名称:
ESR and pH-potentiometric study of the mixed–ligand complex formation in the copper(II)–4-fluorosalicylic acid–N,N-diethylnicotinamide system: Structure and spectral properties of [Cu(4-fluorosalicylate)2(N,N-diethylnicotinamide)2(H2O)2] complex
摘要:
EPR simulation method together with pH-potentiometry combined with UV-Vis spectrophotometry were used for the study of the ternary system 4-fuorosalicylic acid (HA)-N,N-diethylnicotinamide (B)-copper(II) in aqueous solution. The N,N-diethylnicotinamide ligand is a weak donor, its mixed-ligand complexes with 4-fluorosalicylate anions are more favoured. The number of coordinated N,N-diethylnicotinamide molecules increases with decreasing temperature: up to four ones were detected in the coordination sphere of copper(II) in frozen solutions. The formation of [CuH(-1)AB(2)] and [CuH(-1)A] was detected by all methods at neutral pH. At lower pH values, [CuA(2)B(2)] and [CuB] become dominant, and this fact is in good agreement with [CuA(2)B(2)(H2O)(2)] crystals obtained from similar solutions. The structural unit of the [CuA(2)B(2)(H2O)(2)] complex consists of a copper(II) ion, which is monodentately coordinated by a pair of 4-fluorosalicylate anions and by a pair of N,N-diethylnicotinamide in trans positions in the basal plane, and by two water molecules in the axial positions of a tetragonal bipyramid. (C) 2011 Elsevier Ltd. All rights reserved.