bathochromic shift as compared to directly linked phenothiazine functionalized BODIPYs 4a and 4b. The density functional theory (DFT) calculation show that the incorporation of acetylene linkage between phenothiazine and BODIPYs induces coplanarity and results lower HOMO–LUMO gap which leads to red shifted absorption. The unsymmetrical phenothiazine functionalized BODIPYs exhibits higher thermal stability