Synthesis, structures and magnetic properties of polynuclear mixed-valence Mn(II)Mn(III) complexes containing 3-(2-phenol)-5-(pyridin-2-yl)-1,2,4-triazole ligand.
This paper reports the synthesis, crystal structures, and magnetic properties of a series of mixed-valence polynuclear manganese complexes bridged by a dianionic 1,2,4-triazole-based ligand L(2-) (H(2)L = 3-(2-phenol)-5-(pyridin-2-yl)-1,2,4-triazole). Complexes 1 to 3 show a similar binuclear structure, with the central core of [Mn(II)Mn(III)(L)(2)] and some other small molecules also coordinated to the two Mn centers. The two [Mn(II)Mn(III)(L)(2)] subunits can be further connected by different dicarboxylic acids to construct non-charged tetranuclear complexes 4 to 7. In these complexes, each deprotonated dianionic ligand L(2-) acts as a mu(2)-bridged ligand to coordinate two Mn centers via the 1,2,4-triazole ring. Bond valence sum (BVS) calculations and Mn surrounding bond lengths indicate that the Mn center coordinated to the pyridine N atoms in the +2 oxidation state, while another Mn center coordinated to the phenolic O atoms is in the +3 oxidation state. The Mn(III) centre shows Jahn-Teller elongation along one of the axes. Magnetic studies show the presence of ferromagnetic Mn(III)-Mn(II) coupling in the binuclear (1-3) and tetranuclear (4-7) complexes with the magnetic coupling constant (J) ranging from 0.58 to 1.17 cm(-1), based on the Hamiltonian H = -2JS(1) x S(2) (S(1) = 5/2 and S(2) = 2). In all cases both z'J' (intermolecular interactions) and D parameter (Zero Field Splitting of the Mn (III) ion) has been introduced to improve the corresponding fit. The relationship of the coupling interaction between the Mn(II)/Mn(III) and their electronic structures is discussed.
Liu
Hui
H
Department of Chenistry, Nankai University, Weijin Road 94, Tianjin, 300071, PR China.
Tian
Jinlei
J
Kou
Yingying
Y
Zhang
Jingyan
J
Feng
Li
L
Li
Dongdong
D
Gu
Wen
W
Liu
Xin
X
Liao
Daizheng
D
Cheng
Peng
P
Ribas
Joan
J
Yan
Shiping
S
D056831:Coordination Complexes / Q000138:chemical synthesis* / Q000737:chemistry; D018360:Crystallography, X-Ray; D008024:Ligands; D008280:Magnetics; D008345:Manganese / Q000737:chemistry*; D008968:Molecular Conformation; D014230:Triazoles / Q000737:chemistry*
D056831:Coordination Complexes; D008024:Ligands; D014230:Triazoles; C045575:1,2,4-triazole; D008345:Manganese