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32 results on '"Joshi Hem C."'

15. Asymmetric indolylmaleimide derivatives and their complexation with zinc(II)-cyclen

Author

Kaletas, Basak Kukrer, Joshi, Hem C., van der Zwan, Gert, De Cola, Luisa, Fanti, Marianna, Konig, Burkhard, Zerbetto, Francesco, Goubitz, Kees, and Williams, Rene M.

Subjects
Indole -- Chemical properties, Zinc compounds -- Chemical properties, Density functionals -- Usage, Chemicals, plastics and rubber industries
Abstract

The spectroscopic properties of two asymmetric indolylmaleimide derivatives, 4-bromo-3-(1'H-indol-3'-yl)-maleimide and 4-methyl-3-(1'H-indol-3'-yl)maleimide, are investigated and the bromo derivative is crystallized and its x-ray structure is determined. DFT calculations indicated that HOMO-1 to LUMO excitation is mainly responsible for the charge transfer character and that this transition changes its character drastically when Zn-cyclen complexation occurs.

Published
2005

17. Water-induced quenching of salicylic anion fluorescence

Author

Joshi, Hem C., Gooijer, Cees, and Zwan, Gert van der

Subjects
Salicylic acid -- Research, Salicylic acid -- Chemical properties, Fluorescence -- Usage, Anions -- Research, Chemistry, Physical and theoretical -- Research, Chemicals, plastics and rubber industries
Abstract

Salicylic anion abstraction and effusion are analyzed in different solvents and solvent mixtures. The significant Stokes shift observed for this anion is considered to indicate a rapid excited phase proton transfer reaction to its keto form.

Published
2002

26. Contributors

Author

Adhya, Tapan Kumar, Afaq, Uzma, Archana, Bajpai, Rajesh, Banerjee, Debjyoti Bandhu, Banerjee, Saptadipa, Banerjee, Shirsendu, Bhatt, M.K., Bombaywala, Sakina, Bomle, Dhanashree Vijayrao, Chakrabortty, Sankha, Chakraborty, Prasenjit, Costa, Jorge Alberto Vieira, Das, Amlan, Das, Saprativ P., Goveas, Louella Concepta, Gupta, Piyush, Hamid, Shahida, Hirapure, Pradip, Izaguirres, Gabrielle Guimarães, Izhar, Syed Khalida, Joshi, Hem C., Joshi, Penny, Joshi, Yogesh, Kiran, Asha, Kumar, Navneet, Kumar, Ramesh, Kumar, Shravan, Kumar, Sunil, Kumari, Amrita, Kumari, Smita, Lakkakul, Rita, Lopes, Marcella, Mandpe, Ashootosh, Manna, Sourav, Mehrotra, Somya, Mishra, Prateek, Mishra, Shambhavi, Mitra, Biswarup, Mohapatra, Balaram, Morais, Michele Greque de, Moreira, Juliana Botelho, Nayak, Jayato, Nayak, Sneha, Pal, Parimal, Paliya, Sonam, Panda, Jigisha Roy, Pandey, Akanksha, Prakash, Om, Radmann, Elisângela Martha, Rai, Ramesh C., Rana, Neha, Ravinuthala, Srinithya, Reddy, Shreya, Sagar, Narashans Alok, Saha, Romio, Salar, Sapna, Sarkar, Priyabrata, Sen, Sarani, Shukla, Shubhang, Siddiqui, Saba, Sindhu, H.N., Singh, Ragini, Singh, Ramveer, Singh, Yashpal, Suar, Mrutyunjay, Tewari, Lalit M., Tiwari, Nitika, Tripathi, Ankita H., Tripathy, Suraj K., Upadhyay, Santosh K., Upadhye, Vijay, and Zaidi, Madeeha

Published
2022
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28. Revisiting the photochemistry 2,5‐dihydroxy benzoic acid (gentisic acid): Solvent and pH effect.

Author

Adhikari, Meena, Joshi, Neeraj K., Joshi, Hem C., Mehata, Mohan S., Mishra, Hirdyesh, and Pant, Sanjay

Subjects
PH effect, STOKES shift, SOLVENTS, BENZOIC acid, ORGANIC solvents, AQUEOUS solutions, APROTIC solvents, PHOTOCHEMISTRY
Abstract

In the present study, we have reinvestigated photochemistry of 2,5‐dihydroxy benzoic acid (DHBA) in a series of organic solvents of different polarities and the aqueous solution of varying pH from 1 to 14. The investigation was carried out using steady‐state and nanosecond (ns) time‐domain fluorescence measurement techniques at room temperature. Some hitherto not explored spectral features with new insight on different forms of DHBA are reported. It is found that DHBA exists as monoanionic and neutral forms in various polar protic, aprotic, and nonpolar solvents. In aqueous solution (pH 1 to 14), neutral, monoanionic, and dianion forms are found to be responsible for the observed optical spectral profiles. The observed significant Stokes shift in emission is attributed to species undergoing excited‐state intramolecular proton transfer (ESIPT) in different solvents. The analysis presented in this work elucidates and validate the presence of various species and conformers of DHBA. [ABSTRACT FROM AUTHOR]

Published
2021
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32. Asymmetric indolylmaleimide derivatives and their complexation with zinc(II)-cyclen

Author

Hem Chandra Joshi, Burkhard König, Basak Kükrer Kaletas, G. van der Zwan, René M. Williams, Marianna Fanti, K. Goubitz, Francesco Zerbetto, L. De Cola, Kaletas Basak Kuekrer, Joshi Hem C., Van der Zwan Gert, Fanti Marianna, Zerbetto Francesco, Goubitz Kee, De Cola Luisa, Koenig Burkhard, Williams Rene M., Computational Chemistry (HIMS, FNWI), HIMS Other Research (FNWI), Spectroscopy and Photonic Materials (HIMS, FNWI), and BioAnalytical Chemistry

Subjects
Models, Molecular, Indoles, Time Factors, chemistry.chemical_element, Zinc, Photochemistry, Crystallography, X-Ray, Cyclams, Sensitivity and Specificity, Maleimides, chemistry.chemical_compound, Cyclen, Heterocyclic Compounds, Ultrafast laser spectroscopy, Organometallic Compounds, Computer Simulation, Physical and Theoretical Chemistry, Spectroscopy, Maleimide, Molecular Structure, Chemistry, Solvatochromism, Models, Chemical, Excited state, Quantum Theory, Spectrophotometry, Ultraviolet, Steady state (chemistry)
Abstract

The spectroscopic properties of two asymmetric indolylmaleimide derivatives, 4-bromo-3-(1′H-indol-3′-yl)-maleimide and 4-memyl-3-(1′H-indol-3′-yl)maleimide, are investigated. The bromo derivative was crystallized and its X-ray structure was determined. Both compounds are strongly colored while their separate components (indole and maleimide) absorb in the UV region only. To understand the ground- and excited-state behavior, the photophysical properties of the two compounds were studied in detail by steady state and time-resolved absorption and emission spectroscopy. Their solvatochromic behavior was investigated by using the Kamlet-Taft approach, which indicates some charge transfer (CT) character in the excited state. Nano- and femtosecond transient absorption spectroscopy was used for the identification and investigation of the CT state. Furthermore, the effect of the complexation with zinc(II) 1,4,7,11-tetraazacyclododecane (Zn-cyclen) on the photophysical properties of these two compounds was studied. An enhancement of the fluorescence intensity upon self-assembly (up to 90 times) and high association constants were observed, which illustrate the potential use of these compounds as luminescent sensors. DFT calculations indicate that HOMO-1 to LUMO excitation is mainly responsible for the charge transfer character and that this transition changes its character drastically when Zn-cyclen complexation occurs, thus giving it sensor properties. © 2005 American Chemical Society.

Published
2005
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