The new sulphur-containing ligand 4′-(4-methylthiophenyl)-3,2′:6′,3″-terpyridine (L1) and the supramolecular structure of the dinuclear complex [Zn2(μ-L1)(acac)4] (acac = acetylacetonato): The key role of non-covalent S⋯O contacts and C–H⋯S hydrogen bonds

The new terpyridyl ligand 4′-(4-methylthiophenyl)-3,2′:6′,3″-terpyridine (L1) combines with Zn(acac)2 to form the dizinc complex [Zn2(μ-L1)(acac)4] (1) (acac = acetylacetonato). The single crystal structure of 1 shows the existence of two different Zn(acac)2 centres bridged by the L1 ligand through its two 3-pyridyl-nitrogen atoms. The acac and L1 ligands allow the generation of a series of intra- and intermolecular hydrogen bonds of the C–H⋯N, C–H⋯O and C–H⋯π type. In addition, the presence of the CH3–S group in L1 plays a crucial role by providing the non-covalent S⋯O, S⋯H and H(CH3)⋯O contacts, which permit to describe fully this unusual supramolecular network. The NMR spectra of 1 in CDCl3 solution confirm the presence of the two zinc atoms joined by the bridging L1 ligand, but, differently to the solid state, their environments are identical.

► L1 acts as bridge in [Zn2(μ-L1)(acac)4] (1) only using its 3-pyridyl N-atoms.
► The supramolecular structure of 1 involve S⋯O and S⋯H contacts.
► The environment of the two Zn atoms of 1 are different in the solid state.
► In CDCl3 solution the environment of the two Zn atoms in 1 are equivalent.
► The weak interactions are used to explain the solid-state/solution differences in 1.