Herein, the optical metal ion sensing properties of monomers (M1 and M2) containing imidazolerngroup as molecular recognition units and conjugated polymer (P1) carrying thiophine andrnthiazole in their backbone were studied. Absorption and fluorescence emission spectra of thernmaterials considered were not significantly changed in different solvents. Sensing ability of thernmonomers and the polymer solutions to metal ions was carried out using fluorescencernspectrometer. Both monomers were highly selective and sensitive optical chemosensor only tornFe3+ ion in THF, chloroform, and dioxane. The sensing principle was based on fluorescencernquenching by forming complex between Fe3+ and imidazole group in the monomers backbone.rnThe limit of detection values (LOD) for M1 and M2 in THF were 1.386x10-5 mol/L andrn3.902x10-6 mol/L, respectively. Moreover, LOD values for M1 and M2 in chloroform obtainedrnwere 1.315x10-5 mol/L and 3.707x10-5 mol/L, respectively. The sensitivity of the monomersrntowards Fe3+ ion was compared by calculating Stern-Volumer constant (Ksv). The Ksv valuesrnfound for M1 and M2 in THF were 6.474x102 M-1 and 1.495x103 M-1, respectively, and inrnchloroform the Ksv values obtained for M1 and M2 were 3.928x102 M-1 and 5.535x102 M-1,rnrespectively. Results obtained showed that monomer M2 was more sensitive than M1 towardsrnFe3+ in all solvents considered. The fluorescence spectra of conjugated polymer P1 in THF,rntoluene, chloroform, and dioxane was insensitive to all metal ions considered.rnKey words optical chemical sensor; molecular recognition; fluorescence quenching; Stern-rnVolumer constant