Search results for "bond"
showing 10 items of 3527 documents
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…
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…
Recent Advances on the Halo- and Cyano-Trifluoromethylation of Alkenes and Alkynes
2021
Incorporation of fluorine into organic molecules is a well-established strategy in the design of advanced materials, agrochemicals, and pharmaceuticals. Among numerous modern synthetic approaches, functionalization of unsaturated bonds with simultaneous addition of trifluoromethyl group along with other substituents is currently one of the most attractive methods undergoing wide-ranging development. In this review article, we discuss the most significant contributions made in this area during the last decade (2012−2021). The reactions reviewed in this work include chloro-, bromo-, iodo-, fluoro- and cyano-trifluoromethylation of alkenes and alkynes.
Photoactive Yellow Protein Chromophore Photoisomerizes around a Single Bond if the Double Bond Is Locked
2020
Photoactivation in the Photoactive Yellow Protein, a bacterial blue light photoreceptor, proceeds via photo-isomerization of the double C=C bond in the covalently attached chromophore. Quantum chemistry calculations, however, have suggested that in addition to double bond photo-isomerization, the isolated chromophore and many of its analogues, can isomerize around a single C-C bond as well. Whereas double bond photo-isomerization has been observed with x-ray crystallography, experimental evidence for single bond photo-isomerization is currently lacking. Therefore, we have synthesized a chromophore analogue, in which the formal double bond is covalently locked in a cyclopentenone ring and ca…
Scenario modeling for the management of international bond portfolios
1998
We address the problem of portfolio management in the international bond markets. Interest rate risk in the local market, exchange rate volatility across markets, and decisions for hedging currency risk are integral parts of this problem. The paper develops a stochastic programming optimization model for integrating these decisions in a common framework. Monte Carlo simulation procedures, calibrated using historical observations of volatility and correlation data, generate jointly scenarios of interest and exchange rates. The decision maker's risk tolerance is incorporated through a utility function, and additional views on market outlook can also be incorporated in the form of user specifi…
The effects of combining kangaroo care and parental singing on premature infants' and parents' wellbeing and development of parent-infant relationship
2014
After experiencing premature birth, fragile infants have to spend weeks and even months on the ward because of their medical needs. This can be stressful both for parents and infants and increase the risk of early interaction problems and difficulty in bonding. In this qualitative study I was interested to find out what kinds of experiences parents had with parental singing during kangaroo care. I was also interested in examining the nursing staff’s attitudes, observations and thoughts about using music on the ward. I conducted my study within a Kangaroo Families study on the L2 ward at Jorvi hospital, Espoo. My study consists of interviews from 4 mothers that participated in the Kangaroo F…
(R)-(−)-Quinuclidin-3-ol
2013
The structure of the title compound [alternatively called (R)-(−)-1-azabicyclo[2.2.2]octan-3-ol], C7H13NO, at 100 K has hexagonal (P61) symmetry. The structure shows a twist along the C—N pseudo-threefold axis. In the crystal, molecules are linkedviaO—H...N hydrogen bonds, forming infinite chains along thec-axis direction. The crystal studied was twinned by merohedry (twin law: 010, 100, 00-1; population: 0.925:0.075)
Ab initio calculations of CaZrO3 (011) surfaces: systematic trends in polar (011) surface calculations of ABO3 perovskites
2019
Financial support via Latvian-Ukrainian Joint Research Project No. LV-UA/2018/2 for A. I. Popov, Latvian Council of Science Project No. 2018/2-0083 “Theoretical prediction of hybrid nanostructured photocatalytic materials for efficient water splitting” for R. I. Eglitis and J. Kleperis as well as ERAF project No. 1.1.1.1/18/A/073 for R. I. Eglitis and J. Purans is greatly acknowledged.
Ab initio calculations of Nb doped SrTiO3
2010
We present and discuss the results of the large scale Hartree–Fock calculations of Nb impurities substituting for Ti ions in SrTiO3 using ab initio computer code CRYSTAL and several supercells containing up to 135 atoms. The local structure optimisation, the electronic charge redistribution, chemical bond covalence and the band-structure changes induced by the defect are analysed. According to the results of our calculations, Nb is a shallow donor; six nearest O ions are slightly displaced outwards from the Nb ion. The calculated bond population between nearest Ti and O ions (64 me) is much larger than that between Nb and O ions (8 me), since Nb impurity is more ionic than the host Ti.
BaCoO3 monoclinic structure and chemical bonding analysis: hybrid DFT calculations
2021
Cobalt based perovskites have great potential for numerous applications. Contrary to a generally assumed hexagonal space group (SG P63/mmc) model as the ground state of BaCoO3 (BCO), our hybrid DFT calculations with B1WC density functional and the symmetry group–subgroup derived crystal structure model support the ground state of BCO to be indeed monoclinic, in agreement with recent experimental predictions [Chin et al., Phys. Rev. B, 2019, 100, 205139]. We found for the monoclinic BCO that the C-type anti-ferromagnetic low-spin (AFM LS) state (SG P2/c) is energetically only slightly more preferential at 0 K than the ferromagnetic (FM) LS state (SG C2/c). In turn, these monoclinic structure…