Porphyrin-rhodamine conjugates as new materials with sensing ability

Conjugates based on porphyrin (porph) and rhodamine (rh) moieties linked by amide bonds, dyad 1 (porph-spacer-rh) and triad 2 (porph-spacer-rh-spacer-porph), were prepared respectively from precursor 1 and precursor 2. The sensing ability of precursor 1, dyad 1 and triad 2 towards the divalent metal ions Cu2+, Zn2+, Cd2+, Pb2+, Hg2+ and the monovalent Hg+ was explored in solution by absorption and fluorescence spectroscopy as well as in gas phase using matrix-assisted laser desorption/ionization (MALDI)-TOF mass spectrometry. In solution one-metal-per-ligand molar ratio was obtained with precursor 1 and triad 2, however, a two-metal-per-ligand molar ratio was observed with dyad 1. Additionally, the results obtained by MALDI-TOF-MS confirmed the gas-phase sensing abilities of dyad 1 towards all metal ions tested and of triad 2 towards Zn2+. Computational DFT calculations confirm the same stoichiometry. [Display omitted] •Dyad 1 and triad 2, were prepared from precursor 1 and precursor 2, respectively.•Precursor 1, dyad 1 and triad 2 were used to recognize different metal ions in dichloromethane solution. .•Theoretical studies predict complex formation in a stoichiometry of L/M = 1:2 with dyad 1.•Theoretical studies predict complex formation in a stoichiometry of L/M = 1:2 with triad 2.•The recognition of Cu2+, Zn2+, Cd2+, Pb2+, Hg2+ and Hg+ with dyad 1 and triad 2 in gas phase was also explored.