Schiff-base ligands L1 and L2 containing fluorene as fluorophore were synthesized thorough condensation of salicylaldehyde and 2,6-diformyl 4-methylphenol with 6-(9-fluorenyl)-1,4,8,11-tetraazaundecane-5,7-dione, respectively. A comprehensive spectroscopic analysis was performed by elemental analysis, ESI-MS, 1 H and 13C NMR, FTIR, EPR, UV–Vis and emission spectroscopies. Ligand L1 binds copper(II) to form [Cu2(L1)2] 2H2O that crystallizes in orthorhombic system and space group P21/n. Assignments to the UV–Vis and EPR spectra allowed access to Jahn–Teller stabilization energies (EJT) at 6345 and 5435 cm1 for complexes [Cu2(L1)2] 2H2O and [Cu2(L2)](ClO4)4 4H2O, respectively, and to their corresponding spin orbit coupling constants k = 428 and 398 cm1 . The EPR spectrum of [Cu2(L2)] (ClO4)4 4H2O in the solid state showed a half-field DmS = ±2 transition, supporting the dicopper composition. The fluorenyl copper(II) derivatives demonstrated a moderate binding to ct-DNA than the fluorenyl-ligand molecule following the increasing order of (Kb): L1 < [Cu2(L1)2] 2H2O < [Cu2(L2)] (ClO4)4 4H2O.
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https://www.sciencedirect.com/science/article/abs/pii/S0277538718300032
