Design, Spectroscopic Elucidation, Bio-Photonic (Optical) Evaluation of Novel Cd-Based Macrocyclic Complexes

A new series of Cd(II) macrocyclic complexes has been synthesized via template condensation of 1,13-diamino-4,7,10-trioxatridecane with tribulin and its derivatives in the presence of CdCl₂·H₂O (1:1:1 molar ratios). Structural characterization by FTIR, UV-Vis, ¹H & ¹³C NMR, XRD, mass spectrometry, and elemental analyses supports an octahedral geometry. The stability of the complexes in solution phase was validated through time-resolved UV-Visible spectroscopic analysis over 24 h, revealing no detectable signs of dissociation. Photoluminescence properties were examined in the solid state, revealing a common excitation maximum at 230 nm and distinct emission maxima at 467 nm, 395 nm, and 398 nm, respectively. These results demonstrate the significant optical response of Cd(II) macrocycles and highlights their potential for applications in luminescent devices and optical sensors. The antioxidant capacity was assessed using a DPPH-free radical scavenging experiment, which exhibited significant results. The newly synthesized complexes have also been screened for antibacterial and antifungal activities. In vitro antimicrobial screening of the complexes was evaluated against Gram-negative E. coli and Gram-positive S. aureus bacterial strains and A. niger and P. chrysogenum fungal strains. Antimicrobial evaluation demonstrates that these complexes exhibit superior antifungal efficacy compared to the standard drug ketoconazole, highlighting their promise as potent antifungal agents.