Isiah Po-Chun Liu

The nano-scale molecule with the longest delocalized metal–metal bonds: linear heptacobalt(II) metal string complexes [Co7(µ7-L)4X2]

A new type of pyrazine-modulated oligo-alpha-pyridylamino ligands, N2-(pyrazin-2-yl)-N6-(6-(pyrazin-2-ylamino)pyridin-2-yl)pyridine-2,6-diamine (H3pzpz) and N2-(pyrazin-2-yl)-N6-(6-(pyridin-2-ylamino)pyridin-2-yl)pyridine-2,6-diamine (H3tpz), were synthesized and characterized by IR, 1H NMR and MS(FAB). Using and , the linear heptacobalt(II) metal string complexes [Co7(micro7-L)4X2] (L=pzpz3-, X=Cl-, NCS-; L=tpz3-, X=Cl-, X=NCS-) were synthesized and structurally characterized. The structures showed the shortest Co-Co distance (2.194 A) and the longest Co chain (13.5 A) obtained to date with direct Co-Co bonds. The Co-Co distances are in the range 2.194-2.309 A. Electrochemical studies showed two reversible oxidations and one reversible reduction, while all the redox reactions of H3pzpz complexes, and , occurred at higher potentials than H3tpz complexes, and . The complexes are fairly stable to oxidation. Temperature-dependent magnetic research on revealed anomalous magnetic behavior with intermediate magnetic moment values between quartet and doublet states, and deviation from the Curie-Weiss law.

Manipulation of electronic structure via supporting ligands: a charge disproportionate model within the linear metal framework of asymmetric nickel string [Ni7(phdptrany)4Cl](PF6)

This paper describes the synthesis and physical properties of an uniquely asymmetric heptanickel string complex exhibiting a charge disproportionate model along the linear nickel framework.

Transition metal complexes of a super rigid anthyridine ligand: structural, magnetic and DFT studies

Transition metal complexes of iron(II), cobalt(II), nickel(II), copper(II) and zinc(II) with a plane, super rigid ligand, 1,13,14-triaza-dibenz[a,j]anthracene (L), [M2L4](ClO4)4 (M = Fe, Co, Ni, Cu, Zn), were synthesized and their magnetic properties were studied. All complexes are dinuclear, tetracationic complexes bridged by four tridentate ligands. In a complex each L coordinates to two metal atoms with two nitrogen atoms chelating to one metal and the third nitrogen atom mono-coordinating to another metal. Crystal structure analysis indicated that the molecular structures of the five complexes are essentially the same despite significant distortion from the Jahn–Teller effect of the copper complex. The Cu–Cu distance is 2.907(1) A, and all other M–M distances are ca. 3.3 A. Antiferromagnetic couplings were observed for the Fe, Co, Ni and Cu complexes. The exchange parameters were J = −6 and −129 cm−1 for Ni and Cu complexes, respectively. The mechanism was discussed by spin-polarization, superexchange coupling and DFT calculations. The J value obtained from the density functional B3LYP calculations is in good agreement with the experimentally determined value.