Boron difluoroquinazolinone-pyridine (BODIQ-Py)a nd substituted derivatives have been designed and synthesized. Strongemission with high fluorescencequantum yield both in solution (up to 0.99) andi ns olid state (up to 0.60) was achieved in these asymmetric BODIQPys. For 6-halogens ubstituted BODIQPys,t he heavy atomic effect of bromine and iodine was suppressed in solution due to the strong electron-withdrawing ability of the BODIQPy core. As ar esult, 6-iodines ubstituted BODIQPy shows the unusual fluorescence quantum yields (> 0.70) in dichloromethanea nd tetrahydrofuran. In the solid state, the asymmetric structurei nducedaunique dimeric structure, and efficient luminescence was also observed. The formationo fh alogen bonds between carbonyl oxygen and bromine or iodine regulated the stacking mode and enhanced intermolecular interaction, resulting in ad ecline in the fluorescence quantum yield. In addition, al arge Stokes shift was also achieved in these asymmetric BODIQPys.The development of new fluorescent dyes with good emission efficiency both in solutiona nd in the solid state have attracted increasing attention due to their potential applications in many research fields, such as molecular and biomoleculars ensors, [1] solid-state solar concentrators, [2] organic light-emitting diodes [3] and photodynamic therapy. [4] As ac lass of the most importantf luorescent chromophores, boron dipyrromethene (BODIPY)d yesi sk nown to have excellent characteristics in-cluding high photochemical stability, largea bsorption coefficient,a nd high fluorescenceq uantumy ield in solution. [5] But two deficiencieso fBODIPY dyes are their generally small Stokess hift (5-20 nm, in most cases) [6] andl ow fluorescencei n the solid state. [7] Recently,n ew types of difluoroboron (BF 2 )c omplexes through ligand design, [8] such as anilido-pyridine, [9] diketone, [10] pyridomethene, [11] pyrimidine, [12] and pyrazine, [13] have been developed to realize large Stokes shifts (> 80 nm). However, most of them exhibit weak or quenched fluorescencei nt he solid state due to the aggregation-caused quenching( ACQ). A successful strategy to increasing emission efficiency of BF 2 complexes in the solid state is to introduce astructure with aggregation-induced emission (AIE) property. [14] However,t he fluorescenceofthose compounds with AIE properties is usually weak in solution. [15] To designa nd synthesis of asymmetric difluoroboron complexes is ap romising strategy to achievee ffectivee mission both in solution andi nt he solid state, which provides possibilities to reduce the intermolecular p-p stacking interactions and make more energetic differenceb etween the ground and excited states. [9, 16] Until now,t ot he best of our knowledge,t he difluoroboron complexesw ith high effective emission both in solution and solid state were rare. [17] Herein, we report the facile synthesis and fluorescence properties of asymmetric difluoroboronq uinazolinone-pyridine complexes( BODIQPys), which exhibit ultra-high emissione fficienci...