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A square-pyramidal complex [CuII(L)(O2CMe)(H2O)] 1 (HL = 2–[N–(2–phenylazo)carbamoyl]pyridine) has been synthesized using a tridentate deprotonated arylazo-appended pyridine-2-carboxamide ligand. Aerobic reactions of 1 with para-substituted anilines in neat condition at 120 °C afforded isolation of its ortho-arylaminated products [CuII(L−N−C6H4−p−X)] (X = H 2, Me 3, OMe 4, F 5 and Cl 6). The starting brown complex 1 and arylaminated violet complexes 2−6 have been structurally characterized. The electronic spectral feature and redox properties of 1−6 have been examined. Along with CuII/CuI redox, azo-centered cathodic responses were also observed. For 2–6, a characteristic oxidative response due to Cu(II)-coordinated amine oxidation has been observed, modulated by ligand substituents. A linear correlation between the redox potential values of the arylaminated products 2–6 and the Hammett substituent constant σ p for para-substituted anilines has been obtained, to rationalize the proposed mechanistic pathways of the observed ortho-fusion reaction. Density functional theory (DFT) at the B3LYP level and time-dependent (TD)-DFT calculations have allowed to rationalize the experimental results and to interpret the observed electronic transitions, respectively. |
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