Dinuclear and tetranuclear complexes of copper coordinated by an anthracene-based new μ-bis(tridentate) ligand: Synthesis, structure, spectroscopy and magnetic properties. (15th October 2016)

• Record Type: Journal Article
• Authors: Haldar, Shobhraj; Patra, Ayan; Vijaykumar, Gonela; Carrella, Luca; Bera, Manindranath
• Is Part Of: Polyhedron. Volume 117(2016)
• Page Start: 542
• Page End: 551
• Publication Date: 2016-10-15
• Subjects: Anthracene-based ligand -- Copper complex -- X-ray structure -- Spectroscopy -- Magnetic properties; Chemistry, Inorganic -- Periodicals; Chimie inorganique -- Périodiques; Organometaalverbindingen; Anorganische chemie; 546.05
• DOI: 10.1016/j.poly.2016.06.028
• Languages: English
• ISSNs: 0277-5387

Abstract

Graphical abstract: Two new, a dinuclear and a tetranuclear copper complexes supported by an anthracene-based μ-bis(tridentate) ligand have been synthesized and characterized. In solution, the ligand shows excellent binding-cum-chelating ability towards copper(II) ions and the binding events have been evaluated by a combined approach of UV–Vis and fluorescence spectroscopic techniques. The UV–Vis and fluorescence titration spectra confirm the 1:2 binding model between the ligand and copper(II) which have been further supported by single crystal X-ray structures of the complexes. Variable-temperature (2–300 K) magnetic susceptibility measurements of the tetranuclear complex reveal that the copper centers are antiferromagnetically coupled. Abstract: Copper(II) complexes of an anthracene-based new μ-bis(tridentate) ligand, N, N ′-bis[anthracene-2-ylmethyl]- N, N ′-bis[carboxymethyl]-1, 3-diaminopropan-2-ol (H3 acdp) with mixed donating groups, have been studied in solid state as well as in solution. The reaction of stoichiometric amounts of CuSO4 ·5H2 O and the ligand H3 acdp in the presence of NaOH at ambient temperature in methanol-dichloromethane, afforded a new dinuclear copper complex, [Cu2 (acdp)(MeO)(MeOH)2 ] (1 ). On the other hand, the reaction of stoichiometric amounts of Cu(OAc)2 ·H2 O and the ligand H3 acdp in the presence of NaOH at ambient temperature in methanol-dichloromethane yielded, a novel tetranuclear copper complex, [Cu4 (acdp)2 (μ-OAc)2 (MeOH)2 ]·2CH2 Cl2 ·2CH3 OH (2 ). Characterization of the complexes has been carried out by various analytical techniques including single crystal X-ray crystallography. The X-ray structure analyses show that the complex1 consists of a distorted square planar copper center and a distorted square pyramidal copper center with Cu⋯Cu separation of 3.589(4) Å, whereas the complex2 comprises four distorted square pyramidal copper centers with average intra-ligand Cu⋯Cu separation of 3.358(6) Å. The molecular architecture of complex2 is built from the self-assembly of two neutral [Cu2 (acdp)(μ-OAc)] units which are exclusively bridged by two carboxylate functionalities of the ligand. To be acquainted with the binding events of copper(II) ions with H3 acdp and the structural features of the complexes in solution, UV–Vis and fluorescence titration experiments have been executed. The composition of the acdp 3− /Cu 2+ complexes in1 and2 has been found to be 1:2, based on the UV–Vis/fluorescence titration results and further confirmed by X-ray crystallography. Variable-temperature (2–300 K) magnetic susceptibility measurements on powdered microcrystalline samples show that the paramagnetic copper centers in complex2 are antiferromagnetically coupled to one another.