Yong-Mei Tian

Preparation and electrocatalytic performance of Fe–N–C for electroreduction of H2O2

Fe–N–C catalysts were prepared through metal-assisted polymerization method. Effects of carbon treatment, Fe loading, nitrogen source, and calcination temperature on the catalytic performance of the Fe–N–C for H2O2 electroreduction were measured by voltammetry and chronoamperometry. The Fe–N–C catalyst shows optimal performance when prepared with pretreated active carbon, 0.2xa0wt.% Fe, paranitroaniline (4-NA) and one-time calcination. The Fe–N–C catalyst displayed good performance and stability for electroreduction of H2O2 in alkaline solution. An Al–H2O2 semi-fuel cell was set up with Fe–N–C catalyst as cathode and Al as anode. The cell exhibits an open-circuit voltage of 1.3xa0V and its power density reached 51.4xa0mWxa0cm−2 at 65xa0mAxa0cm−2.

A salen-type trinuclear Zn2Gd complex

In the trinuclear title complex, di-μ-acetato-1:2κ2 O:O′;2:3κ2 O:O′-bis{μ-6,6′-dimethoxy-2,2′-[cyclohexane-1,2-diylbis(methanylylidene)]diphenolato}-1:2κ6 O 1,N,N′,O 1′:O 6,O 6′;2:3κ6 O 6,O 6′:O 1,N,N′,O 1′-2-gadolinium(III)-1,3-dizinc hexafluoridophosphate methanol monosolvate monohydrate, [GdZn2(C22H24N2O4)2(CH3COO)2]PF6·CH3OH·H2O, the two ZnII ions are located in the inner N2O2 cavities of two 6,6′-dimethoxy-2,2′-[cyclohexane-1,2-diylbis(methanylylidene)]diphenolate (L) ligands. Both ZnII ions are five-coordinated by two O atoms and two N atoms from the L ligand and one O atom of an acetic acid molecule, giving rise to a square-pyramidal geometry around the ZnII ions. The GdIII ion is nine-coordinated by four O atoms from the outer O2O2 sites of one ligand, and three O atoms from another ligand, in which there is one non-coordinating methoxy O atom. Two further O atom from different acetate ligands complete the nine-coordinate environment.

A series of salen-type asymmetric dinuclear Dy(III) complexes: site-resolved two-step magnetic relaxation process

A series of asymmetric dinuclear dysprosium complexes, namely, [Dy2(L)2(DBM)2(H2O)]·2CH2Cl2 (2), Dy2(L)(DBM)4(H2O) (3), [Dy2(L)(BTFA)4(H2O)]·(Et2O) (4) and Dy2(L)(hmac)4(H2O) (5) (H2L = N,N′-bis(salicylidene)-o-phenylenediamine, DBM = dibenzoylmethane, BTFA = benzoyltrifluoroacetone and hmac = hexamethylacetylacetonate), are structurally and magnetically characterized. Complex 2 is elaborately designed by fine-tuning the local environment of one anisotropic center in a previously studied crystallographically independent {Dy2} SMM (1) displaying a separated two-step relaxation process, and consequently the one-to-one relationship between the spin sites and the relaxation processes is successfully confirmed. In addition, enhanced energy barriers were obtained among complexes 3–5 after introducing highly electron withdrawing groups on β-diketonate ligands. This work sheds light on the source of the complex multiple relaxations and provides a rational design of lanthanide SMMs with improved magnetic properties.

Modulation of the Coordination Environment around the Magnetic Easy Axis Leads to Significant Magnetic Relaxations in a Series of 3d-4f Schiff Complexes

A series of Salen-type Zn(II)-Dy(III) complexes [L1Zn(II)ClDy(III)(acac)2]·H2O (1), [L1Zn(II)BrDy(III)(acac)2]·H2O (2), [L1Zn(II)(H2O)Dy(III)(acac)2]·CH2Cl2·PF6 (3), [L2Zn(II)(H2O)Dy(III)(acac)2]·PF6 (4), and Co(III)-Dy(III) complexes [L1Co(III)Br2Dy(III)(acac)2]·CH2Cl2 (5), [L2Co(III)Cl2Dy(III)(acac)Cl(MeO)] (6), [L2Co(III)Cl2Dy(III)(acac)Cl(H2O)] (7), and [L2Co(III)Cl2Dy(III)(NO3)2(MeO)] (8) heterobinuclear single-molecule magnets (SMMs) were synthesized and magnetically characterized. These complexes were constructed by incorporating diamagnetic Zn(II) and Co(III) ions with acetylacetone (acac) and compartmental Schiff-base ligands (H2L1 = N, N-bis(2-oxy-3-methoxybenzylidene)-1,2-phenylenediamine; H2L2 = N, N-bis(2-oxy-3-methoxybenzylidene)-1,2-diaminocyclohexane). In the Zn(II)-Dy(III) (1-4) system, the coordination environments of the Dy(III) ions are nearly identical, but the apical coordination atom to the Zn(II) ion is different. Complexes 1, 2, and 4 displayed no magnetic relaxation in the absence of external magnetic field, but complex 3 displayed more pronounced SMM behavior with a relaxation energy barrier Ueff/ kB 38 K and magnetic hysteresis at 1.8 K. The SMM performances of 5, 6, and 7 were enhanced significantly by incorporating an octahedral Co(III) instead of square-pyramidal Zn(II) and replacing one of acac- group around Dy(III) ion by a neutral O atom, displaying Ueff of 167, 118, and 75 K as well as magnetic hysteresis up to 3.5 K. These studies indicated that the remote diamagnetic Zn(II) and Co(III) ions played a key role, and the SMM properties were very strongly related to the special coordination atoms configuration around Dy(III) ion. When this coordination configuration around was broken as 8 exhibited, however, it resulted in a dramatically decreased SMM performance. From this work, the key factors that significantly affect the SMM performance of these heteronuclear Zn(II)/Co(III)-Dy(III) SMMs are unambiguously presented.