TIFR
Department of Chemical Sciences
School of Natural Sciences

Calender

January 24, 2018 at 2.30 pm in AG-69

Title :

From destructive to constructive – Using energy to strengthen polymeric materials

Abstract :

In this talk, I will present my plans to design polymers with new capabilities – ones that improve their performance as a response to distinct energy inputs. I will discuss my proposals to develop: 1) polymers that can undergo autonomous strengthening when they experience mechanical force; and 2) polymerization methods that are self-catalyzed and require less energy to perform without sacrificing the material strength of resulting polymer. The former will be achieved by designing synthetic polymers containing mechanoresponsive functional groups that can rearrange to generate strong bases under mechanical actuations. The base in turn will trigger the formation of new polymer chains leading to strengthening of the overall polymeric material. The later project aims at designing new class of phthalonitrile based polymeric resins that undergo self-catalyzed crosslinking or curing. The first generation of these phthalonitrile monomers will contain masked phenolic curing promoters that can be unmasked under mild heating in the presence of suitable additives and then trigger a self-catalyzed polymer curing process.

January 23, 2018 at 2.30 pm in AG-69

Title :

Mechanochemical strengthening of polymeric materials using piezoelectric nanoparticles

Abstract :

Mechanical actuation of synthetic polymers usually results in bond breakage leading to eventual failure. In contrast, biological systems use mechanical force for constructive purposes. For example, bones and muscles heal and become stronger under moderate levels of stress often encountered during exercise. In this talk, I will present my work towards developing synthetic polymeric materials that grow stronger under mechanical activation.

Mechanical force can be harnessed for performing constructive chemistry using the piezoelectric effect. Mechanical activation of piezoelectric nanoparticles generates several volts of electrochemical potential on the nanoscale. I present a method to harness this electro-mechanical reaction to enable polymerization reactions such as atom-transfer radical polymerization (ATRP) and copper-catalyzed azide-alkyne ‘click’ (CuAAC) using piezo reduction to generate a Cu(I) based catalysts. This research project is an entirely new area of polymer mechanochemistry and we were the first to demonstrate piezochemically-activated polymerization reactions. We are now starting to develop polymeric systems in which mechanical stress plays a constructive role. 

 

January 8, 2018 at 4.00 pm in AG-69

Title :

Organic Photocatalysis inside Water-Soluble Supramolecular Cages

January 5, 2018 at 2.30 pm in AG-69

Title :

Making and Breaking of Chemical Bonds with Visible Light

Abstract :

In the recent past visible light photoredox catalysis has gained enormous attention as an energy-efficient and versatile method for chemical synthesis.(1, 2) In my presentations, I will mainly talk about our recent work on visible light photoredox catalysis using stable radical anions of commercially available inexpensive organic dyes.(3-7) The applications of bioinspired consecutive photoinduced electron transfer (conPET)(3, 4, 6, 7) and sensitization initiated electron transfer (SenI-ET)(5) processes will be discussed in the context of breaking and making of stable chemical bonds for useful synthetic transformations.

 

References: 

 

1.  B. Konig, Eur. J. Org. Chem., 1979-1981 (2017).

2.  I. Ghosh, L. Marzo, A. Das, R. Shaikh, B. Konig, Acc. Chem. Res. 49, 1566-1577 (2016).

3.  I. Ghosh, T. Ghosh, J. I. Bardagi, B. Konig, Science 346, 725-728 (2014).

4.  I. Ghosh, B. Konig, Angew. Chem. Int. Ed. 55, 7676-7679 (2016).

5.  I. Ghosh, R. S. Shaikh, B. Konig, Angew. Chem. Int. Ed. 56, 8544-8549 (2017).

6.  A. Das, I. Ghosh, B. Konig, Chem. Commun. 52, 8695-8698 (2016).

7.  L. Marzo, I. Ghosh, F. Esteban, B. Konig, ACS Catal. 6, 6780-6784 (2016).

 

January 4, 2018 at 2.30 pm in AG-80

Title :

Stable Radical Anions in Photocatalysis

Abstract :

In the recent past visible light photoredox catalysis has gained enormous attention as an energy-efficient and versatile method for chemical synthesis.(1, 2) In my presentations, I will mainly talk about our recent work on visible light photoredox catalysis using stable radical anions of commercially available inexpensive organic dyes.(3-7) The applications of bioinspired consecutive photoinduced electron transfer (conPET)(3, 4, 6, 7) and sensitization initiated electron transfer (SenI-ET)(5) processes will be discussed in the context of breaking and making of stable chemical bonds for useful synthetic transformations.

 

References: 

 

1.  B. Konig, Eur. J. Org. Chem., 1979-1981 (2017).

2.  I. Ghosh, L. Marzo, A. Das, R. Shaikh, B. Konig, Acc. Chem. Res. 49, 1566-1577 (2016).

3.  I. Ghosh, T. Ghosh, J. I. Bardagi, B. Konig, Science 346, 725-728 (2014).

4.  I. Ghosh, B. Konig, Angew. Chem. Int. Ed. 55, 7676-7679 (2016).

5.  I. Ghosh, R. S. Shaikh, B. Konig, Angew. Chem. Int. Ed. 56, 8544-8549 (2017).

6.  A. Das, I. Ghosh, B. Konig, Chem. Commun. 52, 8695-8698 (2016).

7.  L. Marzo, I. Ghosh, F. Esteban, B. Konig, ACS Catal. 6, 6780-6784 (2016).

 

December 21, 2017 at 2.30 pm in AG-80

Title :

The electron’s spin and molecular chirality - How are they related and how can they be utilized?

Abstract :

Spin based properties, applications, and devices are commonly related to magnetic effects and to magnetic materials. However, we found that chiral organic molecules act as spin filters for photoelectrons transmission,1  in electron transfer,2 and in electron transport.3

 

The new effect, termed Chiral Induced Spin Selectivity (CISS),4,5  was found, among others, in bio-molecules and in bio-systems. It has interesting implications for the production of new types of spintronics devices,6,7 and on electron transfer in biological systems.8  The basic effect will be explained and various applications and implications will be discussed.

 

References 

 

1.Göhler, B.; Hamelbeck, V.; Markus, T.Z.; Kettner, M.; Hanne, G.F.; Vager, Z.; Naaman, R.; Zacharias,  H. Science 2011, 331, 894.

2.Mishra, D.; Markus, T.Z.; Naaman, R.; Kettner, M.; Göhler, B.; Zacharias, H.; Friedman, N.; Sheves, M.; Fontanesi, C. PNAS,   2013, 110, 14872.

3.Xie, Z.; Markus, T. Z.; Cohen, S. R.; Vager, Z.; Gutierrez, R.; Naaman, R. Nano Letters, 2011, 11, 4652.

4.Naaman, R.; Waldeck, D.H. J. Phys. Chem. Lett. (feature) 2012, 3, 2178.

5.R. Naaman, D. H. Waldeck, Spintronics and Chirality: Spin Selectivity in Electron Transport Through Chiral Molecules, Ann. Rev. Phys. Chem. 2015, 66, 263–81. 

6.O. Ben Dor,  S. Yochelis, A. Radko, K. Vankayala, E. Capua, A. Capua, S.-H. Yang, L. T. Baczewski, S. S. P. Parkin, R. Naaman, and Y. Paltiel, Nat. Comm. 8:14567 (2017).

7.K. Michaeli, V.  Varade, R. Naaman, D. Waldeck, Journal of Physics: Condensed Matter, 29, 103002 (2017) 

8.I. Carmeli, K. S. Kumar, O. Hieflero, C. Carmeli, R. Naaman,  Angew. Chemie  2014, 53, 8953 –8958.

 

December 18, 2017 at 4.00 pm in AG-69

Title : 

Synthesis of TEMPO linked Chromophore Molecules and Their Photophysical Quenching

December 14, 2017 at 2.30 pm in B-333

Title :

Computational Material Design of Two Dimensional Materials and Their Energy Applications

Abstract :

Two-dimensional materials have attracted attention from both fundamental aspects and application. In this work, we will present some of our recent effort to using first-principles based computational tools to design two-dimensional materials for energy applications. We have explored new possible ionic two dimensional materials and discover some that have not been synthesized yet1. Furthermore, their potential applications to adsorption of Li (for battery and hydrogen storage)2 and hydrogen evolution reactions3 are also examined.

 

References :

 

1.Chung-Huai Chang, Xiaofeng Fan, Shi-Hsin Lin, J-L Kuo, Phys. Rev. B, 88, 195420 (2013)

2.S-H Lin, and J-L Kuo, Phys. Chem. Chem. Phys., 16, 20763 (2014)

3.Yun-Wen Chen, Yaojun Du, and J-L Kuo, J. Phys. Chem. C, 118, 20383 (2014)

4.D. B. Putungan, S-H Lin, and J-L Kuo, Phys. Chem. Chem. Phys., 17, 11367 (2015)

 

December 13, 2017 at 11.30 am in AG-66

Title

Vibrational Anharmonicity and IR Spectra of Hydrogen Bonded Clusters

Abstract :

Structure of hydrate proton is typically classified into Eigen (H3O+) and Zundel (H5O2+) forms. While this is a textbook knowledge, it remains very challenging to keep track of their vibrational signatures owing to the strong vibrational coupling. We have developed several computational scheme to reveal the vibrational couplings (from strong to weak) with the hope to link vibrational spectra and the structure of these clusters. Gas-phase ionic spectra collected over the last two decades have provided plenty of experimental vibrational spectra that allow us to examine the vibrational motion of proton in H-bonded cations. In this talk, we will present our recent systematic theoretical studies both different types of Zundel1,2 and H3O+ under different solvation environments3,4. Our theoretical studies engage ab initio treatment on a selected set of quantum degrees of freedom and treat their vibrational anharmonicity/coupling explicitly. If time permits, we will also access the performance of a few approximate treatments on vibrational coupling/anharmonicity to treat larger hydrogen-bonded molecular clusters5

 

References 

 

1.J.A. Tan and J.-L. Kuo. J. Phys. Chem. A., 119, 11320 (2015)

2.J.A. Tan and J.-L. Kuo. Phys. Chem. Chem. Phys., 18, 14531 (2016)

3.J-W Li, M. Morita, T. Takahashi, and J-L Kuo, J. Phys. Chem. A, 119, 10887 (2015)

4.J. Tan, J-W Li, C-c Chiu, H. Huynh, H-Y Liao, and J-L Kuo, Phys. Chem. Chem. Phys., 18, 30721 (2016)

 

5.K-L Ho, L-Y Lee, M. Katada, A. Fujii, and J-L Kuo, Phys. Chem. Chem. Phys., 18, 30498 (2016)

 

 

December 7, 2017 at 2.30 pm in B-333

Title :

Energy Relevant Processes Catalyzed by Corrole Metal Complexes

Abstract:

We have recently introduced corrole metal complexes (metallocorroles) as catalysts for various energy-relevant reactions. This includes those that are of prime importance for the electrochemical splitting of water into its elements, as well as the hydrogen and oxygen evolution reactions. Tuning of the redox potentials, M(I)/M(II) for proton reduction, M(II)/M(III) for oxygen reduction, and M(III)/M(IV)/M(V) for water oxidation (M= Fe, Co, or Mn), is achieved via variations of substituents on the corrole ligand. Practical catalysis is achieved via immobilization onto carbon electrodes, while mechanism-of-action insight is obtained by performing homogenous catalysis and characterization of reaction intermediates. The thus achieved conclusions are used for hypothesis-driven changes in the catalyst’s structures as to achieve the desired properties required for optimal catalytic efficacy and selectivity. This will be demonstrated by the introduction of newly developed catalysts with trifluoromethyl substituents.

 

REFERENCES:

 

•"Metallocorroles as photocatalysts for driving endergonic reactions, exemplified by bromide to bromine conversion", Angew. Chem. 2015, 54, 12370 –12373.

•"Metallocorroles as Non-Precious Metal Catalysts for Oxygen Reduction", Angew. Chem. 2015, 54, 14080 –14084.

•“Metallocorroles as Non-Precious Metal Electrocatalysts for Highly Efficient Oxygen Reduction in Alkaline Media" ChemCatChem 2016, 8, 2832-2837.

•“Metallocorroles as Electrocatalysts for the Oxygen Reduction Reaction (ORR)", Israel J. Chem. 2016, 56, 756– 762 (invited review).

•“Dioxygen bound Cobalt Corroles”, Chem. Commun. 2017, 53, 877-880.

•“Selective CF3 Substitution for Affecting the Physical and Chemical Properties of Gold Corroles” Angew. Chem. 2017, 56, 9837-9841.

•“Corroles as Triplet Photosensitizers”, Coord. Chem. Rev. 2017, 0000.

•“One-pot synthesis of contracted and expanded porphyrins with meso-CF3 groups, from affordable precursors” Angew. Chem. 2017, 56, 0000.

 

December 1, 2017 at 2.30 pm in AG-66

Title :

Exploring the Diverse Conformations and Biological Functions of IDPs

Abstract :

Intrinsically disordered proteins and regions (IDPs/IDRs) constitute about one third of protein sequence space in humans and enable complex conformational and functional behaviors that underlie diverse biological processes.  IDPs can function in the context of discrete multi-component assemblies but recently have been shown to undergo phase separation for form mesoscale cellular structures such as membraneless organelles and transcriptionally silent regions of chromatin.  Due to their heterogeneous and transient conformations, IDPs/IDRs are challenging to characterize at atomic resolution, making it difficult to establish detailed “disorder-function relationships”. We will discuss our multidisciplinary strategies toward understanding the roles of protein disorder in regulation of apoptosis and cell division, nucleolar structure and function, and interactions with small molecules.  A key goal is to illustrate the diversity and uniqueness of disorder-function relationships

November 27, 2017 at 4.00 pm in AG-69

Title :

Femtosecond Stimulated Raman Spectroscopy as a New Tool to Identify Twisted Intramolecular Charge Transfer States

November 23, 2017 at 2.30 pm in AG-80

Title :

Studies on Transition Metal Complexes of Flexible Polydentate Schiff Base Ligands 

Abstract :

The primary objective of this research work was to explore the structure-activity relationship between several kinds of biological, chemical as well as material properties and various complex structures tuned by flexible Schiff base ligands. In this regards several Ni(II) and Cu(II) Schiff base complexes have been synthesized by exploiting the flexibility of the piperazinyl moiety. The specific effectiveness towards DNA/Protein binding and catecholase like properties was observed due to flexibility and nuclearity in case of nickel and copper complexes respectively. Furthermore an interesting counter anion directed flexibility was observed in metal complexes after little modification in Schiff base ligands. Apart from protease, nuclease and catecholase like activities, these complexes have shown effective cytotoxicity towards HeLa cells.

Pseudo-halide promoted and nuclearity driven enhanced corrosion inhibition activity of Zn(II) and Cd(II) Schiff base complexes was also observed to investigate the material applications of Schiff base complexes.

Thus, it could be the stepping stone for further tuning of ligand using flexibility and to develop high nuclearity coordination compounds for more effectiveness in terms of biological and material applications. 

 

November 20, 2017 at 4.00 pm in AG-69

Title :

Synthesis and Comparative Evaluation of Carbon Dots from Glucose Based Saccharides

November 17, 2017 at 2.30 pm in AG-66

Title :

Functional Supramolecular and Polymeric Materials of Extended π-Systems

Abstract :

Hierarchical organization of supramolecular assemblies of π-conjugated molecules plays an important role to device the synthetic systems for efficient lightharvesting1,2. Though supramolecular assemblies of various π-systems are elegantly designed to fine-tune their optical properties, there are several limitations2. Hence, the development of new class of materials is not only important to overcome the existing limitations but also to provide opportunities to uncover their novel properties. In this talk I will discuss about the design, synthesis, optical properties and other novel attributes of two kinds of materials we have developed, namely, organicinorganic soft-hybrids and dynamic conjugated microporous polymers3–6.

 

References:

1. Schenning et al. Chem. Rev. 2005, 105, 1491.

2. Ajayaghosh et al. Chem. Soc. Rev. 2008, 37, 109.

3. K. V. Rao et al. Angew. Chem. Int. Ed. 2011, 50, 1179.

4. K. V. Rao et al. Adv. Mater. 2013, 25, 1713.

5. K. V. Rao et al. Chem. Eur. J. 2012, 18, 4505.

6. K. V. Rao et al. Phys. Chem. Chem. Phys. 2016, 18, 156.