and analyzed statistically. Direct ROS marker H2 O2 levels and indirect OS marker for DNA damage 8-hydroxy-2'-deoxyguanosine was significantly increased in HEV-cases compared to controls, and was associated and prognostic factor for PTD and fetal death in HEV cases. A comparatively lower total serum antioxidant capacity was observed in the FHF cases compared to the control subjects and the AVH cases. Glutathione (GSH) levels and superoxide dismutase (SOD) activity were significantly associated with PTD in the FHF sub-cohorts (p = 0.017) and AVH sub-cohorts (p < 0.001), respectively, and was associated with poor prognosis in HEV cases. The serum H2 O2 levels were found to be negatively correlated with SOD activity (p = 0.016) and GSH levels (p = 0.001) in the HEV-AVH cases; and positively correlated with the viral load in HEV cases (p = 0.023). The ROS-antioxidant imbalance resulting OS plays a detrimental associative role in HEV infected pregnancy complications like PTD and adverse pregnancy outcomes; and holds therapeutic significance.

Energy-efficient biochar production for thermal backfill applications.

The function of engineered thermal backfills surrounding underground pipelines of the crude oil industry is to prohibit heat migration for the design period of 25 to 50 years. Biochar is suitable for reconstituting standard thermal backfill material since it is biochemically inert and has a low heat conductivity. However, the preparation of biochar from biomass involves an energy-intensive pyrolysis process. This study aims to make biochar production energy-efficient via optimizing the pyrolysis temperatures, specifically for thermal backfill applications. Ten distinct biochars were prepared by pyrolyzing two waste biomass, i.e., water hyacinth (WH) and sugarcane bagasse (SB), at temperatures ranging from 300 to 700 °C. The biochars were assessed based on their thermal conductivity, energy consumption, yield, and stability in soil for the design period. The thermal conductivity of produced biochars varied in a narrow range of 0.10 to 0.13 W m-1 K-1 with different pyrolysis temperatures, which is possibly due to marginal differences in their microstructure, mineralogy, and physicochemical properties. The findings revealed that the biochar produced at lowest pyrolysis temperature (300 °C) consumed least energy and produced maximum yield. However, it was not suitable for thermal backfill applications due to its inadequate carbon stability in soil. Therefore, the current study recommends a pyrolysis temperature of 400 °C for thermal backfill applications. The recommended pyrolysis temperature was found to be at least 60% energy efficient in comparison to pyrolysis at 700 °C for both the feedstocks. This study provides crucial insight into the role of pyrolysis temperature for tailoring biochar production for intended applications.

ZRC3308 Monoclonal Antibody Cocktail Shows Protective Efficacy in Syrian Hamsters against SARS-CoV-2 Infection.

We have developed a monoclonal antibody (mAb) cocktail (ZRC-3308) comprising of ZRC3308-A7 and ZRC3308-B10 in the ratio 1:1 for COVID-19 treatment. The mAbs were designed to have reduced immune effector functions and increased circulation half-life. mAbs showed good binding affinities to non-competing epitopes on RBD of SARS-CoV-2 spike protein and were found neutralizing SARS-CoV-2 variants B.1, B.1.1.7, B.1.351, B.1.617.2, and B.1.617.2 AY.1 in vitro. The mAb cocktail demonstrated effective prophylactic and therapeutic activity against SARS-CoV-2 infection in Syrian hamsters. The antibody cocktail appears to be a promising candidate for prophylactic use and for therapy in early COVID-19 cases that have not progressed to severe disease.

Azide-Coordination in Homometallic Dinuclear Lanthanide(III) Complexes Containing Nonequivalent Lanthanide Metal Ions: Zero-Field SMM Behavior in the Dysprosium Analogue.

A series of homometallic dinuclear lanthanide complexes containing nonequivalent lanthanide metal centers [Ln2(LH2)(LH)(CH3OH)(N3)]·xMeOH·yH2O [1, Ln = DyIII, x = 0, y = 2; 2, Ln = TbIII, x = 1, y = 1] have been synthesized [LH4 = 6-((bis(2-hydroxyethyl)amino)-N'-(2-hydroxybenzylidene)picolinohydrazide] and characterized. The dinuclear assembly contains two different types of nine-coordinated lanthanide centers, because the nonequivalent binding of the azide co-ligand as well as the varying coordination of the deprotonated Schiff base ligand. Detailed magnetic studies have been performed on the complexes 1 and 2. Complex 1 and its diluted analogue (15%) are zero-field SMMs with effective energy barriers (Ueff) of magnetization reversal equal to 59(3) K and 66(3) K and relaxation times of τ0 = 10(4) × 10-6 s and 10(4) × 10-8 s, respectively. On the other hand, complex 2 shows a field-induced SMM behavior. Combined ab initio and density functional theory calculations were performed to explain the experimental findings and to unravel the nature of the magnetic anisotropy, exchange-coupled spectra, and magnetic exchange interactions between the two lanthanide centers.

Exploring the efficiency and pollutant emission of a dual fuel CI engine using biodiesel and producer gas: An optimization approach using response surface methodology.

The present study focuses on optimizing the engine operating parameters of a dual-fuel (DF) engine. Producer gas (PG) and Honge oil methyl ester (HOME) are used as primary fuel and pilot fuel respectively for the operation. An experimental design matrix of 20 different combinations was considered using Design of Experiments (DoE), based on the central composite design (CCD) of response surface methodology (RSM). The effects of these combinations were experimentally investigated to calculate the performance and emission characteristics of the engine. The objective of the work is to maximize the Brake thermal efficiency (BTE) and minimize the exhaust gas temperature (EGT), nitrogen oxide (NOx), hydrocarbon (HC), and carbon monoxide (CO) emissions. The RSM model is developed using the experimental data and further, the operating parameters were optimized using the desirability approach. The optimized combination of operating parameters was obtained at 61.10% engine load, compression ratio (CR) of 18, and injection timing (IT) of 23.30° before top dead center (BTDC). The optimum responses corresponding to these operating conditions were found as 14.23%, 354.29 °C, 52.18 ppm, 39.53 ppm, and 0.51% for BTE, EGT, NOx, HC, and CO respectively with an overall desirability of 0.962. The optimized responses were validated experimentally at optimum input conditions and found to be within acceptable error levels. Further, an economic analysis of the optimized DF system is also carried out.

A Phase 3, Randomized, Open-label, Noninferiority Trial Evaluating Anti-Rabies Monoclonal Antibody Cocktail (TwinrabTM) Against Human Rabies Immunoglobulin (HRIG).

BACKGROUND: Limited supply, cost and potential for severe adverse effects observed with the blood derived rabies immunoglobulin products has led to search for alternative therapies. This issue has been addressed by developing an anti-rabies monoclonal antibody cocktail. METHODS: This is a phase 3, randomized, open-label, noninferiority trial conducted in patients with World Health Organization (WHO) category III exposure with suspected rabid animal. Eligible patients were assigned to either the test arm, TwinrabTM (docaravimab and miromavimab) or the reference arm, human rabies immunoglobulin (HRIG; Imogam® Rabies-HT), in a ratio of 1:1. The primary endpoint was the comparison of responder rates between the 2 arms assessed as percentage of those with rabies virus neutralizing antibodies titers ≥0.5 IU/mL on day 14. RESULTS: A total of 308 patients were equally randomized into the 2 arms. In the per-protocol (PP) population, there were 90.21% responders in the TwinrabTM arm and 94.37% in the HRIG arm. The geometric mean of rapid fluorescent foci inhibition test titers in the PP on day 14 were 4.38 and 4.85 IU/mL, for the TwinrabTM and HRIG arms, respectively. There were no deaths or serious adverse events reported. CONCLUSIONS: This study confirmed that TwinrabTM is noninferior to HRIG in terms of providing an unbroken window of protection up to day 84. This trial in healthy adults with WHO category III exposure from suspected rabid animal also establishes the safety of TwinrabTM in patients with 1 WHO approved vaccine regimen (Essen). CLINICAL TRIALS REGISTRATION: CTRI/2017/07/009038.

Green synthesis of gold nanoparticles using an antiepileptic plant extract: in vitro biological and photo-catalytic activities.

Gold nanoparticles are one of the widely used metallic nanoparticle having unique surface plasmon characteristic, offers major utility in biomedical and therapeutic fields. However, chemically synthesized nanoparticle creates toxicity in the living organisms and contradicts the eco-friendly and cost-effective nature. So, developing greener synthetic route for synthesis of gold nanoparticle using natural materials is an enthralling field of research for its effectiveness in synthesizing eco-friendly, non-toxic materials. Moreover, biological components attached as stabilizing agent can exert its own effect along with the advantages of nanoparticle conjugation. In this work, we used for the first time methanolic leaf extract of Moringa oleifera as this fraction of M. oleifera exerts a neuroactive modulation against seizure as evidenced by earlier literature. The green gold nanoparticles synthesized were characterized by different characterization tools, dynamic light scattering and transmission electron microscopy techniques etc. Prepared nanoparticles were biologically (antioxidant, antimicrobial and blood cytotoxicity) characterized to screen their further utility in therapeutic strategies. Characteristics and activities of green gold nanoparticles were compared with conventional citrate stabilized gold nanoparticles. It was observed that green gold nanoparticles prepared using M. oleifera show less cytotoxicity and helps in regeneration of neuronal cells in animal model study. It establishes the fact that conjugation of different plant extract fraction for stabilization of gold nanoparticle may be responsible factor for enhancement of bioactive nature of green gold nanoparticle. In addition, the green gold nanoparticle show efficient photo-catalytic efficiency. Development of such bioactive gold nanoparticles will lead to functional materials for biomedical and therapeutic applications.

Seven-coordinate LnIII complexes assembled from a bulky MesacacH ligand: their synthesis, structure, photoluminescence and SMM behaviour.

The reaction of a bulky acetyl acetone ligand 1,3-dimesitylpropane-1,3-dione (MesacacH) with hydrated lanthanide chlorides in the presence of tetramethylammonium hydroxide afforded a new family of neutral mononuclear LnIII complexes [Ln(Mesacac)3(DMF)] (Ln = Dy (1); Tb (2); Y0.91Dy0.09 (3); and Er (4)). The molecular structures of these complexes were confirmed by single crystal X-ray diffraction studies. The coordination geometries of the LnIII centre were analysed by SHAPE analysis which revealed a capped octahedral geometry in 1-4. Photoluminescence studies showed ligand-sensitized green emissions for 2 with an appreciable quantum yield of 0.83%. Static (dc) and dynamic (ac) magnetic studies of complexes 1 and 3 were performed. The dynamic magnetic study revealed that complex 1 exhibits zero-field slow relaxation of the magnetization without showing a clear maximum in the out-of-phase ac susceptibility plots. However, magnetic dilution of 1 with the YIII metal ion (complex 3) and/or the application of a dc magnetic field induces a strong frequency dependence of the ac susceptibility signals with χ''M peaks in the 3-10 K temperature range, thus supporting field-induced SMM behaviour of 1. The relaxation process takes place through a combination of the Orbach and Raman mechanisms. The fitting of the temperature dependence of the relaxation time to the equation τ-1 = τ0-1 exp(-Ueff/kBT) + BTn, allows the extraction of the effective energy barrier Ueff/kB = 70 K (48.7 cm-1) and pre-exponential parameter of τ0 = 2.7 × 10-7 s for the Orbach mechanism (first term) and the parameters B = 0.04 s-1 K-n and n = 6.11, for the Raman mechanism (second term).

Pentagonal Bipyramidal Ln(III) Complexes Containing an Axial Phosphine Oxide Ligand: Field-induced Single-ion Magnetism Behavior of the Dy(III) Analogues.

A series of neutral homologous complexes [(L)Ln(Cy3PO)Cl] {where Ln = Gd (1), Tb (2), Dy (3), and Er (5)} and [(L)Dy(Ph3PO)Cl] (4) [H2L = 2,6-diacetylpyridine bis-benzoylhydrazone] were isolated. In these complexes, the central lanthanide ion possesses a pentagonal bipyramidal geometry with an overall pseudo D5h symmetry. The coordination environment around the lanthanide ion comprises of three nitrogen and two oxygen donors in an equatorial plane. The axial positions are taken up by a phosphine oxide (O donor) and a chloride ion. Among these compounds, the Dy(III) (3 and 4) analogues were found to be field-induced single-ion magnets.

Molecular enneanuclear CuII phosphates containing planar hexanuclear and trinuclear sub-units: syntheses, structures, and magnetism.

Highly symmetric enneanuclear copper(ii) phosphates [Cu9(Pz)6(µ-OH)3(µ3-OH)(ArOPO3)4(DMF)3] (PzH = pyrazole, Ar = 2,6-(CHPh2)2-4-R-C6H2; R = Me, 2MeAr; Et, 2EtAr; iPr, 2iPrAr; and Ar = 2,6-iPr2C6H3, 2Dip) comprising nine copper(ii) centers and pyrazole, hydroxide and DMF as ancillary ligands were synthesized by a reaction involving the arylphosphate monoester, 1, copper(i)chloride, pyrazole, and triethylamine in a 4 : 9 : 6 : 14 ratio. All four complexes were characterized by single crystal structural analysis. The complexes contain two distinct structural motifs within the multinuclear copper scaffold: a hexanuclear unit and a trinuclear unit. In the latter, the three Cu(ii) centres are bridged by a µ3-OH. Each pair of Cu(ii) centers in the trinuclear unit are bridged by a pyrazole ligand. The hexanuclear unit is made up of three dinuclear Cu(ii) motifs where the two Cu(ii) centres are bridged by an -OH and a pyrazole ligand. The three dinuclear units are connected to each other by phosphate ligands. The latter also aid the fusion of the trinuclear and the hexanuclear motifs. Magnetic studies reveal a strong antiferromagnetic exchange between the Cu(ii) centres of the dinuclear units in the hexanuclear part and a strong spin frustration in the trinuclear part leading to a degenerate ground state.

Influence of N-heterocyclic carbenes (NHCs) on the hydrolysis of a diphosphene.

We report the influence of N-heterocyclic carbenes (NHCs) on the hydrolysis of a diphosphene TerP[double bond, length as m-dash]PTer (1; Ter = 2,6-Mes2C6H3; Mes = 2,4,6-Me3C6H2), a phosphorus-analogue of an alkene. The diphosphene 1 itself is completely inert towards water. However, NHCs have been found to activate 1 towards ready hydrolysis. While sterically less-encumbered NHCs react with 1 affording NHC-adducts which are in equilibrium with 1 in solution, sterically encumbered NHCs do not bind to 1 at all. Interestingly, in both of these situations hydrolysis of the P[double bond, length as m-dash]P motif proceeds efficiently. At low temperatures, sterically less-encumbered NHCs are catalytic while the sterically encumbered NHCs play a catalytic role at room temperature. To gain insight on this striking influence of NHCs on the hydrolysis of diphosphene detailed low-temperature 31P-NMR studies along with theoretical calculations have been carried out. In addition, systematic hydrolysis studies of all the NHCs used in this study have also been performed.

CAAC-Based Thiele and Schlenk Hydrocarbons.

Diradicals have been of tremendous interest for over a century ever since the first reports of p- and m-phenylene-bridged diphenylmethylradicals in 1904 by Thiele and 1915 by Schlenk. Reported here are the first examples of cyclic(alkyl)(amino)carbene (CAAC) analogues of Thiele's hydrocarbon, a Kekulé diradical, and Schlenk's hydrocarbon, a non-Kekulé diradical, without using CAAC as a precursor. The CAAC analogue of Thiele's hydrocarbon has a singlet ground state, whereas the CAAC analogue of Schlenk's hydrocarbon contains two unpaired electrons. The latter forms a dimer, by an intermolecular double head-to-tail dimerization. This straightforward synthetic methodology is modular and can be extended for the generation of redox-active organic compounds.

Structural Diversity in Supramolecular Organization of Anionic Phosphate Monoesters: Role of Cations.

Syntheses and structures of anionic arylphosphate monoesters [ArOP(O)2(OH)]- (Ar = 2,6-CHPh2-4-R-C6H2; R = Me/Et/iPr/tBu) with different counter cations are reported. The counter cations were varied systematically: imidazolium cation, 2-methyl imidazolium cation, N-methyl imidazolium cation, N,N'-alkyl substituted imidazolium cation, 1,4-diazabicyclo[2.2.2]octan-1-ium cation, 4,4'-bipyridinium dication, and magnesium(II) dication. The objective was to examine if the supramolecular structure of anionic arylphosphate monoesters could be modulated by varying the cation. It was found that an eight-membered P2O4H2-hydrogen-bonded dimeric motif involving intermolecular H-bonding between the [P(O)(OH)] unit of the anionic phosphate monoester along with the counter cation is formed with 2-methyl imidazolium cation, N-methyl imidazolium cation, N,N'-alkyl substituted imidazolium cation, 1,4-diazabicyclo[2.2.2]octan-1-ium cation, and magnesium(II) dication; both discrete and polymeric H-bonded structures are observed. In the case of imidazolium cations and 1,4-diazabicyclo[2.2.2]octan-1-ium cation, the formation of one-dimensional polymers (single lane/double lane) was observed. On the other hand, two types of phosphate motifs, intermolecular H-bonded dimer and an open-form, were observed in the case of 4,4'-bipyridinium dication.