Synthesis of Novel Mononuclear Lanthanide (Ln³⁺) Complexes with Indole-3-acetic Acid Hormone, Their Structure and Properties Based on Spectroscopic and In Silico Studies

Abstract

New Gd³⁺, Ce³⁺, Sm³⁺, and Nd³⁺ complexes of indole-3-acetic acid hormone have been synthesized and analyzed by IR, Raman and UV-Vis spectra, XRD, analytical (elemental, EXD, SEM), and theoretical methods. IR spectra of complexes support eight (Gd³⁺ and Ce³⁺) and nine (Sm³⁺ and Nd³⁺) -fold coordinations via three ligands in their mononegative bidentate mode. Broadness in Raman spectrum of Ce³⁺ complex, reflects the possibility for its luminescence or conductivity features. UV-Vis spectra demonstrate weak intraconfigurational 4f–4f transitions within polyhedral geometry, which is known for such inner-transition ions. For most complexes, the optical band gap values have been calculated to be similar to that of the ligand, and the value calculated for Ce³⁺ complex is significantly low, which predicts its semiconductors-like feature. XDR patterns support nano-crystalline nature of HL complex with Sm³⁺. Hirshfeld contact surface has been obtained for two representative complexes (Gd³⁺ and Sm³⁺) by normalized contact distance d _norm, d_e, and d_i models. In-silico study based on drug-likeness software as well as MOE-docking approach have been carried out. Complexes of Gd³⁺ and Sm³⁺ probably can stimulate auxin hormone or raise its efficiency within a plant, which leads to favorable economic and positive results for plant wealth.