Search results for "Pyramid"
showing 10 items of 410 documents
Crystal structure of a rare trigonal bipyramidal titanium(IV) coordination complex: trichlorido(3,3′-di-tert-butyl-2′-hydroxy-5,5′,6,6′-tetramethyl-1…
2017
The title compound, [Ti(C24H33O2)Cl3(C4H8O)], is a rare example of a trigonal–bipyramidal titanium coordination complex with three chloride and two oxygen donor ligands. The asymmetric unit contains two independent molecules having essentially the same conformation. The molecules feature the titanium(IV) metal cation complexed with three chloride ligands, a tetrahydrofuran molecule, and one oxygen atom from the resolved ligand precursor (R)-(+)-5,5′,6,6′-tetramethyl-3,3′-di-t-butyl-1,1′-biphenyl-2,2′-diol, where the remaining phenolic hydrogen atom engages in intermolecular O—H...Cl hydrogen bonding. In one molecule, the THF ligand is disordered over two orientations with refined site occup…
A new copper(II) chelate complex with tridentate ligand: Synthesis, crystal and molecular electronic structure of aqua-(diethylenetriamine-N, N′, N′′…
2015
Abstract The crystals of a new aqua-(diethylenetriamine-N, N′, N′′)-copper(II) sulfate monohydrate have been synthesized by direct interaction of solid copper(II) sulfate pentahydrate with diethylenetriamine (deta). The crystal structure of [Cu(deta)H2O]SO4⋅H2O (1) has been determined by X-ray diffraction methods at 100 K and characterized using X-ray powder diffraction pattern: space group P 1 ¯ , a = 7.2819(4), b = 8.4669(4), c = 8.7020(3) A, α = 83.590(3), β = 89.620(4), γ = 84.946(4)°, Z = 2. The environment of the Cu(II) atom is a distorted, elongated square pyramid which consists of three nitrogen atoms of the deta molecule and oxygen atom of the water molecule in the basal plane of t…
A new copper(II) chelate complex with polyamines as fire retardant and epoxy hardener: Synthesis, crystal and electronic structure, and thermal behav…
2020
A new (ethylenediamine-N,N′)-(diethylenetriamine-N,N′,N″)-copper(II) hexafluoridosilicate complex, [Cu(eda)(deta)]SiF6 (1) (eda – ethylenediamine; deta – diethylenetriamine), was synthesized by direct interaction of anhydrous CuSiF6 with polyethylenepolyamine (pepa – H2N[C2H4NH]nH, where n = 1 (eda) and 2 (deta)). The crystals of 1 were characterized by IR spectroscopy and X-ray diffraction. Compound 1 consists of SiF62− discrete anions and [Cu(eda)(deta)]2+ complex cations whose Cu2+ ions are chelated by eda and deta. The coordination polyhedron of Cu(II) atom is an elongated square pyramid which consists of four nitrogen atoms belonging to NH2 groups of eda and NH2 and NH groups of …
Synthesis, structural, and thermal characterization of a new binuclear copper(II) chelate complex bearing an amine-hardener for epoxy resins
2016
A new di(μ-carbonato)bis[aqua(diethylenetriamine)copper(II)] hexahydrate complex, [{Cu(NH(C2H4NH2)2)(H2O)(μ-CO3)}2]⋅6H2O (1), was synthesized by direct interaction of malachite with diethylenetriamine (dien). The crystals of 1 were characterized by X-ray powder diffraction and IR spectra, as well as structurally characterized. Compound 1 consists of [{Cu(dien)(H2O)(μ-CO3)}2] discrete units whose CO32– anions play the role of bridging ligands combining two Cu(II) chelate cores into a centrosymmetric dimer. The elongated octahedral environment of Cu2+ consists of three nitrogens of dien and an oxygen from CO32– at the base of the bipyramid; the two apical positions of such polyhedron are occu…
Diorganotin(IV) complexes ofD-galacturonic acid: solid-state and solution-phase structural study
2003
Three diorganotin(IV) complexes of D-galacturonic acid (H2GalA; R = Me, n-Bu, Ph), two of which are new derivatives (R = Me, Ph), have been synthesized and their solid-state and solution-phase investigated by IR, Mossbauer, 1H, 13C and 119Sn NMR spectroscopy. The FTIR data suggest that H2GalA, in the dialkyltin derivatives, behaves as a dianionic ligand, coordinating the tin(IV) atom through an ester-type carboxylate and deprotonated alcoholic hydroxo groups, whereas a bridging carboxylate occurs in the diphenyltin(IV) complex. Octahedral and trigonal bipyramidal local geometries on tin(IV) atoms are proposed for dialkyltin(IV)GalA and diphenyltin(IV)GalA complexes respectively on the basis…
Most hippocampal CA1 pyramidal cells in rabbits increase firing during awake sharp-wave ripples and some do so in response to external stimulation an…
2020
Hippocampus forms neural representations of real-life events including multimodal information of spatial and temporal context. These representations, i.e. organized sequences of neuronal firing are repeated during following rest and sleep, especially when so-called sharp-wave ripples (SPW-Rs) characterize hippocampal local-field potentials. This SPW-R –related replay is thought to underlie memory consolidation. Here, we set out to explore how hippocampal CA1 pyramidal cells respond to the conditioned stimulus during trace eyeblink conditioning and how these responses manifest during SPW-Rs in awake adult female New Zealand White rabbits. Based on reports in rodents, we expected SPW-Rs to ta…
Equilibrium and structural studies of complexes with a hexadentate ligand containing amide, amine and pyridyl nitrogen donors. Crystal structures of …
2002
A novel potentially hexadentate ligand, 1,8-bis(2-pyridylcarbamoyl)-3,6-diazaoctane (pyctrien) has been synthesised as its tetrahydrochloride salt; its protonation constants and the stability constants of the copper(II) and nickel(II) chelates have been determined by potentiometry. Amide group deprotonation permits the formation of [MLH−1]+ and [MLH−2] species in all cases, whereas the detection of the neutral or the protonated species depends on the nature of the metal ions. The solid complexes of copper, nickel and cobalt with the neutral and the deprotonated ligand have been synthesised and characterised by IR and UV–VIS spectroscopy. The amidic groups are coordinated through the oxygen …
Surprising solvent-induced structural rearrangements in large [N⋯I+⋯N] halogen-bonded supramolecular capsules
2018
Coordinative halogen bonds have recently gained interest for the assembly of supramolecular capsules. Ion mobility-mass spectrometry and theoretical calculations now reveal the well-defined gas-phase structures of dimeric and hexameric [N...I+...N] halogen-bonded capsules with counterions located inside their cavities as guests. The solution reactivity of the large hexameric capsule shows the intriguing solvent-dependent equilibrium between the hexamer and an unprecedented pentameric [N...I+...N] halogen-bonded capsule, when the solvent is changed from chloroform to dichloromethane. The intrinsic flexibility of the cavitands enables this novel structure to adopt a pseudo-trigonal bipyramida…
Increasing temperature and productivity change biomass, trophic pyramids and community‐level omega‐3 fatty acid content in subarctic lake food webs
2021
Climate change in the Arctic is outpacing the global average and land-use is intensifying due to exploitation of previously inaccessible or unprofitable natural resources. A comprehensive understanding of how the joint effects of changing climate and productivity modify lake food web structure, biomass, trophic pyramid shape and abundance of physiologically essential biomolecules (omega-3 fatty acids) in the biotic community is lacking. We conducted a space-for-time study in 20 subarctic lakes spanning a climatic (+3.2 degrees C and precipitation: +30%) and chemical (dissolved organic carbon: +10 mg/L, total phosphorus: +45 mu g/L and total nitrogen: +1,000 mu g/L) gradient to test how temp…
Special Features of the Hippocampal Formation with Respect to Seizure Conditions
1987
The hippocampus has long been known as a region particularly prone to epileptiform discharges (Kandel et al. 1961). Connections and physiology of this archaic cortical structure are relatively well charac-terized and a wealth of information on features favoring exaggerated neuronal activity has emerged in recent years. The lamellar organization of the hippo-campus (Andersen et al. 1971) may be one of these features; it certainly has facilitated their investigation. Tissue slices cut along the lamellae, perpendicular to the axis of the structure, contain a relatively undisturbed chain of neurons which can be rigorously investigated in vitro. The results from such experiments have allowed mod…