Crystal structure, computational study, optical and vibrational properties of a new luminescent material based on bismuth(III): (C10H28N4)[Bi2Cl10

Abstract

Development of new Bi-based perovskites with various structures offers considerable potential for lead-free solar cells and other optoelectronic devices as they retain the high-performing properties of halide perovskites with high power conversion efficiency and improved long-term and environmental device stability. This work addresses the study of a new chlorobismuthate(III) hybrid compound with the chemical formula (C10H28N4)[Bi2Cl10], prepared at room temperature by the slow evaporation method. The resulting crystals were investigated using Single Crystal X-ray diffraction, which gave an accurate crystal structure determination that allows searching the role played by intermolecular contacts in the self-assembly of the crystal structure using Hirshfeld surface analysis. The compound was additionally characterized using FTIR and Raman spectroscopies correlated by Ab-initio calculations at different levels of theory. The optical study supports the strong absorption of the compound in the visible region showing its luminescent character with emission peaks falling in the blue and near green regions. Natural bond orbital (NBO) calculations suggest a high stability of the new hybrid material attributed to energetically electronic transitions of [Bi2Cl10]4- anion that probably support its interesting optical properties. The shifting of stretching modes assigned to N–H groups belonging to the piperazine ring of the compound toward lower wavenumbers confirms well the interactions observed by NBO calculations between Cl atoms of the anion with these groups. The Raman bands detected below 300 cm−1 were found in perfect agreement with the characteristic of isolated Bi2Cl10 anion, made up of two [BiCl52−] units. The TG-DTA analysis revealed the high stability of the compound and its decomposition at 280°С. Frontier orbital studies showed the gap values of the new hybrid and its low reactivity. Probably, the inert mapped molecular electrostatic potential (MEP) surface predicted on the new material could support its high stability and low reactivity. The complete assignments for this compound in comparison with the organic and inorganic species are also presented. HF/Lanl2dz calculations in n-hexane solution have evidenced an increase in the reactivity of the hybrid and changes of positions and intensities of IR bands, attributed to NH3, NH and CH2 stretching modes, as a consequence of interactions of the anion with those groups belonging to the cation.