ic502271k_si_002.cif (44.2 kB)
Ruthenium(II) and Osmium(II) Mixed Chelates Based on Pyrenyl–Pyridylimidazole and 2,2′-Bipyridine Ligands as Efficient DNA Intercalators and Anion Sensors
dataset
posted on 2015-01-20, 00:00 authored by Sourav Mardanya, Srikanta Karmakar, Dinesh Maity, Sujoy BaitalikWe report herein the synthesis and
characterization of two monometallic ruthenium(II) and osmium(II)
complexes of composition [(bpy)2M(HImzPPy)] (ClO4)2 derived from pyrenylimidazole–10-pyridin-2-yl-9H-9,11-diazacyclopenta[e]pyrene (HImzPPy)
and 2,2′-bipyridine (bpy) ligands. X-ray crystallographic study
shows that both crystals belong to the triclinic system having space
group P1̅. The photophysical properties of 1 and 2 in acetonitrile indicate that the metal-to-ligand
charge-transfer excited state is mainly centered in the [M(bpy)2]2+ moiety of the complexes and slightly affected
by the extended conjugation of the pyrenylimidazole moiety. Both complexes
display one-electron reversible metal-centered oxidative processes
and a number of quasi-reversible reductive processes. The binding
affinities of the complexes toward calf-thymus DNA (CT-DNA) were thoroughly
studied through different methods such as absorption, emission, excited-state
lifetime, circular dichroism, and thermal denaturation of DNA and
a relative DNA binding study using ethidium bromide. All of these
experiments account for the intercalative nature of both 1 and 2 toward CT-DNA as well as their light-switch behavior.
The anion recognition study through different spectroscopic techniques
reveals that both complexes act as “turn-on” luminescence
sensors for H2PO4− and “turn-off”
sensors toward F– and AcO–. The
imidazole N–H proton of the receptors gets deprotonated with
the excessive addition of F– and AcO–, while it interacts with H2PO4– through hydrogen-bonding interaction. Theoretical calculations (DFT
and TD-DFT) were also performed to understand the photophysical properties
of the metalloreceptors.