Synthesis of Strongly Fluorescent Imidazole Derivatives: Structure Property Studies, Halochromism and Fluorescent Photoswitching

  • Anu Kundu
  • Subramanian Karthikeyan
  • Dohyun MoonEmail author
  • Savarimuthu Philip AnthonyEmail author


New series of methoxy and hydroxyl group substituted triphenylamine (TPA)-imidazole fluorescent molecules (5-(diphenylamino)-2-(1H-phenanthro[9,10-d]imidazol-2-yl)phenol (1), 5-(diphenylamino)-2-(1-phenyl-1H-phenanthro[9,10-d]imidazol-2-yl)phenol (2), 5-(diphenylamino)-2-(4,5-diphenyl-1H-imidazol-2-yl)phenol (3), 5-(diphenylamino)-2-(1,4,5-triphenyl-1H-imidazol-2-yl)phenol (4), N-(3-methoxy-4-(1H-phenanthro[9,10-d]imidazol-2-yl)phenyl)-N-phenylbenzenamine (5), N-(3-methoxy-4-(1-phenyl-1H-phenanthro[9,10-d]imidazol-2-yl)phenyl)-N-phenylbenzene amine (6), and N-(3-methoxy-4-(4,5-diphenyl-1H-imidazol-2-yl)phenyl)-N-phenylbenzenamine (7)) have been synthesized that exhibited strong solution fluorescence and molecular structure and conformation controlled fluorescence photoswitching, solid state fluorescence and halochromism. Hydroxyl substituted molecules (1–4) showed moderate to strong fluorescence in solution depend on solvent polarity and very weak solid state fluorescence. Methoxy substituted molecules (5–7) displayed strong fluorescence both in solution and solid state. Solid state structural studies revealed strong intramolecular H-bonding in the crystal lattice. Interestingly, highly twisted structure (6) showed rare light induced reversible fluorescence switching in CHCl3. The observation of isobestic point in time dependent fluorescence photoswitching studies indicated structural isomer conversion. Further, acid sensitive imidazole nitrogen has been made use to demonstrate solid state fluorescence switching via halochromism. Thus the present studies attempted to develop new fluorescent molecules and establish structure-property relationship for designing fluorescence switching materials.

Graphical Abstract

Molecular structure controlled solid state fluorescence, halochromism and a rare fluorescence photoswitching in chloroform have been observed with triphenylamine-imidazole derivatives.


Fluorescence switching Halochromism Fluorescence photoswitching Solid state fluorescence 



Financial support from the Science and Engineering Research Board (SERB), New Delhi, India (SERB No. EMR/2015/00-1891) is acknowledged with gratitude. “X-ray crystallography at the PLS-II 2D-SMC beamline was supported in part by MSIP and POSTECH.

Supplementary material

10895_2019_2437_MOESM1_ESM.pdf (5.1 mb)
ESM 1 (PDF 5246 kb)


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Authors and Affiliations

  1. 1.School of Chemical & BiotechnologySASTRA Deemed UniversityThanjavurIndia
  2. 2.PG and Research department of chemistryKhadirMohideen CollegeAdirampattinamIndia
  3. 3.Beamline Department, Pohang Accelerator LaboratoryPohangSouth Korea

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