Synthesis and physicochemical, DFT, thermal and DNA-binding analysis of a new pentadentate N 3 S 2 Schiff base ligand and its [CuN 3 S 2 ] 2+ complexes.

A new N ₃ S ₂ pentadentate Schiff base ligand derived from 5-bromothiophene-2-carbaldehyde, ( E )- N 1-((5-bromothiophen-2-yl)methylene)- N 2-(2-(( E )-((5-bromothiophen-2-yl)-methylene amino) ethyl ethane-1,2-diamine, is prepared. The ligand and its complexes are subjected to extensive physical and theoretical analyses and the results are consistent with their predicted compositions. Dicationic Cu(ii) complexes ([CuN ₃ S ₂ ]X ₂ ) with a coordination number of 5 are proposed on the basis of the spectral data with N ₃ S ₂ serving as a pentadentate ligand. The prepared complexes display a square pyramidal geometry around the Cu(ii) center. TG shows different thermal behavior for the N ₃ S ₂ ligand and its complexes. Solvatochromism of the complexes is promoted by the polarity of the solvent used. A one-electron transfer Cu(ii)/Cu(i) reversible redox reaction is promoted by CV. SEM and EDS of the free ligand and its complexes support the morphology and composition changes observed upon the complexation of Cu(ii). As an outstanding goal to develop anticancer new metal chemotherapy, preliminary studies of the binding of the desired complexes with DNA were carried out, as it is through judging the strength of interactions that a future drug can be designed and synthesized. The viscosity and absorption results obtained for complex 1 indicated its enhanced CT-DNA binding properties as compared to those of complex 2 with K _b values of 3.2 × 10 ⁵ and 2.5 × 10 ⁵ M ^-1 , respectively.
Competing Interests: The authors declare no conflict of interest.
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