In this work, four free metal-organic dyes were synthesized as a donor-π bridge-acceptor system in a one-pot condensation reaction and were used as sensitizers in DSSCs. To explore the effect of substituents of the efficiency of the DSSCs, three different types of substituents were applied at the –NH position on the imidazole ring: nitrobenzene, alkyl chain and phenyl coded (PP2, PP3 and, PP4) respectively. All these dyes are characterized by 1H NMR, 13C NMR, UV-Vis, and mass spectroscopy. The energy bandgap and structures of all dyes were estimated via applied tools of computational based on the density functional theory method (DFT). The dye PP3 with the alkyl chain substitution displayed the highest power conversion efficiency (PCE) of 2.01% (Jsc = 3.75 mA cm-2, Voc = 0.73 mV, FF = 73.9%) while the PP2 dye with the nitrobenzene substitution showed the lowest energy gap (2.55 eV) and lowest PCE 0.96% (Jsc = 1.59 mA cm-2, Voc = 0.080 mV, FF = 61.6%).