Mahantesha Basanagouda

Synthesis, structure–activity relationship of iodinated-4-aryloxymethyl-coumarins as potential anti-cancer and anti-mycobacterial agents

A series of new iodinated-4-aryloxymethylcoumarins 6, 8 and 10 have been obtained from the reaction of various 4-bromomethylcoumarins 4 with 2-iodophenol 5, 3-iodophenol 7 and 4-iodophenol 9 respectively. All the title compounds were screened for anticancer activity against two cancer cell lines (MDA-MB human adenocarcinoma mammary gland and A-549 human lung carcinoma) and two mycobacterial strains (Mycobacterium tuberculosis H₃₇ RV and Mycobacterium phlei). The SAR results indicate that nine compounds are potent, among these 10h and 10i having chlorine are most effective. This is the first report assigning in vitro anti-mycobacterial, anticancer and structure-activity relationship for this new class of iodinated-4-aryloxymethyl-coumarins.

Solvent Effects on the Electronic Absorption and Fluorescence Spectra of HNP: Estimation of Ground and Excited State Dipole Moments

We report the effect of solvents on absorption and fluorescence spectra of biologically active 3(2H)-pyridazinone namely 5-(2-hydroxy-naphthalen-1-yl)-2-phenyl-2H-pyridazin-3-one (HNP) in different solvents at room temperature. The ground and the excited state dipole moments of HNP molecule was estimated from Lippert’s, Bakshiev’s and Kawski-Chamma-Viallet’s equations using the solvatochromic shift method. The ground state dipole moment (μg) was also estimated by Guggenheim and Higasi method using the dielectric constant and refractive index of solute at different concentrations, the μg value obtained from these two methods are comparable to the μg value obtained by the solvatochromic shift method. The excited state dipole moment (μe) is greater than the ground state dipole moment (μg), which indicates that the excited state is more polar than the ground state. Further, we have evaluated the change in dipole moment (Δμ) from the solvatochromic shift method and on the basis of molecular-microscopic solvent polarity parameterETN

Investigation of role of silver nanoparticles on spectroscopic properties of biologically active coumarin dyes 4PTMBC and 1IPMBC.

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Effect of TiO2 nanoparticles on some photophysical characteristics of ketocyanine dyes

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Photophysical Properties of a Novel and Biologically Active 3(2H)-Pyridazinone Derivative Using Solvatochromic Approach

The absorption and fluorescence characteristics of biologically active coumarin derivatives 4-p-tolyloxymethyl-benzo[h]coumarin (4PTMBC) and 1-(4-iodo phenoxymethyl)-benzo[f]coumarin (1IPMBC) are studied at room temperature in a series of organic solvents and 1,4-dioxane - acetonitrile solvent mixture. The effect of pure solvents on the spectral properties are analyzed using Lippert-Mataga polarity function, Reichardts microscopic solvent polarity parameter, Kamlets and Catalans multiple linear regression approaches. Both general solute - solvent interactions and hydrogen bonding interactions are operative in these systems. However, the contribution of hydrogen bonding interactions is less compared to general solute-solvent interactions. The solvatochromic correlations are used to estimate excited state dipole moment using experimentally determined ground state dipole moment. The bathochromic shift of the emission spectra and the increase in excited state dipole moment indicate the intramolecular charge transfer (ICT) character in the emitting singlet state. The solvation studies in 1,4-dioxane - acetonitrile solvent mixture suggest that these dyes are preferentially solvated by 1,4-dioxane.

Study of Photophysical Properties on Newly Synthesized Coumarin Derivatives

The role of silver nanoparticles on spectroscopic properties of biologically active coumarin dyes 4-p-tolyloxymethyl-benzo[h]coumarin (4PTMBC) and 1-(4-iodophenoxymethyl)-benzo[f]coumarin (1IPMBC) has been investigated using absorption and fluorescence spectroscopy. Silver nanoparticles are synthesized by chemical reduction method and the estimated size by Mie theory is 12 nm. The absorption spectral changes of dyes in the presence of silver nanoparticles suggest their possible interaction with silver nanoparticles. The apparent association constants of the interaction are estimated using Benesi-Hildebrand model. Fluorescence quenching has been observed in both the dyes with the addition of silver nanoparticles. The Stern-Volmer plots of fluorescence quenching are found to be nonlinear showing positive deviation. The magnitudes of quenching rate parameter and fluorescence lifetime measurements indicate the presence of both collisional and static quenching mechanisms. The binding constants and the number of binding sites for the static type of quenching have been estimated from the fluorescence data. The role of diffusion, energy transfer and electron transfer processes in fluorescence quenching mechanism has been discussed.

Synthetic and Structural Studies on Novel 4,3′-Bicoumarins

Abstract Herein, we report an efficient and convenient method for synthesis of benzofuran-3-acetic acids and naphthafuran-acetic acids 5a–p by the reaction of substituted-4-bromomethylcoumarins with aqueous sodium hydroxide at refluxing temperature. The obtained products are characterized by infrared, 1H NMR, 13C NMR, and mass spectral data. Structures 5a and 5e are confirmed by their single x-ray diffraction studies. The advantages of this method are good yields, easy workup, and no chromatographic purifications. GRAPHICAL ABSTRACT

Effect of Plasmonic Silver Nanoparticles’ Size on Photophysical Characteristics of 4-Aryloxymethyl Coumarins

The effect of titanium dioxide (TiO2 ) nanoparticles (NPs) on photophysical characteristics of 2,5-di[(E)-1-(4-dimethylaminophenyl) methylidine]-1-cyclopentanone (2,5-DMAPMC) and 2,5-di[(E)-1-(4-diethylaminophenyl)methylidine]-1-cyclopentanone (2,5-DEAPMC) ketocyanine dyes has been studied using absorption, steady-state and time-resolved fluorescence spectroscopy. The magnitudes of association constants determined based on modified absorption spectrum of dyes due to the presence of TiO2 NPs indicate the interaction of TiO2 NPs with dye molecules. The quenching of fluorescence intensity of dyes by TiO2 NPs is observed and it follows linear Stern-Volmer (S-V) equation. The magnitude of quenching rate parameter suggests the involvement of static quenching mechanism. The involvement of electron transfer process in reducing fluorescence intensity of dyes has been discussed. Also, varying influence of TiO2 NPs on two dyes is explained based on the presence of different alkyl substituent in two dyes.