Luminescent europium and terbium complexes of dipyridoquinoxaline and dipyridophenazine ligands as photosensitizing antennae: structures and biological perspectives

摘要: The europium(III) and terbium(III) complexes, namely [Eu(dpq)(DMF)2(NO3)3] (1), [Eu(dppz)2(NO3)3] (2), [Tb(dpq)(DMF)2Cl3] (3), [Tb(dppz)(DMF)2Cl3] (4), where dipyrido[3,2-d:2′,3′-f]quinoxaline (dpq in 1 3), dipyrido[3,2-a:2′,3′-c]phenazine (dppz 2 4) N,N′-dimethylformamide (DMF) have been isolated, characterized from their physicochemical data, luminescence studies interaction with DNA, serum albumin protein photo-induced DNA cleavage activity are studied. X-ray crystal structures of complexes 1–4 show discrete mononuclear Ln3+-based structures. Eu3+ (1) (2) as [Eu(dppz)2(NO3)3]·dppz (2a) adopts a ten-coordinated bicapped dodecahedron structure bidentate N,N-donor dpq ligand, two DMF three NO3− anions dppz ligands 2. Complexes 3 4 seven-coordinated mono-capped octahedron Tb3+ contains dpq/dppz ligands, Cl− anions. highly luminescent nature indicating efficient photo-excited energy transfer the antenna to Ln3+ generate long-lived emissive excited states for characteristic f → transitions. time-resolved spectra typical narrow emission bands attributed 5D0 7FJ 5D4 f–f transitions ions respectively. number inner-sphere water molecules (q) was determined lifetime measurements H2O D2O confirming ligand-exchange reactions solution. display significant binding propensity CT-DNA giving constant values range 1.0 × 104–6.1 104 M−1 order 2, (dppz) > 1, (dpq). data suggest groove partial intercalation complexes. All also (KBSA ∼ 105 M−1) bovine (BSA) protein. intensity time-gated spectral enhances significantly increasing concentration aqueous buffer medium due displacement bound upon thus reducing non-radiative quenching through O–H oscillator. efficiently cleave supercoiled (SC) ds-DNA its nicked circular (NC) form on exposure UV-A light 365 nm via formation singlet oxygen (1O2) hydroxyl radicals (HO˙) reactive species at micromolar concentrations under physiological conditions.