Tuning emissive color of trivalent terbium ion through environmental factors: optoelectronic insights from theoretical, spectral and computational studies

Abstract

The combination of 4,4,4-trifluoro-1-phenyl-1,3-butanedione (TFPB) and pyrazine (pyz) with Tb³⁺ ions forms two distinct types of complexes, represented by the formulas [Tb(TFPB)₃(L)₂], where L is either H₂O or pyz, and [(Tb(TFPB)₃)₂pyz]. A detailed examination of the impact of the surrounding environment on the photophysical properties of these synthesized complexes was conducted. Photoluminescence (PL) analysis indicated that the magnetic dipole transition (⁵D₄ → ⁷F₅) is dominant in Tb(III)-based systems. The prepared complexes exhibit visible luminescence in both solid and solution media. Remarkably, the luminescence intensity of the mononuclear complex is significantly higher than that of its dinuclear counterpart, highlighting the impact of efficient energy transfer on emission intensity. The CIE color coordinates of these complexes in solution closely align with NTSC standard values. Additionally, modulation of emissive color is evident when the surrounding media (from solid to solution) and solvent nature are altered. Density Functional Theory (DFT) calculations were performed to elucidate the electronic density distribution in the synthesized complexes. Additionally, a comprehensive analysis, including IR, UV, NMR, thermogravimetry and cyclic voltammetry, was conducted, along with theoretical calculations using Judd–Ofelt analysis.