Experimental and computational insights of the new hybrid organic–inorganic compound (C6H9N2)2CdI4 for advanced optoelectronic applications and biological activities

Abstract

This study reports on the synthesis, structural elucidation, and property investigation of the hybrid organic–inorganic compound (C₆H₉N₂)₂CdI₄, which is composed of 2-amino-5-picolinium cations and discrete cadmium tetraiodide anions. The compound was synthesized using a solution-based method, and its crystal structure was determined through single-crystal X-ray diffraction, revealing a triclinic system with the space group P. Structural analysis shows that the isolated [CdI₄]²⁻ tetrahedra are embedded within the crystal matrix and stabilized by an extensive hydrogen-bonding network formed with the protonated organic cations. Scanning electron microscopy (SEM) revealed a densely agglomerated morphology characterized by irregularly shaped grains. Raman spectroscopy provided insights into the vibrational characteristics. Optical absorption measurements exhibited a pronounced π → π* transition at 307 nm, attributed to the aromatic nature of the organic cation, while the absence of low-energy d–d transitions aligns with the closed-shell electronic configuration of Cd²⁺. Noncovalent interaction analyses based on NCIPLOT and Multiwfn, supported by density functional theory (DFT) calculations, highlighted the key role of hydrogen bonding and van der Waals interactions in stabilizing the crystal lattice and governing molecular packing. Thermal behavior investigated by thermogravimetric and differential scanning calorimetry (TGA/DSC) demonstrated high thermal stability of the compound up to approximately 350 °C. In addition, in vitro antioxidant assays revealed significant activity, with DPPH radical scavenging efficiency reaching about 60% at 1 mg ml⁻¹ and a strong Fe³⁺ reduction capability, indicating effective electron-donor behavior. These combined experimental and theoretical results establish clear structure–property relationships and suggest that (C₆H₉N₂)₂CdI₄ is a promising multifunctional material, offering potential for optoelectronic applications as well as emerging biomedical relevance.