Isolation and characterization of novel broad host range bacteriophages of Vibrio cholerae O1 from Bengal

Objectives: We have isolated a total of five newer cholera phages which are novel broad host range to incorporate with the existing phage typing schemes for an extended typing scheme. Materials and Methods: These newly isolated phages were well characterized including the electron micrograph. A total of 300 Vibrio cholerae strains were isolated from the different endemic region in India were included in phage typing study. Results: These phages were found different from the existing phages. Electron microscopic results showed that the phages belonged to myophage and podophage group. Characterization of the phages based on pH, temperature, and organic solvent sensitivity showed differences among the phages used in this study. All the strains of Vibrio O1 were typeable (100%) with the five set of cholera phages. Of these, 40% strains were clustered under Type-1. Conclusion: The newer Vibrio phages are novel and broad host range and will be useful to incorporate with the existing phage typing system for more precisely discriminate the strains of Vibrio cholerae

Catalytic Activity of Group Nine Metallo-porphyrins Towards Small Molecule Activation and Substrate Reactions in Conventional and Novel Ionic Liquid Media

The core objective of this thesis has been to investigate the thermodynamic, kinetic and reactivity behaviors of group 9 metalloporphyrins in a wide range of solvents and reaction media in order to develop reliable, atom-economic and environment friendly catalysts and catalytic systems for activation of small molecules like H2, O2, CO and straight chain alkenes and catalytic transformation of these substrates to commercially viable products and intermediates for commodity chemical manufacturing and renewable energy resources. Equilibrium thermodynamic studies with methanol soluble rhodium porphyrins allowed experimental evaluation of Rh-OCH3 Bond Dissociation Free Energy (BDFE) for (porphyrin)Rh-OCH3 complex. Study of kinetics for simultaneous proton and ligand (methanol) exchange processes in solutions of rhodium porphyrins in methanol/benzene mixed solvent systems showed that rate of proton exchange between two opposite faces of the metalloporphyrin was found to follow a second order dependence on the concentration of methanol in the reaction mixture. The rate of exchange of methanol coordinated to the metal center of meso-tetra(mesityl)porphyrin rhodium(III) species (TMP)Rh III(OCH3)(CH3OH) with methanol molecules in bulk solvent showed unusual undulations with increase in bulk methanol concentration in the reaction medium which has been explained in this thesis to be occurring due to fluctuation in viscosity dependent diffusion free energy for non-ideal methanol/benzene mixed solvent system. Equilibrium thermodynamics for reactions of rhodium porphyrin in methanol with a range of small molecule substrates like methanol, H2, CO, aldehydes, activated and inactivated alkenes have been reported in this thesis. The comprehensive dataset for thermodynamic, kinetic and reaction properties of rhodium porphyrins in methanol thus obtained augments the already existing database for solution thermodynamic and reaction properties of rhodium porphyrins in benzene and water. The prospect of using water soluble cobalt complex of meso-tetra(3,5-disulfonatomesityl) porphyrin (TMPS) as an inexpensive catalyst for oxidation and oxidative cleavage of terminal olefins to generate respectively vicinal diols and aldehydes in environmentally responsible fashion in water using molecular dioxygen as terminal oxidant has been discussed. A series of partially deuterated, low-viscosity, low melting N-butylpyridinium(d5) based ionic liquids were designed as base-stable, environment friendly and thermochemically inert reaction media which would also double as optically transparent spectroscopic solvent for allowing mechanistic evaluation of Rhodium(I) porphyrin catalyzed anti-Markovnikov hydroxylation of terminal unactivated alkenes to generate primary alcohols using conventional 1H NMR and electronic spectroscopic instrumentations. The viability of these newly developed partially deuterated ionic liquids as suitable alternatives for conventional organic solvents for supporting the proposed mechanism-guided rhodium porphyrin catalyzed anti-Markovnikov hydroxylation of unactivated terminal alkenes has been established by preliminary proof-of-principle experiments

Catalytic Activity of Group Nine Metallo-porphyrins Towards Small Molecule Activation and Substrate Reactions in Conventional and Novel Ionic Liquid Media

The core objective of this thesis has been to investigate the thermodynamic, kinetic and reactivity behaviors of group 9 metalloporphyrins in a wide range of solvents and reaction media in order to develop reliable, atom-economic and environment friendly catalysts and catalytic systems for activation of small molecules like H2, O2, CO and straight chain alkenes and catalytic transformation of these substrates to commercially viable products and intermediates for commodity chemical manufacturing and renewable energy resources. Equilibrium thermodynamic studies with methanol soluble rhodium porphyrins allowed experimental evaluation of Rh-OCH3 Bond Dissociation Free Energy (BDFE) for (porphyrin)Rh-OCH3 complex. Study of kinetics for simultaneous proton and ligand (methanol) exchange processes in solutions of rhodium porphyrins in methanol/benzene mixed solvent systems showed that rate of proton exchange between two opposite faces of the metalloporphyrin was found to follow a second order dependence on the concentration of methanol in the reaction mixture. The rate of exchange of methanol coordinated to the metal center of meso-tetra(mesityl)porphyrin rhodium(III) species (TMP)Rh III(OCH3)(CH3OH) with methanol molecules in bulk solvent showed unusual undulations with increase in bulk methanol concentration in the reaction medium which has been explained in this thesis to be occurring due to fluctuation in viscosity dependent diffusion free energy for non-ideal methanol/benzene mixed solvent system. Equilibrium thermodynamics for reactions of rhodium porphyrin in methanol with a range of small molecule substrates like methanol, H2, CO, aldehydes, activated and inactivated alkenes have been reported in this thesis. The comprehensive dataset for thermodynamic, kinetic and reaction properties of rhodium porphyrins in methanol thus obtained augments the already existing database for solution thermodynamic and reaction properties of rhodium porphyrins in benzene and water. The prospect of using water soluble cobalt complex of meso-tetra(3,5-disulfonatomesityl) porphyrin (TMPS) as an inexpensive catalyst for oxidation and oxidative cleavage of terminal olefins to generate respectively vicinal diols and aldehydes in environmentally responsible fashion in water using molecular dioxygen as terminal oxidant has been discussed. A series of partially deuterated, low-viscosity, low melting N-butylpyridinium(d5) based ionic liquids were designed as base-stable, environment friendly and thermochemically inert reaction media which would also double as optically transparent spectroscopic solvent for allowing mechanistic evaluation of Rhodium(I) porphyrin catalyzed anti-Markovnikov hydroxylation of terminal unactivated alkenes to generate primary alcohols using conventional 1H NMR and electronic spectroscopic instrumentations. The viability of these newly developed partially deuterated ionic liquids as suitable alternatives for conventional organic solvents for supporting the proposed mechanism-guided rhodium porphyrin catalyzed anti-Markovnikov hydroxylation of unactivated terminal alkenes has been established by preliminary proof-of-principle experiments

A heuristic approach to evaluate peri interactions versus intermolecular interactions in an over-crowded naphthalene

Octachloronaphthalene (OCN), a serious environmental pollutant, has been investigated by charge density analysis to unravel several unexplored factors responsible for steric overcrowding. The topological features of the enigmatic peri interactions contributing to steric overcrowding are qualified and quantified from experimental and theoretical charge-density studies. A new facet in the fundamental understanding of peri interactions is revealed by NCI (noncovalent interaction) analysis. The potential role of these interactions in deforming the molecular geometry and subsequent effect on aromaticity are substantiated from NICS (Nuclear Independent Chemical Shift) and QTAIM (Quantum Theory of Atoms in Molecules) calculations. The eye-catching dissimilarity in the out-of-plane twisting of OCN renders the molecule in an asymmetric geometry in the crystalline phase compared with symmetric geometry in the optimized solvated phase. This is uniquely characterized by their molecular electrostatic potential (MESP), respectively, and is explained in terms of conflict between two opposing forces-peri interactions, and symbiotic intermolecular Cl...Cl and Cl...pi contacts

Experimental validation of `pnicogen bonding' in nitrogen by charge density analysis

The participation of a nitrogen atom acting as an electrophile in pnicogen bonding, a hitherto unexplored interaction has been established by experimental charge density analysis. QTAIM and NBO analyses ratify this observation

Chemical Bonding Origin of Mechanically Induced Glass Formation in a Coordination Polymer

Mechanically induced glass (MIG) formation of coordination polymers (CPs) is a rare phenomenon, and the origin of the mechanical stability in CPs remains largely unknown. Here, we report accurate X-ray electron densities of three two-dimensional CPs, an orthorhombic Mn(1,2,4-triazole)2(H2PO4)2 (Mn-Tz) CP, which undergoes MIG formation, and the isostructural Co-Tz and Zn-Tz materials, which remain crystalline under mechanical milling. Chemical bonding analysis shows that the framework composed of Mn–N bonds is predominantly ionic in nature, while the Co–N and Zn–N bonds have distinct covalent features. High-pressure single-crystal X-ray diffraction measurements carried out to mimic mechanical milling reveal that Mn-Tz undergoes a pressure-induced phase transition above 3.1 GPa to a new monoclinic γ-phase. The γ-Mn-Tz phase exhibits severe structural instability up to 4.5 GPa due to local distortions caused by folding of the ionic Mn-triazole-Mn framework. In contrast, the covalent frameworks stabilize Co-Tz and Zn-Tz up to 4.6 GPa beyond which they transform to a less distorted different monoclinic β-phase. Our results demonstrate the exclusive role of the nature of metal–ligand bonds on the mechanical stability of CPs, and they further aid the rational design of MIG-forming CPs

Exploring the rare S-H center dot center dot center dot S hydrogen bond using charge density analysis in isomers of mercaptobenzoic acid

Experimental and theoretical charge density analyses on isomers of mercaptobenzoic acid have been carried out to quantify the hydrogen bonding of the hitherto less explored thiols, to assess the strength of the interactions using the topological features of the electron density. The electron density study offers interesting insights into the nature of the S-H center dot center dot center dot S interaction. The interaction energy is comparable with that of a weak hydrogen bond. The strength and directionality of the S-H center dot center dot center dot S hydrogen bond is demonstrated to be mainly due to the conformation locking potential of the intramolecular S center dot center dot center dot O chalcogen bond in 2-mercaptobenzoic acid and is stronger than in 3-mercaptobenzoic acid, which lacks the intramolecular S center dot center dot center dot O bond. The para-substituted mercaptobenzoic acid depicts a type I S center dot center dot center dot S interaction

Chemical Bonding Origin of Mechanically Induced Glass Formation in a Coordination Polymer

Mechanically induced glass (MIG) formation of coordination polymers (CPs) is a rare phenomenon, and the origin of the mechanical stability in CPs remains largely unknown. Here, we report accurate X-ray electron densities of three two-dimensional CPs, an orthorhombic Mn(1,2,4-triazole)2(H2PO4)2 (Mn-Tz) CP, which undergoes MIG formation, and the isostructural Co-Tz and Zn-Tz materials, which remain crystalline under mechanical milling. Chemical bonding analysis shows that the framework composed of Mn–N bonds is predominantly ionic in nature, while the Co–N and Zn–N bonds have distinct covalent features. High-pressure single-crystal X-ray diffraction measurements carried out to mimic mechanical milling reveal that Mn-Tz undergoes a pressure-induced phase transition above 3.1 GPa to a new monoclinic γ-phase. The γ-Mn-Tz phase exhibits severe structural instability up to 4.5 GPa due to local distortions caused by folding of the ionic Mn-triazole-Mn framework. In contrast, the covalent frameworks stabilize Co-Tz and Zn-Tz up to 4.6 GPa beyond which they transform to a less distorted different monoclinic β-phase. Our results demonstrate the exclusive role of the nature of metal–ligand bonds on the mechanical stability of CPs, and they further aid the rational design of MIG-forming CPs