Novel Copper(II) Complexes with Dipinodiazafluorene Ligands: Synthesis, Structure, Magnetic and Catalytic Properties.

The reactions of CuX (X = Cl, Br) with dipinodiazafluorenes yielded four new complexes [CuXL] (X = Cl (), Br (), L = (1R,3R,8R,10R)-2,2,9,9-Tetramethyl-3,4,7,8,9,10-hexahydro-1H-1,3:8,10-dimethanocyclopenta [1,2-b:5,4-b']diquinolin-12(2H)-one) and [(CuX)L]n (X = Cl (), Br (), L = (1R,3R,8R,10R,1'R,3'R,8'R,10'R)-2,2,2',2',9,9,9',9'-Octamethyl-1,1',2,2',3,3',4,4',7,7',8,8',9,9',10,10'-hexadecahydro-1,3:1',3':8,10:8',10'-tetramethano-12,12'-bi(cyclopenta [1,2-b:5,4-b']diquinolinylidene). The complexes were characterized by IR and EPR spectroscopy, HR-ESI-MS and elemental analysis. The crystal structures of compounds , and were determined by X-ray diffraction (XRD) analysis. Complexes - have a monomeric structure, while complex has a polymeric structure due to additional coordinating N,N sites in L. All complexes contain a binuclear fragment {Cu(μ-X)} (X = Cl, Br) in their structures. Each copper atom has a distorted square-pyramidal coordination environment formed by two nitrogen atoms and three halogen atoms. The Cu-N distance is elongated compared to Cu-N. The EPR spectra of compounds - in CHCN confirm their paramagnetic nature due to the d electronic configuration of the copper(II) ion. The magnetic properties of all compounds were studied by the method of static magnetic susceptibility. For complexes and , the effective magnetic moments are ≈ 1.87 and 1.83 (per each Cu ion), respectively, in the temperature range 50-300 K, which are close to the theoretical spin value (1.73 ). Ferromagnetic exchange interactions between Cu(II) ions inside {Cu(μ-X)X} (X = Cl, Br) dimers (/ ≈ 25 and 31 K for and , respectively) or between dimers (' ≈ 0.30 and 0.47 K for and , respectively) were found at low temperatures. For compounds and , the magnetic susceptibility is well described by the Curie-Weiss law in the temperature range 1.77-300 K with ≈ 1.72 and 1.70 for and , respectively, and weak antiferromagnetic interactions ≈ -0.4 K for and -0.65 K for ). Complexes - exhibit high catalytic activity in the oxidation of alkanes and alcohols with peroxides. The maximum yield of cyclohexane oxidation products reached 50% (complex ). Based on the data on the study of regio- and bond-selectivity, it was concluded that hydroxyl radicals play a decisive role in the oxidation reaction. The initial products in reactions with alkanes are alkyl hydroperoxides.