Synthesis And Properties Investigation Of P-Nitro-Azobenzene Dyes Bearing Benzophenone Parts

In recent years, great development of high efficient two-photon absorption materials has been made. The design of photoactive molecules and their properties investigation on two-photon absorption are important research areas.The azo dyes have a higher dipole moment due to the units of"A-Ï€-A","D-Ï€-A"and"D-Ï€-D"chemical structures. Functional molecular moieties can be introduced to nitro-azobenzene molecular backbone via ether bridging bond ot other linking bond. In order to achieve high-efficient visible-light photopolymerization, we have present the design and synthesis of nitro-azobenzene dyes with benzophenone moiety as visible-light photoinitiators, two target compounds: [p-(N-ethyl-N-hydroxyethyl) amino-p'-nitro-azobenzene]-(methylenebezophone) ether and p-(N,N-dihydroxyethyl) amino-p'-nitro-azobenzene]-(methylenebezophone) ether. The dyes can be used as efficient long-wavlength photoinitiators as co-using with triethylamine.The photophyscial properties of these novel photoinitiators have been studied. The absorption spectra of those two compounds (nitro-azobenzene dyes with benzophenone moiety) display obvious overlap effects of reference compounds (nitro-azobenzene dyes) and benzophenone, while they have decreased molar extinction coefficients at visible-light absorption region. Reference and target compounds display weak fluorescence emission as excited at 350nm. Visible-light photopolymerization of methyl acrylate initiated by target compounds have much higher yields than those photoinitiated by refernence dyes sensitization systems. This can be ascribed to their rapid photoinduced intramolecular electron transfer between chromophore part and benzophenone via ether bond. Visible-light photopolymerization yields of methyl acrylate initiated by the photoinitiator with two benzophenone branches have approximately double of those initiated by the photopinitiator with one benzophenone moiety, showing that"branch effect"is an efficient approach on the enhancement of visible-light photopolymerization efficiency. The coinitiating effects of three ethanolamine derivatives were also studied in this paper. We also analyzed the structure of compound by X-ray crystallography. We investigated the electrochemical properties of title compounds as well. The potential shifts could be due to diminishment or enhancement of HOMO with the introduction of benzophenone.