Nonlinear Optical Properties of Organic and Polymer Systems

Present thesis has discussed the design and synthesis of polymers suitable for nonlinear optics. Most of the molecules that were studied have shown good nonlinear optical activity. The second order nonlinear optical activity of the polymers was measured experimentally by Kurtz and Perry powder technique. The thesis comprises of eight chapters.The theory of NLO phenomenon and a review about the various nonlinear optical polymers has been discussed in chapter 1. The review has provided a survey of NLO active polymeric materials with a general introduction, which included the principles and the origin of nonlinear optics, and has given emphasis to polymeric materials for nonlinear optics, including guest-host systems, side chain polymers, main chain polymers, crosslinked polymers, chiral polymers etc.Chapter 2 has discussed the stability of the metal incorporated tetrapyrrole molecules, porphyrin, chlorin and bacteriochlorin.Chapter 3 has provided the NLO properties of certain organic molecules by computational tools. The chapter is divided into four parts. The first part has described the nonlinear optical properties of chromophore (D-n-A) and bichromophore (D-n-A-A-n-D) systems, which were separated by methylene spacer, by making use of DPT and semiempirical calculations.Chapter 4: A series of polyurethanes was prepared from cardanol, a renewable resource and a waste of the cashew industry by previously designed bifunctional and multifunctional polymers using quantum theoretical approach.Chapter 5: A series of chiral polyurethanes with main chain bis azo diol groups in the polymer backbone was designed and NLO activity was predicted by ZlNDO/ CV methods.In Chapter 7, polyurethanes were first designed by computational methods and the NLO properties were predicted by correction vector method. The designed bifunctional and multifunctional polyurethanes were synthesized by varying the chiral-achiral diol compositions

Synthesis and Properties of Polyurethanes of Hexamethylene Di-Isocyanate with Multifunctional Chromophores in the Main Chain

Various polyurethanes containing photoactive bis(azo) and bis(o-nitrobenzyl) groups in the main chain were synthesized by polyaddition reactions of diols such as bis(4-hydroxyphenylazo)-2,20-dinitrodiphenylmethane, 4-hydroxy-3-methylphenylazo- 40-hydroxyphenylazo-2,20-dinitrodiphenylmethane and bis(4-hydroxy-3- methylphenylazo)-2,20-dinitrodiphenylmethane with hexamethylene di-isocyanate (HMDI), in dimethyl acetamide (DMAc) in the presence of di-n-butyltin dilaurate (DBTDL) as catalyst. All of them were characterized by IR, UV-vis, 1H NMR and 13C NMR spectra and also by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and gel permeation chromatography (GPC).

Studies of the voltammetric behavior and determination of diazo reactive dyes at mercury electrode

The electrochemical reduction of two reactive dyes: Procion Red HE-3B 9 (RR120) and Procion Green HE-4BD (RG19) was investigated using cyclic voltammetry, differential pulse and DC, polarography, chronoamperometry and controlled potential electrolysis at mercury electrodes. The bis-azo groups of the RR120 dye are reduced together in one single step of four electrons, the bis-azo groups of the RG19 dye are reduced in two steps owing to the difference in the electron densities promoted by the different substituents in the benzene rings adjacent to the azo groups. The bis-monochlorotriazine reactive groups in both dyes are reduced only in acidic medium in their protonated form, leading to the reduction of the triazine groups. The reduction mechanism of both reactive dyes is discussed. Both dyes can be quantified in aqueous medium by differential pulse polarography in the concentration range of 1 x 10(-7) mol L-1 to 1 x 10(-5) mol L-1 by monitoring the reduction of the chromophore group or the reactive group.

3D culture of bone-derived cells immobilised in alginate following light-triggered gelation

Photoreactive liposomes have been exploited as a means of developing 3D tissue constructs. Liposomes formulated using the photosensitive lipid 1,2-bis(4-(n-butyl)phenylazo-4′-phenylbutyroyl)phosphatidylcholine (Bis Azo PC), which undergoes conformational change on stimulation with long wavelength ultraviolet light, were prepared with entrapped CaCl2 before being incorporated into a 4% alginate solution. It was shown that stimulation of the photosensitive lipid using a light emitting diode (LED) (peak emission at 385 nm, dose equivalent to 9 mJ/cm2) caused the release of liposome-entrapped CaCl2, resulting in cross-linking of the alginate solution and immobilisation of bone-derived cells over a range of seeding densities, approximately 97% of which remained viable for periods of up to 14 days in culture. Entrapment volumes of a variety of liposome types were evaluated and interdigitating fusion vesicles were identified as having the highest payload (24%), however the inclusion of cholesterol as a means of shifting Bis Azo PC sensitivity into the visible light wavelengths resulted in an approximately 10-fold reduction in calcium entrapment. This application of light-sensitised liposomes offers the potential to create complex tissue engineering substrates containing cells immobilised in precise locations, in contrast with substrates onto which cells are seeded post-production. © 2007 Elsevier B.V. All rights reserved.

Development of photosensitive liposomes for the controlled release of drugs

The facility to controlled triggered release from a “cage” system remains a key requirement for novel drug delivery. Earlier studies have shown that Bis-Azo PC based photosensitive liposomes are beneficial for drug delivery. Thus, the aim of this project was to develop photosensitive liposomes that can be used for the controlled release of drugs through UV irradiation, particularly therapeutic agents for the treatment of psoriasis. Bis-Azo PC was successfully synthesized and incorporated into a range of liposomal formulations, and these liposomes were applied for the controlled release of BSA-FITC. Bis-Azo PC sensitized liposomes were prepared via interdigitation fusion method. IFV containing optimum cholesterol amount in terms of protein loading, stability and photo-trigger release of protein was investigated. Further studies investigated the stability and triggered release of the HMT from IFV. Finally, permeation behavior of HMT and HMT-entrapped IFV through rat skin was examined using Franz cell. Results from protein study indicated that the stable entrapment of the model protein was feasible as shown through fluorescence spectroscopy and maximum of 84% protein release from IFV after 12 min of UV irradiation. Moreover, stability studies indicated that IFV were more stable at 4 0C as compared to 25 0C. Hence, DPPC:Chol:Bis-Azo PC (16:2:1) based IFV was chosen for the controlled release of HMT and these studies exhibited that photo-trigger release and stability data of HMT-entrapped IFV are in line with the protein results. Franz cell work inferred that HMT-entrapped IFV attributed to slower skin permeation as compared to HMT. CLSM also demonstrated that HMT can be used as a fluorescent label for the in vitro skin study. Overall, the work highlighted in this thesis has given useful insight into the potentials of Bis-Azo PC based IFV as a promising carrier for the treatment of psoriasis.

Azo-linked corner porphyrin systems: synthesis, crystal structures and spectroscopic investigation

1,2-Bis[10,15-di(3,5-di-tert-butyl)phenylporphyrinatonickel(II)-5-yl]diazene was synthesised via copper catalysed coupling of aminated nickel(II) 5,10-diarylporphyrin (“corner porphyrin”) and its X-ray crystal structure was determined. Two different crystals yielded different structures, one with the free meso positions in a trans-like orientation, and the other with a cis-like disposition. The free meso positions of the obtained dimer have been further functionalised while the synthesis of a zinc analogue has so far been unsuccessful. The X-ray crystal structure of the dinitro derivative of the dinickel(II) azoporphyrin was determined, and the structure showed a cis-like disposition of the nitro groups.

trans-Dichloro-bis-(arylazoimidazole)palladium(II): Synthesis, Structure, Photoisomerization, and DFT Calculation

Reaction between PdCl2 and 1-alkyl-2-(arylazo)imidazole (RaaiR') or 1-alkyl-2-(naphthyl-alpha/beta-azo)imidazole (alpha/beta-NaiR') under reflux in ethanol has isolated complexes of compositions Pd(RaaiR')(2)Cl-2 (5, 6) and Pd(alpha/beta-NaiR')(2)Cl-2 (7, 8). The X-ray structure determination of one of the molecules, Pd(alpha-NaiBz)(2)Cl-2 (7c), has reported a trans-PdCl2 configuration, and alpha-NaiBz acts as monodentate N(imidazole) donor ligand. The spectral (IR, UV-vis, H-1 NMR) data support the structure. UV light irradiation (light source: Perkin-Elmer LS 55 spectrofluorimeter, Xenon discharge lamp, lambda = 360-396 nm) in a MeCN solution of the complexes shows E-to-Z isomerization of the coordinated azoimidazole unit. The reverse transformation, Z-to-E, is very slow with visible light irradiation. Quantum yields (phi(E-Z)) of E-to-Z isomerization are calculated, and phi is lower than that of the free ligand but comparable with those of Cd(II) and Hg(II) complexes of the same ligand. The Z-to-E isomerization is a thermally induced process. The activation energy (E-a) of Z-to-E isomerization is calculated by controlled-temperature experimentation. cis-Pd(azoimidazole)Cl-2 complexes (azomidazole acts as N(imidazole) and N(azo) Chelating ligand) do not respond upon light irradiation, which supports the idea that the presence of noncoordinated azo-N to make free azo (-N=N-) function is important to reveal photochromic activity. DFT calculation of Pd(alpha-NaiBz)(2)Cl-2 (7c) has suggested that the HOMO of the molecule is constituted of Pd (32%) and Cl (66%), and hence photo excitation may use the energy of Pd and Cl instead of that of the photofunctional -N=N-Ar motif; thus, the rate of photoisomerization and quantum yield decrease versus the free ligand values.

Synthesis of Azo Coupled Crown Ethers Containing Transition Metal and other Chromophoric Environments and Their Ion Complexation Properties

The crown ethers, 2,3-benzo-1,4,7,10,13-pentaoxa-cyclopentadeca-2-ene and 2,3, ll,12-dibenzo-l,4,7,10,13,16-hexaoxscyclooctadeca-2,11-diene are incorporated into H,N'-ethylenebis(acetylacetoneimino) nickel(II) and copper(II), phenol, and β-naphthol by diazo coupling reactions. The selective nature of the coupling reaction has-been demonstrated by the isolation of both asymmetric mono- and symmetric bis(glyoxalarylcrownhydrazoneimino) metal(II) complexes. An interesting binuclear complex containing two intramolecularly rearranged (glyoxal-hydrazonearylimino) metal(II) groups joined by 18-crown-6 result8 when bis(arenediazonium)-18-crown-6 is coupled with the metal(I1) Schiff bases. The substituted ethers form cationic salts with NaClO4, KCNS, NH4CNS, 14g(CNS)2 and Ca(CNS)2. All the synthesised ethers exhibit ion selectivity sequence as K+ > Na+ and Ca2+ > Mg2+.

Synthesis of Azo Coupled Crown Ethers Containing Transition Metal and other Chromophoric Environments and Their Ion Complexation Properties

The crown ethers, 2,3-benzo-1,4,7,10,13-pentaoxa-cyclopentadeca-2-ene and 2,3, ll,12-dibenzo-l,4,7,10,13,16-hexaoxscyclooctadeca-2,11-diene are incorporated into H,N'-ethylenebis(acetylacetoneimino) nickel(II) and copper(II), phenol, and β-naphthol by diazo coupling reactions. The selective nature of the coupling reaction has-been demonstrated by the isolation of both asymmetric mono- and symmetric bis(glyoxalarylcrownhydrazoneimino) metal(II) complexes. An interesting binuclear complex containing two intramolecularly rearranged (glyoxal-hydrazonearylimino) metal(II) groups joined by 18-crown-6 result8 when bis(arenediazonium)-18-crown-6 is coupled with the metal(I1) Schiff bases. The substituted ethers form cationic salts with NaClO4, KCNS, NH4CNS, 14g(CNS)2 and Ca(CNS)2. All the synthesised ethers exhibit ion selectivity sequence as K+ > Na+ and Ca2+ > Mg2+.

Fabrication, structural characterization, and applications of Langmuir and Langmuir-Blodgett films of a poly(azo)urethane

The synthesis of a poly(azo)urethane by fixing CO2 in bis-epoxide followed by a polymerization reaction with an azodiamine is presented. Since isocyanate is not used in the process, it is termed clean method and the polymers obtained are named NIPUs (non-isocyanate polyurethanes). Langmuir films were formed at the air-water interface and were characterized by surface pressure vs mean molecular area per met unit (Pi-A) isotherms. The Langmuir monolayers were further studied by running stability tests and cycles of compression/expansion (possible hysteresis) and by varying the compression speed of the monolayer formation, the subphase temperature, and the solvents used to prepare the spreading polymer solutions. The Langmuir-Blodgett (LB) technique was used to fabricate ultrathin films of a particular polymer (PAzoU). It is possible to grow homogeneous LB films of up to 15 layers as monitored using UV-vis absorption spectroscopy. Higher number of layers can be deposited when PAzoU is mixed with stearic acid, producing mixed LB films. Fourier transform infrared (FTIR) absorption spectroscopy and Raman scattering showed that the materials do not interact chemically in the mixed LB films. The atomic force microscopy (AFM) and micro-Raman technique (optical microscopy coupled to Raman spectrograph) revealed that mixed LB films present a phase separation distinguishable at micrometer or nanometer scale. Finally, mixed and neat LB films were successfully characterized using impedance spectroscopy at different temperatures, a property that may lead to future application as temperature sensors. Principal component analysis (PCA) was used to correlate the data.

Molecular architecture of thin films fabricated via physical vapor deposition and containing a poly(azo)urethane

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Poliuretana contendo corante azóico e espaçador tipo bis-carbonato como material para fabricação de filmes nanoestruturados

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Síntese e caracterização de monômeros azo-carbonatos para a preparação de poli(azo-carbonato)s e poli)azo-uretana)s

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Comparative Electrochemical Study of Unsubstituted and Substituted Bis(phthalocyaninato) Rare Earth(III) Complexes

The electrochemistry of homoleptic substituted phthalocyaninato rare earth double-decker complexes M(TBPc)2 and M(OOPc)2 [M = Y, La...Lu except Pm; H2TBPc = 3(4),12(13),21(22),30(31)-tetra-tert-butylphthalocyanine, H2OOPc = 3,4,12,13,21,22,30,31-octakis(octyloxy)phthalocyanine] has been comparatively studied by cyclic voltammetry (CV) and differential pulse voltammetry (DPV) in CH2Cl2 containing 0.1 M tetra-n-butylammonium perchlorate (TBAP). Two quasi-reversible one-electron oxidations and three or four quasi-reversible one-electron reductions have been revealed for these neutral double-deckers of two series of substituted complexes, respectively. For comparison, unsubstituted bis(phthalocyaninato) rare earth analogues M(Pc)2 (M = Y, La...Lu except Pm; H2Pc = phthalocyanine) have also been electrochemically investigated. Two quasi-reversible one-electron oxidations and up to five quasi-reversible one-electron reductions have been revealed for these neutral double-decker compounds. The three bis(phthalocyaninato)cerium compounds display one cerium-centered redox wave between the first ligand-based oxidation and reduction. The half-wave potentials of the first and second oxidations and first reduction for double-deckers of the tervalent rare earths depend on the size of the metal center. The difference between the redox potentials of the second and third reductions for MIII(Pc)2, which represents the potential difference between the first oxidation and first reduction of [MIII(Pc)2]−, lies in the range 1.08−1.37 V and also gradually diminishes along with the lanthanide contraction, indicating enhanced π−π interactions in the double-deckers connected by the smaller, lanthanides. This corresponds well with the red-shift of the lowest energy band observed in the electronic absorption spectra of reduced double-decker [MIII(Pc′)2]− (Pc′ = Pc, TBPc, OOPc).