Construction And Properties Of Red/near Infrared BODIPY Dyes

Boron-dipyrromethene(BODIPY or BDP)dyes are widely used in ion recognition,biological labeling and phototherapy due to their excellent photochemical and physical properties,such as high molar extinction coefficient,high fluorescence quantum yield and good photothermal stability.Abundant modification methods effectively overcome the shortcomings of short absorption and emission wavelengths of classical BODIPY,and make its spectrum cover the region from green light to near infrared,expanding its application in biology.However,there are still many problems,such as low Red/Near infrared(NIR)molar absorptivity,low singlet oxygen generation efficiency,strong dark toxicity,low photothermal conversion efficiency.In order to solve these problems,a series of novel functional dyes were constructed by loading functional groups with reasonable modification methods.The main research contents are as follows:First,the[a]-fused ring asymmetric Red fluoroboron photosensitizer was constructed by the way of selenophene fused ring.The introduction of selenophene effectively extended the?-conjugated system.and reduced the fluorescence quantum yield of BODIPY dyes.These compounds can produce singlet oxygen,especially compound 8,which has strong absorption maximum and weak fluorescence.The singlet oxygen production efficiency is 28%,so it has the potential as a photosensitizer.Second,fusion of sufficient-electron heterocycle rings into the[a]/[b]-position of BODIPY core result in a large red-shift wavelength,thus achieving NIR emitting.we reported the synthesis of non-symmetric benzo[a]fused and thiophene/thieno[3,2-b]thiophene[b]fused BODIPY derivatives 2-3 while remaining a reactive site,and then 4-7 were developed by nucleophilic substitution reactions of 3 position with various nucleophilic agents in good yields.BODIPYs 4 and 6-7 display hypochromic shifted in the absorption and bathochromic shift in the emission with an increase in the solvent polarity due to the formation of resonance structures resulting from the change of C-N distance,which was rationalized by DFT/TD-DFT calculations.In addition,dye 7 have highly selective and sensitive detection for Cu²⁺.The last,the absorption and emission spectra of classic Aza-BODIPY dyes are in the NIR region.By introducing selenophene/thieno[3,2-b]thiophene and other heterocyclic units,the NIR dyes with the maximum absorption peak at 680-850 nm and low fluorescence quantum yield were prepared.Further loading of NMe₂ group display red shifted in the absorption,and form intramolecular photo induced electron transfer(PET),which is helpful to improve the photothermal conversion efficiency.The polymer DSPE-m PEG2000 was used to coat 4f,and the Se-azaBODIPY-NPs with particle size of about 80 nm was obtained.It has good photostability and low dark toxicity.The photothermal conversion rate is up to 40%.It can kill tumor cells efficiently under the irradiation of 808 nm laser,and has the potential as a photothermal agent.