Synthesis And Photochromic Properties Of Pyrazolones Containing Pyridine Ring

Organic photochromic materials have received more and more researchers’ attention at home and aboard for its potential value in information storage, molecular switches, biotechnology areas, etc. Pyrazolone derivatives were a kind of functional materials which has unique structure and photochemical properties. Pyrazolone with good fluorescence properties and excellent fatigue resistance has good application prospect in high-density information storage, fluorescent molecular switches and other fields.In this paper, on the basis of previous research in our laboratory, several pyrazolone derivatives have been synthesized through introducing pyridyl at the 4-position of pyrazolone-ring. The structure of the compounds were confirmed by IR, NMR spectra and mass spectra. The study found that the introduction of the pyridine ring changed the electronic structure of the compounds, so that the color fading reaction was happened under the irradiation of visible light, at the same time, they showed the high contrast fluorescent modulation characteristics.1. Twelve new pyrazolone compounds was synthesized through introduced(iso)nicotinoyl and 2-chloro nicotinoyl at the 4-position of pyrazolone-ring, They were all characterized by NMR and mass spectra to determine the structure, IR spectrum had been used to characterize the molecular structure of compounds. Their optical properties were studied by UV-Vis absorption spectra and fluorescence emission spectra, ten compounds showed the photochromic properties under UV irradiation among them.2. Six novel compounds was synthesized through introduced 4-chloro pyridyl and(4-trifluoromethyl) pyridyl at the 4-position of pyrazolone-ring. They all showed reversible photochromism alternative UV light and visible light. NMR and mass spectra were determined the molecular structure, XRD spectra showed the existed form of the compounds. IR spectrum probes into the structure of the compounds before and after UV irradiation. The photochromic properties and dynamic behavior were studied by UV-Vis spectra and fluorescence emission spectra. Among them, five compounds exhibited high fluorescent contrast and excellent fatigue resistance.3. Three novel pyrazolone compounds were synthesized through introduced 5-bromo pyridyl at 4-position of pyrazolone-ring. They were all exhibited reversible photochromism alternative UV and visible light. NMR and mass spectrum had been used to characterize the structure of compounds. According to fluorescence spectra, 1,3-diphenyl-4-(5-bromo)pyridyl-5-hydroxypyrazole 4-phenyl thiosemicarbazide(DP5Br3PyBP-PTSC) had great fluorescence emission quenching, it also show the maximum level of return under visible light. The excellent fluorescence modulation performance is expected to obtain further development and utilization in the field of fluorescent molecular switches.