Modulation on terahertz absorption properties in Ln^III–[Ag^I(CN)₂] networks

Molecular materials are playing a pivotal role in the advancement of prospective THz technologies. Herein, we have prepared nine isostructural coordination complexes of general formula [Ln^III(H₂O)₃][Ag^I(CN)₂]₃ (LnAg, Ln = La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, and Dy). Vibrational spectroscopy has unveiled gradual changes in the ν(C≡N) stretching frequencies within both infrared (IR) and Raman spectra from LaAg to DyAg, stemming from incremental alterations in crystallographic unit cell parameters and volumes. Similarly, the THz spectra manifest pronounced absorption signals between 1.0 to 1.2 THz, which can be judiciously tuned by varying lanthanide(III) ion and measurement temperature. Ab initio density-functional theory (DFT) calculations of THz spectra elucidate the primary contribution from opposite translational vibrations of Ag atoms and O atoms from H2O around Ln(III) atoms. Furthermore, thin films of LnAg can achieve a large return loss in a broad bandwidth in impedance-matching simulations.