Kong-Qiu Hu

Slow Magnetization Relaxation in NiIIDyIIIFeIII Molecular Cycles

Two cyano- and phenoxo-bridged hexanuclear Ni(II)2Dy(III)2Fe(III)2 (1) and octanuclear Ni(II)4Dy(III)2Fe(III)2 (2) trimetallic cyclic complexes have been obtained. They are the first trimetallic metallocycles. Magnetic studies reveal that 1 and 2 exhibit single-molecule-magnet behavior with an energy barrier of 17.9 K for complex 1 in a 2000 Oe static field and 25.0 K for complex 2 in a zero static field.

Ligand-directed assembly of trinuclear and one-dimensional heterotrimetallic CuIILnIIIFeIII complexes: unusual antiferromagnetic CuIIFeIII coupling via cyano bridges

New heterotrimetallic complexes [Cu(valpn)(H2O)Ln(H2O)3Fe(CN)6]·xH2O (Ln = Gd, x = 3 for complex 1; Ln = Tb, x = 3 for complex 2; Ln = Dy, x = 1.75 for complex 3; H2valpn = N,N′-bis(3-methoxysalicylidene)-1,3-diaminopropane), {[Cu(Me2valpn)]2Ln(H2O)Fe(CN)6·xH2O·yCH3CN}n (Ln = Gd, x = 5, y = 2.5 for complex 4; Ln = Tb, x = 4.5, y = 1.5 for complex 5; Ln = Dy, x = 5.5, y = 2.5 for complex 6; Ln = Y, x = 6, y = 4 for complex 7; H2Me2valpn = N,N′-bis(3-methoxysalicylidene)-2,2-dimethyl-1,3-diaminopropane) have been synthesised by a reaction of Cu(valpn) (or Cu(Me2valpn)), Ln3+ and [Fe(CN)6]3− in a molar ratio of 2 : 1 : 1. Complexes 1–3 have a CuLnFe trinuclear structure, consisting of phenoxo-bridged Cu–Ln and cyano-bridged Ln–Fe moieties. Complexes 4–7 contain phenoxo-bridged Cu2Ln units that are connected by [Fe(CN)6]3− to form a one-dimensional (1D) zig-zag structure. In the trinuclear complexes 1–3, the [Fe(CN)6]3− anion coordinates to Ln3+, whereas it coordinates to Cu2+ in complexes 4–7. Magnetic studies demonstrate that there exists a ferromagnetic interaction between Cu(II) and Gd(III) ions via the phenoxo bridges, while the cyano-bridges transit antiferromagnetic coupling between low-spin Fe(III) and Cu(II) or Gd(III). The fitting to the magnetic susceptibilities of complexes 1 and 4 gave the parameters of JCuGd = 2.392 and 2.945 cm−1, and JFeGd = −0.341 cm−1 and JFeCu = −0.378 cm−1. The ac magnetic measurements reveal that complex 6 shows slow magnetization relaxation with an energy barrier of 12.3 K and a relaxation time of τ0 = 1.65 × 10−6 s, which is typical of a single-chain magnet.

Tunable gas adsorption properties of porous coordination polymers by modification of macrocyclic metallic tectons

By using the semi-rigid ligand tetrakis[4-(carboxyphenyl)oxamethyl]methane acid (H4TCM) and various macrocyclic metallic tectons, eight new Ni(II) coordination polymers, namely, [(NiL1)2(TCM)]·17H2O (1), [(NiL2)2(TCM)]·17H2O (2), [(NiL3)2(TCM)]·18H2O (3), [(NiL4)2(TCM)]·4DMF·10H2O (4), [(NiL5)2(TCM)]·4DMF·9H2O (5), [(NiL6)2(TCM)]·20H2O (6), [(NiL7)2(TCM)]·18H2O (7), [(NiL8)2(TCM)]·4H2O (8) (L1 = 1,8-dimethyl-1,3,6,8,10,13-hexaaza-cyclotetradecane, L2 = 1,3,6,9,11,14-hexaaza-tricyclooctadecane, L3 = 1,3,6,10,12,15-hexaaza-tricycloeicosane, L4 = 1,3,6,8,11,14-hexaaza-tricyclooctadecane, L5 = 4-methyl-1,3,6,8,11,14-hexaaza-tricyclooctadecane, L6 = 1,3,6,8,12,15-hexaaza-tricycloeicosane, L7 = 11-methyl-1,4,8,10,13,15-hexaaza-tricycloicosane and L8 = 3,10-diisobutyl-1,3,5,8,10,12-hexaaza-cyclotetradecane), were synthesized and structurally characterized. Single crystal X-ray analyses reveal that compounds 1–8 exhibit a similar diamondoid (dia) topology network. Regulated by macrocyclic metallic tectons, compounds 1–3 feature a three-dimensional (3D) framework with 7-fold interpenetration, giving rise to a 1D porous channel with size of ca. 1 nm. Compounds 4–7 possess a 3D network with 2D porous channels (porous size ca. 0.5 nm) and 4-fold interpenetration. Compound 8 shows a 3D dense packing arrangement with 2-fold interpenetration. The porosity of compounds 1–7 was confirmed by N2 gas adsorption measurements at 77 K. Furthermore, due to functional groups exposed on the porous surface, activated compound 3 exhibits selective adsorption of CO2 over N2. The results show the crystal structure, stability and gas adsorption can be tuned by the modification of macrocyclic metallic tectons.