Synthesis of (±)-4-Demtthoxy-7 11-Dideoxydaungmy-Cinone

Our continued interest in the total synthesis of natural and unnatural antitumor anthracyclines¹ especially the aglycones such as daunomycinone (1)² and 4-demethoxydaunomycinone (2),³ 11-deoxydaunomycinone(3)⁴ and 4-demethoxy-11-deoxydau-nomycinone (4)⁵ led us to investigate various methods for obtaining these products. Recently we have reported the synthesis of 4-demethoxy-7, 11-dideoxydaunomycinone (5) from 5-methoxy-1-tetralone. Now we wish to report the synthesis of 5 starting from 5-methoxy-1-tetralone (9) which was prepared from 1,6-dimethoxy-naphthalene(8). Umezawa⁷ et al. have reported the total synthesis of 4-demethoxy-ll-deoxydaunomycin(6) and 4-demethoxy-11-deoxy-adriamycin (7) from 5-methoxy-2-tetralone.     

Synthesis of flexible ligands for assembling two metals in close proximity. Magnetic,electrochemical and spectral properties of binuclear copper (II) complexes with different exogenous bridging motifs

Binuclear Cu^II complexes having new flexible heptadentate ligands 2,6-bis{[bis(3,3-N,N-dimethylaminopropyl)amino]methyl}-4-bromophenol [HL¹], 2,6-bis(3,3-N,N-dimethylaminopropyl)amino]methyl}-4-methylphenol [HL²], and 2,6-bis{[bis(3,3-N,N-dimethylaminopropyl)amino]methyl}-4-methoxyphenol [HL³], capable of assembling two copper ions in close proximity have been synthesized. Comparisons of the charge-transfer (CT) features, observed in electronic spectra of these complexes, are correlated with the electronic effect on the aromatic ring of the ligand systems. Cyclic voltammetry has revealed the existence of two reduction couples,

Recent Progress and Emerging Applications of Rare Earth Doped Phosphor Materials for Dye‐Sensitized and Perovskite Solar Cells: A Review

Although the efficiency of Dye‐sensitized and Perovskite solar cell is still below the performance level of market dominance silicon solar cells, in last few years they have grabbed significant attention because of their fabrication ease using low‐cost materials, and henceforth these cells are considered as a promising alternative to commercial photovoltaic devices. However, third generation solar cells have significant absorption in the visible region of solar spectrum, which confines their power conversion efficiency. Subsequently, the performance of current photovoltaics is significantly hampered by the transmission loss of sub‐band‐gap photons. To overcome these issues, rare earth doped luminescent materials is the favorable route followed to convert these transmitted sub‐band‐gap photons into above‐band‐gap light, where solar cells typically have significant light‐scattering effects. Moreover, the rare earth based down/up conversion material facilitates the improvement in sensitization, light‐scattering and device stability of these devices. This review provides insight into the application of various down/up conversion materials for Dye‐sensitized and perovskite solar cell applications. Additionally, the paper discusses the techniques to improve the photovoltaic performance in terms of current density and photo voltage in detail.     

Role of Annealing Atmosphere on Structure,Dielectric and Magnetic Properties of La2CoMnO6 and La2MgMnO6

Polycrystalline samples of La₂MMnO₆ (M = Co and Mg) were prepared by a combined gel‐combustion and high temperature reaction method. The samples were annealed in different oxygen partial pressure (p_O2) and characterized by powder XRD, SQUID magnetometry, ac impedance spectroscopy, and electron paramagnetic resonance techniques. Monoclinic (P2₁/n) and rhombohedral (R$\bar{3}$ ) lattices were observed for La₂CoMnO₆ and La₂MgMnO₆, respectively. On annealing in inert atmosphere, La₂MgMnO₆ partially converted to monoclinic La₂CoMnO₆ type structure, whereas no structural change was observed in La₂CoMnO₆. Dielectric studies of La₂CoMnO₆ indicated relaxor like behavior with polaronic conduction, which systematically decreased with the increase in p_O2 of the annealing atmosphere. Magnetic studies indicated multiple ferromagnetic phase transitions in La₂CoMnO₆ and a spin‐glass like phase transition in La₂MgMnO₆. The fraction of ferromagnetic phases of La₂CoMnO₆ was significantly dependent on the annealing environments. The variations of magnetic and dielectric properties of samples were related to the fluctuation of oxidation state of transition metal ions and oxygen vacancies in the samples.     

Inclusion of Ring A of Cholesterol Inside the β-Cyclodextrin Cavity: Evidence from Oxidation Reactions and Structural Studies

The disposition of cholesterol inside the -cyclodextrin cavity(-CD) was deduced from oxidation of cholesterol secondary alcoholgroups by Ca(OCl)₂ and H₂O₂ in thepyridine–acetic acid system. The amount of cholest-4-ene-3-one formedwas found to be proportional to the concentration of -cyclodextrin,resulting in 56.1% of ketone. The oxidation rate was enhanced by-cyclodextrin and its methyl, polymer and 1 : 1copper(II)–-cyclodextrin derivatives. Detailed investigationsinvolving UV-visible, ¹³C- and ¹H-NMR(T₁, 1D NOE and ROESY) spectroscopic studies were carried out.A binding constant value of 15,385 ± 1500 M^-2 wasobtained for the 2 : 1heptakis-2,6-di-O-methyl--cyclodextrin(DM-CD) : cholesterolcomplex in chloroform from UV studies. Proton and solid state¹³C-CP MAS spectra of the -CD–cholesterol mixtureshowed large magnitude shifts for the protons from the wider end of the-CD cavity as well as those of ring A and ring B of cholesterol. Both1D NOE and ROESY measurements indicated the proximity between ring A andring B protons of cholesterol and the wider end protons of -CD andDM-CD. Besides, analysis of _c,_i and tau;_m from T₁measurements showed not only a lowering of rotational motions but a value of 0.016–0.048 for some of the cholesterol protons, typical of aweak complex. Based on these studies, a probable structure for the 2 : 1complex involving two molecules of -CD/DM-CD was proposed withportions of ring A and ring B being present inside the wider end of the-CD/DM-CD cavity and ring D and the side chain attached atposition 17, projecting into the wider end of the secondCD/DM-CD molecule.     

Hierarchically structured free-standing hydrogels with liquid crystalline domains and magnetic nanoparticles as dual physical cross-linkers

Here we report a modular strategy for preparing physically cross-linked and mechanically robust free-standing hydrogels comprising unique thermotropic liquid crystalline (LC) domains and magnetic nanoparticles both of which serve as the physical cross-linkers resulting in hydrogels that can be used as magnetically responsive soft actuators. A series of amphiphilic LC pentablock copolymers of poly(acrylic acid) (PAA), poly(5-cholesteryloxypentyl methacrylate) (PC5MA), and poly(ethylene oxide) (PEO) blocks in the sequence of PAA-PC5MA-PEO-PC5MA-PAA were prepared using reversible addition-fragmentation chain transfer polymerization. These pentablock copolymers served as macromolecular ligands to template Fe(3)O(4) magnetic nanoparticles (MNPs), which were directly anchored to the polymer chains through the coordination bonds with the carboxyl groups of PAA blocks. The resulting polymer/MNP nanocomposites comprised a complicated hierarchical structure in which polymer-coated MNP clusters were dispersed in a microsegregated pentablock copolymer matrix that further contained LC ordering. Upon swelling, the hierarchical structure was disrupted and converted to a network structure, in which MNP clusters were anchored to the polymer chains and LC domains stayed intact to connect solvated PEO and PAA blocks, leading to a free-standing LC magnetic hydrogel (LC ferrogel). By varying the PAA weight fraction (f(AA)) in the pentablock copolymers, the swelling degrees (Q) of the resulting LC ferrogels were tailored. Rheological experiments showed that these physically cross-linked free-standing LC ferrogels exhibit good mechanical strength with storage moduli G' of around 10(4)-10(5) Pa, similar to that of natural tissues. Furthermore, application of a magnetic field induced bending actuation of the LC ferrogels. Therefore, these physically cross-linked and mechanically robust LC ferrogels can be used as soft actuators and artificial muscles. Moreover, this design strategy is a versatile platform for incorporation of different types of nanoparticles (metallic, inorganic, biological, etc.) into multifunctional amphiphilic block copolymers, resulting in unique free-standing hybrid hydrogels of good mechanical strength and integrity with tailored properties and end applications.     

1H and 13C NMR spectral study of some 3,5-bis[(E)-thienylmethylene]piperidin-4-ones

(1)H and (13)C NMR spectra have been recorded for 3,5-bis[(E)-thienylmethylene]piperidin-4-one (1a), 3',3″-dimethyl-3,5-bis[(E)-thienylmethylene]piperidin-4-one (1b), 5',5″-dibromo-3,5-bis[(E)-thienylmethylene]piperidin-4-one (1c), their 1-methyl derivatives 2a-c and 3,5-bis[(E)-thienylmethylene]-2r,6c-diphenylpiperidin-4-one (3a). For selected compounds 2D spectra have been recorded. The spectral data are used to study the configuration and conformation of these molecules. The chemical shifts are discussed in light of steric, electronic and magnetic anisotropic effects. The magnetic anisotropic effects of thiophene ring and phenyl group are noteworthy. (1)H-(1)H COSY spectrum of 2b suggests that long-range (1)H-(1)H coupling, up to seven bonds, is possible in it. HMBC spectrum of 2b displays the magnetic nonequivalence of C-2 and C-6 and protons at these carbons.     

Regioselective synthesis and structural elucidation of 1,4-disubstituted 1,2,3-triazole derivatives using 1D and 2D NMR spectral techniques

Regioselective synthesis of 2-[1-(2-oxo-2-phenylethyl)-1H-[1,2,3]triazol-4-ylmethoxy]-benzaldehyde derivatives was achieved by [3 + 2] cycloaddition reaction of 2-(prop)-2-ynyloxy-benzaldehyde derivatives with phenacyl azide. The regiochemistry and the spectral assignments of the synthesized triazole derivatives were studied using both 1D and 2D NMR spectral techniques in solution.     

Facile one-pot solvothermal-assisted synthesis of uniform sphere-like Nb2O5 nanostructures for photocatalytic applications

Research on Chemical Intermediates - Preparation of semiconductor nanomaterials with controlled morphology and uniform porous surface is of great interest for enhanced photocatalytic applications....     

New unsymmetrical μ-phenoxo bridged binuclear copper(II) complexes

A series of binuclear Cu^II complexes [Cu₂XL] ⁿ⁺ having two copper(II) ions bridged by different motifs (X = OH^–, MeCO₂ ^–, or Cl^–) have been prepared using the ligands: H₂L¹ = 4-methyl-2-[N-(2-{dimethylamino}ethyl-N-methyl)aminomethyl]-6-[(prolin-1-yl)methyl]phenol, H₂L² = 4-nitro-2-[N-(2-{dimethylamino}ethyl-N-methyl)aminomethyl]-6-[(prolin-1-yl)methyl]phenol, H₂L³ = 4-methyl-2-[N-(2-{diethylamino}ethyl-N-ethyl)aminomethyl]-6-[(prolin-1-yl)methyl]phenol and H₂L⁴ = 4-nitro-2-[N-(2-{diethylamino}ethyl-N-ethyl)aminomethyl]-6-[(prolin-1-yl)methyl]phenol. The complexes have been characterized by spectroscopic, analytical, magnetic and electrochemical measurements. Cryomagnetic investigations (80–300 K) revealed anti-ferromagnetic exchange between the Cu^II ions (–2J in the range –50 to –182 cm^–1). The strength of anti-ferromagnetic coupling lies in the order: OAc > OH > Cl. Cyclic voltammetry revealed the presence of two redox couples, assigned to Cu^II/Cu^II/Cu^II/Cu^I/Cu^I/Cu^I. The first reduction potential is sensitive to electronic effects from the aromatic ring substituents and steric effect on the donor nitrogens (side arm) of the ligand systems.