Chiral BODIPY Dyes Obtained By Crystallization Or Combination With A Chiral Anion

Difluoroboron-dipyrromethenes（BODIPYs）are a class of fluorophores with multifunctional sites and excellent optical properties,e.g.,high fluorescence quantum yield,molar absorption coefficient,as well as photothermal and chemical stability.They are widely used as fluorescent probes/sensors,antennas for light harvesting systems,laser dyes,and singlet oxygen photosensitizers,etc.The BODIPY core,which is planar and rigid,is generally considered achiral on account of the C₂-symmetric axis and mirror plane associated with its averaged structure.Chiral BODIPYs can be obtained by introducing chiral substituents or modifying the core structures themselves to break the centrosymmetry.In literature,several chiral BODIPYs with good circularly polarized luminescence（CPL）and circular dichroism（CD）properties were already reported.With the development of CPL and CD technologies,these luminescent chiral compounds have shown promise in various technological applications,including 3D optical displays,optical storage and processing systems,and enantioselective sensors,etc.In this thesis,chiral BODIPY were obtained via two different approaches:1)direct crystallization,and 2)salt formation with chiral anions.A BODIPY D₁,which crystallizes in one of the 65 Sohncke space groups（P2₁2₁2₁）,were chosen for this study.X-ray diffraction（XRD）experiments were carried out,and the results confirmed that the chiral conformers of BODIPY D₁ spontaneous resolved during the crystallization process.The solid-state CD spectra of D₁ single crystals obtained in achiral solvent and crystalline powders obtained in chiral ethyl D/L-lactates all showed obvious Cotton effects.By comparing the XRD structure of D₁ with its circular dichroism spectra,the absolute configurations of D₁ chiral crystals were unambiguously assigned.Furthermore,the chiral symmetry breaking of BODIPY D₁ crystals was successfully realized by Viedma ripening.Then,a chiral BODIPY salt was obtained by combining chiral phosphate anions BINPHAT with an achiral pyridinium-carrying BODIPY E₂.The formation of the chiral BODIPY salt of E₂ and BINPHAT was confirmed by both ¹H NMR titration experiments and CD spectrometry.In addition,a pyridine-functionalized BODIPY D_2,which is the precursor of E₂,was studied for its optical properties under different p H values,coordination with metal Cd²⁺cations and host-guest interaction with electron-deficient（OTf）₁₀-P[5].Reversible acid-base responsiveness was observed;a rare seven-coordinated Cd²⁺complex was successfully obtained and there was no obvious host-guest interaction between D₂ and（OTf）₁₀-P[5].In short,we have proposed two new strategies to obtain chiral BODIPYs,which paved the way for more chiral luminescent materials.