Preparation and Properties of Stereospecific Coordination Polymers by the Monomolecular Film Method

Abstract

In order to obtain stereospecific coordination polymers, the monomolecular film method was employed at the air/water interface. In order to predict the possibility of the succession, ΔH^Θ, ΔG^Θ for tr ans→cis transformation was estimated from the infrared spect ra change of a free ligand, N, N'-didodecyldithiooxamide [(C₁₂H₂₅)₂dtoaH₂]. The transformation en ergy, 10 kJ.mol^-1, is smoller than the hydrophobic energy of the dodecyl chain. that is, the attempt to prepare the stereospecific polymers at the interface seems to be reasonable. The gathered films of the coordination polymers, (R₂dtoaCu), from a wide (air/copper aqueous solution) interface of the trough were subjected to the futher series of measurements: CHN analyses, IR spectra, magnetic susceptibility, electric conductivity, and differential thermal analysis. The results were discussed in comparison with those fro m the corresponding specimen prepared by an ordinary method of mixing bulk solut ions of the components as follows where R=C₆H₅CH₂, cyclo-C₆H₁₁ C₁₂H₂₅ and C₁₂H₂₅OCOCH₂. 1. the molar ratio of ligands to Cu²⁺ ion in the four coordination polymers of film type was found to be the same as that in the preparation by the bulk type, 2. in the films some IR peaks (860 and 870 cm^-1) which are related to CS stretching of the trans-form in the bulk type specimens with C₁₂H₂₅ or C₁₂H₂₅OCOCH₂ substituents (Figs.2C and 2D)are disappeared, 3. the two substituents of compounds described above are more hydrophobi c than the other two, 4. the results of magnetic measurements suggest their cis-form in the hydrophobic couple of the coordination polymers (Figs.3 C and 3 D).