@article { ISI:000351969900008, title = {First naphthosemiquinone complex of K+ with vitamin K3 analog: experiment and density functional theory}, journal = {Journal of Molecular Structure}, volume = {1088}, year = {2015}, month = {MAY}, pages = {56-63}, publisher = {ELSEVIER SCIENCE BV}, address = {PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS}, abstract = {

Synthesis and characterization of potassium complex of 2-hydroxy-3-methyl-1,4-naphthoquinone (phthiocol), the vitamin K3 analog, has been carried out using FT-IR, UV-Vis, H-1 and C-13 NMR, EPR, cyclic voltammetry and single crystal X-ray diffraction experiments combined with the density functional theory. It has been observed that naphthosemiquinone binds to two K+ ions extending the polymeric chain through bridging oxygens O(2) and O(3). The crystal network possesses hydrogen bonding interactions from coordinated water molecules showing water channels along the c-axis. C-13 NMR spectra revealed that the complexation of phthiocol with potassium ion engenders deshielding of C(2) signals, which appear at delta = similar to 14.6 ppm whereas those of C(3) exhibit up-field signals near delta similar to 6.9 ppm. These inferences are supported by the M06-2x based density functional theory. Electrochemical experiments further suggest that reduction of naphthosemiquinone results in only a cathodic peak from catechol. A triplet state arising from interactions between neighboring phthiocol anion lead to a half field signal at g = 4.1 in the polycrystalline X-band EPR spectra at 133 K. (C) 2015 Elsevier B.V. All rights reserved.

}, keywords = {C-13 NMR, DFT, hydrogen bonding, Naphthosemiquinone, Phthiocol, Vitamin K3}, issn = {0022-2860}, doi = {10.1016/j.molstruc.2015.01.053}, author = {Kathawate, Laxmi and Gejji, Shridhar P. and Yeole, Sachin D. and Verma, Prakash L. and Puranik, Vedavati G. and Salunke-Gawali, Sunita} } @article {43904, title = {Binding selectivity of vitamin K3 based chemosensors towards nickel(II) and copper(II) metal ions}, journal = {Journal of molecular Structure}, volume = {1143}, year = {2017}, month = {SEP}, chapter = {495-514}, abstract = {

The vitamin K3 derivatives 2-methyl-3-[(pyridin-2-ylmethyl)-amino]-1,4-naphthoquinone (M-1), 2-methyl-3-[(pyridin-2-ylethyl)-amino]-1,4-naphthoquinone (M-2), 2-methyl-3-((2-(thiophen-2-yl) methyl)amino)naphthalene-1,4-dione (M-3) and 2-methyl-3-((2-(thiophen-2-yl)ethyl)amino)naphthalene-1,4-dione (M-4) have been synthesized, characterized and studied for their chemosensor abilities towards transition metal ions. Crystal structures of M-1 to M-4 revealed a variety of N-H center dot center dot O, C-H center dot center dot center dot O, C-H center dot center dot center dot pi and pi center dot center dot center dot pi interactions. Minor variations in such interactions by chemical stimuli such as metal ions, results in change in color that can be visualized by naked eyes. It has been shown that electronic structure and H-1 NMR, vibrational as well as electronic spectra from the density functional theory agree well with the experiments. The metal ion binding in ethanol, ethanol-water and in mild base triethylamine brings forth recognizing ability of M-1 toward Ni2+ whereas M-2 exhibits large sensing ability for Cu2+ ion. Interestingly M-1 display varying metal ion binding specificity in different solvents with the association constant in ethanol being 11,786 M-1 for Ni2+ compared to 9462 M-1 for the Cu2+. A reversal in preferential binding of M-2 with the respective association constants being 4190 M-1 and 6370 M-1 is discernible. (C) 2017 Elsevier B.V. All rights reserved.

}, keywords = {Aminonaphthoquinone Molecular-structures, Anthraquinone, Aqueous-solution, Chemosensor, Crystal-structures, Cu(II), Derivatives, DFT, Fluorometric Chemosensors, hydrogen bonding, Naphthoquinone, pi-pi stacking, Recognition, sensors}, issn = {0022-2860}, doi = {10.1016/j.molstruc.2017.04.094}, author = {Patil, Amit and Lande, Dipali N. and Nalkar, Archana and (Gejji, Shridhar P. and Chakrovorty, Debamitra and Gonnade, Rajesh and Moniz, Tania and Rangel, Maria and Pereira, Eulalia and Salunke-Gawali, Sunita} }