Here, naphthalene diamine-based β-diketone derivative (compound LH) was successfully used as a dual signaling probe for divalent cations, Fe 2+ and Cu 2+ ions, in bimodal methods (colorimetric and fluorometric). It showed fluorescent enhancement for Fe 2+ ion by photoinduced electron transfer mechanism and fluorescence quenching for Cu 2+ ion by charge-transfer process. Binding stoichiometry for [LH–(Fe 2+ ) 2 ] and [LH–(Cu 2+ ) 2 ] was found to be 1:2 by Job’s plot method and, the binding constants were calculated as 1.6638 × 10 10 and 9.22929 × 10 8 M –1 , respectively. Compound LH exhibited OR and XOR logic gate behavior with H + , Fe 2+ , and Cu 2+ as inputs. Further, the compound LH and bovine serum albumin binding interaction showed quenching of fluorescence by Förster resonance energy-transfer mechanism.

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We report in this paper that the binding of coumarin 6 (C6) to DNA can be tuned by complexing it with host structures, viz. β-cyclodextrin (β-CD) and C-hexylpyrogallol-4-arene (C-HPA). Because host molecules are used as carriers of small molecules onto target sites, the exposed part of the guest molecule needs to be found out, and the relationship between the host : guest ratio and the mode of binding with the target macromolecule, that is, the DNA needs to be analyzed, in order to comprehend the preferred binding moiety and tune the binding. In this paper, the formation of the inclusion complex of C6 with β-CD and with C-HPA is studied by UV-visible, fluorescence, 2D rotating-frame nuclear Overhauser effect correlation spectroscopy and diffusion-ordered spectroscopy nuclear magnetic resonance spectra and molecular modeling. C6 forms a 1:1 complex with β-CD and a 1:2 complex with C-HPA. The studies on the protonation of C6 in the presence and the absence of the host molecules suggest that the chromone part of C6 is outside the β-CD molecule, whereas it is fully covered by C-HPA. The binding of C6 with calf thymus DNA (ctDNA) occurs through intercalation and hydrogen bonding, and the host-guest structures remain intact on binding with ctDNA. The oxygens of the C6 molecules are exposed when inside the host molecules and aid in the hydrogen bonding with DNA.

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