Solid State Complex Chemistry: Formation, Structure, and Properties of Homoleptic Tetracyanamidogermanates RbRE[Ge(CN₂)₄] (RE = La, Pr, Nd, Gd)

Tetracyanamidometallates with the general formula RbRE­[T­(CN₂)₄] (RE = La, Pr, Nd, Gd; T = Si, Ge) were prepared by solid state metathesis reactions starting from stoichiometric mixtures of RECl₃, A₂[TF₆], and Li₂(CN₂). Reactions were studied by differential thermal analysis that showed ignition temperatures between 360 and 390 °C for the formation of RbGd­[T­(CN₂)₄] with T = Si and Ge. The powder diffraction patterns of RbRE­[Ge­(CN₂)₄] were indexed isotypically to the already known RbRE­[Si­(CN₂)₄] compound. IR spectra of RbLa­[Ge­(CN₂)₄] were measured and compared with those of RbLa­[Si­(CN₂)₄]. ⁷³Ge, ⁸⁷Rb, and ¹³⁹La solid state NMR measurements and density functional theory calculations were used to verify the novel homoleptic [Ge­(CN₂)₄]^4– ion. Luminescence properties of Eu³⁺, Ce³⁺, and Tb³⁺ doped samples are reported