Rationally designed C-3 sulfenylated 2-phenyl-4H-pyrido[1,2-a]pyrimidin-4-one based fluorescent probe for recognition of Fe3+

•Electronically diverse C-3 sulfenylated 2-phenyl-4H-pyrido[1,2-a]pyrimidin-4-ones (3a-3d) have been synthesized.•The developed synthetics were structurally characterised using FT-IR, 1H and 13C NMR and mass spectrometry.•The absorption and emission maxima for all the synthetics were recorded in the range of 365-375 and 406-509 nm respectively.•A stoke shift of 3835 cm−1 was observed for 3b in water/methanol (v/v) that further explored in sensing application.•An abrupt increase in absorption intensity with a decrease in emission maxima of 3b was observed upon Fe3+ addition.