Novel Azobenzene-Functionalized Polyelectrolytes of Different Substituted Head Groups 1: Synthesis,Characterization and Absorption Spectroscopy Studies

A new class of a series of amphiphilic polyelectrolytes functionalized with azobenzene chromophores have been synthesized and thoroughly characterized by various techniques. A facile two stage strategy is developed, and first involved the preparation of a precursor base polymer, designated as P(APEA), by the free-radical copolymerization of the monomers of acrylic acid (AA) and 2-(phenylethylamino)ethyl acrylate (PEA). In the second step, precursor PAPEA polymers are reacted and post-polymer modified with the diazonium salts to synthesize azobenzene polyelectrolyte, PAPEA-R with different substituted R-groups present on the para position of the aromatic ring of the azo chromophores. The PAPEA-R polyelectrolytes are same in their degree of polymerization and repeat unit compositions of AA and PEA monomers, and only differ from each other by the type of R-groups. The copolymers were classified on the basis of the characteristics of their R-groups into the hydrophilic-ionizeable smaller pair of ─SO₃H and ─COOH, the hydrophobic-non-ionizeable smaller pair of ─ H and ─OC₂H₅, and the hydrophobic-non-ionizeable larger octyl pair of ─C₈H₁₇ and ─ C₈F₁₇. The prepared copolymers are also characterized by NMR spectroscopy for structure, GPC for molecular weight, and UV-Visible spectroscopy for absorption determination. In DMF solvent, approximately similar absorption maxima, (λ_max) values were observed for azo chromophore-containing monomers and after incorporating these into their corresponding polymers structures. However, for the self-assembled multilayer thin films, λ_max moved to lower wavelengths to exhibit a blue shift with hydrophobic R-group of ─C₈H₁₇, while this behaviour was not observed for hydrophilic R-group of ─COOH. The shift in λ_max is found to be highly dependent on the type of substituted R-group, and attributed to aggregation of hydrophobic azo chromophores in DMF:H₂O mixture employed for self-assembly. The presence of the ionizeable AA and light-sensitive azo-chromophore functionalized PEA monomers in the PAPEA-R polyelectrolytes impart self-assembling and photoswitchable characteristics, respectively. Through understanding and controlling the solubility and complex solution aggregation behaviour of the different substituted R-groups of azo PEL, their adsorption, thickness, morphology, wetting, molecular-control, and photoresponsiveness can be tailored to enhance the capabilities of the self-assembled multilayer film process in diversified areas of microfluidics, sensing, and controlled release.     

Synthesis, Characterization, and Biological Activity of n -Tributyltin Derivatives of Pharmaceutically Active Carboxylates

 Tributyltin(IV) derivatives of six different pharmaceutically active carboxylates were synthesized. The complexes were characterized by different analytical techniques (elemental analysis; infrared, NMR, and mass spectroscopy). ¹¹⁹Sn NMR data were also recorded in six different coordinating and non-coordinating solvents. The antibacterial activities of the compounds were tested using ten different bacteria relative to the reference drugs ampicillin and cephalexin.     

Synthesis, Characterization of Mixed Ligand Palladium(II) Complexes of Triphenylphosphine and Anilines and their Enzyme Inhibition Studies against β-glucuronidase. The Crystal Structure of trans-dichloro-(m-chloroaniline)(triphenylphosphine)palladium(II)

A number of palladium(II) complexes with Ph₃P and aromatic amines as ligands having the general formula [(Ph₃P)Pd(Ph₃P)(NH₂R)Cl₂] {where R = Ph (1), m-ClC₆H₄ (2), p-ClC₆H₅ (3)} and [Pd(CH₃NHPh)Cl₂] (4), have been synthesized and characterized by elemental analysis, IR, ¹H and ¹³C NMR. The X-ray crystal structure of [(Ph₃P)Pd(m-ClC₆H₄NH₂)Cl₂] · CH₂ Cl₂ (2) shows a distorted square planar environment around the Pd(II) ion with the P–Pd–N and Cl(1)–Pd–Cl(2) bond angles of 174.88(5)° and 176.77(2)° respectively. The complexes were screened for enzyme inhibition activity against β-glucuronidase and found to be active.     

Synthesis,spectroscopic characterization,and biological activity studies of organotin(IV) derivatives of (E)‐3‐(3‐fluorophenyl)‐2‐phenyl‐2‐propenoic acid. Crystal and molecular structure of Et2Sn[OCOC(C6H5)CH(3‐FC6H4)]

The complexes Me₂SnL₂ ( I ), Me₃SnL ( II ), Et₂SnL₂ ( III ), n‐Bu₂SnL₂ ( IV ), n‐Bu₃SnL ( V ), n‐Oct₂SnL₂ ( VI ), Bz₂SnL₂ ( VII ), and Ph₃SnL ( VIII ), where “L” is ( E )‐3‐(3‐fluorophenyl)‐2‐phenyl‐2‐propenoate, have been prepared and structurally characterized by means of elemental analysis, infrared, mass, and multinuclear (¹H, ¹³C, ¹¹⁹Sn) NMR spectral techniques. The spectroscopic results showed that the geometry around the Sn atom in triorganotin(IV) derivatives is four‐coordinated in noncoordinating solvent and behaves as five‐coordinated linear polymers with bridging carboxylate groups or five‐coordinated monomers, both acquiring trans‐R₃SnO₂ geometry for Sn in the solid state. While all the diorganotin(IV) derivatives may acquire trigonal bipyramidal structures in solution due to collapse of the Sn←OCO interaction and octahedral geometries in the solid state, which have been confirmed by the X‐ray crystallographic data of the compound III . The crystal structure of Et₂SnL₂ ( III ) has been determined by X‐ray crystallography and is found skew‐trapezoidal bipyramidal, which substantiates that the ligand acts as an anisobidentate chelating agent, thus rendering the Sn atom six coordinated. The crystal is monoclinic with space group C2₁/n. All the investigated compounds have also been screened for biocidal and cytotoxicity data. © 2006 Wiley Periodicals, Inc. Heteroatom Chem 17:420–432, 2006; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20243     

Novel Azobenzene-Functionalized Polyelectrolytes of Different Substituted Head Groups 3: Control of Properties of Self-Assembled Multilayer Thin Films

Novel azobenzene polyelectrolytes have been used to fabricate biocompatible self-assembled multilayer (SAMU) thin films of variable absorbance, thickness, organization, and morphology. The prepared SAMU films are useful for directed cell growth, and this application relies directly on control of contact and surface energy, and requires the ability to tune the surface characteristics which are critical to their development. The azo polyelectrolytes employed here were similar in their degree of polymerization and repeat unit composition of acrylic acid monomer and azo monomers, and only differ from each other due to the presence of different substituted head R-groups present on the p-position of the aromatic ring of the azo chromophores. Possession of characteristics of both the self-assembly due to acrylic acid groups, and photoswitchability of the azo monomer enable the azobenzene functionalized polyelectrolytes to exhibit novel photo-reversible applications. The azo polyelectrolytes with the substituted R-group pairs of shorter-ionized hydrophilic COOH and SO₃H, shorter-non-ionized hydrophobic H and OC₂H₅, and larger-nonionized hydrophobic octyl C₈H₁₇ and C₈F₁₇ were used as polyanions and counter charge PDAC used as polycation to fabricate the layer-by-layer SAMU films onto glass and silicon substrates. The fabricated SAMU films were also characterized by various techniques. The UV absorption maxima, λ_max p of the SAMU films move to lower wavelength relative to solution to exhibit a blue shift for the hydrophobic R-groups, while this behaviour was not observed for the hydrophilic R-groups. Similarly, the thickness, organization, morphology and other properties of the thin films were found to be dependent on the type of substituted R-groups of the azo polyelectrolytes due to the inter-related factors of ionization, hydrophobicity/hydrophilicity, solubility, and aggregation of azo PEL in the dipping solutions used for fabrication of the SAMU films. Understanding and controlling the adsorption characteristics of azo multilayer thin–film of switchable functionalities are vital to explore their potential for the development and application of new devices in diverse areas of biosensor, drug delivery systems, on-chip microscale chemical process and microfluidics systems.     

Synthesis,Spectroscopic Studies and X-ray Analysis of (<Emphasis Type="Italic">E</Emphasis>)-2-(2-Fluorophenyl)-3-(6-Nitrobenzo[d][1,3]dioxol-5-yl) Acrylic Acid

Abstract  

In the solid-state structure of the title compound, C₁₆H₁₀FNO₆, the configuration about the C=C double bond is E. The compound crystallized in the triclinic system, having space group P-1 with unit cell dimensions a = 5.829(10) ?, b = 8.801(16) ?, c = 13.543(3) ?, α = 87.753(15)°, β = 81.945(15)°, γ = 86.342(14)°. The structure of the molecule is V-shaped and in the crystal the molecules are linked to form inversion dimers connected by pairs of C–H···O hydrogen bonds.     

Synthesis and Structural Characterization of Dibromidobis(N,N′-dimethylthiourea-κS)cadmium(II) and Diiodidobis(N,N′-dimethylthiourea-κS)cadmium(II)

Abstract  

Cadmium(II) complexes, dibromidobis(N,N′-dimethylthiourea-S)cadmium(II), [Cd(Dmtu)₂Br₂] (1) and diiodidobis(N,N′-dimethylthiourea-S)cadmium(II), [Cd(Dmtu)₂I₂] (2), have been prepared and their structures have been determined by X-ray crystal structure analysis. Compound 1 crystallized in the monoclinic space group C2/c, and the metal ion is situated on a twofold rotation axis. Compound 2 also crystallized in a monoclinic space group, P2₁/c, but here the molecules have no crystallographic symmetry. In both compounds the cadmium atom is bonded to two halide ions and to two dimethylthiourea molecules through the sulfur atoms in a tetrahedral environment. The molecules are linked via N–H⋯Halide hydrogen bonds to form infinite one-dimensional chains in 1 and infinite two dimensional networks in 2. The complexes were also characterized by IR and NMR spectroscopy and the data are consistent with the structures of the compounds.