Spectroscopic and structural investigations reveal the signaling mechanism of a luminescent molybdate sensor

Vincent A. Corden, Anne K. Duhme-Klair, Sarah Hostachy, Robin N. Perutz, Nicole Reddig, Hans Christian Becker, Leif Hammarström

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Abstract

A heteroditopic ligand H2-L consisting of a dihydroxybenzene (catechol)-unit linked via an amide bond to a pyridyl-unit and its methyl-protected precursor Me2-L were synthesized, characterized, and their photophysical properties investigated. The three accessible protonation states of the ligand, H2-L+, H2-L, and H-L-, showed distinct 1 H NMR, absorption and emission spectroscopic characteristics that allow pH-sensing. The spectroscopic signatures obtained act as a guide to understand the signaling mechanism of the luminescent pH and molybdate sensor [Re-(bpy)(CO)3(H2-L)]+. It was found that upon deprotonation of the 2-hydroxy group of H2-L, a ligand-based absorption band emerges that overlaps with the Re(dπ)-bpy metal-to-ligand charge transfer (MLCT) band of the sensor, reducing the quantum yield for emission on excitation in the 370 nm region. In addition, deprotonation of the catechol-unit leads to quenching of the emission from the Re(dn)→ bpy 3MLCT state, consistent with photoinduced electron transfer from the electron-rich, deprotonated catecholate to the Re-based luminophore. Finally, reaction of 2 equiv of [Re(bpy)(CO)3(H2-L)]+ with molybdate was shown to give the zwitterionic Mo(VI) complex [MoO2{Re(CO) 3-(bpy)(L)}2], as confirmed by electrospray ionization (ESI) mass spectrometry and X-ray crystallography. The crystal structure determination revealed that two fully deprotonated sensor molecules are bound via their oxygen-donors to a cis-dioxo-MoO2 center.

Original languageEnglish
Pages (from-to)1105-1115
Number of pages11
JournalInorganic Chemistry
Volume50
Issue number3
DOIs
Publication statusPublished - Feb 7 2011

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Inorganic Chemistry

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    Corden, V. A., Duhme-Klair, A. K., Hostachy, S., Perutz, R. N., Reddig, N., Becker, H. C., & Hammarström, L. (2011). Spectroscopic and structural investigations reveal the signaling mechanism of a luminescent molybdate sensor. Inorganic Chemistry, 50(3), 1105-1115. https://doi.org/10.1021/ic1019422