Metal coordination study at Ag and Cd sites in crown thioether complexes through DFT calculations and hyperfine parameters

Abstract

Structural and electronic properties of [C₁₂H₂₄S₆X], [C₁₃H₂₆S₆OX], and [C₁₄H₂₈S₆OX] (X: Ag⁺, Cd²⁺) crown thioether complexes were investigated within the framework of the density functional theory (DFT) using the projector augmented wave (PAW) method. The theoretical results were compared with time-differential perturbed γ-γ angular correlations (TDPAC) experiments reported in the literature using the ¹¹¹Ag→¹¹¹Cd probe. In the case of X=Ag⁺, a refinement of the structure was performed and the predicted equilibrium structures compared with available X-ray diffraction experimental data. Structural distortions induced by replacing Ag⁺ with Cd²⁺ were investigated as well as the electric-field gradient (EFG) tensor at the Cd²⁺ sites. Our results suggest that the EFG at Cd²⁺ sites corresponds to the Ag⁺ coordination sphere structure, i.e., before the structural relaxations of the molecule with X=Cd²⁺ are completed. The results are discussed in terms of the characteristics of the TDPAC ¹¹¹Ag→¹¹¹Cd probe and the time window of the measurement, and provide an interesting tool with which to probe molecular relaxations.