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 |
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Authors: | Terézia Szabó-PlánkaJán Moncol Eszter TóthBéla Gyurcsik Nóra Veronika NagyZuzana Vasková Antal RockenbauerDušan Valigura |
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Institution: | a Department of Physical Chemistry and Materials Sciences, University of Szeged, Aradi vértanúk tere 1, Szeged H-6720, Hungary b Chemical Research Center, Institute of Structural Chemistry, Hungarian Academy of Sciences, Pusztaszeri út 59-67, H-1025 Budapest, Hungary c Department of Inorganic and Analytical Chemistry, University of Szeged, Dóm tér 7, Szeged H-6720, Hungary d Department of Inorganic Chemistry, Slovak Technical University, Radlinskeho 9, 812 37 Bratislava, Slovakia |
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Abstract: | 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−1AB2] and CuH−1A] was detected by all methods at neutral pH. At lower pH values, CuA2B2] and CuB] become dominant, and this fact is in good agreement with CuA2B2(H2O)2] crystals obtained from similar solutions. The structural unit of the CuA2B2(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. |
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Keywords: | Copper(II) complexes 4-Fluorosalicylic acid N N-Diethylnicotinamide Speciation Electron spin resonance pH-potentiometry Crystal structure |
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