Coligand tuning of the DNA binding properties of half-sandwich organometallic intercalators: Influence of polypyridyl (pp) and monodentate ligands (L=Cl, (NH2)2CS, (NMe2)2CS) on the intercalation of (η5-pentamethylcyclopentadienyl)-iridium(III)- dipyridoquinoxaline and -dipyridophenazine complexes

Cyclometalated iridium(III) complex of 6‐hydroxydipyrido[3,2‐a:2′,3′‐c]phenazine: synthesis, and acid–base and avid DNA binding properties

“…In a plot of (ε a − ε f )/(ε b − ε f ) vs [DNA], the DNA-binding constant K b value was derived to be (6.06 ± 0.32) × 10 (n = 0.82 ± 0.04), which is larger than the K b values previously reported for DNA intercalators of [Ru(bpy) 2 (dppz)] 2+ (4.95 × 10 6 M −1 ), [54] {(η 5 -C 5 Me 5 )Ir[(NMe 2 ) 2 CS](dppz)} 2+ (2.9 × 10 6 M −1 ), [6] [Ru(bpy) 2 (hdppz)] 2+ (1.3 × 10 6 M −1 ), [30] [Ru(phen) 2 (hdppz)] 2+ (4.4 × 10 5 M −1 ) [30] and [Ir(ppy) 2 (dppz)] + (2.4 × 10 4 M −1 ). [7] The binding site size n of 0.82 was relatively low for exclusively intercalative binding and this suggests that additional surface stacking of hdppz may involve the DNA interaction at low [DNA] concentrations.…”

“…The other chemicals were obtained from commercial sources and used without further purification. [Ir(ppy) 2 (hdppz)]PF 6 was synthesized according to the route shown in Scheme 2, and the synthetic details are given below. 6 A suspension of [Ir(ppy) 2 …”

“…[48] The composition of [Ir(ppy) 2 6 in neutral water displays two high-energy bands at ∼257 (ε = 31700 M −1 cm −1 ) and 303 nm (28400 M −1 cm −1 ), which can be assigned to ligand-centered (LC) transitions, and one lower-energy absorption band at 385 nm (ε = 28700 M −1 cm −1 ) assigned to metal-to-ligand charge-transfer (MLCT) transitions (Ir → ppy or hdppz), which is comparable to [Ir(ppy) 2 (dppz )] + (dppz = (dipyrido[3,2-a:2 ,3 -c]phenazine-11-yl)-hex-5-ynoic acid) that has dppz-centered IL π -π * and MLCT bands occurring at ∼295 and 393 nm. [49] Indeed, the absorption of complexes made with Ir(III) generally corresponds to the superposition of a different transition involving either the ligands or both the metal and the ligand.…”

“…Although Ru(II) and Rh(III) metallointercalators have been widely studied, only a few reports of related compounds with a central Ir(III) ion have previously appeared. [5 -7] These include [Ir(ppy) 2 (dppzR)] 3+ (dppzR = 7-ethyl acetate-dipyrido[3,2-a:2 ,3 -c]phenazine), which has been employed to follow electron transfer in DNA, [5] DNA intercalators of {(η 5 -C 5 Me 5 )Ir[(NMe 2 ) 2 CS](N-N)} (CF 3 SO 3 ) 2 (N-N = dppz and dppn, where dppn = benzo[i]dipyrido[3,2-a:2 ,3 -c]phenazine), [6] and luminescent dipyridoquinoxaline and dipyridophenazine complexes of the type [Ir(ppy) 2 (N-N)](PF 6 ) (N-N = dpq, dppz and dppn, where dpq = 2-N-butylamidodipyrido[3,2-f :2 ,3 -h]quinoxaline). [7] All the studies revealed that molecular modification of DNA binders would lead to subtle or substantial changes in the binding modes, location and affinities, providing the opportunity to explore various valuable conformation-or site-specific DNA probes and anticancer drugs.…”

Electrochemical Comparison of the Interaction of 5-Nitrouracil with Single- or Double-Stranded DNA at mercury and glassy carbon electrodes

“…The voltammetric changes unequivocally suggest that 5NU is intercalated into the base-stacking domain of the ds-DNA double helix, however, the interaction mode of 5NU molecules with ss-DNA is mainly by electrostatic (by which 5NU bind electrostatically to the negatively charged deoxyribose-phosphate backbone of DNA). It has been reported that the intercalation of DNA with small molecules commonly has stronger strength than electrostatic action [36], thus, the 5NU molecules should have stronger affinity with ds-DNA than ss-DNA. This results are consistent with that reported previously by Ortiz M. et al [37] for the single-stranded DNA interaction with methylene blue using spectroscopic technique.…”