Debdutta Chakraborty

In Quest of a Superhalogen Supported Covalent Bond Involving a Noble Gas Atom

The possibility of having neutral Xe-bound compounds mediated by some representative transition metal fluorides of general formula MX3 (where M=Ru, Os, Rh, Ir, Pd, Pt, Ag, Au and X=F) has been investigated through density functional theory based calculations. Nature of interaction between MX3 and Xe moieties has been characterized through detailed electron density, charge density and bond energy decomposition analyses. The feasibility of having compounds of general formula XeMX3 at 298 K has been predicted through thermodynamic considerations. The nature of interaction in between Xe and M atoms is partly covalent in nature and the orbital interaction is the dominant contributor toward these interactions as suggested by energy decomposition analysis.

Confinement induced thermodynamic and kinetic facilitation of some Diels–Alder reactions inside a CB[7] cavitand

The effect of geometrical confinement on the Diels–Alder reactions between some model dienes viz. furan, thiophene, cyclopentadiene, benzene, and a classic dienophile, ethylene has been explored by performing density functional theory‐based calculations. The effect of confinement has been imposed by a rigid macrocyclic molecule cucurbit[7]uril (CB[7]). Results indicate that all the reactions become thermodynamically more favorable at 298.15 K temperature and one atmospheric pressure inside CB[7] as compared to the corresponding free gaseous state reactions. Moreover, the rate constants associated with the reactions experience manifold enhancement inside CB[7] as compared to the “unconfined” reactions. Suitable contribution from the entropy factor makes the concerned reactions more facile inside CB[7]. The energy gap between the frontier molecular orbitals of the dienes and dienophiles decrease inside CB[7] as compared to that in the free state reactions thereby allowing facile orbital interactions. The nature of interaction as well as bonding has been analyzed with the help of atoms‐in‐molecules, noncovalent interaction, natural bond orbital as well as energy decomposition analyses. Results suggest that all the guests bind with CB[7] in an attractive fashion. Primarily, noncovalent interactions stabilize the host–guest systems.

Host–guest interactions between octa acid and cations/nucleobases

The nature of host–guest interaction in between octa acid cavitand (OA) and some representative cationic guests (Li+, Na+, K+, Be+2, Mg+2, Ca+2, Li3O+, Na3O+, K3O+) as well as heterocyclic moieties like [adenine (A), guanine (G), cytosine (C), thymine (T), uracil (U), and tetrathiafulvalene (TTF)] has been examined with the aid of density functional theory (DFT)‐based computations. Thermochemical results indicate that all the guests bind with OA in a thermodynamically favorable fashion at 298.15 K temperature and one atmospheric pressure. OA exhibits high selectivity in binding the lighter cations/metal cluster cations as compared to the heavier congeners along each given series. Moreover, OA exhibits enhanced affinity as well as selectivity in binding A/G/TTF molecules as compared to C/T/U. Noncovalent interaction and energy decomposition analyses reveal that in addition to the van der Waals interaction, significant contribution from electrostatic as well as orbital interactions dictate the outcome in all the host–guest complexes. Time dependent DFT calculations have been carried out to assess the role of the guests in tuning the electronic properties as well as absorption spectrum of OA.

Effect of functionalization of boron nitride flakes by main group metal clusters on their optoelectronic properties

The possibility of functionalizing boron nitride flakes (BNFs) with some selected main group metal clusters, viz. OLi4, NLi5, CLi6, BLI7 and Al12Be, has been analyzed with the aid of density functional theory (DFT) based computations. Thermochemical as well as energetic considerations suggest that all the metal clusters interact with the BNF moiety in a favorable fashion. As a result of functionalization, the static (first) hyperpolarizability ([Formula: see text]) values of the metal cluster supported BNF moieties increase quite significantly as compared to that in the case of pristine BNF. Time dependent DFT analysis reveals that the metal clusters can lower the transition energies associated with the dominant electronic transitions quite significantly thereby enabling the metal cluster supported BNF moieties to exhibit significant non-linear optical activity. Moreover, the studied systems demonstrate broad band absorption capability spanning the UV-visible as well as infra-red domains. Energy decomposition analysis reveals that the electrostatic interactions principally stabilize the metal cluster supported BNF moieties.

Reactions involving some gas molecules through sequestration on Al12Be cluster: An electron density based study

The viability of sequestering gas molecules (CO, NO, CO2, NO2, N2O, O2, O3, H2O, NH3, H2, CH3OH, CH3F, C2H5F, C2H2, C2H4, HCN, and SO2) on the Al12Be cluster is investigated by carrying out density functional theory based computations. Thermochemical as well as energetic considerations suggest that Al12Be cluster adsorbs the chosen gas molecules in a favorable fashion. The gas molecules attain an activated state on getting adsorbed on the metal cluster as vindicated by Atoms‐in‐Molecule analysis. The possibility of CO oxidation, dissociative addition of CH3F and C2H5F, NH bond decomposition in NH3, dissociation of NO, and hydrogenation of C2H2 reactions on Al12Be cluster has been investigated. Results indicate that all the reactions take place in a thermodynamically favorable way at 298.15 K and one atmospheric pressure. The first five reactions aforementioned are kinetically favorable also and therefore are amenable to ambient temperature and pressure conditions.

Interaction of BN- and BP-doped graphene nanoflakes with some representative neutral molecules and anions

The interaction of BN- and BP-doped graphene nanoflakes with some representative neutral molecules and anions (H2O, HF, SH−, CH3O−, BO2−, F−) has been studied through density functional theory (DFT) calculations. The neutral molecules remain physisorbed whereas all the anions but one remains chemisorbed. Thermodynamically, most of the studied systems are found to be stable. Conceptual DFT-based reactivity descriptors were employed in order to provide rationale behind such observation. The nature of interactions in cases of the anions is predominantly of covalent type whereas the same for neutral molecules is of non-covalent type. The electrostatic and orbital interactions play important roles in stabilising the absorbed moieties. The kinetic stability of the absorbed moieties is confirmed through an atom-centred density matrix propagation simulation at 298 K temperature up to 500 fs. All the studied systems show excellent kinetic stability and remain absorbed up to 500 fs exhibiting rich vibrational and rotational dynamical evolutions.