Synthesis and Characterization of Copper-2,4-Diaminotoluene: Cyclodextrin Nanomaterials

Abstract

The absorption and emission spectral behaviour of 2,4-diaminotoluene (24DAT) was systematically investigated in the presence of varying concentrations of α-cyclodextrin (α-CD) and β-cyclodextrin (β-CD) at approximately pH 3 and pH 7, as well as in different solvents. Spectroscopic analyses were conducted using UV–visible absorption, steady-state and time-resolved fluorescence measurements, complemented by molecular modelling studies. Cu:24DAT:CD nanomaterials were synthesised and subsequently characterised using scanning electron microscopy (SEM), differential scanning calorimetry (DSC), Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and proton nuclear magnetic resonance (¹H NMR) spectroscopy. Under both acidic and neutral conditions, 24DAT exhibited significant absorption and emission shifts upon inclusion complex formation with α-CD and β-CD. In all solvents examined, 24DAT displayed a single broad emission band; however, dual emission was observed in cyclodextrin solutions indicates the occurrence of an intramolecular charge transfer (ICT) process within the molecule. Fluorescence lifetime measurements revealed that the inclusion complexes possess longer lifetimes than free 24DAT, suggesting enhanced photostability upon complexation. SEM–EDX analysis of the nanomaterials confirmed the presence of copper, accounting for 36.04% of the material composition, thereby validating the successful incorporation of Cu into the Cu:24DAT:CD framework.