Research

Spin plays a central role in the chemistry and the spin-dependent magnetic interactions are very important in describing the energetics and electronic structure of open-shell complexes relevant in catalysis and molecular magnetism.  Thus, understanding the magnetic interactions (anti ferromagnetic vs ferromagnetic alignment of spins) in molecular complexes and solids are  of prime importance. Using state-of-the-art computational methods in DFT framework and ab initio framework, we focus on understanding the different type of magnetic interactions (isotropic, mixed valency (double exchange) and anisotropic exchange (orbital dependent)) in variety of organic radicals, transition metal and lanthanide based complexes. We in-depth analyze the mechanism of magnetic exchange interaction and develop the robust magneto-structural correlations to control and predict the magnetic properties in polynuclear framework. 

Open-shell transition metal complexes are ubiquitous in the field of catalysis, biology, material science. To elucidate the electronic structure of these complexes, we employ state-of-the-art computational methods to model the spectroscopic properties such as Nuclear Magnetic Resonance (NMR) and Electron paramagnetic resonance (EPR) spectroscopy, UV-VIS and X-ray absorption properties.  Computational Chemistry play a vital role as it is not only limited to the extraction of these parameters but also to extract the maximum chemical information – such as gaining more insight into the new and exotic chemical species, correlating electronic structure to the reactivity of the complexes and many more. 

Chemistry of f-elements in particular actinides and transactinides is a challenge for modern quantum chemistry because of the complexity of their electronic structure, The presence of high density of electronic states arising from degeneracy or near degeneracy of the orbitals, subtle actinide-ligand covalency, and most importantly, proper treatment of relativistic effects are significant in describing the electronic structure of actinide complexes. Besides this fundamental interest, there is a strong incentive for practical applications of theory to predict the behavior of actinide and trans-actinide species in a variety of circumstances impacting waste repositories and designing selective chemical separation methodologies and storage procedures, designing novel molecule based magnets and catalysts. Using relativistic computational approach, we study the importance of relativistic effects and its treatment, nature of f-ligand covalency, metal-metal bonding, role of spin-orbit interactions and understand the electronic, magnetic, spectroscopic and catalytic properties of actinide complexes. 

Our group is actively involved in computational modeling of catalytic sites and their potential interaction with substrates, prediction of energetic details of various metal-mediated organic transformations. We are actively involved in understanding the fundamentals of small molecule activations (CO2, N2, O2) mediated by transition metal/actinide molecular complexes.  Here we employ state-of-the-art computational methods to explore the electronic structure and reactivity of such systems. These works are carried out closely in collaboration with our experimental collaborators to rationalize and exploit the reactivity. 

Single-molecule magnets (SMMs) are fascinating materials that exhibit magnetic behavior at the molecular level, which is usually seen in bulk materials like ferromagnets. These systems are composed of individual molecules that can function as magnets, with a large magnetic moment and slow relaxation of magnetization at low temperatures. Our research group is dedicated to computational modeling of potential single-molecule magnets (SMMs) with a focus on unraveling their electronic structures and forecasting the next generation of molecular magnets. We employ advanced ab initio computational techniques, including CASSCF, RASSCF, and CASPT2, which enable us to explore the intricate electronic properties underlying the magnetic behavior of these molecules. Building on our findings, we also predict and design hypothetical molecules with the potential to become even more potent SMMs. 

The recent development in the field of computational chemistry allows us to determine the spectroscopic, electronic properties as well as reaction energies to reasonable accuracy. To-date, density functional theory (DFT) methods become routine computer experiment to be performed for the calculations of spectroscopic and electronic properties both by theoreticians and experimentalist. Particularly the metal complexes possess large spin-orbit interactions, complex spin-state energetics, orbital degeneracy which often demand a careful consideration on the selection/choice of the methods to obtain chemically meaningful information about the electronic structure. Our aim is to benchmark computationally challenging and demanding properties such as, magnetic exchange interactions, spin-state energetics, zero field splitting, redox potential, EPR, NMR and Mossbauer parameters of inorganic complexes. Modern DFT methods as well as closed/open-shell DLPNO- CCSD(T) and multireference CASSCF/PT2 methods will be tested to their limits to highlight the applicability and limits of these computational methods for calculations of paramagnetic properties.