Khaya Cellulose Supported Copper Nanoparticles for Chemo Selective Aza-Michael Reactions

We prepared a highly active Khaya cellulose supported poly(hydroxamic acid) copper nanoparticles by the surface modification of Khaya cellulose through graft copolymerization and subsequently amidoximation. The Cunanoparticle (0.05 mol% to 50 mol ppm) was selectively promoted Aza-Michael reaction of aliphatic amines to give the corresponding alkylated products at room temperature in methanol. The supported nanoparticle was easy to recover and reused seven times without significance loss of its activity

Photo-inhibition Effect from Strong Electron Withdrawing Nitro Group in N-[(E)(4-Bromophenyl)Methylidene]-4 Nitroaniline

Light induced effect of N-[(E)-(4-bromophenyl)methylidene]-4nitroaniline was investigated using UV-Vis spectrophotometer. This study revealed that the presence of strong electron withdrawing nitro group inhibited the photo-reactivity of the compound. Mainly, molecular structure and functional groups have tremendous influence on chromophoric compounds. The photoisomerization effect was not found in this compound, due to the photo-inhibition of nitro group present in the molecular system

Synthesis of New Liquid Crystals Embedded Gold Nanoparticles for Photoswitching Properties

A new series of liquid crystals decorated gold nanoparticles is synthesized whose molecular architecture has azobenzenes moieties as the peripheral units connected to gold nanoparticles (Au NPs) via alkyl groups. The morphology and mesomorphic properties were investigated by field emission scanning electron microscope, high-resolution transmission electron microscopy, differential scanning calorimetry and polarizing optical microscopy. The thiolated ligand molecules (3a–c) showed enantiotropic smectic A phase, whereas gold nanoparticles (5a–c) exhibit nematic and smectic A phase with monotropic nature. HR-TEM measurement showed that the functionalized Au NPs are of the average size of 2 nm and they are well dispersed without any aggregation. The trans-form of azo compounds showed a strong band in the UV region at ∼378 nm for the π-π∗ transition, and a weak band in the visible region at ∼472 nm due to the n-π∗ transition. These molecules exhibit attractive photoisomerization behaviour in which trans-cis transition takes about 15 s whereas the cis-trans transition requires about 45 min for compound 5c. The extent of reversible isomerization did not decay after 10 cycles, which proved that the photo-responsive properties of 5c were stable and repeatable. Therefore, these materials may be suitably exploited in the field of molecular switches and the optical storage devices

Synthesis of Poly(hydroxamic acid) Ligand from Polymer Grafted Khaya Cellulose for Transition Metals Extraction

A cellulose-graft-poly(methyl acrylate) was synthesized by free radical initiating process and the ester functional groups were converted into the hydroxamic acid ligand. The intermediate and final products are characterized by FT-IR, FESEM, HR-TEM and XPS technique. The pH of the solution acts as a key factor in achieving optical color signals of metalcomplexation. The reflectance spectra of the[Cu-ligand]n+ complex was found to be a highest absorbance at 99.8 % at pH 6 and it was increased upon increasing of Cu2+ ion concentrations and a broad peak at 700 nm was observed which indicated the charge transfer (π-π transition) metals-Cu complex. The adsorption capacity of copper was found to be superior (336 mg g-1)rather than other transition metals such as Fe3+, Co3+, Cr3+, Ni2+, Mn2+ and Zn2+ were 310, 295, 288, 250, 248 and 225 mg g-1, respectively at pH 6. The experimental data of all metal ions fitted significantly with the pseudo-second-order rate equation. The transition metal ions sorption onto ligand were well fitted with the Langmuir isotherm model (R2>0.99), which suggested that the cellulose-based adsorbent known as poly(hydroxamic acid) ligand surface is homogenous and monolayer. The reusability of the poly(hydroxamic acid) ligand was checked by the sorption/desorption process up to ten cycles without any significant loss in its original sensing and removal performances

Synthesis and Characterization of Liquid Crystalline Azobenzene Chromophores with Fluorobenzene Terminal

Two series of fluorine-substituted benzoate ester type rod-shaped liquid crystals incorporating the azobenzene as side arm linked with terminal double bonds as polymerizable functional groups were synthesized and characterized by polarized-light optical microscopy (POM), differential scanning calorimetry (DSC) and UV–visible spectroscopy investigations. Thus, rod-shaped monomers, namely 4a and 4b having odd and even number of carbon in the terminal group exhibited nematic phase and SmA type phase was found at lower temperature. Compound 5 showed nematic phase whereas compound 6 showed SmA phase. These rod-shaped molecules exhibit strong photoisomerization behaviour in solution. The photoswitching properties of the compounds showed trans to cis isomerization in about 10 s, whereas the reverse process takes place about 120 min in solutions. Proposed materials may have potential to use it in optical storage devices

Synthesis And Comparison Of Liquid Crystal Polymers And Monomers Containing Azobenzene Mesogens

Abstract: The syntheses of novel liquid crystal polymers containing azobenzene moieties were carried out according to convenient route having a acrylate backbone. The azobenzenes are key intermediates of the monomers and the side-chain liquid crystal polymer is the poly [α-{4-[(4-acetylphenyl)diazenyl]phenoxy}alkyloxy]acrylate in which spacer length is varied from 3 to 11 methylene units. The precursors and monomers were characterized by using FT-IR, NMR techniques. The polymers were obtained by conventional free radical polymerization using AIBN as an initiator. The thermal properties of the polymers were studied by using differential scanning calorimetry. The thermal behavior of the polymers are compared with those of the analogous monomers, the α-{4-[(4-acetylphenyl)diazenyl]phenoxy}alkyloxy acrylate and it was found that all polymers exhibited namatic phase near isotropic point and no phase transition observed in the monomers. Abstrak: Polimer hablur cecair kumpulan azobenzena telah disintesis dengan cara yang rengkas dimana akrilat telah digunakan sebagai rangka utama. Azobenzena poli[α-{4-[(4-asetilfenil) diazenil]fenoksi}alkiloksi]akrilat merupakan bahantara utama daripada monomer dan merupakan rantai sisi kepada polimer cecair hablur tersebut dengan panjang kumpulan peruang antara 3 ke 11 unit metilena. Precursor dan monomer telah dicirikan menggunakan teknik FTIR dan NMR. Polimer telah dihasilkan secara pempolimeran radikal bebas konvensional menggunakan bahan pemula AIBN. Sifat terma polimer telah dikaji menggunakan kalorimetri pengimbas pembezaan. Sifat terma polimer telah dibandingkan dengan analog monomer α-{4-[(4-asetilfenil) diazenil]fenoksi}alkiloksi akrilat, dan didapati semua polimer menunjukkan fasa namatik pada titik isotropik tetapi tiada transisi fasa dilihat berlaku pada monomer

Synthesis of ion imprinted polymers for selective recognition and separation of rare earth metals

Lanthanide-ion imprinted polymers (L-IIPs) were synthesized by stoichiometric amounts of rare earth ions and the cavities in the polymers were created for the corresponding lanthanide ions. The maximum sorption capacity, are estimated to be 125.3, 126.5, 127.6, 128.2 and 129.1 mg g-1 for Pr, Nd, Sm, Eu and Gd, respectively at pH 6. In the selectivity study, the L-IIPs exhibit good selectivity to the specific rare earth ions in the presence of coexisting cations. The imprinting results are found to be excellent with some rare earth ions over other competitor rare earth ions with same charge and close ionic radius

6-(Hex-5-enyloxy)naphthalene-2-carboxylic acid

The asymmetric unit of the title compound, C17H18O3, comprises three independent molecules with similar geometries. In each molecule, the carbonyl group is twisted away from the napthalene ring system, making dihedral angles of 1.0 (2), 1.05 (19)� and 1.5 (2)�. The butene group in all three molecules are disordered over two sets of sites, with a refined occupancy ratio of 0.664 (6):0.336 (6). In the crystal, molecules are oriented with respect to their carbonyl groups, forming head-to-head dimers via O—H� � �O hydrogen bonds. Adjacent dimers are further interconnected by C—H� � �O hydrogen bonds into chains along the a-axis direction. The crystal structure is further stabilized by weak C—H� � �� interactions

Crystal structure of (E )-4-{2-[4-(allyloxy)phenyl]diazenyl}benzoic acid

The title compound, C16H14N2O3, has an E conformation about the azobenzene [—N N– = 1.2481 (16) A ˚ ] linkage. The benzene rings are almost coplanar [dihedral angle = 1.36 (7)�]. The O atoms of the carboxylic acid group are disordered over two sets of sites and were refined with an occupancy ratio of 0.5:0.5. The two disordered components of the carboxylic acid group make dihedral angles of 1.5 (14) and 3.8 (12)� with the benzene ring to which they are attached. In the crystal, molecules are linked via pairs of O—H� � �O hydrogen bonds, forming inversion dimers. The dimers are connected via C—H� � �O hydrogen bonds, forming ribbons lying parallel to [120]. These ribbons are linked via C—H� � �� interactions, forming slabs parallel to (001)

Synthesis and Light Induced Characteristics of Siloxane Substituted Azobenzene: An Application for Optical Storage Device

The light induced behaviour of siloxane substituted azobenzene compounds in the presence of alkylene spacers is reported for the first time. Firstly, these photosensitive compounds were synthesized and elucidated the molecular structure by spectral analysis such as NMR, FTIR, and UV/Vis. Photoisomerization effect was evaluated in solution and also in nematic phase. The photosaturation occurred exactly at 29 seconds, whereas thermal back relaxation was observed ranging from 19.8 to 23.8 hours. Long duration of the thermal back relaxation is due to the presence of sterically hindered siloxane group substituted to the azobenzene molecules. Decrease in the duration of cis-trans isomerization was found when the number of alkylene spacers was increased. These siloxane based azobenzene derivatives are useful for the fabrication of optical storage device and molecular switches