Preferential binding of the magnesium ion by anthraquinone based chromogenic receptors

Two new anthraquinone based receptors have been synthesized. A colour change for both these receptors could be detected when group IIA metal ions were added in DMF solution at room temperature. No such colour change was noticed for group IA metal ions. Association constants for these receptors towards Mg2+, Ca2+, Sr2+ and Ba2+ were evaluated by systematic spectrophotomeric titrations and they follow the order KMg(II) ≫ KCa(II) > KSr(II) ≫ KBa(II). The association constants for L1 were found to be higher than those for L2 toward group IIA metal ions. Ab initio quantum chemical calculations have been performed to rationalize these observed results. X-ray structural analysis shows a helical structure for one of the receptor molecules.

Anthraquinone based new receptor molecules have been synthesized. These chromogenic receptors show preferential binding of the Mg2+ ion as compared to other group IA and IIA metal ions. Ab inito calculations show the strongest binding of these receptors with the Mg2+ ion. An X-ray structural study reveals a right handed helical structure for one of the receptor units.Figure optionsDownload as PowerPoint slide