Synthesis,Structure and Luminescent Property of a Novel Lanthanide Metal-Organic Coordination Polymer Yb<Subscript>3</Subscript>(BDC)<Subscript>4.5</Subscript>(DMF)<Subscript>2</Subscript>(H<Subscript>2</Subscript>O)<Subscript>3</Subscript> · (DMF)<Subscript>2</Subscript>

Abstract  A three-dimensional lanthanide metal-organic coordination polymer Yb₃(BDC)_4.5(DMF)₂(H₂O)₃ · (DMF)₂ has been synthesized by the reaction of the lanthanide metal ion (Yb³⁺) with 1,4-benzenedicarboxylic acid (H₂BDC) under mild condition. The compound crystallizes in the triclinic system, space group PI with unit cell parameters a = 10.7428(9) Å, b = 11.2786(9) Å, c = 26.172(2) Å, α = 85.060(2)°, β = 88.1060(10)°, γ = 62.3670(10)°, V = 2798.9 (4) ų, Z = 2. The crystal structure exhibits one-dimensional channels along the [011] direction. The fluorescent results showed that there were two emission peaks at 375 and 420 nm when the compound was excited by a 235 nm excitation. Graphical Abstract  The preparation, X-ray structure and luminescent property are presented for a new lanthanide metal-organic coordination polymer Yb₃(BDC)_4.5(DMF)₂(H₂O)₃ · (DMF)₂.      

Pseudosymmetry in Cr(urea)<Subscript>4</Subscript>(H<Subscript>2</Subscript>O)<Subscript>2</Subscript>·3NO<Subscript>3</Subscript>

Abstract  

The low temperature crystal structure of the complex, Cr(urea)₄(H₂O)₂·3NO₃ (1), displays intriguing pseudosymmetry that complicates the structure determination. 1 crystallises in the centrosymmetric monoclinic space group P2₁/c with Z = 8 and Z′ = 2; a = 18.3338(4) ?, b = 16.5472(4) ?, c = 13.9252(3) ? and β = 106.3260(10)°, V = 4054.19(16) ?³. The two symmetry independent [Cr(urea)₄(H₂O)₂]³⁺ ions in the asymmetric unit both feature coordinated urea (O=C(NH₂)₂) and lie on general positions. A further six independent nitrate anions complete the structure. The unit cell is primitive but the two Cr³⁺ ions are related by a pseudo translation of ?, ?, 0. The deviation from a truly C-centred cell is clear from an examination of geometry of the urea ligands and the hydrogen bonds which they form. The identification of the space group in this case is described and methods for quantifying the degree of deviation from a C-centred cell discussed.     

Synthesis and crystal structure of Na<Subscript>3</Subscript>(H<Subscript>3</Subscript>O)[UO<Subscript>2</Subscript>(SeO<Subscript>3</Subscript>)<Subscript>2</Subscript>]<Subscript>2</Subscript>· H<Subscript>2</Subscript>O

Single crystals of the compound Na₃(H₃O)[UO₂(SeO₃)₂]₂ · H₂O (I) have been synthesized, and their structure has been investigated using X-ray diffraction. Compound I crystallizes in the triclinic system with the unit cell parameters a = 9.543(6)Å, b = 9.602(7)Å, c = 11.742(8)Å, α = 66.693(16)°, β = 84.10(2)°, γ = 63.686(14)°, space group P \(\bar 1\), Z = 2, and R = 0.0734. The uranium-containing structural units of the crystals are [UO₂(SeO₃)₂]^2? chains, which belong to the crystal-chemical group AB ² B ¹¹ (A = UO ₂ ²⁺ , B ² = SeO ₃ ^2? , B ¹¹ = SeO ₃ ^2? ) of the uranyl complexes. The structures of the compounds containing the [UO₂(SeO₃)₂]^2? anionic complexes are compared.     

Synthesis and X-ray diffraction study of [UO<Subscript>2</Subscript>(NO<Subscript>3</Subscript>)<Subscript>2</Subscript>(H<Subscript>2</Subscript>O)<Subscript>2</Subscript>] · 2C<Subscript>12</Subscript>H<Subscript>18</Subscript>O

The compound [UO₂(NO₃)₂(H₂O)₂] · 2C₁₂H₁₈O was synthesized and studied by IR spectroscopy and X-ray diffraction. The structure consists of the neutral island groups [UO₂(NO₃)₂(H₂O)₂], which belong to the crystal-chemical group AB ⁰¹ ₂ M ¹ ₂ (A = UO₂ ²⁺, B ⁰¹ = NO₃⁻, M ¹ = H₂O) of uranyl complexes, and 1-adamantyl methyl ketone molecules. The characteristic features of the association of the complexes [UO₂(NO₃)₂(H₂O)₂] and 1-adamantyl methyl ketone molecules in the crystal structure via hydrogen bonds are considered with the use of Voronoi-Dirichlet polyhedra.     

X-ray diffraction study of Rb<Subscript>2</Subscript>[(UO<Subscript>2</Subscript>)<Subscript>2</Subscript>(CrO<Subscript>4</Subscript>)<Subscript>3</Subscript>(H<Subscript>2</Subscript>O)<Subscript>2</Subscript>] · 4H<Subscript>2</Subscript>O

The compound Rb₂[(UO₂)₂(CrO₄)₃(H₂O)₂] · 4H₂O was studied by X-ray diffraction. The crystals are monoclinic, a = 10.695(2) Å, b = 14.684(3) Å, c = 14.125(3) Å, β = 108.396(4)°, sp. gr. P2₁/c, Z = 4, V = 2104.9(7) ų, and R = 0.0491. The main structural units are layers consisting of [(UO₂)₂(CrO₄)₃(H₂O)₂]^2? anions belonging to the crystal-chemical group A ₂ T ₂ ³ B ²M ₂ ¹ (A = UL ₂ ²⁺ , T ³ and B ² are CrO ₄ ^2? , and M ¹ is H₂O) of uranyl complexes. The uranium-containing layered groups are held together by electrostatic interactions with rubidium cations, as well as by hydrogen bonds with the participation of inner- and outer-sphere water molecules.     

Crystal structure of byelorussite-(Ce) NaMnBa<Subscript>2</Subscript>Ce<Subscript>2</Subscript>(TiO)<Subscript>2</Subscript>[Si<Subscript>4</Subscript>O<Subscript>12</Subscript>]<Subscript>2</Subscript>(F,OH) · H<Subscript>2</Subscript>O

The crystal structure of the mineral byelorussite-(Ce) NaMnBa₂Ce₂Ti₂Si₈O₂₆(F,OH) · H₂O belonging to the joaquinite group was solved and refined to R = 0.033 based on 4813 reflections with I > σ2(I). The parameters of the orthorhombic unit cell are a = 22.301(4) Å, b = 10.514(2) Å, c = 9.669(2) Å, V = 2267.1(8) ų, sp. gr. Ama2, and Z = 4. The structure is composed of three-layer sheets, which consist of dimers of edge-sharing Ti octahedra located between isolated four-membered [Si₄O₂] rings. The sheets are linked to each other by Mn 5-vertex polyhedra to form a heteropolyhedral framework. Large cavities in the framework are occupied by Na 6-vertex polyhedra, Ba 11-vertex polyhedra, and REE 9-vertex polyhedra.     

Hydrogen Atoms Location in Os<Subscript>3</Subscript>(μ-H)(CO)<Subscript>9</Subscript>(μ<Subscript>3</Subscript>, η<Superscript>2</Superscript>-C<Subscript>2</Subscript>H) from Accurate X-Ray Data at 100 K

Abstract  

The structure of the complex Os₃(μ-H)(CO)₉(μ₃, η²-C₂H) has been determined using X-ray data collected at low temperature (100 K); all hydrogen atoms have been located. The asymmetric unit is formed by two molecules joined through hydrogen bonds involving the hydrogen atoms of C₂H moiety and the oxygen atoms of carbonyl groups. The complex crystallizes in the monoclinic space group P2₁/c with a = 12.94040(2), b = 15.4705(2), c = 16.0164(2) ?, β = 106.0860(10)°, and V = 3,080.85(7) ?³, Z = 8. A molecule is formed by a triangular Os₃ cluster, with metal atoms bearing terminal CO groups. The acetylenic residual is formally π-bonded to two Os atoms in a perpendicular mode and σ-linked to the third Os atom. A bridging hydride atom completes the coordination.     

Molecular Structure of [Cu<Subscript>2</Subscript>(MeCN)<Subscript>2</Subscript>(μ-tpy)<Subscript>2</Subscript>][BPh<Subscript>4</Subscript>]<Subscript>2</Subscript>: A Helical Di-Cuprous Terpyridine Complex

Abstract  The molecular structure of [Cu₂(MeCN)₂(μ-tpy)₂][BPh₄]₂ has been determined. The two terpyridine ligands coordinate to the same Cu(I) center in a bidentate configuration, in which the copper adopted a distorted tetrahedral geometry with the four nitrogen donors. The third ring of each terpyridine ligand forms a bridge with a second Cu(I) center, whose tetrahedral coordination sphere is completed by two acetonitrile ligands. The resulting structure represents a section of a double helix. Crystal data: space group C2/c, a = 27.202(5), b = 12.995(3), c = 23.409(5) ?, β = 123.13(3)°; V = 6930(2) ?³, Z = 4, R = 0.0613, wR ₂ = 0.0946. Graphical Abstract  The molecular structure of [Cu₂(MeCN)₂(μ-tpy)₂][BPh₄]₂ has been determined. The terpyridine ligands coordinate in a bidentate fashion to the same Cu center and monodentate to a second Cu center resulting in a double helical structural motif.      

Synthesis and structure of a new hybrid vanadium arsenate: [VO<Subscript>2</Subscript>(phen)]<Subscript>2</Subscript>(H<Subscript>2</Subscript>AsO<Subscript>4</Subscript>)⋅H<Subscript>3</Subscript>O

A new hybrid vanadium arsenate [VO₂(phen)]₂(H₂AsO₄)H₃O 1 (phen = 1,10-phenanthroline) was synthesized under hydrothermal reaction conditions and structurally characterized by single-crystal X-ray diffraction, thermogravimetric analysis (TGA), IR and elemental analyses. Crystal data for 1: monoclinic, P2₁/n, a = 9.175(2) Å, b = 18.638(5) Å, c = 14.482(4) Å, = 102.333(3), V = 2419(1) ų, Z = 4. Compound 1 is composed of discrete tricyclic (VO₂)₂(H₂AsO₄) cluster decorated with two phen ligands. The discrete arsenic–vanadium clusters are extended into three-dimensional supramolecular arrays via – stacking interactions of phen groups.     

Synthesis and Crystal Structures of the Coordination Polymers Pb(PYTAC)<Subscript>2</Subscript> and Pb<Subscript>2</Subscript>(PYTAC)<Subscript>3</Subscript>(NO<Subscript>3</Subscript>) (PYTAC = 2-(pyridin-4-yl)thiazole-5-carboxylate)

Abstract  

Two lead coordination compounds, Pb(PYTAC)₂ (1), and Pb(PYTAC)₂(NO₃) (2), were grown as single crystals via hydrothermal synthesis (PYTAC = 2-(4-pyridyl) thiazole-4-carboxylate). Both compounds have been identified via single crystal X-ray diffraction. Coordination polymer 1 crystallizes in a triclinic space group P-1 (a = 5.5097(4) ?, b = 7.2822(5) ?, c = 11.3134(8) ?, α = 103.5580(10)°, β = 99.4330(10)°, γ = 97.1050(10)°), and forms 2-D layers parallel to the crystallographic (ac) plane. Coordination polymer 2 crystallizes in a triclinic space group P-1 (a = 9.8102(5) ?, b = 10.5972(6) ?, c = 14.8076(8) ?, α = 91.9350(10)°, β = 100.8050(10)°, γ = 103.1350(10)°), and forms an infinite 1-D chains along the a axis.     

Synthesis and crystal structure of [UO<Subscript>2</Subscript>CrO<Subscript>4</Subscript>(C<Subscript>5</Subscript>NH<Subscript>5</Subscript>COO)<Subscript>2</Subscript>(H<Subscript>2</Subscript>O)]·2H<Subscript>2</Subscript>O

Crystals of UO₂CrO₄(C₅NH₅COO)₂(H₂O)] · 2H₂O are synthesized and their structure is studied by X-ray diffraction. The compound crystallizes in the triclinic crystal system. The unit cell parameters are as follows: a = 7.0834(10) Å, b = 10.6358(14) Å, c = 12.9539(17) Å, α = 75.096(2)°, β = 74.490(2)°, and γ = 80.657(2)°; V = 904.1(2) ų, space group P \(\bar 1\), Z = 2, and R = 0.026. The structure is built of [UO₂CrO₄(C₅NH₅COO)₂(H₂O)]₂ centrosymmetric dimers, which are linked into a framework by a system of hydrogen bonds involving inner-sphere and outer-sphere water molecules. The coordination number of the U(VI) atom is seven, and the coordination polyhedron is a pentagonal bipyramid with the oxygen atoms of the uranyl group, two chromate groups, two molecules of isonicotinic acid, and a water molecule at the vertices. The crystal chemical formula of the [UO₂CrO₄(C₅NH₅COO)₂(H₂O)]₂ dimer is represented as AB ² M ₃ ¹ , where AB ² M ₃ ¹ , where A = UO ₂ ²⁺ , B ² = CrO ₄ ^2? , and M ¹ = = C₅NH₄COOH and H₂O.     

Triosmium and triruthenium clusters containing morpholine ligand: X-ray structure of Os<Subscript>3</Subscript>(CO)<Subscript>10</Subscript>(μ-η<Superscript>2</Superscript>-NC<Subscript>4</Subscript>H<Subscript>6</Subscript>O)(μ-H)

Treatment of the labile cluster Os₃(CO)₁₀(CH₃CN)₂ with morpholine in benzene at 60^°C afforded Os₃(CO)₁₀(μ-η²-NC₄H₆O)(μ-H) (1). Decarbonylation of 1 at 128^°C gave Os₃(CO)₉(μ₃-η²-NC₄H₆O)(μ-H) (2), which reacts with PPh₃ at ambient temperature to give an addition product Os₃(CO)₉(μ-η²-NC₄H₆O)(PPh₃)(μ-H) (3). Compound 1 reacted with PPh₃ at 98^°C to give the substitution product 4 which is an isomer of 3. The reaction of Ru₃(CO)₁₂ with morpholine in the presence of Me₃NO in refluxing benzene at 80^°C afforded Ru₃(CO)₉(μ₃-η²-NC₄H₆O)(μ-H) (5). Compounds 1– 5 have been characterized by elemental analysis, infrared, ¹H NMR, and mass spectroscopic data. The molecular structure of 1 has been determined by single crystal X-ray diffraction analysis. Compound 1 crystallizes in the monoclinic space group P2/c with a = 29.598(8) Å, b = 9.202(2) Å, c = 14.496(4) Å, β = 93.19(3)^°, Z = 8, and V = 3942(2) ų. Compound 1 consists of an isosceles triangle of osmium atoms with one elongated Os–Os edge, which is bridged by the hydride and the morpholine ligand.     

Crystal structure and properties of [OsO<Subscript>2</Subscript>(NH<Subscript>3</Subscript>)<Subscript>4</Subscript>]SO<Subscript>4</Subscript> · H<Subscript>2</Subscript>O

The structure of a single crystal of tetraammindioxoosmium(VI) sulfate [OsO₂(NH₃)₄]SO₄ · H₂O, which is synthesized by the reaction of K₂[OsO₂(OH)₄] with (NH₄)₂SO₄ in an aqueous solution, is investigated using X-ray diffraction analysis. The compound crystallizes in the monoclinic crystal system, space group P2₁/c, a = 13.102(2) Å, b = 6.158(3) Å, c = 11.866(2) Å, β = 98.13(2)°, and Z = 4. The [OsO₂(NH₃)₄]SO₄ · H₂O compound has an island structure. Two crystallographically independent osmium atoms are situated at the centers of symmetry, and their octahedral coordination includes two oxygen atoms and four nitrogen atoms of the ammonia molecules. In both octahedra, the osmyl group is linear. The Os-O distances in the octahedra are identical within the standard deviations [Os(1)-O, 1.762(2) Å; Os(2)-O, 1.769(2) Å]. The Os-N bond lengths vary from 2.082(3) to 2.101(3) Å. The cationic complexes, SO₄ groups, and water molecules are linked via the system of hydrogen bonds. The assignment of the absorption bands in the IR spectrum of the compound synthesized is performed, and its thermal behavior in air is studied.     

Crystal Structure and Vibrational Spectra of Erbium Trisodium Bis(Cyclotriphosphate) Nonahydrate,ErNa<Subscript>3</Subscript>(P<Subscript>3</Subscript>O<Subscript>9</Subscript>)<Subscript>2</Subscript> · 9H<Subscript>2</Subscript>O

Abstract The cyclotriphosphate salt, ErNa₃(P₃O₉)₂ · 9H₂O, has been characterized by single-crystal X-ray diffraction [hexagonal, space group , with unit cell parameters of a = b = 30.8451(14), c = 12.8063(8) ?; Z = 18]. The structure consists of alternating layers of [P₃O₉]³⁻ groups, ErO₈ dodecahedra, Na(1)O₆ and Na(2)O₇ polyhedra linked together by water molecules. The P₃O₉ rings are grouped along the c-axis in a P₃O₉–ErO₈ arrangement thereby producing broad, hexagonal channels of diameter of 6.65 ? with a side dimension of 3.907 ?. The absence of coincidences for the majority of the IR and Raman bands observed for the cyclotriphosphate salt is in accord with the centrosymmetric structure of the material. The vibrational spectra have been interpreted on the basis of factor group effects. Graphical abstract We report the crystal structure and vibrational spectra of erbium trisodium bis(cyclotriphosphate)nanohydrate salt ErNa ₃ (P ₃ O ₉ ) ₂ · 9H ₂ O H. Assaaoudi, M. Ijjaali, A. Ennaciri, I. S. Butler* and J. A. Kozinski Crystal structure and vibrational spectra of erbium trisodium bis(cyclotriphosphate) nonahydrate,ErNa₃(P₃O₉)₂ · 9H₂O. Projection of the coordination polyhedra of ErNa₃(P₃O₉)₂ · 9H₂O down the c axis     

Aquanitrilotris(methylenephosphonato)dirubidium [Rb<Subscript>2</Subscript>(H<Subscript>2</Subscript>O){μ<Superscript>12</Superscript>-NH(CH<Subscript>2</Subscript>PO<Subscript>3</Subscript>H)<Subscript>3</Subscript>}]: Synthesis and structure

Aquanitrilotris(methylenephosphonato)dirubidium is a 3D coordination polymer with a layer structure. Space group \(P\bar 1\), Z = 2; a = 8.0380(3) Å, b = 9.0522(4) Å, and c = 10.7837(4) Å; α = 113.252(4)°, β = 105.391(3)°, and γ = 96.182(3)°. Rb atoms populate two symmetrically inequivalent positions with c.n. = 8 and 10; significant difference in O–Rb–O angles in the coordination polyhedra is indicative of the ionic type of Rb–O bonds. In the crystal packing, molecules are connected by not only coordination bonds but hydrogen bonds as well.     

Crystal structure of zinc(II) hydrated trinuclear complex with monoprotonated ethylenediaminetetraacetate anion(3−), [Zn<Subscript>3</Subscript>(H<Emphasis Type="Italic">Edta</Emphasis>)<Subscript>2</Subscript>(H<Subscript>2</Subscript>O)<Subscript>6</Subscript>]

The crystal structure of the [Zn₃(HEdta)₂(H₂O)₆] complex (I) is determined by X-ray diffraction analysis. The crystals are orthorhombic, a = 14.780 Å, b = 29.699 Å, c = 7.032 Å, Z = 4, and space group Pna2₁. The structural units of crystals I are trinuclear linear molecules, in which the peripheral atoms Zn(1) and Zn(2) each coordinate two N atoms and three O atoms of the HEdta ^3? ligand and the O(w) atom of the H₂O molecule, whereas the central Zn(3) atom coordinates four O(w) atoms of the H₂O molecules and two terminal O atoms of the two HEdta ^3? ligands. The HEdta ^3? ligand fulfills a hexadentate chelating—bridging function. The bond lengths are as follows: Zn-O(HEdta), 2.006(4)–2.123(4) Å; Zn-N, 2.214(6) and 2.128(5) Å; and Zn-O(w), 2.006(6)–2.225(5) Å. In structure I, there is a specific contact formed by hydrogen bonds, owing to which the distance between the central atoms of individual molecules appears to be shorter than that in covalently bonded complexes.     

Crystal structure of the solid solution NH<Subscript>4</Subscript>Al<Subscript>0.62</Subscript>Cr<Subscript>0.38</Subscript>(SO<Subscript>4</Subscript>)<Subscript>2</Subscript> · 12H<Subscript>2</Subscript>O

The solid solution NH₄Al_0.62Cr_0.38(SO₄)₂ · 12H₂O was studied by X-ray diffraction. The crystal structure was determined in a series of the maximal subgroups Pa3? > R3? > P1? > P1. Reflections forbidden in sp. gr. Pa3? are indicative of symmetry lower than cubic. In the centrosymmetric models under consideration, all sulfate groups are oppositely oriented with respect to each other. In non-centrosymmetric sp. gr. P1, four of the eight sulfate groups have the same orientation, whereas the other four groups are oriented in an opposite direction.     

Structural Studies of the Isomorphous MCl<Subscript>2</Subscript>(PMe<Subscript>3</Subscript>)<Subscript>4</Subscript> (M = Mo,W) Complexes

Abstract  

The structure of WCl₂(PMe₃)₄ has been determined in order to allow for a comparison with its molybdenum analogue. The complexes are isomorphous, and exhibit trans-pseudooctahedral coordination, with crystallographically imposed [`4]2m\overline{4}2m (D<sub>2d</sub>) symmetry. A significant distortion occurs involving the PMe<sub>3</sub> ligands, through which one opposing pair tilts upward toward one axial chloride ligand, while the other pair tilts in an opposite manner, by 9.33°. The complex crystallizes in the tetragonal space group I[`4]2mI\overline{4}2m, with a = b = 9.4987(4) ?, c = 12.1058(5) ?, V = 1092.25(8) ?³, D _calc = 1.700 at 150(1) K. For a better comparison, the structure of the molybdenum complex was redetermined, at a low temperature. Its space group is also I[`4]2mI\overline{4}2m with a = b = 9.5193(3) ?, c = 12.1083(5) ?, V = 1097.22 ?³, D _calc = 1.426 at 150(1) K. In accord with the larger cell volume, the molybdenum complex possesses slightly longer M–Cl and M–P bonds.     

Crystal structure and properties of K<Subscript>2</Subscript>[OsO<Subscript>2</Subscript>(C<Subscript>2</Subscript>O<Subscript>4</Subscript>)<Subscript>2</Subscript>] · 2H<Subscript>2</Subscript>O

The synthesis and X-ray diffraction study of the compound K₂[OsO₂(C₂O₄)₂] · 2H₂O are performed. The compound crystallizes in the triclinic crystal system, space group P \(\bar 1\), a = 6.545(1) Å, b = 6.835(2) Å, c = 7.595(2) Å, α = 85.76(2)°, β = 65.33(2)°, γ = 71.14(2)°, and Z = 1. The osmium atom is located at the center of symmetry and has a distorted octahedral coordination formed by oxygen atoms: two oxygen atoms of the osmyl group occupy the apical positions [Os-O, 1.730(2) Å], and four oxygen atoms of the oxalate ions lie in the equatorial plane. The K⁺ cation is surrounded by ten oxygen atoms located at different K-O distances in the range from 2.787(2) to 3.158(2) Å. The assignment of the absorption bands in the IR spectrum of K₂[OsO₂(C₂O₄)₂] · 2H₂O is performed. The electronic absorption spectra of the compound are recorded in different solvents, and the thermal behavior in air is studied.     

Synthesis and crystal structure of binuclear molecule Ho<Subscript>2</Subscript>(2-FC<Subscript>6</Subscript>H<Subscript>4</Subscript>COO)<Subscript>6</Subscript>⋅4H<Subscript>2</Subscript>O

The complex Ho₂(2-FC₆H₄COO)₆?4H₂O has been synthesized and structurally characterized by single crystal X-ray diffraction methods. The complex crystallizes in the triclinic system with space group P \(\bar 1\), lattice parameters a = 9.293(8) Å, b = 9.845(8) Å, c = 12.703(11) Å, α = 85.470(14)^°, β = 87.537(12)^°, γ = 62.485(11)^°, V = 1027.5(15) ų, Z = 1, D_calc = 1.998 Mg/m³. The Ho³⁺ ion is in distorted monocapped square-antiprism coordination environment and is coordinated by nine oxygen atoms, seven from five 2-FC₆H₄COO^2? groups, two from two water molecules. Two Ho³⁺ ions are linked together by four bridging carboxylate groups to form a binuclear molecule with inversion center.