Spectrophotometric and Thermal Studies of the Reaction of Iodine with Nickel(II) Acetylacetonate

The reaction of iodine (acceptor) and nickel(II) acetylacetonate (donor) was studied photometrically in different solvents such as chloroform, dichloromethane and carbon tetrachloride at room temperature. The results indicate the formation of a 1: 1 charge-transfer complex in each solvent and the iodine complex is formulated as the triiodide species [Ni(acac)2]2I+.I3-, based on the characteristic electronic absorptions of the I3- ion at 361 and 285 nm, as well as on the far infrared absorption bands characteristic of the I3- ion with C2v symmetry. These bands are observed at 132, 101 and 84 cm-1 and are assigned to na(I-I), ns(I-I) and d(I3-), respectively. The values of the equilibrium constant (K), absorptivity (e) and oscillator strength (f) of the iodine complex are shown to be strongly dependent on the type of solvent used. The important role played by the solvent is suggested to be mainly due to the interaction of the ionic complex with the solvent. The proposed structure of the new solid triiodide charge-transfer complex reported in this study is further supported by thermal and mid-infrared measurements. (South African Journal of Chemistry: 2003 56: 10-14

Preparation, spectroscopic and structural studies on charge-transfer complexes of 2,9-dimethyl-1,10-phenanthroline with some electron acceptors

Charge-transfer (CT) complexes formed in the reactions of 2,9-dimethyl-1,10-phenanthroline (Me2phen) with some acceptors such as chloranil (Chl), picric acid (HPA) and chloranilic acid (H2CA) have been studied in the defined solvent at room temperature. Based on elemental analysis and infrared spectra of the solid CT-complexes along with the photometric titration curves for the reactions, obtained data indicate the formation of 1:1 charge-transfer complexes [(Me2phen)(Chl)] (1), [(Me2phenH)(PA)] (2) and [(Me2phenH)(HCA)] (3), respectively, was proposed. In the three complexes, infrared and 1H NMR spectroscopic data indicate a charge-transfer interaction and as far as complexes 2 and 3 are concerned this interaction is associated with a hydrogen bonding. The formation constants for the complexes (KC) were shown to be dependent upon the nature of the electron acceptors used. The X-ray structure of complex 3 indicate the formation of dimeric units [Me2phenH]2[(HCA)2] in which the two anions (HCA)− are connected by two O–HO hydrogen bonds whereas the cations and anions are joined together by strong three-center (bifurcated) N–HO hydrogen bonds. Furthermore, the cations are arranged in a π–π stacking