Syntheses, structures and magnetic properties of a family of one-dimensional M(Ⅱ)-lanthanide(Ⅲ) (M =Ni(Ⅱ) and Zn(Ⅱ)) coordination polymers

A series of 1D nickel(Ⅱ)/zinc(Ⅱ)-lanthanide(Ⅲ) coordination polymers, [M(μ-L)2Ln(NO3)3]n· solvents (HL =bis(2-pyridylcarbonyl)amine; M = Ni, Ln = Gd (1 · NiGd), Tb (2· NiTb), Dy (3· NiDy), Ho (4· NiHo), Y (5· NiY);M = Zn, Ln =Gd (6· ZnGd), Tb (7· ZnTb), Dy (8· ZnDy), Ho (9· ZnHo); solvents = H2O or H2O-ethanol), was synthesized and characterized. All of the complexes are isostructural at 293 K and crystallize in the orthorhombic space group Fddd. Magnetic measurements were performed on 1-9, where weak ferromagnetic interaction is found in 1 · NiGd, ferromagnetic interaction in 2·NiTb and 3·NiDy, and antiferromagnetic interaction in 4· NiHo. A remarkable dc magnetic field dependence of ac susceptibilities was found in this series of complexes.     

Synthesis, Crystal Structure, and Properties of Inorganic-organic Hybrid M(Ⅱ)-Nb(Ⅴ)(M = Co, Cu)Oxyfluorides

T Two isostructural inorganic-organic hybrid M(Ⅱ)-Nb(Ⅴ)oxyfluorides, namely,M(H<,2>O)<,2>(pyz)NbOF<,5>(M = Co 1, Cu 2; pyz = pyrazine)have been hydrothermally synthesized and structurally characterized. Both compounds possess two-dimensional layer structure constructed by neutral M(H<,2>0)<,2>NbOF<,5> chains inter-connected via bridging pyrazine ligands. The structure is further extended into three-dimensional supramolecular architecture through inter-layer H-bonding interactions between the coordinated water molecules and fluorine ions. The luminescent properties and thermal stability of both compounds have been investigated.     

Syntheses, structures and magnetic properties of a family of one-dimensional M(Ⅱ)-lanthanide(Ⅲ) (M = Ni(Ⅱ) and Zn(Ⅱ)) coordination polymers

A series of 1D nickel(II)/zinc(II)-lanthanide(III) coordination polymers, [M(μ-L)2Ln(NO3)3]n·solvents (HL = bis(2-pyridylcarbonyl)amine; M = Ni, Ln = Gd (1·NiGd), Tb (2·NiTb), Dy (3·NiDy), Ho (4·NiHo), Y (5·NiY); M = Zn, Ln = Gd (6·ZnGd), Tb (7·ZnTb), Dy (8·ZnDy), Ho (9·ZnHo); solvents = H2O or H2O-ethanol), was synthesized and characterized. All of the complexes are isostructural at 293 K and crystallize in the orthorhombic space group Fddd. Magnetic measurements were performed on 1―9, where weak ferromagnetic interaction is found in 1·NiGd, ferromagnetic interaction in 2·NiTb and 3·NiDy, and antiferromagnetic interaction in 4·NiHo. A remarkable dc magnetic field dependence of ac susceptibilities was found in this series of complexes.     

Tunability of the M(II)M(III)/M(II)(2) and M(III)(2)/M(II)M(III) (M=Mn, Co) couples in bis-μ-O,O'-carboxylato-μ-OR bridged complexes

A comparison of the electrochemical properties of a series of dinuclear complexes [M(2)(L)(RCO(2))(2)](+) with M = Mn or Co, L = 2,6-bis(N,N-bis-(2-pyridylmethyl)-sulfonamido)-4-methylphenolato (bpsmp(-)) or 2,6-bis(N,N-bis(2-pyridylmethyl)aminomethyl)-4-tert-butylphenolato (bpbp(-)) and R = H, CH(3), CF(3) or 3,4-dimethoxybenzoate demonstrates: (i) The electron-withdrawing sulfonyl groups in the backbone of bpsmp(-) stabilize the [M(2)(bpsmp)(RCO(2))(2)](+) complexes in their M(II)(2) oxidation state compared to their [M(2)(bpbp)(RCO(2))(2)](+) analogues. Manganese complexes are stabilised by approximately 550 mV and cobalt complexes by 650 mV. (ii) The auxiliary bridging carboxylato ligands further attenuate the metal-based redox chemistry. Substitution of two acetato for two trifluoroacetato ligands shifts redox couples by 300-400 mV. Within the working potential window, reversible or quasi-reversible M(II)M(III)? M(II)(2) processes range from 0.31 to 1.41 V for the [Co(2)(L)(RCO(2))(2)](+/2+) complexes and from 0.54 to 1.41 V for the [Mn(2)(L)(RCO(2))(2)](+/2+) complexes versus Ag/AgCl for E(M(II)M(III)/M(II)(2)). The extreme limits are defined by the complexes [M(2)(bpbp)(CH(3)CO(2))(2)](+) and [M(2)(bpsmp)(CF(3)CO(2))(2)](+) for both metal ions. Thus, tuning the ligand field in these dinuclear complexes makes possible a range of around 0.9 V and 1.49 V for the one-electron E(M(II)M(III)/M(II)(2)) couple of the Mn and Co complexes, respectively. The second one-electron process, M(II)M(III)? M(III)(2) was also observed in some cases. The lowest potential recorded for the E°(M(III)(2)/M(II)M(III)) couple was 0.63 V for [Co(2)(bpbp)(CH(3)CO(2))(2)](2+) and the highest measurable potential was 2.23 V versus Ag/AgCl for [Co(2)(bpsmp)(CF(3)CO(2))(2)](2+).     

Synthesis,crystal structures,and properties of two heterometallic Cu(II)–M(II) (M = Zn,Ni) oxamidato-bridged coordination complexes

Two heterometallic coordination complexes, {[Cu(aeop)Zn(H₂O)₃]₂?·?3H₂O} _n (1) and [Cu(aeop)Ni(H₂O)₄]?·?4H₂O (2) (H₄aeop?=?N-(2-aminoterephthalic acid)-N′-(1,3-propanediamine)oxamidate), have been synthesized and characterized by elemental analyses, IR, UV spectroscopy, thermogravimetric analysis, and X-ray crystal diffraction. Complex 1 features a 1-D chain constructed from neutral tetranuclear units. Complex 2 is a neutral binuclear complex. Through intermolecular hydrogen-bonding interactions, 2 gives a 3-D network structure. The variable temperature magnetic susceptibility measurements (2–300?K) of 2 show a pronounced antiferromagnetic interaction between the copper(II) and nickel(II), and the exchange integral J is equal to ?42.7?cm^?1.     

Interactions of M(z)-X complexes (M = Cu, Ag, and Au; X = He, Ne, and Ar; and z = ±1)

The coupled cluster singles and doubles method with perturbative treatment of triple excitations is applied to calculate the potentials of M(z)-X complexes (M = Cu, Ag, and Au; X = He, Ne, and Ar; and z = ±1). The bond functions and the basis set superposition errors are considered to obtain accurate interaction energies. The potential energy curves of all complexes are obtained. The vibrational energy levels and the spectroscopic parameters for these complexes are determined. The analytical potential energy functions are also fitted based on the potential energies.     

Syntheses, structure, and a Mössbauer and magnetic study of Ba(4)Fe(2)I(5)S(4)

The compound Ba4Fe2I5S4 has been prepared at 1223-1123 K by the "U-assisted" reaction of FeS, BaS, S, and U with BaI2 as a flux. A more rational synthesis was also found; however, the presence of U appears to be essential for the formation of single crystals suitable for X-ray diffraction studies. Ba4Fe2I5S4 crystallizes in a new structure type with two formula units in space group I4/m of the tetragonal system. The structure consists of a Ba-I network penetrated by (1)infinity[Fe2S4] chains. Each Fe atom, which is located on a site with 4 symmetry, is tetrahedrally coordinated to four S atoms. The FeS4 tetrahedra edge-share to form linear (1)infinity[Fe2S4] chains in the [001] direction. The Fe-Fe interatomic distance in these chains is 2.5630(4) A, only about 3% longer than the shortest Fe-Fe distance in -Fe metal. Charge balance dictates that the average formal oxidation state of Fe in these chains is +2.5. The M?ssbauer spectra obtained at 85 and 270 K comprise a single quadrupole doublet that has hyperfine parameters consistent with an average Fe oxidation state of +2.5. The M?ssbauer spectrum obtained at 4.2 K consists of a single magnetic sextet with a small hyperfine field of -15.5 T. This spectrum is also consistent with rapid electron delocalization and an average Fe oxidation state of +2.5. The molar magnetic susceptibility of Ba4Fe2I5S4, obtained between 3.4 and 300 K, qualitatively indicates the presence of weak pseudo-one-dimensional ferromagnetic exchange within a linear chain above 100 K and weak three-dimensional ordering between the chains at lower temperatures.     

Synthesis,crystal structure and magnetic studies of cis-configuration copper(II)—M(II) (M = Ba,Ca) complexes of novel Schiff bases derived from salicylaldehyde and dipeptides

The novel heteronuclear complexes [M(CuL)₂]₂ · nH₂O [M = Ba (1), Ca (2); H₂L = N-salicylideneglycylglycine] were synthesized and characterized, and the crystal structure of complex (1) was determined by X-ray diffraction. The entire structure is held together by an extensive network of H-bonds and – interactions. Variable-temperature magnetic susceptibility measurements (75–300 K) revealed the occurrence of an intramolecular antiferromagnetic interaction in (1) and (2).     

Mössbauer study of sodium ferrates(IV) and (VI)

Sodium ferrates(IV) and (VI) were synthesized by the reaction between Fe₂O₃ and Na₂O₂ in a dry oxygen stream. The Mössbauer data for the obtained samples are presented (for Na₂FeO₃–=0.18(2) mm/s; for Na₄FeO₅–=–0.54(2) mm/s). It was shown that pure K₂FeO₄ and Cs₂FeO₄ can be obtained by heating Fe₂O₃ with apropriate alkali metal peroxides.     

Synthesis and characterization of Mg–M (M: Al,Fe, Cr) layered double hydroxides and their application in the hydrogenation of benzaldehyde

Layered double hydroxides or hydrotalcite-like compounds with different kinds of metal ions (Mg–Al, Mg–Fe and Mg–Cr) in the brucite-like sheets were prepared by a co-precipitation method with Mg/M³⁺ molar ratio of ~2. The hydrotalcites were characterized by chemical analysis, X-ray diffraction, Fourier transform infrared spectroscopy, temperature programmed reduction, SEM microscopy, and specific surface area measurements. The activity is evaluated for benzaldehyde reaction. The selectivity to benzyl alcohol is always 90 % even though benzaldehyde conversion depends on the nature of the metal active phase and reaction conditions.     

Study of series of the M1,M2‖F,Cl,Br quaternary reciprocal systems (M1 and M2 are group 1 s-block elements)

Quaternary reciprocal systems of alkali metal fluorides, chlorides, and bromides were partitioned into simplexes by a geometric method and a graph method. Phase transformations and chemical reactions in the bordering ternary reciprocal systems were described. Conversion lines were experimentally studied, and information on crystallizing phases within the composition prisms of the M₁,M₂‖F,Cl,Br systems (M₁ and M₂ are group 1 s-block elements) was obtained.     

Dependence of the Structure and Properties of (M,Cu)Sr2(Ln,Ca)Cu2O8−δ (1212) and (M,Cu)Sr2(Ln,Ce4+)2Cu2O10−δ (1222) Phases on the Cation M

The composition and structure of (M,Cu)(Sr,Ln)₂(Ln,Ca,Sr)Cu₂O_8– phases, where M = B, Al, Cr, Pb, Bi, Ru, or Mo (1212 type), and (M,Cu)(Sr,Ln(₂(Ln,Ce⁴⁺)₂Cu₂O_10– phases, where M = V, Cr, Mn, Ru, or Mo (1222 type), have been determined. The role of the M cation in the formation of the crystal structures and the superconductivity phenomenon was analyzed. The relationship between the type of M cation and structural parameters was discovered.     

Synthesis and spectral studies on nitrogen donor adducts of bis(4-ethylpiperazinecarbodithioato-S,S′)M(II) (M = Zn,Cd) and use of adducts of cadmium dithiocarbamate for the preparation of cadmium sulfide

[M(4-epzdtc)₂(py)], [M(4-epzdtc)₂(1,10-phen)], and [M(4-epzdtc)₂(2,2′-bipy)] (where M?=?Zn(II), Cd(II); 4-epzdtc^??=?4-ethylpiperazinecarbodithioate) were synthesized and characterized by IR and NMR (¹H, ¹³C, HSQC and HMBC) spectra. A single-crystal X-ray analysis was carried out for [Zn(4-epzdtc)₂(py)]. The N¹³CS₂ chemical shifts of [M(4-epzdtc)₂] and its adducts follow the order: [M(4-epzdtc)₂] (ca 202?ppm)?<?[M(4-epzdtc)₂(py)] (ca 204?ppm)?<?[M(4-epzdtc)₂(N,N)] (N,N?=?1,10-phen, 2,2′-bipy) (ca 206?ppm), due to the change in coordination number. Single-crystal X-ray structural analysis of [Zn(4-epzdtc)₂(py)] showed that zinc is five-coordinate with four sulfurs from dithiocarbamate and one nitrogen from pyridine. This complex adopts a geometry intermediate between the tetragonal pyramid (C_4v) and trigonal bipyramid (D_3h). [Cd(4-epzdtc)₂] and its adducts were used as single source precursors for preparation of CdS. The as-prepared CdS was characterized by powder X-ray diffraction, UV-Vis absorption, and fluorescence spectroscopy. The UV-Vis absorption spectra of CdS particles indicate a blue shift in the absorption spectra due to the quantum size effect.     

Synthesis,crystal structures,and magnetic properties of three K[M(bpb)(CN)2]-based trinuclear sandwich-like heterobimetallic M(III)–Ni(II) (M = Fe,Cr, Co) complexes

Three trinuclear sandwich-type cyanide-bridged M^III–Ni^II complexes, {[Ni(cyclm)[Fe(bpb)(CN)₂]₂}·8H₂O (1), {[Ni(cyclm)[Cr(bpb)(CN)₂]₂}·2H₂O (2), and {[Ni(cyclm)[Co(bpb)(CN)₂]₂}·CH₃OH·2H₂O (3) (cyclm?=?1,4,8,11-tetraazacyclotetradecane), have been synthesized using K[M(bpb)(CN)₂] (M?=?Fe, Cr, Co; bpb?=?1,2-bis(pyridine-2-carboxamido)benzenate) as building block and one Ni(II) compound containing a 14-membered macrocycle ring as assembling segment. All the complexes have been characterized by elemental analysis, IR spectroscopy, and X-ray structure determination. Single X-ray diffraction analysis shows similar sandwich-like structures, in which the two cyanide-containing building blocks are monodentate through one of their two cyanides, coordinated face to face to the central Ni(II). Investigation of the magnetic properties of 1 and 2 reveals ferromagnetic magnetic coupling between the neighboring Fe(III)/Cr(III) and Ni(II) through the bridging cyanide. A best-fit to the magnetic susceptibilities of 1 and 2 based on the trinuclear M₂Ni model leads to magnetic coupling constants J?=?5.47(1)?cm^?1 for 1 and J?=?6.37(2)?cm^?1 for 2.     

Vibrational Properties of LaNb0.8M0.2O4-δ (M=As,Sb, V,and Ta)

LaNb_0.8M_0.2O_4-δ (where M=As, Sb, V, and Ta) oxides with pentavalent elements of different ionic sizes were synthesized by a solid-state reaction method. The vibrational properties of these oxides have been investigated. These studies revealed that the substituent element influences both Debye temperature value as well as the Raman active vibrational modes. Additionally, the low-temperature vibrational properties of LaNb_0.8Sb_0.2O_4-δ have been determined to show the phase transition occurrence at 260 K which is lower than previously reported.     

Preparation and photoluminescent properties of Eu(III) containing M-layered silicates (M = Li,Na, K,Rb, Cs)

Eu(III) containing M-layered silicates (M = Li, Na, K, Rb, Cs) were prepared using the layered silicates, such as ilerite, magadiite, and kenyaite, as a host matrix and the luminescence properties were investigated. The results from the luminescence measurements indicated that the luminescence properties in the EuM-layered silicate system depended strongly on the types of host matrices and alkali cations. Among the EuM-layered silicates, EuM-ilerite exhibited the strongest luminescence intensity for all alkali cations, whereas EuM-kenyaite exhibited relatively weak luminescence intensity. The luminescence intensity was significantly increased by heat treatment at high temperature, mainly due to the phase change of host matrices and the presence of alkali cations in the host matrices. Particularly, the luminescence intensity of EuM-layered silicate calcined at 1,000 °C increased with the increase of the ion size of alkali cations.     

Ion-Exchange Processes M(II) → Fe(III) and Fe(III) → M(II) in Metal Hexacyanoferrate(II) Gelatin-Immobilized Matrices (M = Mn,Co, Ni,Cu, Zn,Cd)

Ion-exchange reactions M²⁺ Fe³⁺ and Fe³⁺ M²⁺ (M = Mn, Co, Ni, Cu, Zn, Cd) were studied in metal(II) hexacyanoferrate(II) gelatin-immobilized matrices M₂[Fe(CN)₆] in contact with aqueous FeCl₃ solutions and Fe₄[Fe(CN)₆]₃ in contact with aqueous MCl₂ solutions. It was shown that in both cases, M²⁺ was replaced by Fe³⁺ and Fe³⁺ was replaced by M²⁺ to some extent, but no complete replacement was observed in the M₂[Fe(CN)₆]–FeCl₃ or Fe₄[Fe(CN)₆]₃–MCl₂ systems under study. No electrophilic substitution Fe³⁺ Mn²⁺ was found to occur in any noticeable degree during the contact of Fe₄[Fe(CN)₆]₃ with aqueous MnCl₂ solutions even when this contact occurred for 1 h and longer.     

Theoretical study of group 11 metal–silonyl complexes: M–SiO and M–(SiO)2 (M = Cu, Ag, or Au)

 The spectroscopic properties of M–SiO and M–(SiO)₂ (1–1 and 1–2 complexes with M = Cu, Ag, or Au) have been theoretically studied. It has been shown that both M–SiO and M–(SiO)₂ compounds in their ground state are bent with a metal–Si bonded structure. The calculated M(ns) spin density agrees well with the electron spin resonance experimental data. From a topological analysis, it has been shown that a rather large charge transfer occurs from the metal towards the SiO moiety, and that the M–Si bond energy correlates with the electron density located at the M–Si bond path (bond critical point). Received: 6 July 2000 / Accepted: 11 October 2000 / Published online: 19 January 2001     

M≡E and M=E Complexes of Iron and Cobalt that Emphasize Three-fold Symmetry (E = O, N, NR)

Mid-to-late transition metal complexes that feature terminal, multiply bonded ligands such as oxos, imides, and nitrides have been invoked as intermediates in several catalytic transformations of synthetic and biological significance. Until about ten years ago, isolable examples of such species were virtually unknown. Over the past decade or so, numerous chemically well-defined examples of such species have been discovered. In this context, the presentreview summarizes the development of 4- and 5-coordinate Fe(E) and Co(E) species under local three-fold symmetry.     

Metalloligand-induced Synthesis of Two Cu(I)–M (M=Ni,Co) Heterobimetallic Coordination Polymers: Structures,Thermal and Luminescence Properties

Two interesting heterobimetallic coordination polymers (CPs), {[Ni(4-pytpy)₂]₂[Cu₄(N(CN)₂)₇](NO₃)(DMF)(DMSO)(H₂O)₄}_n (1) and {[Co(4-pytpy)(N(CN)₂)]₂[Cu₂(N(CN)₂)₄]}_n (2), have been synthesized based on different metalloligands [M(4-pytpy)₂]²⁺ (M=Ni 1, Co 2) (4-pytpy = 4′-(4-pyridyl)-2,2′:6′,2″-terpyridine). CPs 1 and 2 have been well characterized by elemental analysis, IR spectroscopy, thermal analysis and single-crystal X-ray diffraction. Both CPs 1 and 2 crystallize in the triclinic crystal system with the P-1 space group but feature different structures. CP 1 exhibits a unique one dimensional double-chain structure, while CP 2 possesses an infinite 2D network structure. It is interesting to note that the metalloligand [Co(4-pytpy)₂]²⁺ in CP 2 was decomposed into [Co(4-pytpy)]²⁺. Thermal analysis indicates that the chain structure of CP 1 begins to collapse after about 360 °C, while CP 2 can be stable up to 300 °C. The solid-state luminescence properties of CPs 1 and 2 have also been investigated.