Photochemical Sensor Design, Synthesis And Application Of Research

Optical chemosensors have played a vital role in the field of biomedicine owing to their ability to selectively recognize objective molecules with optical information as the ouput signal. They are divided into colorimetric chemosensors and fluorescent chemosensors. In the thesis, we focused on the design and synthesis of optical chemosensors with high selectivity. They are including: 1) two diarylethene derivatives of BTE-1B and BTE-2B as the colorimetric chemosensors for fluoride anions or mercuric ions; 2) stilbene derivatives of DBTS as a multi-functional fluorescent chemosensor for fluoride anions and alkaline earth cations and a ratiometric fluorescent chemosensor of Car-tpy for zinc ions; 3) rhodamine derivatives of Fc-RB as a fluorescent chemosensor for mercuric ions and BODIPY-RB, NA-RB and DANS-RB as fluorescent chemosensors for Cr³⁺ and the application in bioimaging of living cells.1. Colorimetric chemosensors based on diarylethene derivativesDiarylethene derivatives (BTEs) have recently been attracted an increasing attention for their excellent thermal stability and fatigue-resistive property and their potential applications of optoelectronic devices such as optical memories and photoinduced switches. In the present part, two diarylethene derivatives of BTE-1B and BTE-2B including dimesitylboryl groups were synthesized, and their photochromic properties were modulated by fluoride anions or mercuric ions. The modulation mechanism is attributed to the special Lewis acid-base interaction between trivalent boron atom and fluoride anions or the strong complexation interaction between mercuric ions and sulphur atom. Upon addition of fluoride anions, the absorption peaks of BTE-1B and BTE-2B in the open states centred at 340 nm were decreased gradually. The absorption maximum of BTE-1B in the photostationary state was shifted from 560 to 490 nm, and the absorption maximum of BTE-2B in the photostationary state was shifted from 655 to 490 nm upon addition of fluoride anions. On the other hand, the changes of the absorption spectra of BTE-1B and BTE-2B in the open states were not obvious upon addition of mercuric ions. However, the absorption maximum of BTE-1B in the photostationary state shifted from 560 to 490 nm, and that of BTE-2B shifted from 655 to 490 nm. So the photochromic properties of BTE-1B and BTE-2B were modulated by both photonic and chemical stimulus.For practical applications to data storage systems, nondestructive readout capability is indispensable. In the diarylethene systems, nondestructive optical memory has not been solved successfully due to the spectral overlap between the writing light or erasing light and readout light. Up-conversion rare earth nanoparticles (UCNP) can convert near-infrared excitation light into emission at visible wavelengths via the sequential absorption of two or more low energy photons. Moreover, the obvious spectral overlap between the up-conversion emission of UCNP and the absorption of BTEs was measured, so we employed the polymer film loaded with diarylethene derivatives of BTE-1B and BTE-2B incorporating UCNP (LaF₃: Yb, Ho and NaYF₄: Yb, Er). Nondestructive up-conversion fluorescent switches were obtained to make use of intermolecular energy transfer processes.2. Fluorescent chemosensors based on stilbene derivativesStilbene derivatives have recently received a remarkable attention for their intriguing electronic and photophysical properties in the fields of organic electronics. In the present study, a new functional push - pull type compound based on a stilbene derivative of DBTS with aza-15-crown-5 as a donor and a three - coordinate orgnoboron as an acceptor was synthesized. DBTS showed the intense fluorescence in a wide spectra range in different solvents. DBTS can recognize fluoride anions with a high selectivity for the special Lewis acid - base interaction between a trivalent boron atom and a fluoride anion. Upon addition of fluoride anions, the absorption maximum of DBTS in THF solution shifted from 410 to 330 nm, and the fluorescent emission centred at 540 nm was decreased gradually excited by 410 nm. Furthermore, upon addition of alkaline earth ions, the absorption maximum of DBTS in CH3CN solution centred at 410 nm and the fluorescent emission centred at 580 nm both disappeared. In addition, a stilbene derivative of Car-tpy conataining a terpyridine group was synthesized as a ratiometric chemosensor for zinc ions. In THF solution, the fluorescent emission of Car-tpy was shifted from 490 nm to 600 nm in the present of zinc ions.3. Synthesis and bioimaging of fluorescent chemosensors based on rhodamine derivativesRhodamine derivatives are an excellent candidate for fluorescent chemosensors because of their outstanding spectroscopic properties of large molar excinction coefficient and high fluorescent quantum yield. In the present part, fluorescent chemosensors based on rhodamine dyes for chromic ions or mercuric ions were synthesized. Furthermore, the further applications of bioimaging were investigated in living cells.a) A rhodamine derivative of Fc-RB to recognize mercuric ions selectively was investigated. In the present of mercuric ions, Fc-RB was induced into the intense fluorescent ring-open structure from nonfluorescencnt spirolactam form. Accordingly, the colorless solution turned to light red. By means of confocal laser scanning microscopy experiments, Fc-RB can be used as a fluorescent chemosensor for monitoring intramolecular mercuric ions in living cells.b) Based on the spectral overlap between 1,8-naphthalimide or dansylamide emission and rhodamine absorption, rhodamine derivatives of NA-RB and DANS-RB were synthesized to detect chromic ions by fluorescence resonance energy transfer (FRET) process. In the present of chromic ions, NA-RB and DANS-RB were induced into the ring-open form. Accordingly, the solution turned from yellow to light red. The fluorescent peaks were shifted from～540 nm of the emission of 1,8-naphthalimide or dansylamide groups to～590 nm of the ring-open rhodamine, so ratiometric fluorescent chemosensors for chromic ions were performed. Furthermore, NA-RB and DANS-RB were applied in bioimaging for chromic ions in living cells with ratiometric fluorescent methods. They will be of a great benefit to biomedical researchers for studying the bioactivity of chronmic ions in biological systems.In addition, a rhodamine derivative of BODIPY-RB was synthesized to detect chromic ions with the fluorescence increasing signal. FRET process was not obvious because of the weak spectral overlap between boradiazaindacene emission and rhodamine absorption. Interestingly, BODIPY-RB can be used as a fluorescent chemosensor for monitoring the distribution of chromic ions in living cells.