A Novel Bis Tridentate Bipyridine Carboxamide Ligand and Its Complexation to Copper(II): Synthesis, Structure, and Magnetism

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• 作者：Jian Wang ; Brandon Djukic ; Jingyi Cao ; Antonio Alberola ; Fereidoon S. Razavi ; Melanie Pilkington
• 刊名：Inorganic Chemistry
• 出版年：2007
• 出版时间：October 15, 2007
• 年：2007
• 卷：46
• 期：21
• 页码：8560 - 8568
• 全文大小：406K
• 年卷期：v.46,no.21(October 15, 2007)
• ISSN：1520-510X

文摘

A new bis tridentate ligand 2,2'-bipyridine-3,3'-[2-pyridinecarboxamide] H₂L₁ which can bind transition metal ionshas been synthesized via the condensation of 3,3'-diamino-2,2'-bipyridine together with 2-pyridine carbonyl chloride.Two copper(II) coordination compounds have been prepared and characterized: [Cu₂(L₁)(hfac)₂]·3CH₃CN·H₂O (1)and [Cu₂(L₁)Cl₂]·CH₃CN (2). The single-crystal X-ray structures reveal that complex 1 crystallizes in the triclinicspace group P, with the unit cell parameters a = 12.7185(6) Å, b = 17.3792(9) Å, c = 19.4696(8) Å, =110.827(2), = 99.890(3), = 97.966(3), V = 3868.3(3) ų, Z = 4, R = 0.0321 and R_w = 0.0826. Complex2 crystallizes in the monoclinic space group P2₁/n with the unit cell parameters a = 12.8622(12) Å, b = 9.6100(10) Å, c = 19.897(2) Å, = 102.027(3), V = 2405.3(4) ų, Z = 4, R = 0.0409 and R_w = 0.1005. In bothcomplexes the ligand is in the dianionic form and coordinates the divalent Cu^II ions via one amido and two pyridinenitrogen donor atoms. In 1, the coordination geometry around both Cu^II ions is best described as distorted trigonalbipyramidal where the remaining two coordination sites are satisfied by hexafluoroacetylacetonate counterions. In2 both Cu^II ions adopt a (4 + 1) distorted square pyramidal geometry. One copper forms a longer apical bond toan adjacent carbonyl oxygen atom, whereas the second copper is chelated to a neighboring Cu-Cl chloride ion toafford a -Cl-bridged dimerized [Cu₂(L₁)Cl₂]₂ complex. The magnetic susceptibility data for 1 (2 -270 K), reveal theoccurrence of weak antiferromagnetic interactions between the Cu^II ions. In contrast, variable-temperature magneticsusceptibility measurements for 2 reveal more complex magnetic properties, with the presence of a weakantiferromagnetic exchange (J = -10.1 K) between the copper ions in each dinuclear copper complex and astronger ferromagnetic exchange interaction (J = 32.9 K) between the Cu^II ions of the Cu(-Cl)₂Cu dimeric bridgingunits.