An Al³⁺ selective ratiometric fluorescent probe (L) has been synthesized by condensation of 4,5-diaminopyrimidine with 1-pyrenecarboxaldehyde. The structure of L has been confirmed by single crystal X-ray analysis. In the presence of Al³⁺, L exhibits a considerable excimer emission at 445 nm along with the decrease of its monomer emission at 368 nm in DMSO–H₂O (4 : 1, v/v). The lowest detection limit for Al³⁺ is 0.24 μM. Furthermore, L can permeate through the cell membrane and detects intracellular Al³⁺ ions under a fluorescence microscope.

The cooperative action of multiple non-covalent interactions allowed for the assembly of a new series of Pb ^II coordination compounds.

A rhodamine–pyrene hybrid molecule acts as a colorimetric and fluorimetric sensor for Al³⁺ through time dependent PET–CHEF and FRET processes associated with tri-color emission. Intracellular Al³⁺ has been visualized through time dependent blue–green–red emission. The lowest limit of detection for Al³⁺ is 0.02 μM.

An efficient Al³⁺ receptor, 6-(2-hydroxybenzylideneamino)-2H-chromen-2-one (HBC), has been synthesized by condensing salicylaldehyde with 6-aminocoumarin. The molecular structure of HBC has been determined by a single crystal X-ray analysis. It was established that in the presence of Al³⁺, HBC shows 25 fold enhancement of fluorescence intensity which might be attributed to the chelation-enhanced fluorescence (CHEF) process. HBC binds Al(NO₃)₃ in a 1 : 1 stoichiometry with a binding constant (K) of 7.9 × 10⁴ M⁻¹. Fe³⁺ and Mn²⁺ quench the emission intensity of the [HBC + Al³⁺] system to an insignificant extent at a concentration 10 times higher compared to that of Al³⁺. HBC is highly efficient in the detection of intracellular Al³⁺ under a fluorescence microscope.

A new series of Pb^II coordination compounds was assembled with the N′-(1-(2-pyridyl)ethylidene)nicotinohydrazide ligand and various auxiliary inorganic counterions.