Bis-Rhodamine B System as a Tin Detector or Molecular Electronics Device.

In this report, fluorescent systems consisting of two Rhodamine B moieties were designed and synthesized employing the solid-phase synthetic approach. The compounds were tested for their chemosensing behavior upon the addition of various metal ions over UV-vis absorption and fluorescence spectra. Two probes, 1 and 3, exhibited the best affinity to Sn(IV) ions, resulting in strong fluorescence as well as absorbance enhancement with the low detection limits (2.78 and 2.56 μM, respectively). Compound 3 having two excitations as well as emission maxima was used for the construction of the light dimmer with the alarm for detection of too low pH. The system is operated by a change of pH and can be used as a molecular electronic device.