A mixed-valence copper chloride coordination polymer composed of one-dimensional cationic and anionic substructures

A new three-dimensional (3D) coordination polymer [{Cu^IICl₂(Hdatrz)₂}(Cu^I₂Cl₄)]_n (1) that consists of two independent cationic and anionic substructures has been synthesized from the reaction of 3,5-diamino-1,2,4-triazole (datrz) with Cu^ICl and Cu^IICl₂. The cationic subunit, [Cu^IICl₂(Hdatrz)₂]²⁺, has a one-dimensional (1D) structure based on [Cu^IICl₂(Hdatrz)₂Cl₂] octahedral units, while the anionic component [Cu^I₂Cl₄]²⁻ consists of 1D chains of edge-sharing CuCl₄ tetrahedra. The cationic and anionic chains are linked through interionic hydrogen bonding. The protonated datrz ligand plays an essential role in constructing the supramolecular framework. The magnetic Cu^II (d⁹) ion occupies the octahedral center of the cationic substructure, while the non-magnetic Cu^I (d¹⁰) ion resides in the tetrahedral core of the anionic substructure. The temperature-dependent magnetic susceptibility of 1 reveals a typical paramagnetic behavior, and the Curie-Weiss fit shows a magnetic moment of 2.04 μ_B per Cu^II. There is weak antiferromagnetic ordering below a Néel temperature of 2.46 K, presumably due to an antiferromagnetic interaction between neighboring Cu^II ions linked by two Cl ligands. The EPR spectra of 1 suggest that the [Cu^IICl₂(Hdatrz)₂Cl₂] subunit has a tetragonally elongated octahedral geometry and the complex 1 contains mixed-valence Cu^I and Cu^II species. In addition, we discovered a novel molecular compound with a stoichiometry of (H₂datrz)Cl₂ (2), which was prepared by the reaction of concentrated hydrochloric acid with datrz in the absence of copper chlorides. X-ray crystal structure determination shows that the compound consists of an unusual di-protonated H₂datrz²⁺ cation and two charge-compensating Cl⁻ anions.