Synthesis,Physical Properties And Applications Of Photoresponsive Bodipy And Nano For PET-Blocked Sensors

Copper,E.coli and some organic solvents in the environment as pollutants have very harmful health consequences but pyruvate overproduction in the human blood stream is highly injurious due to associated risk of coronary diseases,mental disorders,shocks,heart failures and death.Fluorescence sensors have been applied widely for monitoring these analytes in both human and environment.The design and synthesis of fluorescent chemosensors and probes considerably draw more attention now because of fluorescence-based detection methods which are known for their simplicity and high sensitivity for the detection of these analytes.BODIPY(4,4-difluoro-4-bora-3a,4a-diaza-s-indacene)fluorescent dyes exhibit excellent properties such as easy modification,high fluorescence quantum yield and high molar absorption coefficient.Functionalized BODIPY dyes have broad application prospects in the fields of fluorescent sensors,biomolecules and metal analysis.Unlike pristine BODIPYs,acceptor-BODIPY types,in contrast,are electron deficient owing to electron withdrawing substituents that takes electron by PET(photoinduced electron transfer)mechanism,characterized by fluorescence quenching or low fluorescence intensities.These PET challenged BODIPY dyes have been applied alternatively in a fluorescence turn-on sensing detection of analytes in strategic PET-blocking process.Studying PET-blocked sensors will pave the way for developing new BODIPY based dyes.In account of this,we summarize the progress of BODIPY compounds and PET-blocked dyes.Four new nitrophenyl-BODIPY conju-gates and one nano-BODIPY assembly were prepared and characterized structurally,chemically and photo-physically for sensing or detection.Furthermore,the PET-blocking photophysical prop-erties were investigated.In closing,compounds were used as sensors for the detection of ethyl acetate(EA),or copper(II),pyruvate and E.coli and more.The novelty and important results are shown in the following:1.A hyperchromic and the bathochromic solvent turn-on dyes,BDPPhOH and BDP(PhOH)₂,new BODIPYs(4,4-difluoro-4-bora-3a,4a-diaza-s-indacene)were synthesized,characterized by¹HNMR,¹³CNMR,and mass spectrometric analysis to established structure.In addition,they were also investigated for photophysical and chemical properties.The challenge with BDPPhOH((4-(5,5-difluoro-1,3,7,9-tetramethyl-10-(4-nitrophenyl)-5H-4l4,5l4-dipyrrolo[1,2-c:2',1'-f][1,3,2]di-azaborinin-2-yl)phenyl)methanol)and BDP(PhOH)₂ have been weak fluorescence intensity due to photoinduced electron transfer process(PET).Another challenge was refining the PET-plagued NO₂-BODIPY with a donor conjugate in a donor acceptor design,capable/suitable for solvent H-bonding induced aggregate self-assembly emission enhancement turn-on in AIEE(aggregate in-duced emission enhancement).Like many PET-plagued dye sensors,a suitable medium was needed to turn-on the fluorescence.The solution led to novel solvent turn–on dyes which turn on both in hydrophobic H-bond donating solvents and solvent induced self-assembly media–new PET-blocking dyes turn-on are described in EA,PE,DMSO and THF.The mechanism of detection was based on donor-photoinduced electron transfer(d-PET)solvents inhibition.The design in-volved a meso-nitrophenyl conjugate and the hydroxy benzyl functionality at the 2-position for hydrophobic hydrogen bonding self-assembly d-PET-inhibition.Donor-PET process involving electron transfer from the donor fluorophore core to acceptor substituent is confirmed by fluores-cence quenching-with the negative?G_PET values of BDPPhOH as-0.2249 and-0.0151 respec-tively.Strategically,d-PET was inhibited or blocked by H-bonding from ethyl acetate and self-assembly H-bond donor,benzyl alcohol-conjugate with the NO₂-group.This leads to H-bond turn-on and aggregate induced emission enhancement(AIEE)via HO-and NO₂ in BDPPhOH and BDP(PhOH)₂ confirmed by DFT calculation.From the molecular structure of BDPPhOH and the electrostatic potential map in the DFT calculation,the polar groups such as NO₂-,BF₂-,and HO-are evenly distributed in the molecular backbone.This is beneficial for formation of self-aggrega-tion of BDPPhOH in solutions and it is confirmed by the SEM image.Our results demonstrate high fluorescence intensities of BDPPhOH in ethyl acetate(EA),petroleum-ether(PE).The same changes were found in the CV analyses.DFT analysis and calculations confirmed H-bonding flu-orescence turn-on in both EA solvated BDPPhOH and(O-N=O---H-O-)hydrogen bond induced aggregate of BDPPhOH in PE.The donor(HO-)and acceptor(nitro-)conjugated BODIPY inter-actions led to a total inhibition of d-PET and exponential fluorescence turn-on in BDPPhOH.Our results demonstrate donor(HO-)and acceptor(nitro-)conjugated BODIPY as guest responsive d-PET fluorescence dyes.Besides the properties investigated,one advantage of BDPPhOH and BDP(PhOH)₂ worthwhile mentioning are their high synthetic yield,ease of modification and syn-thetic usage as starting material or intermediate to other derivatives.2.A novel fluorescence probe,BDP-DPA(N-(4-(5,5-difluoro-1,3,7,9-tetramethyl-10-(4-ni-trophenyl)-5H-4l4,5l4-dipyrrolo[1,2-c:2',1'-f][1,3,2]diazaborinin-2-yl)benzyl)-1-(pyridin-2-yl)-N-(pyridin-2-ylmethyl)methanamine),was designed and synthesized for the detection of Cu²⁺through PET-blocking mechanism.The structure of BDP-DPA was characterized by ¹HNMR,liq-uid chromatography mass spectrometry(LC-MS)for its molecular ion peak m/z(657)in positive ion mode.Owing to strong electron-withdrawing meso-nitrophenyl substituent on BODIPY-core,BDP-DPA suffers from low fluorescence intensity,a consequence of photoinduced electron trans-fer(PET)process of electron migration from LUMO BODIPY-core to LUMO-acceptor.The mod-ification with DPA(bis(pyridin-2-ylmethyl)amine),dipicolylamine was an attempt to reduce PET as well as serving as receptor for Cu²⁺ion detection but due to NO₂-group,the effect is minimal,since the lone-pair on-N=rather quenches emission like reductive-PET(a-PET)sensors,con-firmed by its low fluorescing intensity in DCM(541nm).To solve the problem,a solvotochromic analysis carried-out indicated a high hyperchromic and bathochromic shift in PE(547nm),THF(548nm),EA(547nm)with dimension range of 520–697nm compared to DCM(541nm)in the range of 520-610nm.The DFT of precursor BDPPhOH suggested PE,THF and EA formed intermolecular H-bonding and aggregation which may possibly be the reason for the colorimetric and fluorimetric turn-on in the ground and the excited states.DFT calculations confirmed H-bond-ing fluorescence turn-on in both EA solvated BDPPhOH and(O-N=O---H-O-)hydrogen bonding induced PET-blocking.The intermolecular solvent induced H-bonding fluorescence turn-on is due to the H-CH₂-group of EA and NO₂-group(O-N=O---H-O-)in BDP-DPA.The donor(H-CH₂-)EA and acceptor(nitro-)conjugated BODIPY interactions led to a total inhibition of d-PET dye and exponential fluorescence turn-on in BDP-DPA.In PE high turn-on is by aggregate induced emission enhancement.Fluorimetric titration with copper ion after PET inhibition shows a differ-ent spectral curve from that of its water spectra.A new method for sensing and quantifying water in THF is identified.SEM pictures confirm copper interaction/binding with BDP-DPA and CV analysis of the metal complex suggest a possible BDP-DPA-Copper complex application as pho-tooxidation catalyst for water splitting.3.Though significant in many biological process,over-dose of copper has caused diseases owing to its toxic,oxidative effect and Cu²⁺deficiency like anemia-like symptoms,neutropenia,bone abnormality and hypopigmentation.Knowing the seriousness of this problem,significant research efforts have been spent on improving Cu²⁺detection in water samples.Though reports on fluorometric detection methods have been significantly accurate and sensitive,most of these chemosensors are challenged with lack of stability and storage.Based on these problems,we de-scribe a fluorescence nano-polymer imprint for copper sensing based on BODIPY fluorophore.A coordination complex-based displacement was successfully used to synthesize a BODIPY fluo-rescent chemosensor(B-DPA)of copper bearing DPA.This was structurally characterized by HNMR,¹³CNMR,LCMS and UV-Visible absorption spectra.MS(ESI)Calculated for([B-DPA+cu²⁺+Cl^-])=633.44,m/z=633.31 confirmed B-DPA-copper complex.The binding ability of B-DPA toward different metal ions displays high selectivity for copper(II)ions and the fluo-rescence probe was quenched with the addition of various concentrations of Cu²⁺upon the excita-tion at 510nm.A new nano-BPP was obtained by the self-assembly of B-DPA-copper complex with dopamine and followed polymerization.Nano-BPP can extract copper(II)forming new Nano-BPPCu.Solid UV analysis BODIPY absorption at 500nm,polymeric absorption at DPA at340nm and new absorption as a result of aggregate induced emission enhancement at 754nm.In particular,Nano-BPP could be recovered after Nano-BPPCu was treated with acid.Thus,the Nano-BPP is a recyclable poly-chelator and sensor for copper overload situations in human body and in the environment for decreasing the copper pollution of water resources.SEM images and fluorimetric titration confirms fluorescent nano polymer copper imprinted successfully synthe-sized.4.Like BDPPhOH,apart from investigating hydrogen bonding induced PET inhibition with resulting unique selectivity of solvent induced fluorescence turn-on,two more fascinating results were obtained with NIR emission turn-ons.Firstly,BDP(PhOH)₂ interaction with+E.coli leads to NIR emission enhancement at emission wavelength of 628nm from 522nm absorption with106nm Stokes'shift.Fluorescence absorption and emission changed significantly to near infrared wave length of 647nm emission,following BDP(PhOH)₂ interaction with pyruvate from absorp-tion wavelength of 420nm corresponding to 227nm stokes'-shift.This makes BDP(PhOH)_2,one of the best sensors for pyruvate ever discovered,under just visible light irradiation at room tem-perature in an enolate PET blocking pi-extension mechanism.To confirm whether DMSO-water was not the cause of red bathochromic shift in fluorescence,DMSO in water ratio of BDP(PhOH)2solution absorbed in the blue(349nm),for 4:1-DMSO-water,but rest had very low intensities at a wavelength of 545nm.This analysis confirmed that the solvent had no influence on the emission.Thus,a new NIR-BDP(PhOH)₂ aggregate,a new PET-blocked BODIPY-dye sensor effective for rapid detection/sensing+E.coli and pyruvate is duly synthesized.