En-Qing Gao

A New Class of Heterobinuclear Complexes: Crystal Structure and Magnetism of Copper(II)-Nickel(II) Complexes Incorporating Two Different Macrocyclic Ligands

Three novel oxamido-bridged heterobinuclear copper(II)-nickel(II) complexes incorporating two different tetraazamacrocyclic compounds were synthesized and characterized by IR, ESR, and electronic spectra. They are of the formulas [(CuL1)Ni(rac-cth)](ClO)42⋅H2O (1), [Cu(L2)Ni(rac-cth)](ClO4)2⋅0.5 EtOH (2), and [(CuL3)Ni(rac-cth)](ClO4)2⋅H2O (3). L1, L2, and L3 are the dianions of diethyl 5,6,7,8,16,17-hexahydro-6,7-dioxo-15H-dibenzo[e,n][1,4,8,12]tetraazacyclopentadecine-13,19-dicarboxylate, diethyl 5,6,7,8,15,16-hexahydro-6,7-dioxodibenzo[1,4,8,11]tetraazacyclotetracine-13,18-dicarboxylate, and diethyl 5,6,7,8,15,16-hexahydro-15-methyl-6,7-dioxodibenzo[1,4,8,11]tetraazacyclotetradecine-13,18-dicarboxylate, respectively, and rac-cth is rac-5,7,7,12,14,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane. The crystal structures of 1 and 2 were determined by single-crystal X-ray analysis. The NiII ion is pseudooctahedrally coordinated. The coordination geometry around the CuII ion in 2 is slightly distorted square planar, while that in 1 shows significant distortion towards a tetrahedral structure. The temperature dependence of the magnetic susceptibility for 1 and 2 was analyzed by means of the Hamiltonian Hˆ=−2JSˆ1⋅Sˆ2, leading to J=−63.9 and −67.4 cm−1 for 1 and 2, respectively.

Synthesis and magnetism of the first tetranuclear copper(II)–iron(III) complexes of macrocyclic oxamides

Abstract Four novel tetranuclear macrocyclic complexes of the formula [(CuLi)3Fe](ClO4)3·3H2O (i=1–4, Li are the dianions of the [14]N4 and [15]N4 macrocyclic oxamides, namely 2,3-dioxo-5,6:13,14-dibenzo-7,12-bis(ethoxycarbonyl)-1,4,8,11-tetraazacyclotetradeca-7,11-diene, 2,3-dioxo-5,6:13,14-dibenzo-9-methyl-7,12-bis(ethoxycarbonyl)-1,4,8,11-tetraazacyclotetradeca-7,11-diene and 2,3-dioxo-5,6:14,15-dibenzo-7,13-bis(ethoxycarbonyl)-1,4,8,12-tetraazacyclotetradeca-7,12-diene] have been prepared and characterized. These complexes are the first examples of oxamido-bridged Cu(II)–Fe(III) heterometallic species. Cryomagnetic studies on [(CuL1)3Fe](ClO4)3·3H2O (1) and [(CuL3)3Fe](ClO4)3·3H2O (3) (77–300 K) revealed that the Cu(II) and Fe(III) ions interact antiferromagnetically through the oxamido bridge, with the exchange integral J=−30.8 cm−1 for 1 and J=−28.7 cm−1 for 3 based on H =−2J ∑ S i S j . The interaction parameters have been compared with that of the related [Cu3Mn] compound.

Heterobinuclear copper(II)–nickel(II) complexes of macrocyclic oxamide with diamines and tetraazacyclam as blocking ligands: synthesis, crystal structure and magnetic properties

Three novel oxamido-bridged heterobinuclear copper(II)–nickel(II) complexes derived from macrocylic oxamido compound with diamines and tetraazacyclam as blocking ligands were synthesized and characterized by IR, ESR and electronic spectra. Their formula is [Cu(L)Ni(en) 2 ](ClO 4 ) 2 ·0.5C 2 H 5 OH·H 2 O ( 1 ), [Cu(L)Ni(tmd) 2 ](ClO 4 ) 2 ·4H 2 O ( 2 ) and [Cu(L)Ni( rac -cth)](ClO 4 ) 2 ·CH 3 OH ( 3 ), where L=1,4,8,11-tetraazacyclotradecanne-2,3-dione, en=1,2-diaminoethande, tmd=1,3-diaminopropane and rac -cth is rac -5,7,7,12,14,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane. The crystal structures of the three complexes have been determined. The structures consist of binuclear units in which the copper(II) ion is in a square-planar environment and linked to the nickel(II) ion via the exo - cis oxygen atoms of the oxamido macrocyclic ligand, with Cu⋯Ni separations of 5.311 ( 1 ), 5.420 ( 2 ) and 5.307 A ( 3 ), respectively. The temperature dependence of the magnetic susceptibility for 1 , 2 and 3 was analyzed by means of the Hamiltonian Ĥ =−2 JŜ Ni Ŝ Cu , leading to J =−52.8, −45.7 and −56.9 cm −1 for 1 , 2 and 3 , respectively.

Magnetic properties of new copper(II) and [copper(II)]3-manganese(II) complexes of [14]N4 macrocyclic oxamides

Four new complexes of [14]N4 macrocyclic oxamides, namely [CuL1], [CuL2], [(CuL1)3Mn](ClO4)3 and [(CuL2)3 Mn](ClO4)3 [L1 and L2 are the dianions of 2,3-dioxo-5,6: 3,14-dibenzo-7,12-bis(ethoxycarbonyl)-1,4,8,11-tetraazacyclotetradeca-7,11-diene (H2L1) and 2,3-dioxo-5,6:13,14-dibenzo-9-methyl-7,12-bis(ethoxycarbonyl)-1,4,8,11-tetraazacyclo-tetradeca-7,11-diene (H2L2), respectively], have been prepared and characterized. The observed magnetic susceptibilities of the [(CuL1)3Mn] (ClO4)3 complex over the ca. 2–300 K range have been fitted to theoretical equations based on the Heisenberg spin Hamiltonian Ĥ=−2JŜMn(ŜCu1+ ŜCu2+ŜCu3) and molecular field approximation. The results indicated that both the intramolecular and intermolecular magnetic interactions are antiferromagnetic with JCuMn= −19.8cm−1 and zJ′=−1.41cm−1.

Synthesis, crystal structure and magnetic properties of a new dialkoxo-bridged diiron(III) complex

Abstract A new dialkoxo-bridged diiron(III) complex, [Fe2(N3)2(L)2](ClO4)2 (1) [HL=bis(benzimidazol-2-ylmethyl)(2-hydroxyethyl)amine], was synthesized and characterized. According to X-ray crystallographic studies on the solvated species 1·2C2H5OH, each Fe(III) ion lies in a highly distorted octahedral environment, and two Fe(III) ions are bridged by the ethoxyl oxygens from two L ligands. Cryomagnetic analyses indicated a moderate antiferromagnetic interaction between the high-spin Fe(III) ions, with J=−21.3 cm−1.

Synthesis, Crystal Structure and Magnetic Properties of a Terephthalato-bridged Binuclear Nickel(II) Complex

A new terephthalato-bridged binuclear nickel(II) complex with a tetraazamacrocyclic compound as the terminal ligand, [Ni 2 (cth) 2 (µ-TPHA)](ClO 4 ) 2 (1) [cth= rac -5,7,7,12,14,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane] has been synthesized and characterized. According to X-ray crystallographic studies on the solvated species 1·2CH 3 OH, each Ni(II) ion lies in a distorted octahedral environment, and the terephthalato ligand bridges two Ni(II) ions in a bis bidentate fashion. Cryomagnetic measurements revealed Curie-Weiss behaviour with è = m 1.4 K. Such behaviour may be due to a very weak intramolecular superexchange interaction through the extended bridge, a weak intermolecular exchange interaction or the local zero-field splitting of Ni(II) ions.

Synthesis and Magnetic Properties of New Tetranuclear Copper(II)–Nickel(II) Complexes of Macrocyclic Oxamides

Four new oxamido-bridged [CuII3NiII] complexes of [14]N4 and [15]N4 macrocyclic oxamides have been prepared and characterized, and the magnetic interaction between the Cu(II) and Ni(II) ions has been investigated.

Crystal structure of the addition compound of [Ni(meso-cth)][Cr(ox)2(bpy)](H2O)(ClO4) with weak coordination bonds and hydrogen bonds

A new ionic complex [Ni(meso-cth)][Cr(ox)2(bpy)](H2O)(ClO4) [meso-cth = meso-5,7,7,12,14,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane, ox = oxalato ainon, bpy = 2,2′-bipyridine] was prepared and its structure was determined. The complex was found to crystallized in monoclinic space group P2(1)/n, with a = 13.6000(4) Å, b = 18.763(5) Å, c = 14.995(4) Å, β =106.958(5)°, V = 3659.9(17) Å3, and Z = 4. The structure consisted of cationic [Ni(meso-cth)]2+, anionic [Cr(ox)2(bpy)]−, and perchlorate anions; the cationic [Ni(meso-cth)]2+ and anionic [Cr(ox)2(bpy)]− units were related by weak coordination bonds and hydrogen bonds.

Spin topology and ferromagnetic coupling: synthesis and magnetic properties of [CuII3CrIII] tetranuclear complexes of [14]N4 macrocyclic oxamides

Three novel tetranuclear macrocyclic complexes, [(CuL1)3Cr](ClO4)3·3H2O (1), [(CuL2)3Cr](ClO4)3·3H2O (2) and [(CuL3)3Cr](ClO4)3·3H2O (3) [L1, L2 and L3 are the dianions of three [14]N4 and [15]N4 macrocyclic oxamides, namely 2,3-dioxo-5,6:13,14-dibenzo-7,12-bis(ethoxycarbonyl)-1,4,8,11-tetraazacyclotetradeca-7,11-diene,2,3-dioxo-5,6:13,14-dibenzo-9-methyl-7,12-bis(ethoxycarbonyl)-1,4,8,11-tetraazacyclotetradeca-7,11-diene and 2,3-dioxo-5,6:14,15-dibenzo-7,13-bis(ethoxycarbonyl)-1,4,8,12-tetraazacyclotetradeca-7,12-diene, respectively], have been prepared and characterized. These complexes are the first examples of Cu3Cr species exhibiting spin topology with all the spins parallel in the ground state. Cryomagnetic studies on (1) (2–300 K) and (3) (77–300 K) revealed that the CuII and CrIII ions interact ferromagnetically through the oxamido bridge, with the exchange integral J = 6.7 cm−1 for (1) and J = 6.3 cm−1 for (3) based on Ĥ = −2J∑ŜiŜj. The ferromagnetic interaction has been rationalized in terms of strict orthogonality of the magnetic orbitals. The oxamido bridge is also more efficient than the oxalato bridge at propagating the ferromagnetic interaction.

Synthesis and Characterization of New Cu(II) and [CuIIMnII] Complexes of Macrocyclic Oxamides

Abstract Two new Cu(II) complexes of [14]N4 and [15]N4 macrocyclic oxamides. [CuL1] and fCuL2] [L1 and L2 are the dianions of 2, 3-dioxo-5, 6:14, 15-dibenzo-7, 13-bis(ethoxycarbonyl)-l, 4, 8, 12-tetraazacyclotetradeca-7, 12-diene and 2, 3-dioxo-5, 6:9, 10:13, 14-tribenzo-7, l 2-bis(ethoxycarbonyl)-1, 4, 8, 11 -tetraazacyclo-tetradeca-7, 11-diene, respectively], have been prepared by the template reactions of 2, 2′-(oxalyldiimino)bis(phenylglyoxylate) with diamines and cupric acetate in the presence of triethylamine. Using the strategy of “complexes as ligands”, two tetranuclear complexes of the formula [(CuL1)3Mn](ClCO4)2 and [(CuL2)3Mn](ClO4)2 have been synthesized. The complexes have been characterized by means of elemental analyses, IR and electronic spectra, conductivity and magnetic susceptibility measurements.