A novel TICT-based molecular rotor: synthesis, crystal structure and application in high resolution imaging of sweat pores

Abstract

We report the synthesis, characterization and X-ray crystal structure of a naphthalimide–methoxyquinoline (NI–HQ) based molecular rotor. NI–HQ crystallizes in a triclinic crystal system with a centrosymmetric Pi space group, and it showed strong emission at 436 nm in cyclohexane, 496 nm in CH₂Cl₂ and 562 nm in DMSO due to the TICT state supported by theoretical calculations. The aggregation studies in mixed aqueous solvents and various photophysical parameters in different polarity solvents further confirmed the existence of the TICT state. NI–HQ showed strong fluorescence in the solid state with λ_max at 470 nm, displaying cyan color with CIE color coordinates x = 0.17, y = 0.28. We explored NI–HQ for the development and visualization of LFPs up to levels 1–3 using powder-dusting and wet methods (70% H₂O–CH₃CN solution). The radius, shape and area of sweat pores and widths of the ridges could be differentiated by microscopic techniques. The study on the effect of NI–HQ on the stability of dsDNA using gel electrophoresis showed no degradation of dsDNA. We have demonstrated that NI–HQ offers opportunities for long-term (3 months) storage of developed fingerprints, development of latent fingerprints after 20 days of aging and stained latent fingerprints.