Solvent free synthesis and spectral analysis of 2,4-dimethyl-6-(1-phenyl-1H-benzimidazol-2-yl)phenol: on/off fluorescence, inter and intramolecular hydrogen bonding

Abstract

2,4-dimethyl-6-(1-phenyl-1H-benzimidazol-2-yl)phenol (DPBP) has been prepared and characterized by ¹H NMR, ¹³C NMR, mass spectral studies and elemental analysis. DPBP shows On/off fluorescence system (fluorescence enhancing and quenching) by tuning with Fe³⁺ metal ion and H₃PO₄. Addition of Fe³⁺ ions into DPBP results in quenching of fluorescence. Other cations, including Zn²⁺, Ni²⁺, Pb²⁺, Ca²⁺, Co²⁺, Cd²⁺ and Mg²⁺ had little effect in the fluorescence intensity. The addition of H₃PO₄ with Fe³⁺-DPBP complex results in the enhanced fluorescence due to the detachment of Fe³⁺-DPBP complex. Dual emission has been observed by DPBP in non-polar solvent medium whereas single emission was observed in polar solvents due to Intra and Intermolecular hydrogen bonding respectively. Shorter wavelength emission of DPBP is due to enol rotamer and longer wavelength emission of DPBP is due to keto rotamer.

Keywords:

• Fe³⁺-DPBP complex
• intra-intermolecular hydrogen bonding
• dual emission
• on/off fluorescence

Declaration of interests

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.