Molecular variation and fluorescent turn-on detection of chromium(III) by three ESIPT-reactive 2,2'-(1,4-phenylenebis(5-phenyl-1H-imidazole-4,2-diyl))diphenols

•Novel isoelectronic bis-imidazole 1–3 were synthesized as fluorescent sensor candidates based on ESIPT motivation.•Stokes shifts ranging from 87 nm to 124 nm evidenced presence of the desired ESIPT capability.•The ligands display blue-shifted emission turn-on sensitivity towards chromium(III) with observed molecular differences.•Sensors 2 and 3 displayed remarkable selectivity results for Cr+3.•It was concluded that the ESIPT feature proved to be a vital building block for fluorescent sensor designs.