title: Synthesis, Fluorescence Spectra, Redox Property and the DNA Binding Studies of 7-phenylacenaphtho[1,2-b]quinoxalin-7-ium chloride: Evidences of the Formation of Neutral Radical Analogue.
abstract: Reaction of acenaphthoquinone with N-phenyl-o-phenylenediamine in methanol in presence of HCl yielded 7-phenylacenaphtho[1,2-b]quinoxalin-7-ium chloride, [1][Cl]. [1][Cl] is brightly fluorescencent in dichloromethane (λex = 403 nm and λem = 442, 464, 488 nm) and water (λex = 408 nm and λem = 545 nm). Density functional theory (DFT) and time dependent (TD) DFT calculations on [1](+) at the B3LYP level of the theory elucidated that the origin of the lower energy excitation at around 400 nm is due to π → π(*) transition. [1](+) is redox active and exhibits a reversible cathodic wave at -0.66 V referenced to Fc(+)/Fc couple due to [1](+)/[1](•) redox couple. Electrogenerated neutral radical analogue [1](•) was characterized by electron paramagnetic resonance (EPR), UV-vis spectra and DFT calculations. DNA binding studies using the techniques of UV-vis absorption, fluorescence, circular dichroism (CD) spectra, viscosity, gel electrophoresis, hydrodynamic, isothermal titration calorimetry (ITC) and UV optical melting studies of [1][Cl] revealed that [1](+) is a strong DNA intercalator obeying neighbor exclusion principle. ITC experiment authenticated that the binding of [1](+) to DNA is entropy driven.
authors.affiliation: Department of Chemistry, R. K. M. Residential College, Narendrapur, Kolkata, 700103, India.
authors.forename: Suman
authors.initials: S
authors.lastname: Kundu
authors.affiliation: VJRC R&D Center, Vijaygarh Jyotish Ray College, Bijoygarh, Kolkata, 700 032, India.
authors.forename: Ananya
authors.initials: A
authors.lastname: Banerjee
authors.affiliation: VJRC R&D Center, Vijaygarh Jyotish Ray College, Bijoygarh, Kolkata, 700 032, India.
authors.forename: Arpan
authors.initials: A
authors.lastname: De
authors.affiliation: Biophysical Chemistry Laboratory, Organic and Medicinal Chemistry Division, CSIR-Indian Institute of Chemical Biology, Kolkata, 700032, India.
authors.forename: Asma Yasmeen
authors.initials: AY
authors.lastname: Khan
authors.affiliation: Biophysical Chemistry Laboratory, Organic and Medicinal Chemistry Division, CSIR-Indian Institute of Chemical Biology, Kolkata, 700032, India.
authors.forename: Gopinatha Suresh
authors.initials: GS
authors.lastname: Kumar
authors.affiliation: Department of Chemistry, R. K. M. Residential College, Narendrapur, Kolkata, 700103, India.
authors.forename: Ranjan
authors.initials: R
authors.lastname: Bhadra
authors.affiliation: Department of Chemistry, R. K. M. Residential College, Narendrapur, Kolkata, 700103, India. ghosh@pghosh.in.
authors.forename: Prasanta
authors.initials: P
authors.lastname: Ghosh
mesh_terms: D000073:Acenaphthenes / Q000138:chemical synthesis* / Q000737:chemistry*; D000818:Animals; D002417:Cattle; D060326:Chemistry Techniques, Synthetic; D004247:DNA / Q000737:chemistry*; D004583:Electrons; D005609:Free Radicals / Q000737:chemistry; D008958:Models, Molecular; D008968:Molecular Conformation; D010084:Oxidation-Reduction; D011789:Quantum Theory; D011810:Quinoxalines / Q000138:chemical synthesis* / Q000737:chemistry*; D013050:Spectrometry, Fluorescence; D044366:Transition Temperature
chemical_list: C000610106:7-phenylacenaphtho(1,2-b)quinoxalin-7-ium; D000073:Acenaphthenes; D005609:Free Radicals; D011810:Quinoxalines; D004247:DNA; C427203:calf thymus DNA
keywords: 7-phenylacenaphtho[1,2-b]quinoxalin radical; 7-phenylacenaphtho[1,2-b]quinoxalin-7-ium chloride; Biophysical studies; DNA intercalator