80 research outputs found
Особливості реалізації графічного конвеєру при візуалізації тривимірних моделей приміщень університету
В більшості систем комп‘ютерної графіки застосовується графічний конвеєр – логічна група послідовно виконуваних обчислень (етапів), які в результаті дають синтезовану сцену на екрані комп‘ютера. Серед основних – етапи геометричних перетворень та візуалізації. Результат виконання кожного з цих етапів впливає на кінцевий вигляд синтезованої сцени, тому їх коректне завершення є необхідною умовою отримання якісного зображення
Ferromagnetic Coupling Through the End-to-End Thiocyanate Bridge in Cobalt(II) and Nickel(II) Chains
The preparation, spectroscopic characterization,
and X-ray crystal
structure of two novel one-dimensional compounds of formula [M<sup>II</sup>(tppz)(NCS)(μ-1,3-NCS)]<sub><i>n</i></sub> [tppz = 2,3,5,6-tetrakis(2-pyridyl)pyrazine and
M = Co(<b>1</b>) and Ni (<b>2</b>)] are reported. <b>1</b> and <b>2</b> are isomorphous compounds, and they crystallize
in the <i>P</i>2<sub>1</sub>/<i>n</i> space group.
Their structures are made up of zigzag chains of cobalt(II) (<b>1</b>) and nickel(II) ions (<b>2</b>) bridged by single
end-to-end thiocyanate groups with a tridentate <i>tppz</i> molecule and a terminally bound thiocyanate-<i>N</i> ligand
achieving distorted MN<sub>5</sub>S octahedral surroundings around
each metal center. The main source of the distortion of the ideal
octahedron is due to the geometrical constraints issued from the occurrence
of two fused five-member chelate rings of the tridentate <i>tppz</i> ligand, the values of the N–M–N bond angles covering
the range 75.58(9)–78.66(9)°. The M–N bond lengths
vary in the range 2.025(3)–2.116(29 (<b>1</b>) and 2.001(2)–2.079(2)
Å (<b>2</b>), and they are shorter than the M–S
bond distance [2.6395(10) (<b>1</b>) and 2.5225(9) Å (<b>2</b>)]. The values of the intrachain metal–metal separation
are 6.4197(7) (<b>1</b>) and 6.3257(5) Å (<b>2</b>). The magnetic properties of <b>1</b> and <b>2</b> have
been investigated in the temperature range 1.9–300 K. Both
compounds exhibit intrachain ferromagnetic interactions with values
of the magnetic coupling (<i>J</i>) of +4.60 (<b>1</b>) and +7.82 cm<sup>–1</sup> (<b>2</b>) [the spin Hamiltonian
being defined as <i>Ĥ</i> = −<i>J</i>Σ<sub><i>i</i> = 1</sub><sup><i>n</i>–1</sup><i>Ŝ</i><sub><i>i</i></sub><i>Ŝ</i><sub><i>i</i>+1</sub>]
Self-Assembly of the Hexabromorhenate(IV) Anion with Protonated Benzotriazoles: X‑ray Structure and Magnetic Properties
Two
novel Re<sup>IV</sup> compounds of formulas [HBTA]<sub>2</sub>[Re<sup>IV</sup>Br<sub>6</sub>] (<b>1</b>) and [HMEBTA]<sub>2</sub>[Re<sup>IV</sup>Br<sub>6</sub>] (<b>2</b>) [BTA
= 1<i>H</i>-benzotriazole and MEBTA = 1-(methoxymethyl)-1<i>H</i>-benzotriazole] have been synthesized and magneto-structurally
characterized. <b>1</b> and <b>2</b> crystallize in the
triclinic system with space group <i>P</i>1̅. In both
compounds, the rhenium ion is six-coordinate, bonded to six bromo
ligands in a regular octahedral geometry. Short Re<sup>IV</sup>–Br···Br–Re<sup>IV</sup> contacts, π–π stacking, and H-bonding
interactions occur in the crystal lattice of both <b>1</b> and <b>2</b>, generating novel supramolecular structures based on the
Re<sup>IV</sup>. The different dispositions of the cations and the
intermolecular Br···Br contacts in <b>1</b> and <b>2</b> play an important structure–property role, with the
magnetic properties of <b>1</b> and <b>2</b> revealing
a significant antiferromagnetic coupling between Re<sup>IV</sup> ions
through intermolecular Br···Br interactions. In <b>1</b>, these interactions account for a maximum in the magnetic
susceptibility at ca. 10 K
Slow Relaxation of the Magnetization in a 4,2-Wavelike Fe<sup>III</sup><sub>2</sub>Co<sup>II</sup> Heterobimetallic Chain
The reaction of the low-spin iron(III) complex [Fe(dmbpy)(CN)<sub>4</sub>]<sup>−</sup> (<b>1</b>) with fully solvated
cobalt(II) ions affords the cyanide-bridged heterobimetallic chain
{[Fe<sup>III</sup>(dmbpy)(CN)<sub>4</sub>]<sub>2</sub>Co<sup>II</sup>(H<sub>2</sub>O)<sub>2</sub>}<i><sub>n</sub></i> ·
4<i>n</i>H<sub>2</sub>O (<b>2</b>), which exhibits
intrachain ferromagnetic coupling and double slow relaxation of the
magnetization
Homo- and heterometallic complexes constructed from hexafluoroacetylacetonato and Schiff-base complexes as building-blocks
<p>Three new homo- and heterotrimetallic complexes have been synthesized and crystallographically characterized: [Cu<sub>2</sub>(saldmpn)<sub>2</sub>(<i>μ</i>-OCH<sub>3</sub>)<sub>2</sub>Cu<sub>2</sub>(hfac)<sub>2</sub>] (<b>1</b>), [Ni<sub>2</sub>(valaepy)<sub>2</sub>(hfac)<sub>2</sub>] (<b>2</b>), [Cu(saldmpn)Co(hfac)<sub>2</sub>] (<b>3</b>) [H<sub>2</sub>saldmpn is the Schiff-base resulting from condensation of salicylaldehyde with 2,2-dimethyl-1,3-diaminopropane and Hvalaepy results from the reaction of <i>o</i>-vanillin with 2-(2-aminoethyl)pyridine)]. The structure of <b>1</b> consists of a neutral tetranuclear species that can be viewed as resulting from mutual coordination of one {(hfac)Cu(<i>μ</i>-OCH<sub>3</sub>)<sub>2</sub>(Cu(hfac)} and two {Cu(saldmpn)} building blocks. Compound <b>2</b> is a binuclear complex that results from two {Ni(hfac)(valaepy} fragments, the nickel(II) ions bridged by the two phenoxide-oxygens. The heterobinuclear complex <b>3</b> results from coordination of the [Cu(saldmpn)] metalloligand to cobalt(II) from the {Co(hfac)<sub>2</sub>} unit. The magnetic properties of <b>1–3</b> have been investigated from 1.9 to 300 K. An overall ferromagnetic behavior is observed for <b>1</b> and <b>2</b> leading to <i>S</i> = 2 low-lying spin state for each one. In the case of <b>3</b>, a non-magnetic ground state results because of the occurrence of an intramolecular antiferromagnetic coupling between the copper(II) ion and the high-spin cobalt(II) ion, this last one behaving as an effective spin <i>S</i><sub>eff</sub> = ½ at low temperatures where only the ground Kramers doublet of Co(II) is thermally populated. The values of the intramolecular magnetic couplings in <b>1–3</b> are compared with those from the literature on related systems.</p
Homo- and heterometallic complexes constructed from hexafluoroacetylacetonato and Schiff-base complexes as building-blocks
<p>Three new homo- and heterotrimetallic complexes have been synthesized and crystallographically characterized: [Cu<sub>2</sub>(saldmpn)<sub>2</sub>(<i>μ</i>-OCH<sub>3</sub>)<sub>2</sub>Cu<sub>2</sub>(hfac)<sub>2</sub>] (<b>1</b>), [Ni<sub>2</sub>(valaepy)<sub>2</sub>(hfac)<sub>2</sub>] (<b>2</b>), [Cu(saldmpn)Co(hfac)<sub>2</sub>] (<b>3</b>) [H<sub>2</sub>saldmpn is the Schiff-base resulting from condensation of salicylaldehyde with 2,2-dimethyl-1,3-diaminopropane and Hvalaepy results from the reaction of <i>o</i>-vanillin with 2-(2-aminoethyl)pyridine)]. The structure of <b>1</b> consists of a neutral tetranuclear species that can be viewed as resulting from mutual coordination of one {(hfac)Cu(<i>μ</i>-OCH<sub>3</sub>)<sub>2</sub>(Cu(hfac)} and two {Cu(saldmpn)} building blocks. Compound <b>2</b> is a binuclear complex that results from two {Ni(hfac)(valaepy} fragments, the nickel(II) ions bridged by the two phenoxide-oxygens. The heterobinuclear complex <b>3</b> results from coordination of the [Cu(saldmpn)] metalloligand to cobalt(II) from the {Co(hfac)<sub>2</sub>} unit. The magnetic properties of <b>1–3</b> have been investigated from 1.9 to 300 K. An overall ferromagnetic behavior is observed for <b>1</b> and <b>2</b> leading to <i>S</i> = 2 low-lying spin state for each one. In the case of <b>3</b>, a non-magnetic ground state results because of the occurrence of an intramolecular antiferromagnetic coupling between the copper(II) ion and the high-spin cobalt(II) ion, this last one behaving as an effective spin <i>S</i><sub>eff</sub> = ½ at low temperatures where only the ground Kramers doublet of Co(II) is thermally populated. The values of the intramolecular magnetic couplings in <b>1–3</b> are compared with those from the literature on related systems.</p
Two-Dimensional Coordination Polymers Constructed by [Ni<sup>II</sup>Ln<sup>III</sup>] Nodes and [W<sup>IV</sup>(bpy)(CN)<sub>6</sub>]<sup>2–</sup> Spacers: A Network of [Ni<sup>II</sup>Dy<sup>III</sup>] Single Molecule Magnets
Three
isomorphous two-dimensional (2D) coordination polymers of general
formula {[Ni<sup>II</sup>(valpn)Ln<sup>III</sup>(NO<sub>3</sub>)(H<sub>2</sub>O)(μ-NC)<sub>4</sub>W<sup>IV</sup>(bipy)(CN)<sub>2</sub>]·<i>x</i>H<sub>2</sub>O·<i>y</i>CH<sub>3</sub>CN}<sub><i>n</i></sub> have been synthesized by reacting Ph<sub>4</sub>P[W<sup>V</sup>(CN)<sub>6</sub>(bipy)] with the heterodinuclear
[Ni<sup>II</sup>Ln<sup>III</sup>(valpn)(O<sub>2</sub>NO)<sub>3</sub>] complexes [H<sub>2</sub>valpn = 1,3-propanediyl-bis(2-iminomethylene-6-methoxyphenol),
bipy = 2,2′-bipyridine, and Ln = Gd (<b>1</b>), Dy (<b>2</b>), and Tb (<b>3</b>) with <i>x</i> = 2 (<b>1</b>), 3.9 (<b>2</b>), and 3.35 (<b>3</b>) and <i>y</i> = 2.50 (<b>1</b>), 2 (<b>2</b>), and 1.8 (<b>3</b>)]. Their crystal structures consist of [Ni<sup>II</sup>Ln<sup>III</sup>] 3d-4f nodes which are connected by [W<sup>IV</sup>(bipy)(CN)<sub>6</sub>]<sup>2–</sup> diamagnetic linkers resulting from the
reduction of W<sup>V</sup> to W<sup>IV</sup> during the reaction process.
The Ni(II) and Ln(III) ions occupy the inner and outer coordination
sites of the dideprotonated valpn ligand, respectively, and they are
doubly bridged by the phenoxo oxygen atoms of such a ligand. The value
of Ni(II)···Ln(III) separation through this bridge
is 3.4919(10) (<b>1</b>), 3.4760(10) (<b>2</b>), and 3.4799(9)
(<b>3</b>) Å, and those of the angles at the bridgehead
phenoxo atoms are 106.6(2) and 107.3(2) (<b>1</b>), 106.9(2),
and 107.8(2) (<b>2</b>) and 106.5(2)–106.8(2)° (<b>3</b>). Each W(IV) is eight-coordinated with a bidentate bipy
molecule and six cyanide-carbon atoms building a somewhat distorted
square antiprism environment. The rare-earth cations are nine-coordinated,
the donor atoms describing a monocapped square antiprism for <b>1</b> and <b>3</b> and a tricapped trigonal prism for <b>2</b>. Magnetic susceptibility measurements in the temperature
range 1.9–300 K show the occurrence of ferromagnetic interactions
between the Ni(II) and Ln(III) ions in <b>1</b>–<b>3</b>. Frequency-dependent alternating susceptibility signals
were observed for the Dy<sup>III</sup> derivative below 8.0 K under
an applied dc field of 2500 G indicating the presence of slow magnetic
relaxation with values of the pre-exponential factor (τ<sub>0</sub>) and energy barrier (<i>E</i><sup>#</sup>) of ca.
5.7 × 10<sup>–8</sup> s and 15.9 cm<sup>–1</sup>, respectively. Complex <b>2</b> constitutes the first example
of a 2D 3d-4f heterobimetallic single molecule magnet (SMM)
Effect of Protonated Organic Cations and Anion−π Interactions on the Magnetic Behavior of Hexabromorhenate(IV) Salts
Two novel Re<sup>IV</sup> compounds
of formula (Hbpym)<sub>2</sub>[Re<sup>IV</sup>Br<sub>6</sub>]·4H<sub>2</sub>O (<b>1</b>) and (H<sub>4</sub>biim)[Re<sup>IV</sup>Br<sub>6</sub>]·4H<sub>2</sub>O (<b>2</b>) [Hbpym<sup>+</sup> = 2,2′-bipyrimidinium
cation and H<sub>4</sub>biim<sup>2+</sup> = 2,2′-biimidazolium
dication] have been prepared and magnetostructurally characterized. <b>1</b> and <b>2</b> exhibit distinct crystal packing, and
the presence of weak intermolecular contacts, such as Re–Br···Br–Re
(<b>1</b> and <b>2</b>), Re–Br···(H<sub>2</sub>O)···Br–Re (<b>1</b> and <b>2</b>), and Re–Br···π···Br–Re
(<b>2</b>), lead to different magnetic behaviors. While <b>1</b> is antiferromagnetic, <b>2</b> is a ferromagnetic
compound and indeed the first example of ferromagnetic salt based
on the hexabromorhenate(IV) anion. These results suggest a straightforward
synthetic route to the preparation of new ferromagnetically coupled
Re<sup>IV</sup> compounds
Oxotris(oxalate)niobate(V): An oxalate delivery agent in the design of building blocks
<p>This work concerns the oxalate delivery process that occurs when using (NH<sub>4</sub>)<sub>3</sub>[NbO(C<sub>2</sub>O<sub>4</sub>)<sub>3</sub>]·6H<sub>2</sub>O as a suitable oxalate source in the synthesis of two compounds, [Cu(dmphen)(C<sub>2</sub>O<sub>4</sub>)(H<sub>2</sub>O)] (<b>1</b>) and [{Cu(dmphen)(CH<sub>3</sub>OH)}<sub>2</sub>(μ-C<sub>2</sub>O<sub>4</sub>)](ClO<sub>4</sub>)<sub>2</sub> (<b>2</b>) (dmphen = 2,9-dimethyl-1,10-phenanthroline). {[Fe{HB(pz)<sub>3</sub>}(CN)<sub>2</sub>(μ-CN)]<sub>2</sub>[{Cu(dmphen)}<sub>2</sub>(μ-C<sub>2</sub>O<sub>4</sub>)]}∙<i>x</i>CH<sub>3</sub>OH (<b>3</b>) (2.0 ≤ <i>x</i> ≤ 2.4) was obtained by reacting <b>2</b> and PPh<sub>4</sub>[Fe{HB(pz)<sub>3</sub>}(CN)<sub>3</sub>]∙H<sub>2</sub>O [ = tetraphenylphosphonium and = tris(pyrazolyl)borate]. Crystal structures of <b>1</b>–<b>3</b> have been determined by single-crystal X-ray diffraction experiments: <b>1</b> is a mononuclear trigonal bipyramidal copper(II) species, <b>2</b> is a centrosymmetric oxalato-bridged dicopper(II) complex, and <b>3</b> consists of centrosymmetric tetranuclear units with intramolecular iron–copper and copper–copper distances around 5.010(1) and 5.1833(9) Å, respectively. Variable-temperature magnetic measurements of <b>2</b> and <b>3</b> were carried out from 50 to 350 (<b>1</b>) and 1.9 to 300 K (<b>3</b>). A strong antiferromagnetic interaction between copper(II) ions occurs in <b>2</b> (<i>J</i> = −340 cm<sup>−1</sup>, the spin Hamiltonian being defined as ). Analysis of the magnetic data of <b>3</b> shows magnetic interactions across the oxalate (<i>J</i><sub>1</sub> = −341 cm<sup>−1</sup>) and single cyanide (<i>J</i><sub>2</sub> = +12.9 cm<sup>−1</sup>) … (<i>J</i><sub>2</sub> = +12.9 cm<sup>−1</sup>) bridges . Simple symmetry considerations of the interacting magnetic orbitals in <b>2</b> and <b>3</b> provide a clear picture of the exchange pathways involved in these complexes.</p
Synthesis, Structure, and Magnetic Properties of Regular Alternating μ-bpm/di-μ-X Copper(II) Chains (bpm = 2,2′-bipyrimidine; X = OH, F)
The preparation and X-ray crystal structure of four 2,2′-bipyrimidine
(bpm)-containing copper(II) complexes of formula {[Cu<sub>2</sub>(μ-bpm)(H<sub>2</sub>O)<sub>4</sub>(μ-OH)<sub>2</sub>][Mn(H<sub>2</sub>O)<sub>6</sub>](SO<sub>4</sub>)<sub>2</sub>}<sub><i>n</i></sub> (<b>1</b>), {[Cu<sub>2</sub>(μ-bpm)(H<sub>2</sub>O)<sub>4</sub>(μ-OH)<sub>2</sub>]SiF<sub>6</sub>}<sub><i>n</i></sub> (<b>2</b>), {Cu<sub>2</sub>(μ-bpm)(H<sub>2</sub>O)<sub>2</sub>(μ-F)<sub>2</sub>F<sub>2</sub>}<sub><i>n</i></sub> (<b>3</b>), and [Cu(bpm)(H<sub>2</sub>O)<sub>2</sub>F(NO<sub>3</sub>)][Cu(bpm)(H<sub>2</sub>O)<sub>3</sub>F]NO<sub>3</sub>·2H<sub>2</sub>O (<b>4</b>) are reported. The structures
of <b>1</b>–<b>3</b> consist of chains of copper(II)
ions with regular alternation of bis-bidentate bpm and di-μ-hydroxo
(<b>1</b> and <b>2</b>) or di-μ-fluoro (<b>3</b>) groups, the electroneutrality being achieved by either hexaaqua
manganese(II) cations plus uncoordinated sulfate anions (<b>1</b>), uncoordinated hexafluorosilicate anions (<b>2</b>), or terminally
bound fluoride ligands (<b>3</b>). Each copper(II) ion in <b>1</b>–<b>4</b> is six-coordinated in elongated octahedral
surroundings. <b>1</b> and <b>2</b> show identical, linear
chain motifs with two bpm-nitrogen atoms and two hydroxo groups building
the equatorial plane at each copper(II) ion and the axial position
being filled by water molecules. In the case of <b>3</b>, the
axial sites at the copper atom are occupied by a bpm-nitrogen atom
and a bis-monodentate fluoride anion, producing a “step-like”
chain motif. The values of the angle at the hydroxo and fluoro bridges
are 94.11(6) (<b>1</b>), 94.75(4) (<b>2</b>), and 101.43(4)°
(<b>3</b>). In each case, the copper–copper separation
through the bis-bidentate bpm [5.428(1) (<b>1</b>), 5.449(1)
(<b>2</b>), and 5.9250(4) Å (<b>3</b>)] is considerably
longer than that through the di-μ-hydroxo [2.8320(4) (<b>1</b>) and 2.824(1) Å (<b>2</b>)] or di-μ-fluoro
[3.3027(4) Å (<b>3</b>)] bridges. Compound <b>4</b> is a mononuclear species whose structure is made up of neutral [Cu(bpm)(H<sub>2</sub>O)<sub>2</sub>F(NO<sub>3</sub>)] units, [Cu(bpm)(H<sub>2</sub>O)<sub>3</sub>F]<sup>+</sup> cations, uncoordinated nitrate anions,
and crystallization water molecules, giving rise to a <i>pseudo</i>-helical, one-dimensional (1D) supramolecular motif. The magnetic
properties of <b>1</b>–<b>3</b> have been investigated
in the temperature range 1.9–300 K. Relatively large, alternating
antiferro- [<i>J</i> = −149 (<b>1</b>) and
−141 cm<sup>–1</sup> (<b>2</b>) across bis-bidentate
bpm] and ferromagnetic [α<i>J</i> = +194 (<b>1</b>) and +176 cm<sup>–1</sup> (<b>2</b>) through the dihydroxo
bridges] interactions occur in <b>1</b> and <b>2</b> [the
Hamiltonian being defined as <i>H</i> = −<i>J</i>∑<sub><i>i</i>=1</sub><sup><i>n</i>/2</sup> (<i>S</i><sub>2<i>i</i></sub>·<i>S</i><sub>2<i>i</i>–1</sub> –
α<i>S</i><sub>2<i>i</i></sub>·<i>S</i><sub>2<i>i</i>+1</sub>)]. These values compare
well with those previously reported for parent examples. Two weak
intrachain antiferromagnetic interactions [<i>J</i> = −0.30
and α<i>J</i> = −8.1 cm<sup>–1</sup> across bpm and the di-μ-fluoro bridges, respectively] whose
values were substantiated by density functional theory (DFT)-type
calculations occur in <b>3</b>
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