Modified 1H-phenanthro[9,10-d]imidazole derivative with the double acetohydrazide as fluorescent probe for sequential detection of Ni2+ and Al3+ with 'on-off-on' response

Compound L exhibits Ni2+ to Al3+ relay recognition in DMF/H2O (1:9, v/v, HEPES 20 mM, pH = 7.4) solution with 'on-off-on' response. The different binding modes of probe L with Ni2+ and Al3+ were explained and confirmed by 1H NMR spectra.149