Luminescent supramolecular heterometallic macrocycles and their encapsulation on cholate gels

Abstract

The metal complex formed by coordination of Zn(II) to 1,7-bis(4-methylpyridine)-4-(2- naphthylmethyl)-1,4,7-triazaheptane (ZnL2+) was reacted in aqueous solution with [Pd(NO3)2(en)] and [Pt(NO3)2(en)] salts to form the self-assembled heterometallic macrocycles [Zn2L2Pd2(en)2]8+ and [Zn2L2Pt2(en)2]8+, respectively. Pd(II) and Pt(II)- coordination modulates the original emission of ZnL2+ arising from the presence of the naphthalene chromophore and the formation of the macrocycles can be monitored due to the PET process occurring with coordination of Pd(II) and Pt(II) to the pyridine units of ZnL2+. Additionally, several studies reveal that these heteromacrocycles can be encapsulated in Zn(II)-cholate hydrogels giving rise to soft materials with tunable emissive properties. Preliminary analysis show also that the addition of the metallic species in micromole concentration to the cholate hydrogels resulted in an improved mechanical strength of the final materials.