Fluorescence imaging mitochondrial copper(Ⅱ) via photocontrollable fluorogenic probe in live cells

Monitoring mitochondrial derived copper（Ⅱ） in live cells is highly demanded, but accurately detecting is unmet due to the interference with cytoplasmic copper（Ⅱ）. Herein, we have reported the design,synthesis and characterization of photocontrollable fluorogenic probe, MCu-3, which is equipped with a photo-labile group（nitrobenzyl group） and mitochondria targeting unit（triphenylphosphonium salt）.This novel probe showed an intense fluorescence enhancement in response to copper（Ⅱ） without interference from other metal cations in the biological condition（p H 6–9）. The detection limit is 1.7 ×10^（-7） mol/L in HEPES buffer. The confocal fluorescence imaging results demonstrated MCu-3 can visualize mitochondrial copper（Ⅱ） in live mammalian cells. The clear advantage of our photocontrollable method is successful to avoid the influence of cytoplasmic copper（Ⅱ） during mitochondria specific detection.

Elucidation of Acceleration Mechanisms by a Photosensitive Onium Salt for Nitroxide-Mediated Photocontrolled/Living Radical Polymerization

The acceleration mechanisms by a photosensitive onium salt for the nitroxide-mediated photocontrolled/living radical polymerization (photo-NMP) were determined. The photo-NMP of methyl methacrylate was performed by irradiation at room temperature using 4-methoxy-2,2,6,6-tetramethylpiperidine-1-oxyl (MTEMPO) as the mediator and (2RS, 2’RS)-azobis(4-methoxy-2,4-dimethylvaleronitrile) as the initiator. The polymerization was accelerated in the presence of (4-tertbutylphenyl)diphenylsulfonium triflate (tBuS) to produce a polymer with a molecular weight distribution as narrow as the polymerization in its absence. (±)-Camphor-10-sulfonic acid or 2-fluoro-1-methylpyridinium p-toluenesulfonate had no effect on the polymerization speed, suggesting that tBuS did not serve as the photo-acid generator for the photo-NMP. It was found that the acceleration of the polymerization was based on the electron transfer from MTEMPO into tBuS in the excited state to temporarily generate a free radical propagating chain end and an oxoaminium salt (OAS), the one-electron oxidant of MTEMPO. This electron transfer mechanism was verified on the basis of the fact that the photo-NMP in the presence of tBuS was still accelerated by triphenylamine, the electron transfer inhibitor, to partly produce a polymer with an uncontrolled molecular weight. The formation of an uncontrolled molecular weight polymer indicated the generation of a free radical propagating chain end due to the deactivation of the OAS by the triphenylamine. It was deduced that tBuS served as the electron acceptor from MTEMPO in the excited state to temporarily produce a free radical propagating chain end along with OAS, resulting in the acceleration of the polymerization.

Molecular System Based on Novel Photochromic Biindenylidenedione Derivative Demonstrating Photomodulation of Magnetism

Stable nitronyl nitroxide radical and imino nitroxide radical were incorporated into the benzene rings of novel photochromic 7,7＇-dimethyl-[2,2＇-bi-lH-indene]-3,3＇-diethyl-3,3＇-dihydroxy-l,l＇-dione （1）, leading to the synthesis of novel multifunctional compounds 4 and 5. The photochromic properties, ESR spectroscopy and magnetic proper- ties of the title compounds were investigated. Compounds 4 and 5 possess visible photochromism upon photoirra- diation, and their ESR signals undergo secular broadening after photoirradiation. The magnetic susceptibility meas- urement shows that the antiferromagnetic interaction of 4 and 5 becomes stronger after photoirradiation. In compounds 4 and 5 there are two kinds of spin centers after photoirradiation： one is nitroxide radical, and the other is photo-generated radicals from two indanone moieties. Our results demonstrated that the colour and magnetic properties of compounds 4 and 5 could be modulated by photoirradiation.