Synthesis, structure, and properties of N,N′-bis[2-(1-pyrazolyl)ethyl]-pyridine-2,6-dicar☐amido copper(II)

Abstract

The pentadentate dipeptide ligand N,N′-bis[2-(1-pyrazolyl(ethyl]pyridine-2,6-dicar☐amide (PyPz2PH2) (1) (H denotes dissociable amide H) has been synthesized. The Cu(II) complex of this ligand namely, [Cu(PyPz2P)] (2), has been isolated and structurally characterized. Complex 2 crystallizes in the triclinic space group P1¯ with a = 7.743(3), b = 9.427(2), c = 12.809(3)Å, α = 71.01(2), β = 80.38(2), γ = 70.54(2)°, V = 831.8(4)Å and Z = 2. The structure was refined to R = 4.13% by using 3313 (I > 2σ(I)) data. The dianionic pentadentate ligand coordinates to Cu(II) in a distorted square pyramidal fashion. The Cu center is lifted out of the mean basal plane by 0.32Å. The spectral parameters of 2 have been compared with those of an analogous complex [Cu(Py3P)] that contains pyridine rings in place of pyrazoles on a similar ligand framework. Such comparison indicates that pyridine nitrogens coordinate to Cu(II) more strongly than 2-pyrazolyl nitrogens.