Research

"This page is always under construction"

1.  Gas phase spectroscopy in supersonic molecular jet

2. Study various photo-induced phenomena (proton transfer, electron transfer, charge transfer, energy transfer) in newly designed molecular systems: Spectroscopy, thermodynamics, reaction kinetics, rotational dynamics and solvent-relaxation dynamics

3.Characterizing the interaction of various molecular probes (especially, non-covalent/H-bonding interaction)  with biological, biomimicking and supramolecular assemblies to extract novel insights into the fundamental mechanism of interaction

4.Design, Synthesis and development of artificial chemosensor/receptor toward multidimensional applications 

5. Development of multifunctional materials 

6.Theoretical Modelling: Silico modelling using G03/09 suit, Molecular docking and Molecular dynamics simulations

Gas phase spectroscopy

    Although the nature around us is full of stable molecules in which the atoms are held together with covalent bonds, it is the weak forces that govern their mutual interactions and hence lend them the properties that they exhibit. Hydrogen bonding interaction is omnipresent and has been an active area of investigation for several decades. We are interested in the study of weakly H-bonded clusters of simple self designed molecules capable of proton and electron/charge transfer to explore such weak interactions in gas phase. Basic photo-physical properties of excited state proton-transfer and charge transfer demonstrating molecules are also targeted minutely using gas phase spectroscopic techniques. Laser induced fluorescence (LIF) and Dispersed fluorescence (DF) spectroscopy and related gas phase spectroscopic techniques are ideal in achieving much finer vibrational signatures of isolated molecules compared to conventional condensed phase studies where unavoidable solvent perturbation obscures the fine vibrational structures. Coupled with theoretical calculations, these studies can reveal structure and possible interactions at the molecular level.  Our next goal is to produce clusters of chiral host (R- or S-) with some chiral solvents (R- or S-) in cooled jet. Selective clusters formation will be done with chiral host (solvent) to form preferential clusters (RR or SS or RS or SR). Weak interactions in homo-chiral clusters (RR or SS) are different from those in hetero-chiral clusters (RS or SR), and thus chiral recognition could be possible through selective cluster formation.

We are trying to develop a TOFM spectroscopic set up which is to be coupled with our presently working jet set up to study charged molecular fragments (obtained via two-photon photodissociation), and our target is to study molecules responsible for ozone-hole formation (viz, ClOOCl) and size selected molecular clusters in this set up.

Study various photo-induced phenomena (proton transfer, electron transfer, charge transfer, energy transfer) in newly designed molecular systems

    Proton transfer in hydrogen bonded systems is a central mechanistic and kinetic step in many important reactions and plays a crucial role in many elementary reactions of living systems. Various types of proton transfer reactions, depending on acidity and basicity, adiabatic and non-adiabatic interactions, strong versus weak hydrogen bonding interactions and whether te reaction is taking place in the ground or excited state, have been categorized. Among them, excited state intramolecular proton transfer (ESIPT) reaction is particularly of immense importance and has received considerable attention. In this category we focus mainly on unique systems with proton donor and acceptor sites within the same molecule where cyclic intramolecular hydrogen bonded (IMHB) ring in the ground state facilitates proton transfer in the excited state of the molecule.

     Photo-induced Intramolecular charge transfer (ICT) reaction is an elementary process in the chemistry of excited states. Due to this phenomenon a charge separation results due to transfer of electronic charge from a donor (D) to an acceptor (A) site within the same molecule. The first observation of dual fluorescence in the benchmark molecule 4-N,N-dimethylaminobenzonitrile (DMABN) by Lippert et al. was a major breakthrough in the realm of photoinduced donor-acceptor (D-A) charge transfer processes. In our lab we focus on such flexible ICT producing molecules  and their unique polarity sensitive photo-physics with future plans of fashioning fluorescent sensors from them.

    Fluorescence resonance energy transfer (FRET), the non-radiative transfer of energy from an excited donor fluorophore to a suitable acceptor fluorophore, is an important physical phenomenon with wide range of applications in structural biology and biochemistry for measuring distances between fluorophores in the 10-80Å range. Due to its sensitivity to distance, FRET has been used to investigate molecular level interactions. The mechanism behind FRET is that energy is transferred in a nonradiative fashion from an excited donor fluorophore to a nearby acceptor fluorophore by means of intermolecular long-range dipole-dipole interactions.

Characterizing the interaction of various molecular probes (especially, non-covalent/H-bonding interaction) with biological, biomimicking and supramolecular assemblies to extract novel insights into the fundamental mechanism of interaction

    Weak interactions, especially hydrogen bonding is the pillar of bio-evolution, as it’s responsible for the helicity of DNA and it remains the key mechanism of complementary base pairing. So, it’s important to explore this phenomenon in vitro in condensed phase, especially using various biomimetics and supramolecular assemblies. Some self designed simple molecules, in our case the fluorescent ones are used to probe those micro-heterogeneous environments to get a fair idea of the mechanism behind life. In order to use a molecule as a probe for the aforesaid environments, it’s important first to decipher its basic photo-physical behavior in different solvents differing in polarity, viscosity and hydrogen bonding ability, as well as to study its pH sensitivity to get an approximate insight of the related bio-environments.

    The interaction of drugs with relevant biological receptors is a field of research which still promises viability to significant exploration. Our research interests include an attempt to unravel the effect of drug-binding on the protein secondary and tertiary structures so as to rationalize the applicability of the drug molecule as a therapeutic agent. Furthermore, the complexity and multidimensional nature of such interactions in vivo prompted us to extent such problems by applying in vitro techniques which encourage the use of different biomimetic assemblies which can mimic, at least in part, the physicochemical properties of various biological microenvironments. Our lab is also motivated by the dire ramification and the lack of substantial literature in the field of interaction of prospective drugs for detrimental diseases with various biological and biomimicking assemblies to extract novel insights into the fundamental mechanism of interactions, thermodynamics and kinetics of interaction processes and so forth.

Design, Synthesis and development of artificial chemosensor/receptor toward multidimensional applications

    Heavy/transition metals (Hg2+, Cu2+, Fe2/3+, Zn2+, etc), anions (F-, CN-, H2PO4-, etc) and some neutral molecules (SO2, CO2, TNT, etc.) are dangerous to health or to the environment when it exceeds their natural accumulation limit. So, the development of artificial chromogenic/fluorogenic sensors (host) for environmentally and biologically important ions (cations/anions) and molecules (guest), is the main focus of our current research interest. Again, the construction of interesting host-guest supramolecular architecture is of emerging area in the field of crystal engineering. We are trying to focus on the development of generalized structural mimics for the future construction of interesting host-guest self-assemblies with its sensory actions.

Development of multifunctional materials

    Development of multifunctional properties in a single molecular framework (MOFs, COFs, etc.) drawing an utmost interest in the current chemical research, where the researcher discovers a set of well defined materials with emerging applications such as porosity with electrical conductivity, porosity with optical properties, etc. Such synergism, where two different functionalities are combined, opens up a new window for designing and synthesizing multifunctional materials. We are currently working in this field where we are trying to develop such materials with multidimensional functional properties.                                            

Angew. Chem. Int. Ed., DOI: 10.1002/anie.201205439.

Theoretical Modelling

    To get the better insights into the photophysical properties/electronic structure-property relationships result from various experimental observations, we have performed theoretical/silico model optimization using Gaussian 03/09 suit.  

    Advanced quantum chemical techniques (docking and simulation studies) are applied to decipher the potential roles of various weak interactions (particularly hydrogen bonding, Van-der-Walls interactions, etc.) in controlling the fundamental photophysics of various organic compounds which in turn offer prospective insights toward design-modification and adaptive control for the spectral properties in future applications.