Sulfate‐Bridged Dimeric Copper(II) Complexes with Three‐Dimensional Network: Synthesis, Structure and DFT Studies

Abstract

The 1:1 reaction of the diacetyl monoxime‐2‐pyridyl hydrazone HL1 (1) and the pyridine‐2‐carboxaldehyde‐2‐imidazoline hydrazone hydrobromide HL2 (2) with copper(II) sulfate pentahydrate in methanol affords a series of new sulfate‐bridged dimeric copper(II) complexes, [CuII2(HL1)2(μ‐SO4)2]·4H2O (1a) and [CuII2(HL2)2(μ‐SO4)Br2]·2H2O (2a), respectively. The room temperature magnetic moments of the complexes 1a and 2a are 1.82 μβ and 1.84 μβ, respectively. The bands appearing in the UV region (200–340 nm) are characteristic of the ligands HL1 (1) and HL2 (2). In complexes 1a and 2a, these ligand centred bands are accompanied by multiple bands extending into the visible region (370–480 nm). The association constant (Kass, UV/Vis) was found to be (1.120 ± 0.002) × 105 for 1a and (1.196 ± 0.002) × 104 for 2a at 298 K determined using UV/Vis spectroscopy. On excitation at 285 nm, ligand 1 emits strongly in the 364 nm region due to an intraligand 1(π–π*) transition. Upon complexation with copper(II), the emission peak is slightly blue shifted (354 nm, F/Fo 0.89) with a little quenching in the emission intensity as expected for divalent copper. Complexes 1a and 2a exhibit two consecutive oxidation couples for two copper(II) centres in deionised distilled water under a nitrogen atmosphere. DFT and TDDFT calculations were performed and the results are highly consistent with the spectroscopic behaviour of the complexes. The molecular structures of dinuclear 1a (Cu···Cu 4.555 Å) and 2a (Cu···Cu 6.106 Å) have been determined by single‐crystal X‐ray diffraction studies.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)

Three copper complexes containing the sulfur-bridged bis-pyridine ligands, 2,2′-dithiodipyridine and di-2-pyridyl sulfide

“…The single-crystal X-ray structural analysis revealed that 1 crystallized in the triclinic space group P-1, and the asymmetric unit consists of one Cu, one dps, one coordinated SO 2À 4 , one coordinated water, and two lattice waters. The Cu 2+ cation exhibits a slightly distorted square pyramidal geometry [22], contains the same μ-SO 2À 4 ligand, but the Cu 2+ cation located in a more distorted square-pyramidal geometry, and the Cu···Cu distance (4.555 Å) is shorter than that in 1. Copper complexes with sulfur-bridged bis-pyridine 3181…”

Effect of Nanospace Confinement on the Catalytic Activity and Stability of a Chiral Schiff Base Complex (CuL; L=C22H24N2O4): A Combined Experimental and Theoretical Study

“…The angle aO1-Cu2-O2 in the dimeric complex is also larger than its experimental value by approximately 7 8. [38] The HOMO and LUMO orbitals of the three complexes are shown in Figure 8. The HOMO and LUMO of each complex are mostly concentrated on the aromatic p moiety of the ligand system.…”

A new chromogenic agent for iron(III): Synthesis, structure and spectroscopic studies

“…29,30 2.4b Synthesis of [Fe III (HL) 2 ]Cl 3 , 1a: To a stirred methanolic solution of anhydrous iron(III) chloride (0⋅03 g, 0⋅2 mmol) was added a solution of HL, 1, (0⋅03 g, 0⋅4 mmol) in methanol (5 ml) and the resulting reddish-pink solution was stirred for 0⋅5 h. The solvent was evaporated by rotary evaporator and recrystallized from methanol. Yield.…”

“…The association constant (K ass ) of complexes can be estimated spectrophotometrically (figure 1) according to the (1), 29,31 where X represents the absorption intensity, X lim represents the absorption intensity at full complexation, C 0 is the initial concentration of the ligand, C H and C G are the corresponding concentrations of the ligand and metal ion during titration. The K ass (UV-Vis) was found to be (6⋅4865 ± 0⋅004) × 10 5 for 1a which was higher than 1b (K ass (UV-Vis) 1⋅1960 ± 0⋅002) × 10 5 ) at 298 K.…”