Structural characterization and photophysical properties of a luminescent trinuclear zinc(II) complex exhibiting multiple coordination geometries

Abstract

A luminescent trinuclear zinc(II) complex, tris(μ-2,3-toluenedithiolato)-1:2κ²S¹;1:2κ²S^1′, 2:3κ²S²;3κS^2′, 1:3κ²S³;3κS^3′-bis(2,2′-bypyridine)-1κ²N,N′,2κ²N,N′-trizinc, containing 3,4-dimercaptotoluene (tdt) and 2,2′-bipyridine (bpy) has been synthesized and found to have the trinuclear formulation Zn₃(tdt)₃(bpy)₂ (I). The complex crystallizes in the monoclinic space group P2₁/n with a = 11.7247(12), b = 20.134(2), c = 17.7376(18) Å and β = 103.743(2)^∘. The complex has two heteroleptic zinc(II) centers exhibiting similar distorted trigonal bipyramidal geometries with the third homoleptic zinc(II) center displaying a flattened tetrahedral geometry. Present in the solid state are both intra- and intermolecular π–π interactions. The complex is emissive at 77 K in the solid state with an emission maximum at 574± 2 nm with a luminescence lifetime of 7.4± 0.4 ns. The unstructured emission is assigned as a metal-mediated ligand-to-ligand π–π^* charge transfer transition.