Rihong Liu,Baicheng Feng,Fanuan Yu,Huifen Xin,Rong Qu,Yan Jin
This paper presents the design and synthesis of nine ionic photogenerating acid generators (PAGs) based on iodonium salts. The compounds were characterized using 1H NMR, 13C NMR, 19F NMR and UV, the structures and properties of 9 PAGs molecules were determined. The maximum ultraviolet absorption wavelength of each PAGs is in the range of 200-250nm, with a wide absorption domain, making it highly applicable. In addition, Using the uneven discoloration of Rhodamine B (RB) in the presence of acid, the acid production efficiency of 9 PAGs under 254nm ultraviolet irradiation was quantitatively measured in acetonitrile. It was found that all 9 PAGs underwent I-C cleavage and generated specific acids and other photolysis products. The mechanism for the heteroclitic cleavage of the I-C bond to generate acid was backed by calculations using time-dependent density functional theory (TD-DFT).
Xiao-Na Ma,Xue-Jie Tan,Dian-Xiang Xing,Qi-Cheng Sui,Jian-Min Liu,Chen-Xing Xu,Yun Liu
Two families of bis(imido) symmetrical Schiff bases based on 4-methoxybenzaldehyde and thiophene-2-carbaldehyde linked by three lengths of alkyl groups (propane → butane → dodecane) have been prepared and characterized by 1 H and 13 C NMR, Q-TOF mass spectroscopy , IR and elemental analysis . The structures and conformations of four of them have been established by X-ray single-crystal diffraction analysis. It is interesting that different linking groups and different conformations hardly have effect on several properties. For example, they have nearly the same melting points, the same UV–Vis absorption spectra and the same fluorescence emission spectra. Spectral interpretations were guided by time-dependent DFT calculated transition energies and oscillator strengths , which agree well with the experimental UV–Vis spectra. TD-DFT calculations reveal that they share nearly the same transition mechanism, i. e. both bands are largely originated from the π → π* transitions and have little or nothing to do with the alkyl bridge. However, there are also important differences based on the identity of the terminal groups. For example, similar dimers 1 and 2 crystallize in very different space groups P 4 3 2 1 2 (No. 96) and P 2 1 / n (No. 14), and another set of similar dimers 4 and 5 crystallize in P 2 1 / n (No. 14) and P 2 1 2 1 2 1 (No. 16), respectively. This illustrates the flexible nature of these dimers in forming a variety of different packing motifs. The results of this research suggest that the rational design and prediction of crystal structures are more difficult than optical properties , even though similar weak interactions can be controlled in assembling the molecules.
A series of bispyrazolopyridine (BPP) dyes with electron deficient or electron rich aromatic rings were synthesized, and their optical properties were evaluated. Dyes 3a-c connect the BPP unite with electron deficient moieties (pyridine ( 3a ), nitrobenzene ( 3b ), benzonitrile ( 3c )) by a single bond; dyes 3d-e consist of BPP and electron rich moieties (anisole ( 3d ), N,N -diethylaniline ( 3e )). Their optical properties in five organic solvents and water solution were investigated. They show absorption at 310–375 nm and emission at 400–580 nm in organic solvents. Meanwhile, dyes 3a and 3c-d have high fluorescence quantum yield in organic solvents (40%–84%) and aqueous solution (69%–89%), and they also exhibit excellent light stability. The pH-influenced optical properties tests indicate dyes 3a-e show different fluorescence intensities from alkaline (pH = 10.0) to acid condition (pH = 1.0). The protonation of BPP units and aromatic rings was used to explain their emission property, while (TD)DFT calculations were developed to understand the differences in the optical properties.
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