TPE–monoTpy and TPE–diTpy compounds (TPE = tetraphenylethene, Tpy = 2,2′:6′,2′′-terpyridine) were prepared and showed significant red shifts in fluorescence upon coordination to Zn(NO3)2 in THF : HEPES (1 : 4) solutions. These in situ prepared Zn(II) complexes have achieved highly selective ratiometric fluorescent recognition of histidine even in the presence of other natural amino acids and metal cations. This fluorescent recognition of histidine is visually observable with distinctive color changes from yellow to blue under UV irradiation. The mechanism for the interaction of the Zn(II) complexes with histidine was studied by UV-Vis absorption, NMR and MS.
