Active Bromoaniline–Aldehyde Conjugate Systems and Their Complexes as Versatile Sensors of Multiple Cations with Logic Formulation and Efficient DNA/HSA-Binding Efficacy: Combined Experimental and Theoretical Approach

Two
fluorescence active bromoaniline-based Schiff base chemosensors,
namely, (E)-4-bromo-2-(((4-bromophenyl)­imino)­methyl)­phenol
(HL1) and (E)-2-(((4-bromophenyl)­imino)­methyl)­phenol
(HL2), have been employed for the selective
and notable detection of Cu2+ and Zn2+ ions,
respectively, with the simultaneous formation of two new metal complexes
[Cu­(L1)2] (1) and [Zn­(L2)2] (2). X-ray single crystal analyses indicate
that complexes 1 and 2 are tetra-coordinated
systems with substantial CH...π/π...π stacking interactions
in the solid-state crystal structures. These two complexes are exploited
for the next step detection of Al3+ and Hg2+ where complex 2 exhibits impressive results via turn-off
fluorescence quenching in (DMSO/H2O) HEPES buffer medium.
The sensing phenomena are optimized by UV–vis spectral analyses
as well as theoretical calculations (density functional theory and
time-dependent density functional theory). The combined detection
phenomena of the ligand (HL2) and complex 2 are exclusively utilized for the first time to construct
a molecular memory device, intensifying their multisensoric properties.
Furthermore, the DNA- and human serum albumin (HSA)-binding efficacies
of these two complexes are examined by adopting electronic and fluorometric
titration methods. Complex 2 shows a higher DNA-binding
ability in comparison with complex 1, whereas in the
case of HSA, the reverse situation is observed. Finally, the binding
modes of both the complexes with DNA and HSA have been investigated
through molecular docking studies, suggesting good agreement with
the experimental results.