Preparation of Copper –3-Aminophenol–Cyclodextrin Nanomaterials and Study of 3-Aminophenol–Cyclodextrin Inclusion Complexes at Different pH Conditions

The spectral behavior of 3-aminophenol (3AP) with α-cyclodextrin (α-CD), β-cyclodextrin (β-CD) in pH ~2, pH ~7, pH ~11 and copper nano was investigated using UV–visible absorption, steady-state and time-resolved fluorescence, PM3 calculations, SEM, DSC, FTIR, XRD, and sup1/supH NMR techniques. 3AP exhibited a single emission band at the same wavelength in α-CD at pH ~2 and pH ~7, whereas dual emission was observed at pH ~11. Across all solvents, the absorption and emission maxima of 3AP resembled those of 3-anisidine. In β-CD, the emission intensity at pH ~7 and pH ~11 decreased at the shorter-wavelength (normal emission) band and increased at the longer-wavelength band, suggesting the presence of an intramolecular charge-transfer (ICT) process in 3AP. The lifetimes of the inclusion complexes were longer than that of the free 2AP molecule. The geometrical restriction of the α-CD cavity likely limits the free rotation of the amino and hydroxyl groups, thereby enhancing the intensity of the IPT emission. The calculated HOMO–LUMO energy gap, total energy, free energy, enthalpy, entropy, dipole moment, and zero-point vibrational energy of the CD: 3AP complex differed significantly from those of the isolated 2AP, α-CD and β-CD molecules, and both the vertical and horizontal bond lengths between the amino and hydroxy groups are smaller than the β-CD cavity size confirming the formation of an inclusion complex. The lifetimes of the 3AP–CD inclusion complexes were longer than that of free 3AP. SEM-EDX analysis confirmed the presence of 48% carbon, 47.3% oxygen, and 3.3% copper in the nanomaterials. In DSC, XRD, and FTIR analyses, new peaks appeared along with a substantial reduction in the intensity of characteristic bands for the nano Cu-3AP-CD complex, indicating successful complex formation and structural modification.