Formation of mononuclear and polynuclear d-block metal complexes from 1,4,7-tris(3-hydroxypropyl)-1,4,7-triazacyclononane: crystal structures, spectroscopic studies, and magnetic properties

Four new d-block metal complexes formulated as [Ni^II(H3thptacn)]Cl₂·H₂O (1), [Mn^IV(thptacn)]ClO₄ (2), [Cu^II₃(Hthptacn)₂](ClO₄)₂ (3), and [Cd^II₂(H3thptacn)₂Cl₂][B(C₆H₅)₄]₂ (4) were obtained from the macrocyclic ligand 1,4,7-tris(3-hydroxypropyl)-1,4,7-triazacyclononane (H3thptacn) either through solvent diffusion or by evaporation of their solutions. These complexes were characterized by single crystal X-ray structural determination, elemental analysis, and routine spectroscopic methods. Complexes 1 and 2 exhibit similar mononuclear structures with the metal centers being surrounded by both the backbone nitrogen atoms and the pendant coordinating alcohol/alkoxide groups. Complex 3 is a linear trinuclear cluster, where three Cu(II) centers are combined together by the bridging alkoxide groups in a centro-symmetric pattern. Two chloride groups join two Cd(II) atoms each chelated by one triply protonated ligand H3thptacn to afford dinuclear compound 4 with a symmetry center. When coordinating to different d-block metals, the macrocyclic ligand exhibits four types of binding modes with various dissociation status on its pendant alcohol groups and different numbers of these pendant groups participating in coordination. The magnetic measurements revealed significant zero-field splitting for mononuclear Ni(II) and Mn(IV) complexes. A moderate antiferromagnetic interaction between the neighboring Cu(II) centers governs the magnetic properties of 3 with J = −166(3) cm⁻¹.