Thesis and Guide details:
Details of CSIR Fellowship/ Associateship held, if any or from other sources/ agencies.
Significant foreign assignments:
(a) Significant contributions to science and/ or technology development by the nominee
based on the work done in India during most part of last 5 years:
The primary objective has been to investigate intermolecular interactions such as hydrogen bonding and π-stacking. Infrared spectroscopy of the donor stretching vibrations is one of the major tools to investigate hydrogen bonding as the donor stretching directly reports the hydrogen bond formation. Several empirical correlations that relate the red-shift in the donor stretching frequencies to various properties of donor and/or acceptor are reported in the literature. It has been observed that these empirical rules are not universal and are dependent on the nature of the. We have demonstrated that the red-shifts in the donor stretching frequencies are linearly correlated with the electrostatic component of the total energy and more interestingly, the total stabilization energy has almost no correlation with the red-shits and is modulated by the dispersion component [Phys. Chem. Chem. Phys. 2014, 16, 25247-25250]. This work has been extended to several series of hydrogen bonded complexes by our group and others and now can be viewed as a universal rule.
Molecules as with multiple hydrogen bonding sites offer a unique opportunity to investigate competitive hydrogen bonding. Phenylacetylene with the absence of lone pair electrons and strongly acidic/basic groups is an unusual molecule, wherein the available sites for hydrogen bonding cannot be ranked into known hierarchical pattern. Several hydrogen bonded complexes of phenylacetylene with a wide variety of solvent molecules were investigated. The diversity of intermolecular structures formed by phenylacetylene with various reagents is remarkable. The nature of intermolecular interaction with various reagents is the result of a subtle balance between various configurations and competition between the electrostatic and dispersion energy terms, while trying to maximize the total interaction strength. Phenylacetylene senses the electrostatic potential of the approaching molecule and acts as a hydrogen bonding chameleon [ChemPhysChem 2011, 12, 26-46].
π-Stacking is yet another important class of intermolecular interaction, which is not understood at molecular level. The key challenge in the detailed understanding of the strength and orientational preferences of the π-stacking interaction is its relatively low stabilization energy and the shallowness of the potential energy surfaces, which can lead to rapid inter-conversion to structures which are close in energy and not necessarily π-stacked. Investigations on gas phase π-stacked complexes are extremely sparse. Using phenylacetylene as a probe molecule, we have demonstrated the propensities for the formation of π-stacked complexes in the gas phase [Phys. Chem. Chem. Phys. 2011, 13, 16706-16712; Phys. Chem. Chem. Phys. 2011, 13, 5514-5525; Phys. Chem. Chem. Phys. 2015, 17, 9090-9097]
Intermolecular Coulombic decay (ICD) is an efficient and fast charge migration process following ionization of inner valence electron. The primary difference in the electron transfer and the ICD process is that for the electron transfer the acceptor state is a bound while for the ICD the acceptor state lies in the continuum.
(b) Impact of the contributions in the field concerned:
(i) N-heteroaromatics have propensity to form π-stacking, however do have competition with hydrogen bonding in the lower analogues. Formation of π-Stacking can be predicted based on the number of nitrogen atoms in the ring.
(ii) A universal law for the red-shifts in the donor stretching frequencies have been demonstrated, which enables the understanding of the hydrogen bonding vis-à-vis IR spectroscopic experiments.
(iii) Experimental demonstration of Intermolecular Coulombic decay in van der Waal’s clusters following ionization on inner valance electrons. It is believed that the free radicals generated as well as the low energy electron generated in the ICD process can have adverse effects in biology, such as DNA damage. On the contrary it is believed that ICD process can trigger the photolyase enzymes which then lead to DNA repair mechanism.
(iv) Our work on phenylacetylenes has inspired groups of Prof. Aruanan from IISc, Prof. Desiraju from IISc and Prof. K. S. Viswanathan from IISER Mohali.
Places where work of last 5 years has been referred/ cited in Books, Reviews:
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The achievements already been recognised by Awards by any learned body:
The Awardee a fellow of the Indian National Science Academy/Indian Academy of Sciences/National
Academy of Sciences/Others:
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Internatiional Conference Symposium:
List of Awardee's 10 most significant publications.
List of Awardee's 5 most significant publications during the last 5 years
List of Awardee's 5 most significant publications from out of work done in India
during the last five years:
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as author):
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