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Published in Chad A. Mirkin, Spherical Nucleic Acids, 2020
Ryan V. Thaner, Ibrahim Eryazici, Robert J. Macfarlane, Keith A. Brown, Beyongdu Lee, SonBinh T. Nguyen, Chad A. Mirkin
Finally, while attempting to assemble a CsCl superlattice with 10 and 15 nm AuNP cores (but comparable hydrodynamic radii) using trebler linkers, we observed a new crystalline phase that corresponds to the L43d space group (Fig. 43.3; the cubic unit cell is isostructural with Th3P4). This unexpected and complex lattice structure was initially observed in atomic systems when lithium was exposed to high-pressure conditions; to our knowledge, this lattice has never been observed in DNA-directed crystallization and only once previously in a colloidal system [14]. This new Th3P4-type structure was consistently observed (over 20× with slight variations in DNA design) and only when using treblers. Compared to the other binary superlattices previously formed using DNA, this structure is significantly more complex with a large unit cell (lattice parameter of 93.59 nm) containing twelve 15 nm and sixteen 10 nm particles as opposed to the lattice parameter of 38.24 nm and one-to-one particle ratio for the analogous CsCl unit cell [5b].
Nuclear Fuel Materials
Published in C. K. Gupta, Materials in Nuclear Energy Applications, 1989
Thorium in its chemical form as thorium oxide is of interest in commercial reactors. It is usually crystalline, although an amorphous form exists. It has a fluorite crystal structure and therefore it is isostructural with UO2 and PUO2. The trio forms continuous binary and ternary solid solutions. This is a desirable feature indeed. Pure ThO2 has a thermal conductivity 10% higher than pure UO2. It has a melting point of 3300°C and its theoretical density is 9.82 g cm−3. The oxide, in partnership with UOz and PUO2, has drawn interest in various reactor concepts as indicated in the section on thorium utilization. For reactor applications, pellet forms of these mixed oxide ceramics produced by conventional powder metallurgy (powder preparation, mixing, pressing, and sintering) are used. The coated particle fuel represents a radical departure from the traditional pellet forms of fuel. This specially designed fuel form is used in HTRs, particularly in HTGRs, which, as has already been pointed out, represents the most important of the currently advanced reactor systems from the point of view of thorium utilization.
xTe Semimagnetic Semiconductors
Published in R D Tomlinson, A E Hill, R D Pilkington, Ternary and Multinary Compounds, 2020
Elena I. Rogachcva, Igor M. Krivulkin
As it follows from the obtained results, in the interval of x≈0,01−0,0125 there is shaxp growth in heat capacity that is the evidence of a phase transition. Since in the range of solid solutions x≈0–0,02 unit cell parameter decreases monotonously, the phase transition is of an isostructural type. It can be assumed that it has percolation nature and corresponds to the transition from “the impurity gas state” (region of diluted solid solutions) to “the impurity liquid state” (region of concentrated solid solutions). Since we observed anomalies of properties at small impurity concentrations in many solid solutions [2, 7, 12–14], one can suggest that this phenomenon has a universal character and inherent in any solid solution.
Synthesis, characterizations, crystal structures, BSA-binding, molecular docking, and cytotoxic activities of nickel(II) and copper(II) coordination complexes with bidentate N,S-chelating ligand
Published in Journal of Coordination Chemistry, 2019
N. Noorussabah, Mukesh Choudhary, Achintya Jana, Neeladri Das, B. Mohan, K. Ahmad, S. Sangeeta, S. Bharti, M. K. Mishra, S. R. Sharma
Literature reveals that the syntheses and structural studies of Cu(II) and Ni(II) complexes of 2-methoxybenzylidine derivative of 4-phenylthiosemicarbazide with molecular docking into the grooves of target DNA- and BSA-binding is missing and, to date, no further investigations are considered; this impelled us to make the present study. Inspired by recent studies on metal-coordinated Schiff bases for their BSA- and protein-binding [35–37] and based on our good experience on Schiff base Ni(II) and Cu(II) coordinated complexes [38–41], in this article we plan to synthesize, characterize, and study their molecular docking and BSA-binding of three novel nickel(II) [Ni(L)2] (1) and copper(II) [Cu(L)2] (2a) and [Cu(L)2] (2b) complexes with (E)-1-(2-methoxybenzylidine)-4-phenylethiosemicarbazone (HL) as bidentate N,S-ligand. A solid-state structure is planned to be determined by X-ray analysis. The crystal structure determination also confirmed that the structures of all complexes are isostructural. The refined single-crystal structures are further subjected to molecular docking into the grooves of target DNA and binding affinity of complexes with the DNA and interacting residues of DNA was evaluated and discussed. Further protein binding constant (Kb), quenching constant (KSV) and number of binding sites (n) of complexes towards BSA was determined by using fluorescence spectroscopy. The cytotoxic/antiproliferative potential of the synthesized compounds on human cell lines was also investigated by MTT assay.
Review: Downsizing effect on 2-D and 3-D spin crossover metal-organic frameworks
Published in Journal of Coordination Chemistry, 2019
Christina D. Polyzou, Vassilis Tangoulis
As described in the Introduction, the group of Real reported in 2001 the first paradigm of a 3-D bimetallic SCO Hofmann-type MOF, extending the dimensionality and thus, the cooperativity, a parameter difficult to control through intermolecular forces. The 3-D coordination polymers with formulas [Fe(pz)MII(CN)4].nH2O [M = Ni, n = 2 (2a); M = Pd, n = 2.5 (2b); M = Pt, n = 2 (2c)] were synthesized by mixing an aqueous solution of K2[Ni(CN)4] with stoichiometric amounts of pz and Fe(BF4)2·6H2O in 1: 1 MeOH/H2O ratio. Due to the poor crystallinity of the products, ab initio crystal structure measurements revealed the 3-D structure in the absence of single-crystals. Crystal structure analysis showed that 2a crystallizes in tetragonal space group P4/m, while 2b and 2c were proven isostructural with the help of powder X-ray diffraction. The 3-D network consists of (i) six-coordinate FeII ions whose coordination sphere is filled with four equatorial N donors from the cyano groups and two trans-axial N donors from the pz ligands, (ii) a square-planar [Ni(CN)4]2– moiety linked by the cyano bridges, and (iii) pz bridges formed between the irons [7].
Synthesis, crystal structure, magnetic, spectroscopic, and theoretical investigations of two new nitronyl-nitroxide complexes
Published in Journal of Coordination Chemistry, 2021
Cristian Andrei Spinu, Céline Pichon, Gabriela Ionita, Teodora Mocanu, Sergiu Calancea, Mihai Raduca, Jean-Pascal Sutter, Mihaela Hillebrand, Marius Andruh
The new compounds, (Et3NH)[M(hfac)2L] (M = Ni 1, Zn 2), have been synthesized by reacting the metal precursors, [M(hfac)2(H2O)2], with the paramagnetic proligand, HL, in the presence of triethylamine, which was added for deprotonation of the phenolic group. The PXRD patterns for 1 and 2 confirm the purity of the crystalline phases (Figures S1 and S2). Since the two compounds are isostructural, only the crystal structure of 1 will be described in detail. Its crystal structure consists of anionic complex, [Ni(hfac)2L]- (Figure 1) and organic cation, Et3NH+. The nickel ion has an octahedral geometry, coordinated by four oxygen atoms from the hfac- ligands and two others from L- (one phenoxido and one aminoxyl oxygen). The Ni–O oxygen distances vary between 2.008(4) and 2.072(4) Å. The N–O bond within the aminoxyl group coordinated to NiII (1.305(5) Å) is longer than the one within the uncoordinated NO group (1.266(5) Å). The complex is chiral and both enantiomers cocrystallize within the same crystal (Figure 2). The crystal structure of the complex anion in 2 is illustrated in Figure S4. Selected bond distances and angles for 1 and 2 are collected in Table 2. The diffuse reflectance spectra of the ligand and the two complexes are displayed in Figure 3. Compound 1 shows, apart from the bands arising from the organic ligands, two other bands which are due to the d–d transitions: 3A2 → 3T2 (1122 nm) and 3A2 → 3T1 (751 nm), assuming the Oh point group.