Solvent-driven multiply configurable on/off fluorescent indicator of the pH window: a diethylenetriamine bearing two end pyrene fragments.

Fluorescence behaviors of a simple-structured molecule (L), a diethylenetriamine bearing two end pyrene fragments, have been investigated in water. Effects of adding a less-polar organic solvent (acetonitrile: MeCN) on the emission behaviors have been studied by means of steady-state and time-resolved fluorescence measurements. L dissolved in water shows dual-mode fluorescence consisting of monomer and excimer emissions. The monomer emission shows an "on-off" intensity profile against the pH window (pH 2-12), whereas the excimer emission shows an "off-on" profile. Upon MeCN addition, the monomer emission maintains the "on-off" profile. In contrast, the "off-on" profile of the excimer emission is drastically changed: L shows two more types of profiles, "off-on-off-on" and "off-on-off", along with the MeCN concentration increase, thus behaving as a multiply configurable fluorescent indicator of the pH window. The MeCN-driven excimer emission switching of L is triggered by (i) the decrease in stability of the intramolecular ground-state dimer (GSD) formed between the end pyrene fragments, which suppresses the direct photoexcitation of GSD (suppression of the "static" excimer formation), leading to a decrease in the excimer emission intensity at basic pH; and (ii) the decrease in polarity of solution, which allows formation of a "dynamic" excimer via a monomer-to-excimer transition, resulting in an enhancement of the excimer emission intensity at acidic-neutral pH.

pH- and H2O-driven triple-mode pyrene fluorescence.

[reaction: see text] A simple-structured molecule L1, a diethylenetriamine bearing two end pyrene fragments, demonstrates triple-mode fluorescence consisting of monomer and short- and long-lived excimer emissions in water, which are precisely controlled by pH and an addition of a less-polar organic solvent.

A fluorescent molecular logic gate with multiply-configurable dual outputs.

A simple molecule, L, diethylenetriamine bearing anthracene fragments at both ends, behaves as a fluorescent molecular logic gate with "multiply-configurable dual outputs", capable of demonstrating five different logic functions operated by proton (H+) and transition metal cations (Mn+) as inputs.

A molecular switch with pH-controlled absolutely switchable dual-mode fluorescence.

[reaction: see text] A simple-structured molecule (L1) bearing anthracene fragments at both ends of diethylenetriamine chain behaves as a fluorescent molecular switch with pH-controlled absolutely switchable dual-mode fluorescence in water; each mode consists of monomer (pH <9) and excimer (pH >9) emissions.