Metal Meets Nucleobase: A Cd(II)-Adenine Complex with Bridging Supramolecular Architectures and Antibacterial...

A mononuclear Cd(II) complex, [Cd(9BuA)₂(H₂O)₂(DMF)NO₃]NO₃ (1) derived from 9-butyladenine (9BuA) has been synthesized and characterized using elemental analysis, Fourier transform infrared ¹H NMR, and single-crystal X-ray diffraction analysis. Crystallographic analysis reveals a distorted octahedral coordination environment around the Cd(II) center, where two 9BuA ligands, two water molecules, a DMF molecule, and a nitrate ion coordinate through N and O atoms. The complex exists as a monocation stabilized by an additional noncoordinated nitrate counterion. Hirshfeld surface analysis and electrostatic potential mapping highlight the dominance of hydrogen-bonding interactions (CH…O, NH…O, OH…O, etc.), which collectively stabilize the 3D crystal packing. Energy framework analysis identifies 18 dimeric interactions, with the most stable dimers stabilized by strong Coulombic forces, resulting in total interaction energies between -145.3 and -376.3 kJ mol^-1. The photophysical investigation shows chelation-enhanced fluorescence due to ligand rigidification upon coordination. In vitro antibacterial assays of complex 1 against six bacterial strains-three Gram-positive (Mammaliicoccus lentus, Staphylococcus cohnii, Bacillus cereus) and three Gram-negative (Enterobacter cloacae, Klebsiella pneumoniae, Shigella sonnei)-reveal selective and potent activity. To the best of current knowledge, this study presents the first structurally and biologically characterized Cd(II) complex of a modified adenine derivative, integrating detailed supramolecular and photophysical analyses with antibacterial evaluation.