Ferromagnetic End-to-End Azides and Tetrahedral Cobalt: Unusual Findings in the M-BPA-Pseudohalide2 System

Two novel unusual compounds [Co(NCO)(2)(bpa)] (1) and [Cu(N-3)(2)(bpa)] (2) with cyanate and azide pseudohalides are shown in this work. These compounds have been characterized by X-ray diffraction measurements, Fourier transform-infrared (FT-IR) and UV-visible spectroscopies, thermogravimetric studies, electron spin resonance (ESR) spectroscopy, and magnetic measurements. Compound 1 shows a one-dimensional (1D) structure with the cobalt atoms bridged by bpa ligands and with the metal atoms showing an unusual tetrahedral coordination sphere. Compound 2 shows a two-dimensional (2D) structure, where the copper(II) ions are bridged by double 1,3-azido ligands to form chains that are joined through single bpa bridges to give the global 2D structure. Magnetic measurements show predominance of spin orbit coupling for the cobalt compound (1), while ferromagnetic interactions, unusual for the 1,3-azido bridging, are observed in compound 2. This compound represents the first example of copper-double (mu(1,3)-azido)-bridged chain exhibiting ferromagnetic interactions through this kind of bridging.