Synthesis, crystal structure, thermal decomposition, and XPS studies of homo and heterotrinuclear Cu(II)–Cu(II)–Cu(II) and Cu(II)–Ni(II)–Cu(II) complexes obtained from salpn type ligands

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In this study, a mononuclear CuL complex was prepared by the use of bis-N,N′-(salicylidene)-1, 3-propanediamine (LH₂) and Cu²⁺ ion. NiCl₂ and NiBr₂ salt were treated with this complex in dioxanewater medium and two new complexes [(CuL)₂NiCl₂(H₂O)₂] and [(CuL)₂NiBr₂(H₂O)₂)] with Cu(II)–Ni(II)–Cu(II) nucleus structure were obtained. In addition to this bis-N,N′-(2-hydroxybenzyl)-1,3-diaminopropane (L^HH₂) was prepared by the reduction of LH₂ with NaBH₄ in MeOH medium. The treatment of this reduced complex with Cu²⁺ ion resulted a complex [(CuL^H)₂CuCl₂] with a structure of Cu(II)–Cu(II)–Cu(II). The complexes prepared were characterized by the use of elemental analysis, IR spectroscopy, thermogravimetric and X-ray diffraction methods. The crystal structures of [(CuL)₂NiBr₂(H₂O)₂] (СIF file CCDC 1448402) and [(CuL^H)₂CuCl₂] (СIF file CCDC 1448401) complexes were elucidated. It was found that halogen ions are coordinated to terminal Cu²⁺ ions which are in a distorted square pyramid coordination sphere. It was determined that the central Cu(II), which joins terminal square pyramidal Cu(II), was coordinated only by the phenolic oxygens of the ligand while the central Ni(II) was coordinated by two phenolic oxygens of the organic ligand and two water molecules. These complexes were investigated by XPS and it was found that the terminal and central Cu²⁺ ions were different in Cu(II)–Cu(II)–Cu(II) complex. Also, the thermal degradation of the CuLH complex unit was observed to exothermic in contrast to the expectations.