Three Novel Copper–Radical Complexes: Syntheses, Crystal Structures, and Magnetic Properties

Abstract

Three novel copper–radical complexes [Cu(PhCOO)2(NITpPy)2(H2O)2] (1), [Cu2(Me3CCOO)4(NITpPy)2] (2), and [{Cu2(Me3CCOO)4(NITpPy)}n] (3) [NITpPy = 4,4,5,5‐tetramethyl‐2‐(4‐pyridyl)‐2‐imidazoline‐1‐oxyl 3‐oxide] were synthesized and characterized structurally as well as magnetically. It is noteworthy that the syntheses of complexes 2 and 3 are similar except for the temperature of the reaction between Cu(Me3CCOO)2·2H2O and the NITpPy radical ligand. Our magnetic study of complexes 1 and 2 reveals that the antiferromagnetic interactions occur with a J value around –10 cm–1 between copper(II) and radicals when radicals use the pyridine nitrogen atom connected to the copper(II) ion. Yet the best‐fit parameters of complex 3 reveal that significant ferromagnetic interactions (J2 = 20.5 cm–1) take place in the copper radical when radicals coordinate the copper(II) ion with nitroxide directly.

Four Discrete Transition Metal Complexes Involving Pyridyl‐substituted Nitronyl Nitroxide: Syntheses, Crystal Structures, and Magnetic Properties

“…The Cu II ion is four‐coordinate in a square planar CuN2–O2 environment, which is occupied by two nitrogen atoms (N1, N1A) from NITpPy ligands and two deprotonated p ‐toluate oxygen atoms (O3, O3A). The Cu–N and Cu–O bond lengths [1.9982(14) Å and 1.9893(13) Å] are comparable to those in previously reported Cu‐NITpPy complexes 20. In NITpPy ligands, the N–O bond lengths are 1.270(2) Å [N(2)–O(1)] and 1.259(3) Å [N(3)–O(2)], which is intermediate among those observed in copper complexes with coordinated NITpPy radicals 4,10.…”

“…The fragment O1–N2–C6–N3–O2 is nearly planar, and forms a dihedral angle of 31.8° with the plane of the pyridine ring. It should be noted that the short distance (3.98 Å) was observed between the two oxygen atoms of uncoordinated nitroxide groups of two adjacent radicals (Figure 2), similar to the complex [Cu‐(NITpPy) 2 (PhCOO) 2 ],20 which indicates that there might be intermolecular interactions in complex 1 .…”

CuII-Azide Polynuclear Complexes of Three Different Building Clusters with the Same Schiff-Base Ligand: Synthesis, Structures, Magnetic Behavior, and Density Functional Theory Studies

“…The magnetic exchange in the basic centrosymmetric core can be modeled as Cu( S 1 )- J 1 -Cu( S 2 )- J 2 -Cu( S 3 )- J 1 -Cu( S 4 ) and as the two central Cu II ions are bridged by double symmetric EO-azido bridges, while the peripheral Cu II ions are bridged by a single EO-azido group J 1 and J 2 are not expected to be identical. ,, A reasonable fit can be obtained for noninteracting tetranuclear units applying the conventional Hamiltonian: H = prefix− J 1 ( S 1 S 2 + S 3 S 4 ) − J 2 S 2 S 3 …”