Transition metal chemistry of oxime-containing ligands,VI: magnetic and structural properties of mono (pyridine-2-aldoxime) dithiocyanato iron (II) and mono (6-methylpyridine-2-aldoxime) dithiocyanato iron (II) complexes

The complexes of pyridine-2-aldoxime (HPOX) and 6-methylpyridine-2-aldoxime (HMPX) with iron (II) thiocyanate of the type [Fe(L)(NCS)₂] (L=HPOX and HMPX) have been prepared and characterized. A study of X-ray, magnetic, vibrational spectra (conventional and far-infrared), electronic spectra andMössbauer spectra has indicated that these complexes have polymeric, pseudo octahedral, coordination geometry with linear bridging thiocyanate ligands. The electronic spectra of mono complexes show a larger, low symmetry, ligand field than that present in [Fe(L)₂(NCS)₂] complexes. UnperturbedMössbauer spectra show a large quadrupole splitting, E _Q, and smaller isomer shift values in these iron (II) thiocyanate complexes. The magnetically perturbedMössbauer spectra of these iron(II) thiocyanate complexes at room temperature show that the principal component of the electric field gradient tensor is positive and corresponds to ad _xy (⁵B₂) ground state.With 2 Figures     

Direct synthesis of Poly(Ԑ-Caprolactone)-block-poly (glycidyl methacrylate) copolymer and its usage as a potential nano micelles carrier for hydrophobic drugs

Ring-opening (ROP) and enzymatic copolymerization (ECP) are among the most widely used approaches for synthesizing copolymers of polycaprolactone (PCL). It involves multiple-step reactions and the utilization of enzymes that make the process a lot more complicated, time consuming, and expensive. Atom transfer radical polymerization (ATRP) has been adopted to synthesize a novel amphiphilic copolymer in our study. The study presents a method to eliminate the ROP/ECP multiple steps in monomer polymerization thus making the process simpler and smoother. The synthesis of cationic polymer micelles copolymer of PCL-PGMA (polycaprolactone grafted poly glycidyl methacrylate) was carried out using direct functionalization of hydroxy group in crude PCL to achieve a higher degree of functionalization, i.e., 12.8% for macroinitiator. FTIR and ¹H-NMR confirmed the successful synthesis of the copolymer with better control over the molecular weight with a PDI (1.84). DSC and XRD results showed the reduction of crystallinity by 86.81%, making copolymer more compatible for drug delivery application. The synthesized copolymer was further converted to nano-micelles drug carrier having an average size of 96.08 ± 21.22 nm. The drug encapsulation efficiency achieved was 60.0 ± 1.7%, and nano-micelles rendered a slow and controlled release of naproxen with long-term storage stability.     

Cooperative Effect of Noncovalent Interactions on Tetrel Bonding in Halogenated Silanes

Tetrel bond, a weak noncovalent interaction between the σ-hole of a Group IV element (silicon in our case) and the cloud of an electronegative element (oxygen in our case) is the focus of this work. The percentage strengthening of tetrel bond has been investigated by optimizing 16 binary complexes of halogenated silane and water of general formula SiX_nH_4−n−H₂O and 16 ternary complexes, of general formula NaX−SiX_nH_4−n−H₂O, where X=F, Cl, Br and I and n=1, 2, 3 and 4 at various levels of theory defined within the formalism of density functional theory (DFT). With the addition of NaX, tetrel bond between Si and O in SiX_nH_4−n−H₂O gets strengthened up to 49 %, owing to cooperativity effect exerted by hydrogen bonding between X and H in the ternary complex NaX−SiX_nH_4−n−H₂O. In the series of complexes studied here, overall stabilization due to cooperativity lies between 10 kJ/mol to 170 kJ/mol. This large extent of reinforcement due to cooperativity has never been showcased before. The exceptional stabilization and reinforcement owe its genesis to the transformation of the ternary complex into a cluster orchestrated by the H-bonding in most of the cases and covalent bonding in few of the cases.     

Synthesis of Peptide Cysteine Dimedone Using Fmoc-Cys(Dmd)-OH: Glutathione Cysteine Dimedone as a Probe in Investigating the Sulfenic Acid Mediated Oxidation of Glutathione

Dimedone is the most widely used chemical probe for detection of cysteine sulfenic acid in peptides and proteins. The reaction of dimedone with cysteine sulfenic acid results in the formation of unique cysteine dimedone motif containing thioether bridge. Based on the structure of cysteine dimedone residue in polypeptide, a new building block of Fmoc-Cys(Dmd)-OH was developed for solid phase synthesis of peptide cysteine dimedone. Mass spectrometric sequencing of synthetic peptides have confirmed successful incorporation of cysteine dimedone in peptide chain using HBTU/HOBt as a coupling agent. The new method permits synthesis of peptides containing both cysteine thiol and cysteine dimedone in the same sequence which was difficult to achieve by conventional methods. The synthetic peptide of glutathione cysteine dimedone was used as a standard in probing the air-mediated oxidation of thiol to disulfide form of glutathione. The co-elution of standard peptide and reaction mixture of oxidation of glutathione in presence of dimedone using RP-HPLC have confirmed the formation of glutathione cysteine sulfenic as an intermediate in the air-mediated oxidation of glutathione. The synthetic peptides of cysteine dimedone may find application in the field of redox proteomics and generation of antibodies against modified cysteine residue.     

Regioselective Arylation and Alkynylation of 2,3‐Dibromo‐1H‐inden‐1‐one by Suzuki?Miyaura and Sonogashira Cross‐Coupling Reactions

Suzuki? Miyaura reactions of 2,3‐dibromo‐1H‐inden‐1‐one afforded a wide range of arylated 1H‐inden‐1‐ones. Sonogashira cross‐coupling reactions gave alkynylated indenones. The reactions proceeded with very good regioselectivity in the less sterically hindered and more electron‐deficient position 3.     

Metformin and glitazones: does similarity in biomolecular mechanism originate from tautomerism in these drugs?

This theoretical study attempts to find out similarity between metformin and glitazone class of antidiabetic drugs. It was found that some tautomeric forms of both metformin and thiazolidinedione ring of glitazones have similar molecular electrostatic potential (MESP) surface and may bind to a common complementary surface. Complexation and docking studies were also carried out in order to support this hypothesis. Copyright © 2007 John Wiley & Sons, Ltd.     

Reactions of dichloro-bis(cyclopentadienyl)titanium(IV) with bidentate Schiff bases

A series of Cp₂Ti(SB)Cl complexes, whereSB is the anion of bidentate Schiff bases derived from salicylaldehyde and different primary aminesviz o-anisidine,m-anisidine,o-phenetidine,o-chloroaniline,m-chloroaniline,m-nitroaniline, α-naphthylamine and benzylamine, have been synthesised by the reaction of dichloro-bis(cyclopentadienyl) titanium(IV), Cp₂TiCl₂, and bidentate Schiff base (sbh) in a 1:1 molar ratio in refluxingthf in the presence of triethylamine. The new derivatives have been characterised on the basis of their elemental analyses, conductance measurements and spectral (IR,¹Hnmr and electronic) studies     

Synthesis of functionalized triarylmethanes by combination of FeCl3-catalyzed benzylations of acetylacetone with [3+3] cyclocondensations

Functionalized triarylmethanes are prepared in two steps by FeCl₃-catalyzed benzylation of acetylacetone to give 3-(diarylmethyl)pentane-2,4-diones and subsequent formal [3+3] cyclization of the latter with 1,3-bis(trimethylsilyloxy)-1,3-dienes.     

Cyclization vs. Elimination Reactions of 5‐Aryl‐5‐hydroxy 1,3‐Diones: One‐Pot Synthesis of 2‐Aryl‐2,3‐dihydro‐4H‐pyran‐4‐ones

2‐Aryl‐2,3‐dihydro‐4H‐pyran‐4‐ones were prepared in one step by cyclocondensation of 1,3‐diketone dianions with aldehydes. The use of HCl (10%) for the aqueous workup proved to be very important to avoid elimination reactions of the 5‐aryl‐5‐hydroxy 1,3‐diones formed as intermediates. The TiCl₄‐mediated cyclization of a 2‐aryl‐2,3‐dihydro‐4H‐pyran‐4‐one with 1,3‐silyloxybuta‐1,3‐diene resulted in cleavage of the pyranone moiety and formation of a highly functionalized benzene derivative.