Synthesis, characterization, DNA binding and DNA photocleavage of two new dipyrromethenes and their ruthenium (II) and N-methylated analogs
Date of Award
M.S. in Chemistry
Department of Chemistry
Advisor: Shawn Swavey
Two new bridging ligands have been synthesized by solvent-free reactions of substituted benzaldehydes, 3-methoxy-4-hydroxy benzaldehyde and flurobenzaldehyde, with isoquino[5,6-c]pyrrole resulting in two new organic chromophores with two peripheral nitrogen coordination sites capable of metal interaction. The ligands have been characterized by 1HNMR, mass spectroscopy, elemental analysis, UV/Vis spectroscopy, and cyclic voltammetry. Both ligands display low energy π-π* transitions above 500 nm with modest molar absorptivities. To make chromophores water soluble, N-methylated dipyrromethenes were synthesized and show bathochromic shifts compared to the neutral dipyrromethenes, which suggests that localized positive charge on the peripheral nitrogen of N-methylated compounds stabilize the π* orbitals. When coordinated to two ruthenium (II) bis(bipyridyl) groups, the new bimetallic complexes generated give an overall 2+ charge. The electronic transition of the bimetallic ruthenium (II) complexes display typical bipyridyl intraligand π-π* transitions at 295 nm and metal-to-ligand charge-transfer transitions above 500 nm with molar absorptivities greater than 40000 M-1cm-1. Oxidation of the ruthenium (II) metal centers to ruthenium (III) occurs at potentials above 0.80 V versus the Ag/ AgCl reference electrode. Binding studies with calf thymus DNA (ctDNA) show intrinsic binding constants as high as 105 M-1 (106 M-1 for Ru2-IsoQvan, complex III) indicating very strong interactions of N-methylated and ruthenium compounds with DNA. In this study, the N-methylated and ruthenium compounds are water-soluble and show the ability to photonick plasmid DNA when irradiated with low-energy light above 550 nm for brief periods of time. In addition, one of the complexes, Ru2-IsoQvan (complex III), shows the ability to initiate double-strand breaks of plasmid DNA by gel electrophoresis. Studies indicate that the photoinduced mechanism of Ru2-IsoQvan (complex III) is quite complex and both type I and type II pathways are involved resulting in both the formation of singlet oxygen and radicals. In addition, singlet oxygen is responsible for DNA double-strand breaking.
Ligands (Biochemistry) Synthesis, Ligands (Biochemistry) Properties, Photosensitizing compounds, Chemistry
Copyright 2016, author
Wang, Mengyu, "Synthesis, characterization, DNA binding and DNA photocleavage of two new dipyrromethenes and their ruthenium (II) and N-methylated analogs" (2016). Graduate Theses and Dissertations. 1154.