Synthesis Of Based-on Phenanthro[9,10-d]imidazol And Rhodamine Dyes And Application

Fluorescent dyes which act as organic functional materials are widely applied in manyfields including chemistry, physics, biology, environmental science, medicine. Fluorescentdyes with excellent performance have attracted more and more attention in electroluminescentmaterials and fluorescent probe. Efficient solid-state fuorescent dyes are required in the fieldsof fundamental research and optoelectronic materials. Relative to inorganic fluorescentmaterials, organic fluorescent materials exhibit some good property, such as the flexiblestructure, high luminous efficiency, wide color range, large film area, and so on. Thus, thedevelopment of solid-emissive fluorophores has attracted great attention, especially solid-statered fuorescent dyes. Amajor hurdle faced in the design of solid-emissive dyes is to overcomefluorescence self-quenching in solid state. So it is very challenging to rationally design newdyes of solid-emissive red fluorophores, in particular, based on novel frameworks. We designa series of phenanthro[9,10-d]imidazol–quinoline boron difluoride (PQBD) with redfluorescent in solid. The design strategy for PQBD is formulated based on the followingconsiderations:1) Selection of the phenanthro[9,10-d]imidazol moiety. It is known thatphenanthro[9,10-d]imidazol dyes have large Stokes shifts (up to100nm), which arefavourable for solid-state emission by minimizing reabsorption and self-quenching. Inaddition, the phenanthro[9,10-d]imidazol moiety possesses an aromatic NH, which can betaken advantage to coordinate with boron fluoride for enhancement of fluorescence quantumyields. Furthermore, the phenanthro[9,10-d]imidazol moiety can function as an effectiveelectron donor.2) Selection of the quinoline unit. The aromatic N atom of quinoline can beused as a ligand for boron complex. Furthermore, in PQBD, the quinoline moiety bears apositive charge and thus can serve as an electron acceptor. Hence, withphenanthro[9,10-d]imidazol and quinoline moieties operating as electron donor and acceptor,respectively, PQBD may be considered as an effective donor (D)-acceptor (A) system, whichis desirable for absorption and emission in the long wavelength. Based on this, we designedand synthesized a series of PQBD dye with red solid-state emission and high fluorescencequantum yield. The fluorescence quantum yield of PQBD1is0.90in dichloromethane,solid-state fluorescence quantum yield is0.184. Crystal structure data display that there is noπ-π accumulation in crystal to hinder the solid-state fluorescence quenching。Fluorescent sensing is widely applied in diverse fields such as the biological markers,enzyme analysis, environmental analysis, cell staining, clinical test and diagnosis due to its high sensitivity, good reproducibility, good cell membrane permeability, simple operation andsitu detection. In addition, by combining with fluorescence microscopy, fluorescent sensingand bio-imaging can be exploited as a powerful approach to investigate biomolecules ofinterest with high temporal and spatial resolution. Fluorescent sensors are requisite moleculartools for sensing and bio-imaging. Up to date, a large volume of fluorescent sensors have beendeveloped. However, most of them exhibit fluorescence signal variations only in one channel.By contrast, dual-channel based sensors have fluorescence signal changes in two distinctchannels. This may reduce the potentials errors due to false positive or artifacts arising fromenvironmental factors. Inspired by the spectral feature of dual-channel based sensors, wereasoned that three-channel based sensors could have fluorescence signal variations in threedistinct channels. Thus, in principle, three-channel based fluorescent sensors should be muchmore reliable to eliminate potential false positive or artifacts, as the fluorescent signals inthree different channels can be used for mutual corroboration. We design and synthetize anovel compound1as a novel organic white light-emitting dye, which emit light with threedifferent channels, red, green, and blue. Compound1is composed of two subunits,1H-phenanthro[9,10-d]imidazol and3-hydroxychromone moieties connected by a rigid andconjugated phenyl linker. Compound1is further applied as a unique platform to develop thefluorescent sensor for hydrogen sulfide (H2S) by structural modification with2,4-dinitrobenylmoiety. Thereby, compound4is essentially nonfluorescent in all the three emission channels.However, upon interaction with hydrogen sulfide, the2,4-dinitrobenyl moiety can be uncagedto release compound1, and consequently, the fluorescent turn-on signals in all the threeemission channels can be observed. The H2S fluorescent probe has better selectivity, andimaging to H2S with three channel fluorescence in live cells.Iit is relatively challenging to discriminate Zn2+and Cd2+metal ions by Fluorescentsensing due to the fact that they lie in the same group in the periodic table. We designcompound L as a new single fluorescent probe which is capable of reporting Zn2+and Cd2+with distinct fluorescence signals using the fluorescence sensing mechanism of intramolecularcharge transfer. Probe L is composed of a1H-phenanthro [9,10-d]imidazol moiety and a8-hydroxyquinoline unit. The selection of1H-phenanthro[9,10-d]imidazol dye is based on theconsiderations that it can function both as a fluorescent dye and an electron donor in apush-pull system.8-hydroxyquinoline moiety was chosen as the potential binding unit formetal ions and electron acceptor in the push-pull system. The studies of Job‘s plot, massspectroscopy, DFT calculations, and1H NMR spectroscopy reveal that the new probe likelyhas distinct binding modes to Zn2+and Cd2+.Gold complexes have been extensively used in chemistry, medicine, and biology, however, the gold ion has potential toxicological effects on the human body, so the detectionof gold species has received intense attention. A number of irreversible fluorescent goldchemodosimeters based on gold-promoted reactions have been reported. However, it is stillchallenging to develop reversible fluorescent gold sensors. We design a new reversible andselective chemosensor for gold ions by incorporating a8-hydroxyquinoline moiety oncompound2, which the nitrogen and oxygen atom of8-hydroxyquinoline can participate inthe coordination and form a semicircle cavity to enhance the gold ion coordination ability.Chemosensor1exhibited favorable features including fast response, reversibility, highsensitivity with a large fluorescence (100-fold) enhancement and a low detection limit of48nM, high selectivity for Au3+over Cu2+, working well at physiological pH, and good cellmembrane permeability. These desirable attributes render the sensor suitable for fluorescentimaging of gold ions in living cells.