Synthesis And Properties Of Novel Boron-containing Organic Optoelectronic Functional Molecules

Recent years have witnessed the rapid development of organoboron-containing optoelectric functional molecules and its extensive applications in various fields.The vacant p-orbital of trivalent boron atom has brought it interesting characteristic features.First,it endows boron with strong ?-electron acceptability leading to an efficient delocalization with a adjacent organic ?-system and making boron center an excellent ?-electron acceptor in the excited state.When an electron-donating amino group is present in the trivalent boron-based ?-framework,the system usually shows intense intromolecular charge-transfer transition,which brings intriguing photophysical properties.Second,the vacant ?-orbital is readily attacked by nucleophiles making tricoordinate boron compounds a strong Lewis acid.And this property is also used as a design principle for teracoordinate boron-based functional molecules.For example,when a nitrogen or oxygen atom,which contains an lone pair electron,is present at right position,the lone pair electron can complexed with the vacant p-orbital of trivalent boron atom generating an intromolecular coordination compound.And the tricoordinate boron becomes tetracoordinate boron which renders the ?-system planar and enhance the electronic interactions.In this paper,we designed several organic optoelectronic functional molecules based on the tricoordinate and tetracoordinate boron and the work can be divided in two parts as flollows:1?We choosed BODIPY dye,the most classical teracoodinate boron-based molecule,as research target and devoted to develop an direct intromolecuar cyclization for the construction of ring-fused BODIPY dye.We found an simple H2SO4-induced intromolecular cyclization reaction of P-2-(methylsulfinyl)phenyl BODIPY to synthesize the benzothieno[b]-fused BODIPYs.The method has two significant advantages:First,both symmetrical and unsymmetrical benzothieno[b]-fused BODIPYs can be obtained.However,traditional methods for synthesis of ring-fused BODIPY usually started from ring fused pyrrole,which can only leads to symmetrical ring-fused BODIPY and requires multiple synthetic route.Second,a deborylation reaction was observed in the course of cyclization affording benzothieno[b]-fused dipprin derivatives which were important precursors for consruction of functional porphyrin molecules.Finally,we investigated the impact of the ring-fused structure to the photophysical properties of BODIPY dye.And it was found that compared with the unstrained aryl substituted BODIPY,the ring-fused structure can elevate the HOMO energy levels more efficiently and endow the whole system excellent properties,such as emission in red region,higher quantum yields,intense absorption and reversible oxidation and reduction potentials.2?In the second part,we focused on the triarylborane-based ?-system.We introduced the most classical B/N based D-?-A structure into the chiral 1,1'-binaphthyl framework in which the two boryl groups and two amino groups are arranged at the 2,2' and 6,6' positions of the binaphthyl backbone.It was found that the simple changes of amino groups caused dramatic changes of photophysical properties affording different functional fluorescent dyes.When the amino group was sterically hindered diphenylamino group(BNPh-BNaph),it can suppress the rotation of the two naphthyl units of binaphthyl framework.As a result,BNPh-BNaph possesses high quantum yields in both solutions and solid state showing potential applications as chiral circularly polarized luminescence(CPL)dyes and its chiral photophysical properties is undergoing testing.When the amino group was small sized dimethylamino group(BNMe-BNaph),the two naphthyl units can rotate freely leading different structures and thus bring intriguing properties.So BNMe-BNaph shows characteristic dual emission.Further study revealed that relative intensity of short and long emission wavelength in dual emission changes regularly as the temperature varies,which caused remarkable the fluorescent color changes from green to orange as the temperature decreases from 323 K to 223 K.And the ratios of emission intensities of long and short wavelengths in dual emission exhibit good linear relationship in a certain temperature range making BNMe-BNaph a potential highly sensitive colorimetric and ratiometric fluorescent thermometer.