Square planar Pd(II) complexes derived from 1-ethyl-3-phenylthiourea, 3-mercapto-4-methyl-1,2,4-triazole and 2-mercapto-5-methyl-1,3,4-thiadiazole: Syntheses, spectral, structural characterization and photoluminescence properties

• [Pd(eptu)2] (1), [Pd(Hmmtrz)4]Cl2 (2) and [Pd(Hmthd)4]Cl2·2CHCl3 (3) are reported.
• In all compounds the metal ion adopts a square planar geometry.
• Pd(II) is bonded through two N and two S atoms from two Heptu ligands in complex 1.
• In complexes 2 and 3, Pd(II) centre is bonded through four thione S of Hmmtrz/Hmthd.
• Complexes 1–3 are fluorescent materials.
• The structures of complexes are stabilized by various types of hydrogen bonds.

The reaction of PdCl2 with 1-ethyl-3-phenyl-thiourea (Heptu), 3-mercapto-4-methyl-4H-1,2,4-triazole (Hmmtrz) and 2-mercapto-5-methyl-1,3,4-thiadiazole (Hmthd) respectively, yielded three new complexes [Pd(eptu)2] (1), [Pd(Hmmtrz)4]Cl2 (2) and [Pd(Hmthd)4]Cl2·2CHCl3 (3). These complexes have been isolated in pure form and characterized by elemental analyses, IR, NMR and single crystal X-ray diffraction technique. In all compounds the metal ion adopts a square-planar geometry. Two nitrogen and two sulfur atoms from the monoanionic eptu ligand in complex 1 are bonded to Pd(II) centre in trans fashion. Complexes 2 and 3 are salt-like and the metal centre is bonded through four neutral ligands. The electrical neutrality in these complexes is maintained by the presence of two chlorides as counter ions. Migration of hydrogen, within the ligand framework in complexes 2 and 3, from sulfur to nitrogen is observed that resulted in the thione form of the ligand and its coordination to the metal centre in both the complexes. Complex 2 is stabilized by intermolecular CH⋯N and intramolecular NH⋯Cl hydrogen bonding leading to an extended structure. Complex 3 is stabilized by intermolecular CH⋯S hydrogen bonding. Complexes 1–3 are fluorescent materials which upon excitation at 31 000, 38 600 and 32 300 cm−1 exhibit an emission at 25 200, 27 000 and 26 700 cm−1, respectively.

Three new complexes, [Pd(eptu)2] (1), [Pd(Hmmtrz)4]Cl2 (2) and [Pd(Hmthd)4]Cl2·2CHCl3 (3) derived from 1-ethyl-3-phenyl-thiourea, 3-mercapto-4-methyl-4H-1,2,4-triazole and 2-mercapto-5-methyl-1,3,4-thiadiazole are reported. Complexes 1, 2 and 3 are fluorescent materials which upon excitation at 31 000, 38 600 and 32 300 cm−1 exhibit an emission at 25 200, 27 000 and 26 700 cm−1, respectively.Figure optionsDownload as PowerPoint slide