title: Influence of molecular structure on the photoluminescence of 2-methyl benzimidazolium picrate: a new fluorescent material.
abstract: This work reports the structural and photo luminescent characterization of the 2-methyl benzimidazolium picrate salt for the first time. This new material exhibits the π-π stacking of aromatic rings involving the benzimidazolium cation and picrate anion, which is additionally supported with a rare n→π interaction as well as with the extended networks of intermolecular hydrogen bonds in the solid state. The FT-IR and UV characterizations further support the solid state structural features of the salt. However, the spectroscopic results reveal that the stacking of ion pairs, which is observed in the solid state, is not maintained in solution. The DSC result indicates that the material is stable under ambient temperature conditions. Interestingly, upon photo excitation at 325 nm in the solid state, the material shows an unusual red emission around 615 nm, which is probably attributed to the supramolecular stacked nature of the ion pairs, along with a usual picrate centered green emission at 530 nm. However, the fluorescence measurement in solution, wherein the stacking of ion pairs are not maintained, shows only a single peak at lower wavelength. These observations highlight the influencing role of the supramolecular stacking interactions on the photoluminescence of the material, due to which, a chemical sensing action may be envisaged.
authors.affiliation: Department of Chemistry and Applied Chemistry, PSG College of Technology, Coimbatore 641 004, India.
authors.forename: M
authors.initials: M
authors.lastname: Obulichetty
authors.forename: D
authors.initials: D
authors.lastname: Saravanabharathi
mesh_terms: D001562:Benzimidazoles / Q000737:chemistry*; D018360:Crystallography, X-Ray; D005456:Fluorescent Dyes / Q000737:chemistry*; D008745:Methylation; D008958:Models, Molecular; D010851:Picrates / Q000737:chemistry*; D017550:Spectroscopy, Fourier Transform Infrared
chemical_list: D001562:Benzimidazoles; D005456:Fluorescent Dyes; D010851:Picrates; C005858:picric acid
keywords: 2 – Methyl benzimidazolium picrate; Ion pairs; Photoluminescence; Supramolecular stacking; X –ray structure