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Two nickel (II) complexes, [Ni(Hcdcp) (H2O)3] (1) (H3cdcp = 3-(4-carboxylatephenyl)-2,6-pyridinedicarboxylic acid) and [Ni3(Hdcdcp)2(H2O)6]n (2) (H4dcdcp = 3-(2,4-dicarboxylatephenyl)-2,6-pyridinedicarboxylic acid) have been synthesized under hydrothermal conditions and characterized by elemental analysis and single-crystal X-ray diffraction. For complex 1, Ni(II) ion is coordinated by three water molecules and a deprotonated H3cdcp ligand in chelate mode to form a mononuclear complex; for complex 2, three Ni(II) ions are connected into trinuclear clusters which are further linked into 2D layers by pentadentate Hdcdcp3− ligands in alternant bis-(bridging) and chelate coordination modes; the two complexes are both extend to 3D supramolecular polymers by hydrogen bonds. Thermogravimetric analysis (TGA) and powder X-ray diffraction (PXRD) are also carried out to determine their thermal stability and phase purity. Magnetic measurement for complex 2 reveals that weak antiferromagnetic interactions occur between the bridging trinuclear Ni( II ) ions.

Based on 8-hydroxyquinoline Schiff base derivative and auxiliary ligand β-diketonate, two new dinuclear lanthanide complexes [Gd2(L1)2(bfac)4] (1) and [Dy2(L2)2(acac)2(CH3OH)2]•CH3OH (2) (HL1 = 2-[((4-phenethyl)-imino)methyl]-8-hydroxyquinoline, H2L2 = 2-[((4-methyl)-2-(arboxyl)-imino)]methyl]-8-hydroxyquinoline, Hbfac = hexafluoroacetylacetonate, Hacac = acetylacetonate,) were successfully isolated and characterized. Structural analysis reveal that complexes 1 and 2 both contain a binuclear Ln2 cluster, in which two eight-coordinated Ln(III) ions are located in distorted dodecahedral geometry and bridged by phenoxide oxygen atom. In addition, their magnetic properties are investigated in detail. The results suggest that ferromagnetic interactions between adjacent Gd3+ ions can be observed in 1, which exhibits remarkable magnetic refrigeration properties with -ΔSmax = 17.74 J kg−1 K−1 (T = 2.0 K and ΔH = 7.0 T). Complex 2 displays slow magnetic relaxation behaviors with ΔE/kB ≈ 2.16 K and τ0 ≈ 1.38 × 10−5 s.

A novel coordination polymer {[Mn2(L)4/3(H2O)3]⋅2H2O}n (1), was synthesized by the hydrothermal reaction of 4,4′-[(5-carboxy-1,3-phenylene)bis(oxy)]dibenzoic acid (H3L) with manganese(II) chloride tetrahydrate (MnCl2⋅4H2O) in an aqueous solution. The single X-ray diffraction indicated that the coordination polymer 1 had a three-dimensional (3D) framework. A trinuclear Mn unit is utilized as a building block connected via oxygen atoms of carboxylate group to form a two-dimensional layer structure. The interlayers connected by the ligands result in a 3D architecture. The coordination polymer 1 was characterized by the infrared spectroscopy, elemental analysis and powder XRD. According to magnetic susceptibility measurements the coordination polymer 1 can be characterized with the antiferromagnetic coupling interaction of J = −3.21 cm−1. Furthermore, the thermogravimetric analysis revealed good thermal stability for the coordination polymer 1.

A new chelating radical ligand NIT-1′-MeBzIm (1) (NIT-1′-MeBzIm = 2-{2′-[(l’-methyl)benzimidazolyl]}-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide) and three corresponding complexes [M(NIT-1′-MeBzIm)2(NO3)(CH3OH)]·(NO3)(CH3OH) (M = Ni (2), Co (3)), [Zn(NIT-1′-MeBzIm)2(CH3OH)2]·(ClO4)2(H2O)2(CH3OH) (4) have been prepared and structurally characterized by X-ray diffraction method and variable-temperature magnetic susceptibility measurements. In the crystal structures, radical 1, complexes 3 and 4 crystallize isomorphously in monoclinic, with the space groups are P2(1)/n, P2(1)/c, and P2(1), respectively. Complex 2 crystallizes in orthorhombic space group Pna2(1). The metal ions of the three complexes embed in distorted octahedron geometry centers and coordinated by two NIT-1′-MeBzIm radicals from the equatorial positions to form trans configuration, the axial positions are occupied by one methanol molecule and one nitrate anion for 2 and 3, but by two methanol molecules for 4. Magnetic measurement demonstrates that the intramolecular exchange couplings in 2 and 3 are antiferromagnetic with J = −41.25 and −38.1 cm−1, where the spin Hamiltonian is defined as Ĥ = −2J(Ŝrad1 ŜM + ŜM Ŝrad2) based on the molecular structure of radical-metal-radical, while that in 4 is weak ferromagnetic with J = 1.65 cm−1 where the spin Hamiltonian is defined as Ĥ = −2JŜ1Ŝ2 within the complexes. Intermolecular exchange couplings in 1 is also weak ferromagnetic with J = 1.32 cm−1 where the spin Hamiltonian is defined as Ĥ = −2JŜ1Ŝ2 between radical and radical. Compounds 2–4 exhibit intermolecular antiferromagnetic interaction with the zJ′ = −0.52 cm−1, θ = −0.75 K and zJ′ = −0.49 cm−1 for compounds 2, 3 and 4, respectively, which should ascribe to the weak interactions. The crystal structures for 1–4 have intermolecular hydrogen bonding interactions (and π–π piling interactions for 1 and 3) which form the single crystals into 1-D, 2-D, 3-D structures and seems to play an important role in molecular packing and in magnetic coupling.

Two complexes of formulas [Ni(IM-MeImz)2(SCN)2]·CH3CH2OH (1) and [Mn(IM-MeImz)2(SCN)2]·3H2O (2), where IM-MeImz = 2-(5-Methylimidazol-4-yl)-4,4,5,5-tetramethyl-2-imidazoline-1-oxyl, have been synthesized and characterized by single-crystal X-ray diffraction. The X-ray analysis demonstrates that IM-MeImz ligand is coordinated to metal ion with the κ2 N(MeImz), O(IM) mode to avoid steric hindrance with the methyl group in complex. In the solid state, the complexes 1 and 2 are linked by intermolecular hydrogen bonds, leading to two-dimensional structure. The variable-temperature magnetic susceptibility of both compounds suggests that the metal ions and radicals are ferromagnetically coupled with J = 2.78 and 1.11 cm−1 for complexes 1 and 2, respectively.

A new nitronyl nitroxide NIT2-bithph ( 1 ) and its manganese(II) compound [Mn(hfac) 2 (IMHBithph)] 2 ·(NIT2-bithph)(C 6 H 14 ) ( 2 ) (hfac = hexafluoroacetylacetonate; NIT2-bithph = 4,4,5,5-tetramethyl-2-(bithiophenal-2-yl)imidazoline-1-oxyl-3-oxide; IMHBithph = 1-hydroxy-2-bithiophenal-4,4,5,5-tetramethyl-4,5-dihydro- 1H-imidazole) have been synthesized and structurally characterized by X-ray diffraction methods. The units of compound 1 were connected as one-dimensional chain by the intermolecular hydrogen bonds which afford an intermolecular antiferromagnetic interaction between nitronyl nitroxide radicals within the chain ( J = −1.89 cm −1 ). Compound 2 resulting from the reaction of Mn(hfac) 2 ·2H 2 O and NIT2-bithph is dinuclear and includes the reduced amidino-oxide form of NIT2-bithph, it is made up of three parts: a [Mn(hfac) 2 (IMHBithph)] 2 dimer unit, an uncoordinated NIT2-bithph radical and a noncoordinated solvent molecule of hexane, the molecule of radical is hydrogen bonded to its reduced form. Two reduced IMHBithph ligands bridge the two manganese(II) ions through their amidino-oxide oxygen atoms resulting in a small intramolecular antiferromagnetic interaction between the manganese ions ( J = −1.55 cm −1 ).

A novel nickel(II) complex, Ni(NIT2-thz)2(NO3)2 (NIT2-thz=2-(2′-thiazole)-4,4,5,5-tetrmethylimidazoline-1-oxyl-3oxide) was synthesized, the crystal structure and magnetic properties were mainly discussed in the present work. In the title compound, each nickel(II) ion is chelated by two NIT2-thz ligands through oxygen atoms of nitroxide group and nitrogen atoms of thiazole group forming two six-membered rings at equatorial positions, together with the coordination of two oxygen atoms from two nitrate anions at axial positions, which formed a elongated octahedral geometry. By the intermolecular interactions, the molecules were connected as a 2D network. Magnetic measurements show that there are moderate ferromagnetic interactions between the Ni(II) ions and the radicals (J=43.47 cm−1).