Ming-Ming Miao

Synthesis and Magnetism of Isophthalato-Bridged Manganese(II) Binuclear Complexes with Each Spin State S = 3/2

Abstract Four novel manganese(II) binuclear complexes have been synthesized and characterized, namely [Mn2(IPHTA)(L)4](CIO4)2 (L denotes 2,2′-bipyridyl (bpy), 1,10-phenanthroline (phen), 4,4′-dimethyl-2,2′-bipyridyl (Mezbpy) and 5-nitro-1,10-phenanthroline (NO2-phen), respectively), where IPHTA is the isophthalate dianion. Based on IR, elemental analyses, conductivity measurements, ESR and magnetic susceptibility, these complexes are proposed to have extended isophthalato–bridged structures and to consist of two manganese(II) ions in which each manganese(II) ion has a pyramidal environment with a quartet ground state (S = 3/2). The temperature dependance of mangnetic susceptibility for [Mn2(IPHTA)(phen)4](CIO4)2 was measured over the range 4–300 K and the observed data were successfully simulated by an equation based on the spin Hamiltonian operator , giving the exchange integral J = - 1.60 cm−1. This indicates weak anti-ferromagnetic spinexchange interaction between the metal ions.

First oxalate-bridged dinuclear MnII-VIVO complexes: Synthesis and magnetic properties

Abstract Three novel MnII-VIVO μ-oxalato complexes have been synthesized and characterized, namely [MnVO(ox)2(L)2] [L denotes, 1,10-phenanthroline (phen), 2,2′-bipyridyl (bpy) and 4,4′-dimethyl-2,2′-bipyridyl (Me2bpy), respectively], where ox stands for the oxalate dianion. Based on IR, elemental analysis, conductivity measurements and EPR, these complexes are proposed to have extended oxalato-bridged structures consisting of vanadyl ions and manganese(II) ions, in which each vanadium(IV) has a distorted square-pyramidal environment and each manganese(II) ion has a distorted octahedral environment. The temperature dependence of magnetic susceptibility for [MnVO(ox)2 (phen)2] · H2O was measured over the range 4.1–300 K and the observed data were successfully simulated by an equation based on the spin Hamiltonian operator ( H = −2J S 1 S 2 ), giving the exchange integral J= −30.9 cm−. This indicates antiferromagnetic spin exchange interaction between MnII and VOII ions.

Syntheses and magnetism of trinuclear copper(II) 1,2-ethylenebis(oxamido) complexes

Abstract Four novel trinuclear copper(II) complexes have been synthesized, namely {[Cu(ebo)][Cu(L)] 2 } (ClO 4 ) 2 , where ebo denotes 1,2-ethylenebis(oxamido) and L is 2,2′-bipyridyl (bpy), 4,4′-dimethyl-2,2′-bipyridyl (Me 2 bpy), 1,10-phenanthroline (phen) or 5-nitro-1, 10-phenanthroline (NO 2 -phen). Based on IR, elemental analyses, conductivity measurements and electronic spectra these complexes are proposed to have oxamidobridged structures and to consist of three copper(II) ions in which each metal ion has a square planar environment. The temperature dependence of the magnetic susceptibility of [Cu(ebo)][Cu(NO 2 -phen)] 2 (ClO 4 ) 2 ·2H 2 O has been studied in the 4–200 K range, giving the exchange integral J = −80.9 cm −1 . The result revealed the operation of an antiferromagnetic spin-exchange interaction between the adjacent copper ions.

Synthesis, characterization and magnetic analysis of binuclear nickel(II) terephthalato complexes

Six new binuclear nickel (II) complexes have been synth-esized and characterized, namely: [Ni2(4X-TP-HA)(L)4](ClO4)2 [L = 1,10-phenanthroline (phen), 5-nitro-1,10-phenanthroline (NO2-phen) or 2,2′-bipyridyl (bipy)], where 4X-TPHA is the tetrabromoterephthalate dianion (X = Br) or the tetraiodoterephthalate dianion (X = I). Based on i.r. spectra, elemental analyses and conductivity measurements, these complexes are proposed to have terephthalato-bridged structures containing two NiII ions, each in a distorted octahedral environment. The temperature dependences of the magnetic susceptibility for [Ni2(4Br-TPHA)(phen)4]- (ClO4)2·H2O (1) and [Ni2(4I-TPHA)(phen)4]-(ClO4)2·- 2H2O (4) were measured over the 4–300K range and the observed data indicate weak antiferromagnetic spin exchange interaction between the metal ions.

2–Hydroxy–1,3–propylene bis (oxamato)–bridged new NiIICuIINiII trinuclear complexes with an S = 3/2 high-spin ground state: synthesis and magnetism

Four new heterotrinuclear complexes have been synthesized and characterized, namely {[Ni(L)2]2[Cu(pbaOH)]}(ClO4)2, where pbaOH denotes 2–hydroxy–1,3–propylenebis(oxamato) and L = 1,10–phenanthroline (phen), 5-nitro-1,10-phenanthroline (NO2–phen), 2,2′–bipyridyl (bpy) and 4,4′–dimethyl–2,2′–bipyridyl (Me2bpy). The temperature dependence of the magnetic susceptibility of {[Ni(phen)2]2[Cu(pbaOH ]}(ClO4)2·H2O has been studied in the 4–300 K range, giving an exchange integral J = −94 cm− . The χMT versus T plot exhibits a minimum at ca. 93 K, characteristic of this type of coupled polymetallic complex with an irregular spin-state structure.

Syntheses and magnetic properties of O-phenylenebis(oxamato)-bridged CoIICuIICoII complexes

Four new heterotrinuclear complexes have been prepared and characterized, namely {[Co(L)2]2[Cu (opba)]}(ClO4)2, where opba=o-phenylenebis(oxamato) and L=1,10-phenanthroline (phen), 5-nitro-1,10-phenanthroline (NO2-phen), 2,2′-bipyridyl (bpy) and 4,4′-dimethyl-2,2′-bipyridyl (Me2bpy). The temperature dependence of the magnetic susceptibility of {[Co(phen)2]2[Cu(opba)]}(ClO4)2 has been studied in the 4–300K range, the χ MT versus T plot exhibits a minimum at ca. 131K, but abnormal magnetic behaviour below 83K.

First oxalate-bridged pentanuclear [Cu(L)]3[Mn(ox)3]2 complexes: synthesis and magnetism

Two novel CuII3MnIII2 pentanuclear oxalato complexes have been synthesized and characterized, namely [Cu(L)]3[Mn(ox)3]2 [L = 1,10-phenanthroline(phen) and 2,2′-bipyridyl(bipy)] where ox is the oxalate dianion. Based on i.r., elemental analyses and electronic spectra, thesecomplexesareassignedtoextendedoxalato-bridged structures consisting of two manganese(III) ions and three copper(II) ions, in which each manganese(III) has a distorted octahedral environment and each copper(II) ion a distorted square pyramidal environment. The temperature dependance of the magnetic susceptibility for [Cu(phen)]3[Mn(ox)3]2·4H2O was measured over the 4.2–300K range and the observed data indicates antiferromagnetic spin exchange interaction between the CuII and MnIII ions.

Oxalate-bridged mixed-valence trinuclear manganese(II)-manganese(III)-manganese(II) complexes: synthesis and magnetism

SummaryTwo novel MnII-MnIII-MnII oxalato complexes have been synthesized and characterized, namely [Mn2Mn(ox)3(L)4](ClO4) [L = 1,10-phenanthroline (phen) or 5-nitro-1,10-phenanthroline (NO2-phen), respectively], where ox stands for the oxalate dianion. Based on i.r., elemental analyses and electronic spectra, these complexes are proposed to have extended oxalatobridged structures consisting of MnII and MnIII ions, in which MnIII and each MnII ion has a distorted octahedral environment. The temperature dependence of magnetic susceptibility for [Mn2Mn(ox)3(phen)4] (ClO4) was measured over the 4.1–300 K range and the observed data were successfully simulated by an equation based on the spin-Hamiltonian operator (Ĥ = -2J(Ŝ1Ŝ2 + Ŝ2Ŝ3)), giving the exchange integral J = -1.57cm−1. This indicates weak antiferromagnetic spin exchange interaction between MnII and MnIII ions.

Synthesis and magnetic properties of new nickel(II)-copper(II)-nickel(II) trinuclear complexes with irregular spin-state structure

SummaryFour novel heterotrinuclear complexes were prepared, namely {[Ni(L)2]2[Cu(pba)]}(ClO4)2, where pba = pro-pylene-1,3-bis(oxamato) and L = 1,10-phenanthroline (phen), 5-nitro-1,10-phenanthroline (NO2-phen), 2,2′-bipyridyl (bpy), 4,4′-dimethyl-2,2′-bipyridyl (Me2bpy). Based on i.r., elemental analyses, conductivity measurements and electronic spectra oxamato-bridged structures are proposed for these complexes, consisting of two nickel(II) ions, each in a distorted octahedral environment, and a copper(II) ion in a square planar environment, respectively. The temperature dependence of the magnetic susceptibility of {[Ni(phen)2]2[Cu(pba)]}(ClO4)2·H2O was studied in the 4–300 K range, giving the exchange integral J = - 106 cm−1. TheXscmT versusT plot exhibited a minimum at ca. 98 K, characteristic of this kind of coupled polymetallic complex with an irregular spin-state structure. E.s.r. spectra of these complexes clearly indicated a strong rhombicity withg1 = 5.20,g2 = 2.29 andg3 = 2.02 (approximately), which agrees with an anisotropicS = ±1/2 Kramer doublet in the ground state.

Synthesis and magnetism of μ-1,3,5-benzenetricarboxylatocopper(II) trinuclear complexes

SummaryThree new CuII trinuclear complexes, namely [Cu3(BZT)(phen)3(ClO4)3]·6H2O (1), [Cu3(BZT)(Nphen)3 (ClO4)3]·6H2O (2) and [Cu3(BZT)(bipy)3 (ClO4)3]·3H2O (3) (BZT) = 1,3,5-benzenetricarboxylato, phen = 1,10-phenanthroline, Nphen = 5-nitro-1,10-phenanthroline, bipy = 2,2-bipyridyl, have been synthesized, with 1,3,5-benzenetricarboxylato as the bridged ligand, and characterized by elemental analysis, and i.r. and electronic reflection spectra. We propose that the complexes have an extended 1,3,5-benzenetricarboxylatobridged structure containing three CuII atoms. The variable-temperature magnetic susceptibilities of the complexes were measured in the 77–300 K range. The magnetic coupling parameters are consistent with an antiferromagnetic exchange model based on the Hamiltonian operator [Ĥ=−2J(Ŝ1Ŝ2+Ŝ1Ŝ3+Ŝ2Ŝ3, where S1=S2=S3=1/2, giving the antiferromagnetic coupling parameters of 2J = − 18.6 cm-1 for (1)–(3).