Palladium(II) complexes with 1,2,4-triazole derivative & ethylene diamine as ligands, synthesis, characterization, luminesence study & crystal structure determination

چکیده مقاله

Complexes [Pd(aemptrz)Cl₂] (1) and [Pd₂(μ-mptrz)₂(mptrz)₂(en)]·CH₃OH (2) (where aemptrz is 1‐(1‐(λ²‐azanyl)ethyl)‐4‐methyl‐5‐(λ¹‐sulfanyl)‐4H‐1λ⁴,2,4‐triazole, mptrz is 4-methyl-4H-1,2,4-triazole-3-thiolato and en is ethylene diamine) were synthesized by the reaction of 4-methyl-4H-1,2,4-triazole-3-thiol (Hmptrz) (1) or a mixture of (Hmptrz) and ethylene diamine (2) with PdCl₂. Complexes [Pd₂(μ-mptrz)₄] (3) and [Pd₂(μ-mptrz)₂(mptrz)₂(en)] (4) were obtained by similar methods, but using Pd(OAc)₂ instead of PdCl₂. The four complexes were thoroughly characterized by elemental analysis, IR, UV–Vis, ¹H NMR, luminescence spectroscopy as well as single-crystal X-ray diffraction method. Central Pd(II) ions in 1 are tetra-coordinated by two chloride atom in the cis-positions, one sulfur atom and one nitrogen atom to form PdNSCl₂ coordination sphere, presenting slightly distorted square planar geometry around Pd atom. In complex 2, the Pd1 atoms are coordinated to four triazole units via four Pd–S bond (PdS₄ square-plane) and the Pd2 atoms are coordinated to two of these triazole units together with the two N atoms of ethylene diamine ligand (PdN₄ square-plane). In complex 3 the two Pd(II) centers are connected together by four bridging triazole ligands providing a paddle wheel-like arrangement. The Pd1 atom in complex 4 has a square-planar coordination involving the S atoms from four mptrz⁻ ligands (two terminals and two bridged triazole) and the Pd2 atom is coordinated by two nitrogens of ethylene diamine and two nitrogens of the two bridged triazole ligand. Complex 1 has τ₄ value (the geometric parameter) of 0.043, which fits with a slightly distorted square planar geometry. Considering the Pd⋯Pd contact, the stereochemistry of the palladium(II) ion in 2, 3 and 4 suggest a distorted square pyramid with a geometrical factor τ₅ = 0.042, 0.013 and 0.040, respectively. The luminescence properties of the free ligand as well as the complexes 1–4 were investigated in solution. © 2017 Elsevier Ltd