Computation of the IR bands in polyimide films containing holmium and gadolinium

Polymers containing lanthanide ions have recently been studied as potential magnetic shielding materials for the electronics industry. It was the objective of this dissertation to investigate how lanthanide ions are bonded to the host polymer matrix in these systems using an ab initio method to simulate IR spectra. Holmium(III) and gadolinium(III) ions were used in this study to anticipate the future modeling of magnetic materials that require the high number of unpaired spins or high magnetic susceptibility these ions afford. Lanthanide-laden polyimide films were made using Pyre-M.L. and Syntorg IP608; Pyre-M.L. is the uncyclized polyamic-acid precursor to Kapton R and provided the maximum opportunity for lanthanide chelation. In contrast, Syntorg IP608 is a fully imidized polymer, very similar in structure to KaptonR, and served only as a physical carrier for lanthanide ions.; To probe the speciation of the lanthanide environment in these systems, the coordinating ability of the host polyimides for the Ho(III) and Gd(III) ions was investigated by FTIR down to 50 cm−1 and by ab initio modeling of the chelation site in the polymer. For the Pyre-M.L. systems, mid-range IR showed that a minimum of 10% of the sites had reacted and that complexation at the carboxyl groups of the non-imidated sites involved at least bidentate coordination. A comparison of the experimental far IR spectra to simulated IR, computed by the ROHF/SBKJC method in GAMESS, revealed that the speciation of the Ln(III) in the host is a mixture of bi- and tridentate chelation, with a possible coordination number of eight.; In addition to the polymer models, simple carboxylate and β-diketonate complexes of the lanthanides were modeled to lend validation to the complexed polymer results. The bond lengths and simulated IR spectra of LnCl₃ salts were also computed and found to be in nearly quantitative agreement with experiment.; Other analytical methods applied to the films were microanalysis, magnetic circular dichroism, magnetic susceptibility and compleximetric titration. Based on the shielding tests and the type of binding discovered through these analytical techniques, suggestions were made to improve the synthetic pathway in for the production of optically transparent materials of higher magnetic permeability.