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In Situ Formation of Semichelating Ligands: A Strategy for Tuning the Magnetic Coupling in Azide-Bridged Copper(II) Complexes

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Abstract

Five CuII complexes of trinuclear [Cu3(L1)2(N3)6] (1), one-dimensional chain [Cu5(L2)2(N3)10]n (2), trinuclear [Cu3(L3)2(N3)6] (3) and dinuclear [Cu2(L4)2(N3)2Cl2] (4) and [Cu2(L5)2(N3)2Cl2] (5) (L1–5=RCH2OR′, R=substituted pyrazole or imidazole, R′=Me, Et or nPr) were synthesized by the reaction of CuCl2⋅2 H2O, sodium azide with RCH2Cl in CH3OH, C2H5OH or n-C3H7OH. The ether ligands L1 and L2 can be alternatively prepared by the alcoholysis of RCH2Cl in the presence of sodium azide, whereas the ligands L3–5 form in corresponding alcohols without azide. For complexes 15, the oxygen atom of the ether ligands is located at the Jahn–Teller axis of CuII with the long Cu[BOND]O separations of 2.377(3)–2.830(3) Å. The nitrogen atoms of bridging azides are located in the equatorial or basal planes of CuII ions, favoring strong magnetic coupling. The Cu-Nazido-Cu bridging angles in complexes 13 are 98.8(2)°–101.6(1)°, leading to ferromagnetic coupling, whereas the Cu-Nazido-Cu angles in complexes 4 and 5 are close to 103°, leading to antiferromagnetic coupling.

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