Development of hydrophobic polyurethane film from structurally modified castor oil and its anticorrosive performance

Hydrophobic polyurethane (PU) films are widely used for various commercial and industrial applications due to their excellent water repelling and self-cleaning property. Nevertheless, achieving appreciable hydrophobicity in PU film is quite a challenge. Herein, we report on the development of a novel hydrophobic PU (fluorinated polyurethane [FCO-PU]) film and comprehensively evaluate its anticorrosive property. The FCO-PU was prepared by structural modification of castor oil (CO) through attachment of long fluorocarbon chains as pendant groups onto the backbone of CO. A model PU film (CO-PU) was also prepared from unmodified CO to compare the properties of FCO-PU film. All intermediate compounds, FCO-PU and CO-PU films were characterized by various spectroscopic techniques. Morphological, thermal and mechanical properties of the PU films were analyzed by field emission scanning electron microscopy (FESEM), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and dynamic mechanical thermal analysis (DMTA) studies. Successful introduction of long fluorocarbon chains into the FCO-PU film is reflected by its high hydrophobicity with a water contact angle of 119.1°, compared to the model CO-PU film with a water contact angle of 84.4°. Anticorrosive properties of the PU films were evaluated by polarization technique and electrochemical impedance spectroscopy under corrosive environment and the obtained results reveal a significant corrosion resistance (corrosion rate: 6.72 × 10⁻⁶ mm/year) behavior by the FCO-PU film. This work represents an effective strategy for the backbone modification of CO to develop novel functional PU materials.     

UV-visible spectroscopic study of solvation in ternary solvent mixtures: ketocyanine dye in methanol + acetone + water and methanol + acetone + benzene

Solvation characteristics of a ketocyanine dye have been studied in completely miscible ternary solvent mixtures, namely, methanol + acetone + water and methanol + acetone + benzene, by monitoring the solvatochromic absorption band of the dye. The maximum energy of absorption (E) of the solute in a ternary solvent mixture differs significantly from the mole fraction average of the E values in the component solvents. Results in the corresponding binary solvent mixtures also show a deviation of the E value from the mole fraction averaged E values. The results have been explained in terms of preferential solvation using a two phase model of solvation. The excess or deficit over the bulk composition of a solvent component in the vicinity of the solute molecule in a ternary solvent mixture has been estimated using the knowledge of solvation in the corresponding binary mixtures.     

Ligand assisted homolytic cleavage of the Ru-Ru single bond in [Ru2(CO)4] core and the chemical consequence

The Ru-Ru single bond in [Ru₂(CO)₄(MeCN)₆][BF₄]₂ remains intact in the reaction with 2-i-propyl-1,8-naphthyridine (ⁱPrNP) and the isolated product is the cis-[Ru₂(ⁱPrNP)₂(CO)₄(OTf)₂] (1) obtained via crystallization in the presence of [n-Bu₄N][OTf]. The 2-t-butyl-1,8-naphthyridine (^tBuNP), on the contrary, leads to the oxidative cleavage of the Ru-Ru single bond resulting in the trans-[Ru(^tBuNP)₂(MeCN)₂][BF₄]₂[NC(Me)C(Me)N] (2). The anti-[NC(Me)C(Me)N]²⁻ is the product of the two-electron reductive coupling of two acetonitrile molecules. The phenoxo appendage in 2-(2-hydroxyphenyl)-1,8-naphthyridine (hpNP) brings the identical effect of the scission of the Ru-Ru bond but the process is non-oxidative and the product obtained is the cis-[Ru(hpNP)₂(CO)₂][BF₄] (3). The bis-(diphenylphosphino)methane (dppm) in dichloromethane oxidatively cleave the Ru-Ru bond leading to chloro bridged [Ru(μ-Cl)(dppm)(CO)(MeCN)]₂[BF₄]₂ (4). All the complexes have been characterized by the spectroscopic and electrochemical measurements and their structures have been established by X-ray diffraction study.     

A facile chemoenzymatic approach to natural cytotoxic ellipsoidone A and natural ellipsoidone B

Starting from citraconic anhydride (3) a facile four-step synthesis of deoxyellipsoidone 8 has been reported with 37% overall yield. An elegant six-step access to naturally occurring cytotoxic ellipsoidone A (1) and ellipsoidone B (2) has been reported with good overall yields, via the conversion of itaconic anhydride (9) to the acetoxymethylmaleic anhydride (11), regioselective sodium borohydride reduction of anhydride 11 to acetoxymethylbutyrolactone 12, Knoevenagel condensation of lactone 12 with 5-methylfurfural, selenium dioxide induced oxidation of the formed butenolide 13 and an Amano PS catalyzed deacylation of the formed diacetoxybutenolide 14 as a pathway.     

Spectroscopic and docking studies of the binding of two stereoisomeric antioxidant catechins to serum albumins

The interactions of two stereoisomeric antioxidant flavonoids, catechin (C) and epicatechin (EC) with bovine serum albumin (BSA) and human serum albumin (HSA), have been investigated by steady state and time resolved fluorescence, phosphorescence, circular dichroism (CD), FTIR and protein–ligand docking studies. The steady-state fluorescence studies indicate a single binding site for both the ligands. FTIR spectra suggest that in both the albumins, C and EC stabilize the α-helix at the cost of a corresponding loss in the β-sheet structure. CD studies have been carried out using (±)C, and both the epimers (+)C and (?)C. The low temperature phosphorescence and protein–ligand [(+), (?) and (±) forms of C and EC] docking studies indicate that the ligands bind in the proximity of Trp 134 of BSA and Trp 214 of HSA, thereby changing their solvent accessible surface areas (ASA). Asn 158 and Glu 130 side chains are found to be within the hydrogen bonding distance from the phenolic –OH groups of C and EC in the case of BSA complex. C and EC are located within the binding pocket of sub-domain IIa of HSA.     

Vanadium(IV)-oxo Corrole Catalyzed Selective Oxidative Cleavage of Alkenes to Aldehydes

A practical and efficient protocol for oxidative cleavage of olefinic bonds especially in arylated olefins has been demonstrated. Herein, an oxo[5,10,15-tris(4-nitrophenyl)corrolato]vanadium (IV) complex (cat.), has been successfully synthesized and the existence of two tautomeric forms of this complex in solution has been established. Oxo[5,10,15-tris(4-nitrophenyl)corrolato]vanadium (IV) (cat.) in the presence of H₂O₂ cleaves olefinic bonds to yield the corresponding aldehyde compounds. In general, a high valent, oxo-(porphyrinoid)-metal complex catalyzes the epoxide formation reactions, however, in the present case, we have observed the exclusive formation of aldehydes. The reaction offered aryl aldehydes with good yields and excellent selectivity. A mechanism was also proposed for these catalysis reactions.