Aluminum ion complex formation with 3-hydroxyflavone in Langmuir and Langmuir–Blodgett films

The flavonoid 3-hydroxyflavone (3HF) is insoluble in water at room temperature and it presents a poor spreading behavior at the air–water interface. The strategy used in this work for preparation of liquid monolayers was to spread pure 3HF and 3HF/hexadecanol mixtures on aluminum aqueous solution. The flavonoid is spontaneously spread at the air–liquid interface by its complex formation with aluminum ions present in the subphase. The complex formation was evident from visual inspection of the colored layer formed after spreading and compression of the monolayers. Also, the UV–visible spectra recorded for LB films prepared with different flavonoid/alcohol proportions attest the formation of a complex between the flavonoid and aluminum ions. The modifications recorded for the UV–Vis spectra of 3HF and 3HF–Al3+ complex in solution were interpreted by molecular orbital calculations.