Nonlinear Optical Properties of Water-Soluble Polymeric Dyes with Biological Applications

NLOphoric imidazole-fused fluorescent anthraquinone dyes

The Z-scan and DFT techniques were explored to investigate the non-linear optical properties of anthraquinone fused imidazole-based D-π-A dyes. With the help of UV-visible spectral analysis, pH study, CV analysis, HOMO-LUMO interaction, MEP plots, and quinoidal character the influence of intramolecular charge transfer characteristics and H-bonding process on electronic and photophysical studies of anthraquinone derivatives were understood. The dyes 2-(4-(diethylamino)-2-hydroxyphenyl)-3H-anthra[1,2-d]imidazole-6,11-dione (AQ1) and 2-(2-hydroxynaphthalen-1-yl)-1H-anthra[1,2-d]imidazole-6,11-dione (AQ2) displayed a single emission with pronounced Stokes shift and thermal stability (upto 290 °C). The dye AQ1 exhibited strong charge transfer character which is explained by the ICT process leading to high nonlinear susceptibility χ⁽³⁾ in AQ1 3.43 × 10^-13 e.s.u relative to the dye AQ2 which has only ESIPT core. But, the dye AQ2 6.27 J cm^-2 showed better optical limiting value. The NLO properties of AQ1 and AQ2 were computed by DFT functionals based on Hartree Fork (HF) percentage exchange. The dye AQ1 exhibits noticeable NLO properties. The global hybrid functionals with HF composition beyond 50% (BHHLYP, M06-HF) and the long rang corrected functionals (CAM-B3LYP, ωB97, and ωB97X) demonstrated comparable NLO properties relative to B3LYP and PBE0. It was observed that the combined effect of ICT and the H-bonding cores enhance the NLO properties. The experimental findings (Z-scan) were successfully correlated with theoretical (DFT) results.

Poly(arylene ether)s with aromatic azo-coupled cobalt phthalocyanines in the side chain: synthesis, characterization and nonlinear optical and optical limiting properties

A novel poly(arylene ether) with azo-coupled cobalt phthalocyanine in the side chain (PAE-azo-CoPc) was prepared by 1,2-benzodinitrile, anhydrous cobaltous chloride and a novel azobenzene-containing poly(aryl ether) (PAE-azo-DCN) via a nucleophilic substitution polycondensation based on a novel bisfluoro monomer, 4-[(3,4-cyanophenyl)diazenyl]phenyl-2,6-difluorobenzoate. The obtained polymers were characterized and evaluated by FT-IR, ¹H NMR, DSC and TGA. PAE-azo-CoPc exhibited higher glass transition temperature and better thermal stability than PAE-azo-DCN because of the introduction of cobalt phthalocyanine groups. The results of Z-scan measurements demonstrated that PAE-azo-CoPc showed reversible saturable absorption and positive refraction, and PAE-azo-DCN showed saturable absorption and negative refraction. By calculation, PAE-azo-CoPc exhibited larger third-order nonlinear optical susceptibilities than that of PAE-azo-DCN. The results of optical limiting measurements demonstrated that the PAE-azo-CoPc exhibited an excellent optical limiting response.

A novel poly(arylene ether) with azo-coupled cobalt phthalocyanine in the side chain was prepared by 1,2-benzodinitrile, anhydrous cobaltous chloride and a novel azobenzene-containing poly(aryl ether).

Nonlinear Optical Materials for the Smart Filtering of Optical Radiation

The control of luminous radiation has extremely important implications for modern and future technologies as well as in medicine. In this Review, we detail chemical structures and their relevant photophysical features for various groups of materials, including organic dyes such as metalloporphyrins and metallophthalocyanines (and derivatives), other common organic materials, mixed metal complexes and clusters, fullerenes, dendrimeric nanocomposites, polymeric materials (organic and/or inorganic), inorganic semiconductors, and other nanoscopic materials, utilized or potentially useful for the realization of devices able to filter in a smart way an external radiation. The concept of smart is referred to the characteristic of those materials that are capable to filter the radiation in a dynamic way without the need of an ancillary system for the activation of the required transmission change. In particular, this Review gives emphasis to the nonlinear optical properties of photoactive materials for the function of optical power limiting. All known mechanisms of optical limiting have been analyzed and discussed for the different types of materials.

Molecular design confirmation for proposition of improved photophysical properties in a dye-intercalated layered double hydroxides

In the present research, Zn₂Al layered-double hydroxide (LDH) intercalated with Acid Red 27 was prepared by coprecipitation method, while solutions of Zn(ii) and Al(iii) nitrate salts reacted with an alkaline solution of Acid Red 27.

Synthesis and Characterization of New Push-Pull Anthraquinones Bearing an Arylthienyl-Imidazo Conjugation Pathway as Efficient Nonlinear Optical Chromophores

Compounds 1 were synthesized, in good to excellent yields (72-87%), through condensation of formyl-arylthiophene precursors 2 with 1,2-diaminoanthraquinone in ethanol at reflux, followed by cyclisation of the imine intermediate with Pb(OAc)4 in acetic acid at room temperature. Evaluation of the thermal, linear and NLO properties of these compounds was carried out. The  values of chromophores 1, measured by hyper-Rayleigh scattering (HRS) technique, are several times larger (49-67) than that of the standard reference molecule p-nitroaniline (pNA). Due to their excellent thermal stability, (Td = 341-446 oC), and good NLO properties, arylthienyl-imidazo-anthraquinones 1 could be used as new efficient and thermally stable NLO materials.

Spectroscopic analysis and DFT calculations of a food additive carmoisine

FT-IR and Raman techniques were employed for the vibrational characterization of the food additive Carmoisine (E122). The equilibrium geometry, various bonding features, and harmonic vibrational wavenumbers have been investigated with the help of density functional theory (DFT) calculations. A good correlation was found between the computed and experimental wavenumbers. Azo stretching wavenumbers have been lowered due to conjugation and pi-electron delocalization. Predicted electronic absorption spectra from TD-DFT calculation have been analysed comparing with the UV-vis spectrum. The first hyperpolarizability of the molecule is calculated. Intramolecular charge transfer (ICT) responsible for the optical nonlinearity of the dye molecule has been discussed theoretically and experimentally. Stability of the molecule arising from hyperconjugative interactions, charge delocalization and C-H ...O, improper, blue shifted hydrogen bonds have been analysed using natural bond orbital (NBO) analysis.

TIME-RESOLVED SPECTROSCOPY OF ORGANIC DENDRIMERS AND BRANCHED CHROMOPHORES

Organic dendrimers have been considered for a number of optical applications and are now of great interest for the purpose of enhanced nonlinear optical effects. In order to understand the mechanism of the enhanced effects in branched structures it is important to probe the fundamental excitations and the degree of intramolecular interactions utilizing various spectroscopic techniques. In this review, the nonlinear optical and excited state dynamics of different dendritic and other branching chromophore structures are discussed. The methods of two-photon absorption, time-resolved fluorescence, transient absorption, and three-pulse photon echo peak shift are discussed in regards to the degree of intramolecular coupling in the macromolecular systems. These techniques are also used for a comparison of the dynamics in the linear molecular analog systems as well. Thus, this review focuses on the aspect of intramolecular interactions in a branched system and its importance to enhanced nonlinear optical effects useful for modern optical devices.

Optical excitations in organic dendrimers investigated by time-resolved and nonlinear optical spectroscopy

Our research is concerned with the optical properties of covalently bound branched multichromophore systems. The presence of strong intramolecular interactions in dendrimers and other branched macromolecules has stimulated new approaches toward improved energy transfer and light-emitting and enhanced nonlinear optical materials, as well as the possibility of delocalized (exciton) excitations in molecular aggregates. This Account summarizes some of our investigations, which combine the use of different time-resolved techniques to examine the dynamics in organic (conjugated) branched structures and provide important structure-function correlations necessary for applications.