title: Photophysical aspects of biological photosensitizer Kynurenic acid from the perspective of experimental and quantum chemical study.
abstract: In the present contribution, we have explored ground and excited state spectroscopic properties of an antiexcitotoxic and anticonvulsant drug, Kynurenic acid (KA), through steady-state absorption, emission and time-resolved emission spectroscopy and quantum chemical calculations. The main focus of this article is to illustrate the effects of various parameters such as the nature of the solvents and pH of the medium on the spectral properties of KA which confirms the presence of different neutral and ionic species in the ground and excited states. The molecule KA exists mainly as keto- or anionic form in the ground state, whereas the main contribution of its emission is arising from the keto tautomer in the excited state. Quantum chemical calculations by Density Functional Theory (DFT) method has been effectively employed to correlate the experimental findings. The ground and excited state properties of KA ascertained by means of experimental and theoretical method reveal that it resembles well with other two compounds, 4-hydroxyquinoline and xanthurenic acid formed by the decomposition of UV filters.
authors.affiliation: Department of Chemistry, Jadavpur University Raja S.C. Mallick Road, Kolkata 700 032, India.
authors.forename: Anuva
authors.initials: A
authors.lastname: Samanta
authors.affiliation: Department of Chemistry, University of Calcutta 92, A.P.C. Road, Kolkata 700 009, India. Electronic address: nguchhait@yahoo.com.
authors.forename: Nikhil
authors.initials: N
authors.lastname: Guchhait
authors.affiliation: Department of Chemistry, Jadavpur University Raja S.C. Mallick Road, Kolkata 700 032, India. Electronic address: sbjuchem@yahoo.com.
authors.forename: Subhash Chandra
authors.initials: SC
authors.lastname: Bhattacharya
mesh_terms: D006863:Hydrogen-Ion Concentration; D006912:Hydroxyquinolines / Q000737:chemistry; D007736:Kynurenic Acid / Q000737:chemistry*; D008958:Models, Molecular; D017319:Photosensitizing Agents / Q000737:chemistry*; D011789:Quantum Theory; D013050:Spectrometry, Fluorescence; D013056:Spectrophotometry, Ultraviolet; D014977:Xanthurenates / Q000737:chemistry
chemical_list: D006912:Hydroxyquinolines; D017319:Photosensitizing Agents; D014977:Xanthurenates; C028330:xanthurenic acid; D007736:Kynurenic Acid; C034010:4-hydroxyquinoline
keywords: Density Functional Theory; Fluorescence spectroscopy; Kynurenic acid; Photoinduced process; Polarized Continuum Model