Fluorescence detection of Zn2+ and Cd2+ is of continuing interest due to their significant importance in biological and environmental sciences. Strict discrimination of Zn2+ and Cd2+ by fluorescent probe molecules has still been a challenging task because of the small difference in ionic radii of these group 12 metal ions. In this study, three heptadentate fluorescent probes with a common 2,6-lutidylenediamine core and four quinoline/ isoquinoline sidearms are presented. The N,N,N',N'-tetrakis(2- quinolylmethyl)-2,6-lutidylenediamine (TQLN) exhibits Zn2+-specific specific fluorescence enhancement via an excimer formation, while the N,N,N',N'-tetrakis(1-isoquinolylmethyl)-2,6-lutidylenediamine (1-isoTQLN) responds specifically to Cd2+ at the short wavelength region by monomer emission. The N,N,N',N'-tetrakis(3- isoquinolylmethyl)-2,6-lutidylenediamine (3-isoTQLN) responds to both Zn2+ and Cd2+ at different emission wavelengths, acting as a dual sensor with hybrid properties of TQLN and 1- isoTQLN. Methoxy-substituted derivatives of 1- and 3-isoTQLN were also examined. [ABSTRACT FROM AUTHOR]