Environment-sensitive　fluorescent　probes　are　commonly　utilized　in　various　fields,　including　fluorescence　sensing　and　imaging.　This　paper　describes　the　synthesis　and　photophysical　properties　of　a　novel　class　of　solvatochromic　fluorophores　that　incorporate　biisoindolylidene　as　the　core　backbone.　This　study　investigates　the　structure-property　relationships　of　these　newly　developed　fluorophores.　The　central　biisoindolylidene　acts　as　an　efficient　electron　acceptor,　and　by　modifying　the　aryl　ring　substituent　at　the　3,3＇　position,　the　photophysical　properties　of　the　fluorophores　can　be　significantly　enhanced,　particularly　in　terms　of　photoluminescence　quantum　efficiency.　Furthermore,　when　an　electron-donor　group　replaces　the　aryl　ring　at　the　3,3＇　position,　intriguing　solvatochromic　behavior　is　observed.　This　leads　to　a　red-shift　in　the　maximum　emission　wavelength　and　an　increase　in　the　Stokes　shift　with　increasing　solvent　polarity.　In　solvent　dimethyl　sulfoxide　(DMSO),　the　maximum　emission　wavelength　can　reach　up　to　750　nm,　with　a　Stokes　shift　of　approximately　150　nm.　Finally,　the　potential　application　of　the　fluorophore　in　the　detection　of　volatile　acids　is　explored　in　a　preliminary　manner.　(c)　2024　Published　by　Elsevier　B.V.　on　behalf　of　Chinese　Chemical　Society　and　Institute　of　Materia　Medica,　Chinese　Academy　of　Medical　Sciences.