Optical Investigation of a Non-Centrosymmetric Tetrachlorocobaltate (II) Hybrid, in the Presence of Two Distinct Pyridine Molecules

A novel compound, (C₆H₅N₂)(C₆H₇N₂O)[CoCl₄], crystallizes in the non-centrosymmetric space group (Cc). It displays a unique arrangement resulting from the presence of two distinct monoprotonated organic molecules (C₆H₅N₂)⁺ and (C₆H₇N₂O)⁺, as well as isolated tetrachlorocobaltate (II). The cohesion between these organic and inorganic edifices is ensured by the presence of hydrogen bonds and π-π interactions, which are analyzed in more detail by Hirshfeld surface analysis. This paper also presents experimental results from FT-IR and Raman spectroscopy, discussing the vibrational modes of the different groups present in this compound. Additionally, the article includes a theoretical analysis using density functional theory DFT calculations.

The optical study, by UV–Visible absorption, shows a wide band gap exceeding 2.00 eV. The significant β value indicates that the new compound is a promising material for non-linear optical devices. When excited with 375 nm light, the system exhibits bright yellow and orange emissions in aggregated states, which effectively serve as building blocks of white light. This emission, located approximately in the saturated white light region, corresponds to CIE chromaticity coordinates of (0.3978, 0.4178).