Proton motion inside [(DMF)₂H]₂[W₆Cl₁₄]: structural, Raman and luminescence studies

Area of Science:

• Inorganic Chemistry
• Solid-State Chemistry
• Supramolecular Chemistry

Background:

• Protonation of N,N-dimethylformamide (DMF) by polyoxometalate clusters can lead to the formation of proton-coupled dimeric cations.
• Understanding the behavior of protons within hydrogen-bonded systems is crucial for various chemical and physical phenomena.

Purpose of the Study:

• To investigate the proton behavior and structural characteristics of [(DMF)2H]+ dimers within the [(DMF)2H]2[W6Cl14] crystal.
• To explore the temperature-dependent interactions and photoluminescence properties of these dimeric units.

Main Methods:

• Single crystal X-ray diffraction (XRD) for structural analysis.
• 1H MAS NMR, Raman spectroscopy, and photoluminescence (PL) spectroscopy for studying proton dynamics and electronic properties.
• Density Functional Theory (DFT) calculations to analyze vibrational modes.

Main Results:

• Identification of two types of [(DMF)2H]+ dimers (cisoidal and transoidal) with distinct OO distances and cation-anion interactions.
• Observation of temperature-dependent differentiation in dimer interactions and proton motion, transitioning between single-well and double-well potentials.
• Discovery of solid-state photoluminescence from dimeric units, with temperature-dependent behavior indicating distinct luminescent centers.

Conclusions:

• The study provides the first detailed characterization of proton behavior in [(DMF)2H]+ dimers, revealing complex hydrogen bonding and structural dynamics.
• The findings highlight the influence of temperature on dimer interactions, proton potentials, and photoluminescence, offering insights into supramolecular assembly and energy transfer.