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Organic/inorganic hybrid multilayer films with noncentrosymmetrically orientated azobenzene chromophores were fabricated by the sequential deposition of ZrO2 layers by a surface sol-gel process and subsequent layer-by-layer (LbL) adsorption of the nonlinear optical (NLO)-active azobenzene-containing polyanion PAC-azoBNS and poly(diallyldimethylammonium chloride) (PDDA). Noncentrosymmetric orientation of the NLO-active azobenzene chromophores was achieved because of the strong repulsion between the negatively charged ZrO(2) and the sulfonate groups of the azobenzene chromophore in PAC-azoBNS. Regular deposition of ZrO(2)/PAC-azoBNS/PDDA multilayer films was verified by UV-vis absorption spectroscopy and quartz crystal microbalance measurements. Both UV-vis absorption spectroscopy and transmission second harmonic generation (SHG) measurements confirmed the noncentrosymmetric orientation of the azobenzene chromophores in the as-prepared ZrO2/PAC-azoBNS/PDDA multilayer films. The square root of the SHG signal (I(2omega)(1/2)) increases with the increase of the azobenzene graft ratio in PAC-azoBNS as the number of deposition cycles of the ZrO(2)/PAC-azoBNS/PDDA films remains the same, while the second-order susceptibility chi(zzz)(2) of the film decreases with the increase of the azobenzene graft ratio. Furthermore, the present method was successfully extended to realize the noncentrosymmetric orientation of azobenzene chromophores in multilayer films when small organic azobenzene compounds with carboxylic acid and/or hydroxyl groups at one end and sulfonate groups at the other end were used. The present method was characterized by its simplicity and flexibility in film preparation, and it is anticipated to be a facile way to fabricate second-order nonlinear optical film materials.

In the presence of molecular oxygen or hydrogen peroxide, 1-naphthylamine (1-NA) was catalytically converted into bis(4-oxo-benzo-2-cyclohexen-1-yl) amine (BOBCHA) over metalloporphyrin catalysts through an oxidative-coupling way. UV–vis, IR, NMR, MS, mp determinations and elemental analysis were employed for product characterization. A possible catalytic mechanism based on in situ UV–vis and EPR determinations was proposed. A spectrophotometric method was established for quantitative analysis of the product according to its characteristic absorption at λ max = 465 nm. The influences of reaction conditions, such as solvents, temperature, reaction time, medium alkalinity, as well as species and amount of the catalysts were discussed in detail.

Naphthol is selectively converted into 2-hydroxy-1,4-naphthoquinone (HNQ) by relatively cheap and clean oxidant of molecular oxygen under air pressure in an alkaline solution over iron porphyrin catalysts. E.g. Fe–porphyrin (TMOPPFeCl) catalyst shows high activity (62%) and selectivity (100%) for the oxidation of naphthol to HNQ by O2 under air-pressure at 45 °C in alkaline media, where a recycle of the porphyrin catalysts is relatively simple because the product HNQ of catalytic oxidation is unsolvable in the alkaline media and separation of the porphyrin catalysts with HNQ is easily used by the filtration. Obviously, this reaction combines the advantages of high activity, high selectivity, a clean oxidant of molecular oxygen, mild conditions such as air-pressure and low temperature (45 °C), as well as recycled catalysts. Moreover, this reaction is investigated by in situ infrared spectroscopy, and a band at 881 cm−1 appears, which is possibly assigned to peroxide species. The band at 881 cm−1 completely disappears after exposure to 2-napthol, forming the reaction product HNQ. Therefore, it is proposed that peroxide species are active intermediates for the reaction.

Ultrathin films with noncentrosymmetrically orientated azobenzene chromophores were constructed using a combination of layer-by-layer adsorption of polyelectrolytes and the surface sol-gel process.

The azobenzene-containing polyanion PAC-azoBNS was alternately assembled with the polycation diazoresin (DAR) to construct photo-cross-linkable multilayer films of PAC-azoBNS/DAR that contain photolabile groups of azobenzene. Upon mild UV irradiation, the interaction between PAC-azoBNS/DAR multilayers was converted from electrostatic interaction to covalent bonds. Because of the free carboxylic acid groups presented in the film, the photo-cross-linked multilayer film favors the selective permeation of positively charged species. After photolysis of the photo-cross-linked PAC-azoBNS/DAR films with intense UV irradiation, azobenzene groups decompose to produce imine groups, and a photo-cross-linked robust film containing free carboxylic acid and imine groups was fabricated. The resultant film allows the permeation of negatively charged species and meanwhile shows a pH-switchable permselectivity for positively charged species. Because of the covalently cross-linking structure, the photolyzed cross-linked PAC-azoBNS/DAR film shows high reversible switching behavior and has high stability in solution with high ionic strength.