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|標題:||Weak antiferromagnetic coupling for novel linear hexanuclear nickel(II) string complexes (Ni-6(12+)) and partial metal-metal bonds in their one-electron reduction products (Ni-6(11+))||作者:||Chien, C.H.
|關鍵字:||di(2-pyridyl)amide dpa ligands;crystal-structure;multiple bonds;magnetic-properties;6-diphenylphosphino-2-pyridonate ligands;tripyridyldiamido dianion;trichromium chains;tricobalt compound;molecular wires;quadruple bonds||Project:||Dalton Transactions||期刊/報告no：:||Dalton Transactions, Issue 26, Page(s) 3249-3256.||摘要:||
The preparation, crystal structures, magnetic properties and electrochemistry of novel linear hexanuclear nickel string complexes (Ni-6(12+)) and their corresponding 1-e(-) reduction products (Ni-6(11+)) are reported. In these complexes, the hexanickel chain is in a symmetrical arrangement ( approximately D-4 symmetry) and is helically supported by four bpyany( 2-) ligands [ bpyany( 2-) = the dianion of 2,7-bis(a-pyridylamino)-1,8-naphthyridine]. The Ni-6(12+) complexes show that the two terminal nickel ions have high-spin states ( S = 1) and the four inner ones have low-spin states ( S = 0). The two terminal nickel ions exhibit weak antiferromagnetic coupling of ca. - 5 cm(-1). All of Ni-6(12+) complexes display three reversible redox couples at about - 0.70, - 0.20 and + 1.10 V ( vs. Ag/AgCl). The first reduction wave at about - 0.20 V suggests facility of 1-e(-) reduction for the Ni-6(12+) compounds. The reaction of Ni-6(12+) complexes with hydrazine afforded the 1-e(-) reduction products (Ni-6(11+)). As far as we are aware, the shortest bond distance of 2.202 angstrom with a partial metal - metal bond was observed in Ni-6(11+) compounds. The magnetic results of these Ni-6(11+) compounds are in agreement with a localized model, in which the two terminal nickel ions are in a spin state of S = 1 whereas the central Ni(3) - Ni( 4) pair in a spin state of S = 1/2. The N-6(11+) compounds show relatively strong antiferromagnetic coupling of about 60 cm(-1) between the terminal and the central dinickel ions.
|Appears in Collections:||化學系所|
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