The formation of fluorescent alkali metal and alkaline earth complexes by 1-(2-{10-[2-piperazinoethyl]-9-anthryl}ethyl)piperazine and alkaline earth complexes by 4-(2-{10-[2-(1,4-thiazinan-4-yl)ethyl]-9-anthryl}ethyl)thiomorpholine in acetonitrile

The formation of fluorescent alkali metal and alkaline earth complexes of 1-(2-{10-[2-piperazinoethyl]9- anthryl} ethyl) piperazine ( 1) and alkaline earth complexes by 4-(2-{10-[2-(1,4-thiazinan-4-yl) ethyl]-9-anthryl} ethyl) thiomorpholine ( 2) in acetonitrile is reported. Both ( 1) and ( 2) have 'fluorophore - spacer - receptor' structures in the sequences 'anthracene - dimethylene - piperazine' and 'anthracene - dimethylene - thiomorpholine', respectively. Complexation by alkali metal ions and alkaline earth ions, Mm+, modulate photoinduced electron transfer ( PET) to increase the fluorescence of ( 1) and complexation of alkaline earth ions similarly increases the fluorescence of ( 2). The two receptors of ( 1) and ( 2) may either complex Mm+ singly to form [ML](m+) or cooperatively to form a 'sandwich' complex [ML'](m+) characterized together by complexation constant K-1 and quantum yield phi(1). They may also complex two Mm+ in [M2L](2m+) characterized by K-2 and phi(2). Typical data are exemplified for (1) and Mm+ = Na+ by K-1 = 1.33 x 10(5) dm(3) mol(-1) (phi(1) = 0.02) and K-2 = 4.20 x 10(2) dm(3) mol(-1) (phi(1) = 0.07), for (1) and Mm+ = Ca2+ by K-1 = 3.2 x 10(6) dm(3) mol(-1) (phi(1) = 0.34) and K-2 = 1.32 x 10(4) dm(3) mol(-1) (phi(2) = 0.54), and for (2) and Mm+ = Ca2+ by K-1 = 2.29 x 10(4) dm(3) mol(-1) (phi(1) = 0.20) and K-2 = 8.0 x 10(2) dm(3) mol(-1) (phi(2) = 0.57) at 298.2 K and I = 0.05 mol dm(-3) (NEt4ClO4). These data are compared with those for the alkaline earth complexes of 4-{2-[10-(2-morpholinoethyl)-9-anthryl] ethyl} morpholine. In 40 : 60 (v/v) 1,4-dioxan/water, protonation modulates PET to increase the fluorescence of (1) H-4(4+) and ( 2) H-2(2+). (The pK(a) values of (1) H-4(4+) are 9.02, 8.06, 4.32, and 2.96 at 298.2 K and I = 0.05 mol dm(-3) (NEt4ClO4).) The syntheses of (1) and (2) are reported.