The title transformations are oxygen atom transfer, twin isomerization and regiospecific imine oxidation.Bispyridyldiazole ligands have furnished new oxygen atom transfer reagents of coordination type Re^VOCl₃(NN) which undergo a slower transfer to PPh₃ than the corresponding azole reagents. The rate of twin isomerization (linkage and geometrical) of meridional azole complexes of coordination type Re^III(OPnP)Cl₃(NN) to facial Re^III(PnPO)Cl₃(NN) decreases rapidly asn increases in the interval 1–4 (PnP is Ph₂P(CH₂)_nPPh₂). An α-diimine chelate of type Re^V(NPh)Cl₃(NN) is shown to undergo facile oxidation to the corresponding iminoamide complex Re_VI(NPh)Cl₃(NN) upon treating with dilute nitric acid. The reaction proceeds via regiospecific nucleophilic addition of waterto the more polarized imine function.

The apo-Calfumirin-1 (CAF-1) binds to Ca²⁺ with high affinity and also to Mg²⁺ with high positive cooperativity. The thermal unfolding curves of wtCAF-1 monitored at neutral pH by CD spectroscopy are reversible and show different thermal stabilities in the absence or presence of Ca²⁺ and Mg²⁺ ions. Metalfree wtCAF-1 shows greater thermal stability than EF-IV mutant protein. We observed that GdnHCl-induced unfolding of apo-wtCAF-1 monitored by CD and fluorescence spectroscopies increases co-operative folding with approximately same C$_m$ values. Binding of Ca²⁺ and Mg²⁺ ions to CAF-1 dramatically altered the fluorescence and CD spectra, indicating metal ion-induced conformational changes both in the wild-type and mutant proteins. The hydrophobic probe, ANS is used to observe alteration in surface hydrophobicity of the protein in different ligation states. In apo-wtCAF-1, the exposed hydrophobic surfaces are able to bind ANS which is in contrast to the unfolded or the metal ions ligated conformations. Isothermal titration calorimetry (ITC) resultsshow two possible independent binding sites of comparable affinity for the metal ions. However, their binding to the EF-IV E helix-loop-F helix mutant apo-protein happens with different affinities. The present study demonstrates that Ca²⁺ or Mg²⁺ binding plays a possible role in the conformational stability of the protein.

Thermal stability and thermal expansion of bromo trimer synthon mediated hexagonal inclusion compounds of 2,4,6-tris(4-bromophenoxy)-1,3,5-triazine (BrPOT) with dichloromethane (DCM), tetrahydrofuran (THF) and hexamethyl benzene (HMB) and also the guest-free form of BrPOT are reported. Each of these three guests produced two concomitant inclusion compounds with BrPOT. The thermal stability of the solvate lattice increases with decreasing cavity size. The channel network of the DCM inclusion compound is stable only for a few seconds at room temperature outside the mother liquor, whereas the cage network of the DCM solvate is stable for months under similar conditions. Thermal expansions of the lattices depend upon the network, guest content as well as the type of guest molecules. The guest-free form exhibits the least thermal expansion in this series of systems.

Two analogous tripodal ligands, namely, 1,3,5-tris(benzimidazol-1-ylmethyl)-2,4,6-triethylbenzene (1-Et) and 1,3,5-tris(benzimidazol-1-ylmethyl)-2,4,6-trimethoxybenzene (1-OMe) have been used for complexation with silver(I) tetrafluoroborate. A trinuclear Ag(I) salt, formulated as $\mathbf{[Ag_3(1-Et)_2]^{3+}(BF_4){}^{−}_{3}\bullet 7CH_3CN\bullet yH_2O}$ was formed in the complexation reaction of 1-Et with silver(I) tetrafluoroborate, which consists of a trigonal prismatic cation formed by three bicoordinated Ag(I) coordinated with two 1-Et ligands. In case of the 1-OMe ligand, however, a one dimensional ladder, formulated as $\mathbf{[(Ag(1-OMe)OH_2)^{+}(BF_4)^{−}\bullet MeOH]_{\infty}}$ was obtained which is constituted of a tetracoordinated Ag(I) center in a distorted tetrahedral environment. The crystal structures of the ligand hydrates namely $\mathbf{1-Et\bullet H_2O}$ and $\mathbf{1-OMe\bullet 3.6H_2O}$ have been discussed along with the structure of methanol solvate-hydrate of 1-Et. The imidazole rings of the Bim groups in 1-Et in the crystal structures of the ligand as well as in its coordination complex with the Ag(I) are pointed inward with respect to the central ring, whereas it is pointed outwards in the crystal structures of 1-OMe as well as its Ag(I) complex.

A new class of efficient colorimetric chemosensors derived from 4-[(nitro substituted-phenyl)-hydrazonomethyl]-1-phenyl-1H-pyrazole-3-carboxylate have been synthesized and characterized. The synthesized receptors exhibit instant color change from yellow to dark purple along with significant bathochromicshifts when interacted with fluoride ions. The UV-Visible and ¹H NMR titration experiments revealed that 4-[(4-nitro-phenyl)-hydrazonomethyl]-1-phenyl-1H-pyrazole-3-carboxylate derivatives showed selective sensing of fluoride ions in preference to Cl⁻, Br⁻, I⁻, PF⁻⁻, HSO₄⁻, ClO₄⁻ , CH₃COO⁻ and H₂PO₄⁻ ions while 4-[2,4-dinitro-phenyl)-hydrazonomethyl]-1-phenyl-1H-pyrazole-3-carboxylate derivatives showed sensing of acetate, dihydrogen phosphate ion and fluoride ion in organic media.

Extensive computer simulations with deep eutectics made of acetamide (CH₃CONH₂) and lithium salts (LiX) have been performed at 303 K and 350 K to identify the solution-phase microstructures in these media and investigate the anion dependence of the size and lifetime distributions of these microstructures. In addition, we explore how the added electrolyte interferes with the natural hydrogen bonded (H-bonded) network structure of liquid acetamide. For this purpose several radial distribution functions have been analysedand visualised. The results reveal that amide–amide H-bond interaction decreases significantly upon the addition of electrolyte, and the interactions of Li⁺ and X⁻ (X⁻ being NO⁻3 , Br⁻ and ClO⁻4 ) with CH₃CONH₂ lead to heterogeneous solution structures. Furthermore, we have obtained the cluster size and lifetime distributions in order to estimate the size of local microstructures and their stability. Both these distributions are analysed by separating the contributions arising from (a)CH₃CONH₂−CH₃CONH₂, (b)Li⁺−CH₃CONH₂ and (c) Li⁺−X⁻ interactions. The size distribution of Li⁺−X⁻ clusters is found to be different from those for the other two. Also, the lifetime distributions show a pronounced anion dependence and suggest cluster stability time up to a fewnanoseconds.

Concanavalin A (ConA) is a plant lectin having industrial and biological applications. Concanavalin A changes conformation upon exposure to different stress conditions, like exposure to sodium dodecyl sulphate, guanidine hydrochloride, varying hydronium ion potential, etc. The conformational changes were studied using circular dichroism spectroscopy and the structural rigidity of ConA was explored using fluorescence spectroscopy, taking tryptophan as an intrinsic and 8-anilino-1-naphthalenesulfonic acid as an extrinsic fluorescence probes, in different stress conditions. ConA loses the quaternary structure in all the studied stress conditions, which further leads to denaturation of the protein. However, the mechanism of denaturation varied with the studied conditions, like different SDS concentrations and hydronium ion potentials, wherein the proteinundergoes a conformational rearrangement from β-sheet to α-helix. Moreover, GdnHCl triggered complete denaturation of ConA into a predominantly random coil conformation. The results suggested that denaturation of ConA follows different pathways depending on the chemical properties and concentrations of the denaturants used.

Phosphate diesters are well known to form intermolecular H-bonded dimeric structures in their solid-state. Recently, we reported 2,6-(CHPh)₂-4-iPr-phenyl substituted phosphate diester exists as H-bonded monomeric molecular structure along with water dimer in the solid-state. Herein we report 2,6-(CHPh)₂-4-iPr-phenyl substituted phosphate diester forms a monomeric molecular structure in the solid-state upon cocrystallization with dimethylformamide, DMF(Me₂NCHO). The -CHO group of DMF simultaneously acts as an H-bond acceptor to P-OH and an H-bond donor to P=O moieties. We also used the alcohols, ROH (R = Me, Et, iPr, and tBu), for crystallisation of 2,6-(CHPh)₂-4-iPr-phenyl substituted phosphate diester. In these instances, solvent-incorporated dimeric structures are found in the solid-state. We also report the syntheses and molecular structures of anionic phosphate diesters of 2,6-(CHPh)₂-4-iPr-phenyl substitutedphosphate diester possessing various counter cations. Moreover, we also report the syntheses and molecular structures of phosphate diesters based on (-)-menthol, (?)-menthol and (?)/(-)-menthol. These exist as H-bonded dimers in the solid-state.