Synthesis,crystal structure and magnetic property of a one-dimensional copper(II) complex with 2,5-dimethylpyrazine-1,4-dioxide as bridging ligand

A one-dimensional polynuclear copper(II) complex [Cu(μ_1,6-dmpzdo)(SCN)₂] _n (where dmpzdo?=?2,5-dimethylpyrazine-1,4-dioxide) has been synthesized and its crystal structure determined by X-ray crystallography. The coordination geometry of Cu(II) atom is a square plane and each Cu(II) ion is connected by two μ_1,6-dmpzdo bridging ligands, leading to the formation of a one-dimensional chain. ESR spectra indicate magnetic coupling between the bridged Cu(II) ions. The fitting of the variable-temperature magnetic susceptibility data (4–300?K) gave 2J?=??68.69?cm^?1.     

Magnetic study on a two-dimensional coordination polymer with mixed bridging ligands

A two-dimensional coordination polymer, [Co(mu(1,3)-SCN)(2)(mu(1,6)-dmpzdo)](n)() (where dmpzdo = 2,5-dimethylpyrazine-1,4-dioxide), has been synthesized and its crystal structure determined by X-ray crystallography. In the complex, the adjacent Co(II) ions are coordinated by mu(1,3)-SCN(-) bridging ligands which forms a one-dimensional chain along the a axis; the one-dimensional chains are further connected by mu(1,6)-dmpzdo bridging ligands which leads to the formation of a two-dimensional layer on the ac plane. The theoretical calculations reveal that a ferromagnetic coupling exists between the mu(1,3)-SCN(-) bridging Co(II) ions and an anti-ferromagnetic interaction between the mu(1,6)-dmpzdo bridging Co(II) ions, and the anti-ferromagnetic interaction is stronger than the ferromagnetic interaction. The fitting of the variable-temperature (34-300 K) magnetic susceptibilities reveals that there is an anti-ferromagnetic coupling between the bridging Co(II) ions with the magnetic coupling constant J = -3.52 cm(-1).     

Synthesis,crystal structure and magnetism of a three-dimensional Mn(II) coordination polymers with 2,5-dimethylpyrazine-1,4-dioxide as bridging ligand

A novel three-dimensional Mn(II) coordination polymer, {[Mn(μ_1,6-dmpzdo)₃]?·?(ClO₄)₂} _n , has been synthesized with 2,5-dimethylpyrazine-1,4-dioxide (dmpzdo) as a bridging ligand and its crystal structure determined by X-ray crystallography. The complex crystallizes in a trigonal system with a space group R-3 and a?=?11.6672(14), b?=?11.6672(14), c?=?16.652(4)?Å. In the complex each Mn(II) is coordinated by six μ_1,6-dmpzdo bridging ligands and each μ_1,6-dmpzdo bridging ligand coordinates two Mn(II) ions, forming a three-dimensional structure. The variable temperature (4–300?K) magnetic susceptibility data gave the magnetic coupling constant 2J?=??0.30?cm^?1.     

Synthesis,crystal structure and magnetic properties of a novel manganese(II)-nitronyl nitroxide-azido(μ<Subscript>1,1</Subscript> and μ<Subscript>1,3</Subscript>) one-dimensional complex

A novel one-dimensional manganese(II) complex containing nitronyl nitroxide radical [Mn₂(IM2-py)₂(Ac)₂(μ_1,1-N₃)(μ_1,3-N₃) · EtOH] _n was synthesized and characterized structurally and magnetically. It crystallizes in the monoclinic space group p2₁/n. Each Mn(II) ion is six-coordinated in a distorted octahedral environment. The two N atoms of the nitronyl nitroxide radical and the two O atoms of acetate ligands are in the equatorial plane, whereas the two different azido bridging ligands are in trans axial position. Mn(II) ions are linked by nitrogen atom of μ_1,1-azido and oxygen atoms of two carboxy groups to form a Mn-Mn unit. Mn-Mn units are linked by azido ligands through μ_1,3 bridging style to form a one-dimensional chain. The compound is connected by the coordination bonds, π-π interactions and hydrogen bonds as a three-dimensional structure. Magnetic susceptibility data support that there are stronger antiferromagnetic interactions between the radical and Mn(II) ion, weak antiferromagnetic interactions between the Mn-R units, and very weak antiferromagnetic interactions between the R-Mn-Mn-R units.     

Synthesis, properties, and molecular and crystal structure of hexaaquacopper(IV) bis(diaquacuprato-μ3-trihydroxyglutarato)germanate(IV) dihydrate [Cu(H2O)6][Ge(μ3-Thgl)2{Cu(H2O)2}2] · 2H2O

A procedure for the synthesis of the heteropolymetallic germanium(IV) and copper(II) complex with trihydroxyglutaric acid (H₅Thgl) [Cu(H₂O)₆][Ge(μ₃-Thgl)₂{Cu(H₂O)₂}₂] · 2H₂O (I) was developed and the complex was isolated for the first time in the solid state. The product was characterized by elemental analysis, powder X-ray diffraction, thermogravimetry, and IR spectroscopy. Compound I was studied by X-ray crystallography. The crystals are monoclinic, a = 10.216(2)?, b = 12.272(3)?, c = 10.679(2)?, β = 93.13(3)°, V = 1336.9(5)?³, Z = 2, space group P2₁/n, R1 = 0.0261 for 3616 reflections with I > 2σ(I). Compound I is composed of bimetallic [Ge(μ₃-Thgl)₂{Cu(H₂O)₂}₂]²⁻ anions, [Cu(H₂O)₆]²⁺ cations, and water molecules of crystallization. In the centrosymmetric trinuclear complex anion, the Ge(1) atom is bound by two fully deprotonated bridging ligands to two Cu atoms. The Ge(1) atom is coordinated at distorted octahedron vertices by six hydroxyl oxygen atoms of two Thgl⁵⁻ ligands (average Ge(1)-O distance is 1.8874(13)?). The Cu coordination polyhedron in the anion is an extended square pyramid (4 + 1) formed by the bridging hydroxyl oxygen atom (Cu(1)-O(3), 2.0039(12) ?), two carboxyl oxygen atoms (average CU(1)-O distance is 1.9674(14)?) of two Thgl⁵⁻ ligands, and two water oxygen atoms in equatorial and axial positions (Cu(1)-O, 1.9761(13) and 2.3643(14)?, respectively). In the centrosymmetric cation, the Cu coordination polyhedron is an extended square bipyramid (4 + 2). The equatorial Cu-O bond length is 1.9428(14) ? (average), the axial Cu-O bond is elongated to 2.5151(14)?. The cations and anions are combined by H-bonds.     

Synthesis,Crystal Structure and Magnetism of A 1-D Polymeric Manganese(II) Complex with 2-Hydroxyl-2-Hydroxylate-Malonate as Bridging Ligand

A one-dimensional chain complex {Na[MnL(H₂O)₂]} _n (L = 2-hydroxyl-2-hydroxylate-malonate trivalent anion) has been synthesized and its crystal structure determined by X-ray crystallography. In the complex each Mn ion is located in a distorted octahedral environment with two oxygen atoms O(7) and O(8) from terminal ligands of two H₂O molecules, and four other coordinating oxygen atoms O(1), O(5), O(3A) and O(6A) from two bridging ligands, respectively. Each bridging ligand provides four coordinating oxygen atoms, in which O(6) comes from the hydroxylate, O(5) from the hydroxyl, and O(1) and O(3) from two carboxylate groups, respectively. The O(1) and O(5) atoms coordinate to one Mn ion and the O(3) and O(6) atoms coordinate to another Mn ion; a one-dimensional chain is thereby constructed. The variable-temperature magnetic susceptibility of the complex was measured in the 4–300 K range. The magnetic coupling parameter is consistent with an antiferromagnetic exchange and generates the antiferromagnetic coupling parameter, 2J=–0.0544 cm^–1.     

Synthesis,Characterization and Crystal Structure of a One-Dimensional Chain Copper Bipyridine Complex Bridged Through an Azobispyridine Ligand

The copper complex {[Cu(2,2'-bpy)(azpy)(H₂O)(ClO₄)} _n 1 (2,2'-bpy=2,2'bipyridine, azpy=4,4'-azopyridine), has been synthesized and characterized. X-ray analysis reveals that copper is coordinated by two N atoms of 2,2'-bpy, two N atoms from two bridging azpy ligands, one O atom of coordinated water and O atom from ClO-₄ and has a distorted octahedral coordination environment in complex 1. Copper ions are linked to each other through bridging azpy ligands to form a one-dimensional chain. Stacking the one-dimensional chains results in the formation of rhombic channels with ca. 6Å x 6Å. Variable-temperature magnetic susceptibility studies show that there is a weak antiferromagnetic interaction between the copper ions.     

Synthesis,crystal structure and magnetism of a one-dimensional Cu(II) coordination polymer with monodeprotonated 2,2′-bypyridine-3,3′-diol as bridging ligand

A new one-dimensional copper(II) coordination polymer, [Cu(μ-HL)(H₂O)₂(NO₃)] _n (HL = monodeprotonated 2,2′-bypyridine-3,3′-diol), was synthesized and its crystal structure determined by X-ray crystallography. In the crystal Cu(II) is located a distorted octahedral coordination geometry and each HL coordinates two Cu(II) ions with its two N atoms and an O atom of deprotonated hydroxyl, giving a one-dimensional chain. The variable-temperature (2–300 K) magnetic measurements, analyzed using a one-dimensional Cu(II) magnetic interaction formula, indicate the existence of very weak ferromagnetic coupling with 2J = 0.014 cm^?1.     

A one-dimensional barium(II) coordination polymer with a coordinated nitro group of 2-nitrobenzoate

The aqueous reaction of barium carbonate with 2-nitrobenzoic acid (2-nbaH) results in the formation of a one-dimensional coordination polymer, catena-poly[[hexa(aqua)dibarium(II)]bis[(μ ₂-2-nitrobenzoate-O,O,O-NO₂)(μ ₂-2-nitrobenzoate-O,O,O′)]] 1. On heating at 100°C compound 1 is dehydrated to anhydrous barium bis(2-nitrobenzoate) 2. The anhydrous compound can be re-hydrated to 1 on exposure to water vapour. Compounds 1 and 2 were characterized by elemental analysis, IR and UV-Vis spectra, DSC thermograms, weight loss studies and the structure of 1 was determined. 1 and 2 can be thermally decomposed to BaCO₃ by heating at 800°C. The polymer [[Ba(H₂O)₃]₂(μ ₂-2-nba-O,O,O-NO₂)₂ (μ ₂-2-nba-O,O,O′)₂] _n 1 crystallizes in the centrosymmetric triclinic space group Pī and all atoms are located in general positions. The polymeric structure is based on a dimeric unit and consists of three water molecules coordinated to a central Ba(II) and two unique 2-nitrobenzoate (2-nba) anions, one of which (μ ₂-2-nba-O,O,O-NO₂) functions as a tridentate ligand and is linked to a Ba(II) through the oxygen atom of the-NO₂ group and forms a monoatomic μ ₂-carboxylate bridge between two symmetry related Ba(II) ions with a Ba···Ba distance of 4·5726(14) ?. The second unique 2-nba anion (μ ₂-2-nba-O,O,O′) also functions as a tridentate ligand with the carboxylate oxygen atoms linked to a Ba(II) ion in a bidentate fashion and one of the carboxylate oxygen atoms forming a monoatomic bridge between two symmetry related Ba(II) ions resulting in a Ba···Ba separation of 4·5406(15) ?. These differing tridentate 2-nba ligands link {Ba(H₂O)₃} units into a one-dimensional polymeric chain extending along b axis. In the infinite chain each nine coordinated Ba(II) is bonded to three water molecules and further linked to six oxygen atoms of four different 2-nitrobenzoate anions with alternating pairs of Ba(II) ions in the chain bridged by a pair of (μ ₂-2-nba-O,O,O-NO₂) and (μ ₂-2-nba-O,O,O′) ligands resulting in alternating Ba···Ba distances of 4·5406(15) and 4·5726(14) ? across the chain. Dedicated to Prof. S. K. Paknikar on the occasion of his 73rd birthday.     

Syntheses,Crystal Structures,and Magnetic Properties of Carboxylate-Bridged Copper(II) Complexes with Bis(2-Pyridylmethyl)Amino Acids

Tetradentate Schiff-base carboxylate-containing ligands, bis(2-pyridylmethyl)amino-5-valeric acid (Hpmva) and bis(2-pyridylmethyl)amino-6-caproic acid (Hpmca), react with copper(II) perchlorate to give rise to the carboxylated bridged chain complexes {[Cu(μ-pmva)(H₂O)](ClO₄)}_n (1) and {[Cu(μ-pmca)(H₂O)](ClO₄)}_n (2). These complexes have been characterized by X-ray crystallography, spectroscopic, and variable-temperature magnetic susceptibility measurements. In 1 and 2, each of the copper(II) ions exhibit CuN₃O₂ coordination environments with the three nitrogen atoms of the ligand and one oxygen atom belonging to the carboxylate group of an adjacent molecule occupying the basal position and a water molecule coordinated in the axial position. The electronic spectra of the complexes are significantly affected by the coordination geometry. Magnetic susceptibility measurements indicate that complexes exhibit very weak ferromagnetic interactions.     

Crystal structure and strong antiferromagnetic interaction of a terephthalate-bridged binuclear copper(II) Complex, [{Cu(dipn)}2(μ-TPHA)](ClO4)2 (dipn = N-(3-aminopropyl)-1,3-propanediamine)

Three binuclear copper(II) complexes bridged by three different bridging ligands: μ-TPHA (terephthalato), μ-PHTA (phthalato) and μ-TCB (tetracarboxylatobenzene) have been synthesized. The crystal structure of [{Cu(dipn)}₂(μ-TPHA)](ClO₄)₂ where dipn = N-(3-aminopropyl)-1,3-propanediamine was solved at room temperature. The [{Cudipn}₂(μ-TPHA)](ClO₄)₂ complex consists of a μ-terephthalato bridging binuclear copper(II) cationic unit and two non-coordinated perchlorate anions. The TPHA ligand bridges in a bismonodentate fashion. The environment of the copper(II) ion is a distorted plane-square-planar coordination sphere. The magnetic properties of the three complexes have been investigated in the 75–300 K range, and show that the geometry of the Cu^II atom is the important factor for magnetic interactions in the terephthalato bridging binuclear copper(II) complexes. This revised version was published online in June 2006 with corrections to the Cover Date.     

Synthesis and magneto-structural correlation of a new maleato bridged copper(II) coordination polymer

A one-dimensional (1-D) copper(II) coordination polymer [Cu(maleate)(2,2′-bipyridyl)] _n ·2H₂O has been synthesised. Single crystal X-ray diffraction study reveals that maleate ion bridges two adjacent copper(II) centres along the chain in a syn–anti fashion. A complete cryomagnetic investigation of the title complex correlates well with the distorted square pyramidal geometry of the central copper(II) ion and bridging nature of the maleate. A τ value of 0.26 indicates the distortion towards tbp coordination allowing the magnetic orbital to acquire some character leading to a weak antiferromagnetic interaction having J = −0.26 cm⁻¹. The complex has also been firmly established from several other instrumental techniques like Fourier transform infrared (FT-IR) and EPR spectroscopies.     

Structure and magnetic properties of a novel heterospin 1-D chain complex containing both Cu(II) and nitroxide radicals as spin branches

A novel heterospin one-dimensional (1-D) chain complex containing both Cu(II) and nitroxide radical ligands, {[Cu(tcph)(H₂O)₄][Cu(tcph)(NIT3Py)₂]·2H₂O} _n (1) (H₂tcph = tetrachloro-phthalic acid, NIT3Py = 2-(3′-pyridyl)-4,4,5,5-tetramethyl-imidazoline-1-oxyl-3-oxide), has been synthesized and structurally characterized. The structure consists of neutral chains of copper(II) ions bridged by tcph and coordinated alternatively by nitroxide radicals as spin branches and solvated water as co-ligand. The magnetic data were fitted using an approximate theoretical model based on population analysis to obtain the coupling parameter values of J _Cu2-Rad = 22.4 cm⁻¹ and J′_Cu1-Cu2 = −2.4 cm⁻¹, indicating the intramolecular ferromagnetic interaction between Cu(II) and NIT3Py and weak antiferromagnetic interaction between Cu1 and Cu2 linked by tcph.     

Thiocyanato-copper(II) complexes derived from a tridentate amine ligand and from alanine

Two thiocyanato-Cu(II) complexes including mononuclear dithiocyanato Cu(Me₃dpt)(NCS)₂ (1) and the polymeric 1D [Cu(d,l-Ala)(μ_N,S–NCS)(H₂O)] _n (2) were synthesized and structurally characterized (Me₃dpt = bis(N-methyl-3-propyl)methylamine, Ala = alaninate anion). The IR spectrum of complex 1 confirmed the N-bonding coordination mode of the thiocyanate groups, and its visible spectrum revealed the square pyramidal geometry around the central Cu²⁺ ion. Single X-ray crystallography of 1 showed that the Cu(II) center displays square pyramidal geometry with severe distortion toward trigonal bipyramidal environment. Complex 2 forms a 1-D polymeric chain with the NCS⁻ acting as a μ_N,S-ligand. A distorted SP geometry around the Cu²⁺ centers was achieved by the O and N atoms of alaninato anion, the aqua ligand and by the N and S atoms of the bridging thiocyanate groups. Hydrogen bonds of the type N–H···O, N–H···S and O–H···O are formed in this complex leading to the extension of the 1D chain to a supramolecular network.     

Synthesis, crystal structures and properties of the novel mononuclear copper(II) and tetranuclear cobalt(II) complexes with 3,6-bis-(3,5-dimethylpyrazolyl)-pyridazine

A novel monomer copper(II) complex [Cu(L)₂(SCN)] · ClO₄ (1) and a tetranuclear cobalt(II) complex [Co₄(L)₄(N₃)₄](OH)₄ · 2H₂O (2)(L = 3,6-bis-(3,5-dimethylpyrazolyl)-pyridazine) have been synthesized and structurally characterized. Single crystal X-ray analyses show that the Cu(II) atom is in a distorted trigonal bipyramidal coordinated environment consisting of four N atoms of L and one N atom of SCN⁻ in complex (1), and the monomer is extended to a 1D chain by the weak intermolecular π...π stacking interactions. In the complex (2), four Co(II) atoms are linked by four bridging azido groups in μ-1,1-N₃ (end-on) coordination mode to form a tetranuclear configuration. The fungicidal activity of the title compounds have been studied, and the results show that there are certain activities against several bacteria for the complexes and the ligand. Furthermore, two complexes exhibit blue emission fluoresce in the solid state at room temperature.     

Supramolecular self-assembly of two Cu(II) complexes with 1,2,4-triazole derivatives: syntheses,crystal structures and magnetic properties

Two two-dimensional coordination complexes, {[Cu₄(BTM)₆(OPA)₄] · 4DMF · 3H₂O} _n (1) and {[Cu(BDTM)(OH)](ClO₄) · 2H₂O} _n (2) (BTM = bis(1,2,4-triazol-1-yl)methane, BDTM = bis(3,5-dimethyl-1,2,4-triazol-1-yl)methane, OPA²⁻ = ortho-phthalic dianion, DMF = N,N-dimethylformamide), were synthesized and structurally characterized. Each Cu(II) ion locates in a distorted square pyramidal geometry in 1, in which OPA²⁻ ligands bridge Cu²⁺ ions along a axis to form a magnetic transmission chain and BTM ligands act as flexible spacers to construct the two-dimensional layer structure. In 2, each Cu²⁺ ion adopts tetra-coordination geometry to two hydroxyl groups and two triazolyl nitrogen atoms from two different BDTM ligands. Two hydroxyl groups bridge two Cu²⁺ ions to form a rhombic diamond, and four BDTM ligands connect four diamonds to form a 36-membered macrocyclic structure with large channels along a axis. Magnetic properties revealed that both OPA²⁻ and OH⁻ mediate anti-ferromagnetic interactions between Cu²⁺ ions with J = − 0.06(3) and −301.9(2) cm⁻¹ for 1 and 2, respectively. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Coordination chemistry of copper(II) complexes with N4, N4S2, and N4O2 donor macrocyclic ligands: Biological aspects—antifungal, synthesis, spectral studies, and magnetic moments

Three macrocyclic ligands and their complexes with copper(II) salts (with anions Cl⁻, NO ₃ ⁻ , and NCS⁻) were prepared and investigated using a combination of microanalytical analysis, melting point, molar conductance measurement, magnetic susceptibility measurement, and electronic, IR and ESR spectral studies. Ligands L¹, L², and L³ having N₄, N₄O₂, and N₄S₂ core, respectively, and all the donor atoms of these ligands are bonded with Cu, which is confirmed by a seven-line pattern observed at half-field in the frozen (H₂O: MeOH = 10: 1 at pH 10) solution ESR spectrum. The polycrystalline ESR data (g _∥ = 2.20–2.27, g _⊥ = 2.01–2.05, and A _∥ = 120–270) of all the complexes together with the high asymmetry geometry suggest that all complexes appear to be near the static distortion (CuN₄O₂ and CuN₄S₂ chromophore geometry). The electronic spectra of the complexes involve two bands at the same intensity corresponding to a cis-distorted octahedral geometry. A common structural feature of both ligand L² and ligand L³ is that two different donor atoms at five-membered heterocyclic aromatic ring due to this N₄O₂ and N₄S₂ chromophore form stable six-membered chelate rings with metals via these two, Cu-O and Cu-S, new interactions comparatively to the first macrocyclic ligand, which has four-membered N,N′-chelate rings. The cyclic voltammetric studies point to a two-step electron transfer indicating the reduction of the two copper atoms to copper(I), i.e., Cu(III)Cu(II) ⇄ Cu(II)Cu(I) ⇄ Cu(I)Cu(0). The molar conductance for the complexes corresponds to 1: 2 and is nonelectrolyte in nature. The magnetic moment (μ_eff) of the complexes lie in the range between 1.80–1.96 μ_B. Finally, these complexes were screened for their antimicrobial activity against Aspergillus-niger of fungal strains. The text was submitted by the authors in English.     

One-dimensional coordination polymer of copper(I) thiocyanate with the Schiff base ligand N,N′-bis(3,4-dimethoxybenzylidene)butane-1,4-diamine: synthesis, crystal structure, spectroscopic and thermal properties

Abstract  

A new one-dimensional polymeric copper(I)–thiocyanate complex with the Schiff base ligand N,N′-bis(3,4-dimethoxybenzylidene)butane-1,4-diamine, {Cu₂((μ _N,N′ -3,4-MeO-ba)₂bn)(μ_1,3-NCS)₂} _n , was synthesized and characterized by elemental analysis, ¹H and ¹³C NMR, FT–IR spectroscopy, and thermal analysis. The thermal behavior of the complex was studied using thermogravimetry in order to evaluate thermal stability and thermal decomposition pathways. The molecular structure of the complex was determined by single-crystal X-ray diffraction which revealed that the coordination geometry around the copper(I) ion is distorted trigonal. The Schiff base ligand (3,4-MeO-ba)₂bn acts as a bis-monodentate and bridging ligand (μ _N,N′ ) and coordinates via two N atoms to the metal centers and adopts an E,E conformation. The coordination spheres of the metal atoms are completed by the N and S atoms from two thiocyanate anion bridges (μ_1,3-NCS), forming a zigzag chain propagating along [001].     

A Supramolecular Star-like Tungstoarsenate(V) with Uranyl Cations: [(NH4)12(UO2(H2O))6(UO2(μ2-H2O))6(α-AsW9O34)6]18?

A supramolecular tungstoarsenate(V) containing UO₂ ²⁺ cations has been isolated by reaction of the ammonium salt of lacunary sandwich-type anion [As₂W₁₈(UO₂)₂O₆₈]¹⁴⁻ in aqueous solution of Ce^IV (pH 3.5). The product prepared as NH₄ ⁺ salt, (NH₄)₁₈[(NH₄)₁₂(UO₂(H₂O))₆(UO₂(μ₂-H₂O)₆(α-AsW₉O₃₄)₆]·74H₂O (I), have been characterized by single crystal X-ray diffraction, elemental analysis, IR, and UV/vis spectroscopy. The anion consists on six lacunary α-AsW₉O₃₄ ⁹⁻ anions linked by twelve UO₂ ²⁺ cations which resembles a star (six-member). The single crystal structure of I reveals two types uranium atoms; six uranium atoms in the central of anion form two U₃O₃ trigonal bridging groups in which each uranium atom bounds to three oxygen atoms of one AsW₉ and two bridging water ligands. The other uranium atoms form two equatorial bonds to one AsW₉ and two equatorial bonds to two other AsW₉ fragments. The UV/vis spectroscopy confirms the strong coordination of oxygen atoms of α-AsW₉O₃₄ ⁹⁻ anions to uranyl cations in the equatorial plane.