Association of a terpyridine ligand with lanthanide and copper(II) nitrates

Reactions between the 1,3-bis(6-methylpyridin-2-yl)pyridine ligand L, C17H15N3 and LnIII (1a, 1b, 1c, 1d) or a mixture of LnIII and CuII nitrates (2a, 2b, 2c, 2d) resulted in a series of respectively novel mono- and heterodinuclear complexes, where LnIII=Sm (a), Eu (b), Tb (c), Dy (d). The compounds were characterized by elemental analysis, ESI-MS and IR spectra, furthermore we obtained crystals of [H2L][Eu(NO3)5] (1b) and [CuL2][Eu(NO3)5] (2b) suitable for XRD characterization. In the crystal structures the Eu ions are 10-coordinated with quite a narrow range of Eu-O distances which are between 0.2436 and 0.2556 nm. In 1b the ligand molecule is protonated in both terminal rings, and the N-H groups are involved in the N-H···O hydrogen bonds with the same oxygen atom of one of the nitro groups. These hydrogen bonds connect the ions in 1b into the complex which is the principal building block of the structure. In 2b the [CuL2]2+ counterions are present; the Cu is octahedrally coordinated by all nitrogen iatoms of two L molecules which are therefore almost perpendicular to each other. The electrostatic interactions between the charged species are in both cases the main driving force of the crystal packing.