Extended bis(benzothia)quinodimethanes and their dications were synthesized as stable species. The neutral compounds mainly have a quinoidal structure in the ground state but show increased diradical character with extension of the central quinodimethane unit. The dications exhibit similar electronic absorption spectra, NMR spectra, NICS values, and diatropic ring currents to their aromatic all-carbon acene analogues and thus can be regarded as genuine isoelectronic structures of pentacene, hexacene, and heptacene, respectively. Our research gave some insights into the design and synthesis of stable longer acene analogues.

Tri(4-iodo-2,3,5,6-tetrachlorophenyl)methane (2) is reported as a general building block for the synthesis of various π-conjugated polychlorotriphenylmethyl (PTM) radicals. Three push-pull-type triphenylamine-substituted PTM radicals with different substitution patterns were prepared and all exhibited intense inter-valence charge-transfer bands and large two-photon absorption (TPA) cross sections. Moreover, increase of solvent polarity also resulted in improved TPA response. The charge-transfer character of the relevant excited states provoked the efficient photo-generation of charges, anions in the PTM and cations in the amine arms, driven by the amphoteric redox character and the small coupling between donor and acceptor.

Two stable boron dipyrromethene (BODIPY)-based antiaromatic macrocycles, Mc-Fur and Mc-Th, were synthesized through a one-pot Knoevenagel condensation reaction between a BODIPY precursor and furan-2,5-dicarboxaldehyde or thiophene-2,5-dicarboxaldehyde, respectively. H NMR spectroscopic characterization of the two macrocycles supported their highly antiaromatic character. The oxidation properties of the two macrocycles were studied through electron spin resonance spectroscopy and UV/Vis absorption spectrophotometry, which suggested the formation of a stable monoradical cation species on first oxidation followed by an aromatic dicationic species on subsequent oxidation. Both molecules have a nearly planar π-conjugated backbone and show a strong tendency to aggregate in solution due to efficient stacking of the antiaromatic macrocycles. Transient absorption and two-photon absorption (TPA) measurements in solution and aggregated states of the macrocycles revealed that aggregation resulted in large enhancement of TPA cross sections and increased excited-state lifetimes, in accordance with the decrease in the antiaromatic character in the aggregated state.

A highly π-acidic dipyridinium-naphthalene diimide acceptor shows anion-π interactions with halides and PF6-. Lewis basicity and redox potential of the anion affect the chemistry, and photophysical and electrochemical properties, as well as both ionic and electrical conductivities. Our results provide insights into doping, degradation and ion transport mechanisms in organic n-type semiconductors.

New temperature-responsive hydrogels containing various composition of N-acryloyl morpholine (AM) and N-isopropyl acrylamide (NIPAM) were prepared by free-radical solution polymerization using poly(ethyleneglycol) diacrylate (PEGDA) as the chemical crosslinker. The gels were responsive to changes in external temperature, and exhibited the volume phase transition phenomenon. The gels swelled extensively in water at 23 °C, with water-uptake of more than 90 % at swelling equilibrium. The influence of molecular heterogeneity of the gels in terms of comonomer and crosslinker composition on the swelling capacity and equilibrium water uptake was evaluated. The dye adsorption capacity of the gels at room temperature was studied using Congo red as a model dye. The gels displayed significant adsorption capacity of the dye, and the adsorption capacity was found to be dependent on the hydrophilic character of the gel.The characteristic adsorption parameters were determined using the Langmuir isotherm model.The value of equilibrium binding constant was below 1 which indicated favorable adsorption of dye by the hydrogels. The dye release behavior was studied below and above the volume phase transition temperature of the gels. The dye release from the gels was about 95 % at temperatures above the volume phase transition temperature of the gels. These gels can be used as reversible sorbents in the efficient removal of Congo red from waste water.A c c e p t e d M a n u s c r i p t 2 INTRODUCTION Hydrogels are cross-linked three-dimensional polymer networks that can absorb large amounts of water and remain insoluble. Depending on the nature of chemical units along the polymer chain, these materials can be made to respond to changes in certain external stimuli such as pH, temperature, ionic strength, illumination, and magnetic field (1-5), and are called stimuliresponsive, intelligent, smart, or environmentally sensitive polymers. The potential response to these stimuli is changes in phase, shape, volume or optical properties. Due to their excellent properties such as biocompatibility, elasticity, and water-uptake capacity, hydrogels have found applications in skin care products, targeted drug delivery systems, enzyme immobilizations, dye sorbents and chemical sensors (5-10). In many of these applications, the swelling property and strength of the hydrogel plays an important role which has been the subject of research interest in recent years.The development of new sorbents to remove organic or heavy metal pollutants from organic effluents produced in textile, paper, leather, and plastic industries represents an intensive and popular area of research. The main source of water and land pollution is by effluents from textile and leather industries. As a result of dying process, these industrial effluents are colored and contain synthetic organic dyes which are hazardous to the environment and biological activities in water bodies.These organic dyes are also mutagenic and carcinogenic in nature and hence very hazardous to human health...