Mössbauer Spectroscopy on Antimony Borosulfates Reveals Weak Coordination Behavior.

Area of Science:

• Inorganic Chemistry
• Solid-State Chemistry
• Materials Science

Background:

• Borosulfate chemistry previously featured a modular system with a 3D anion.
• Antimony's lone pair and cation size significantly influence crystal structures in borosulfates.

Purpose of the Study:

• To investigate antimony borosulfate compounds (SbX[B(SO4)2]4) with various monovalent cations.
• To discover and characterize new borosulfate structures and their properties.
• To understand the coordination behavior of the borosulfate anion using advanced spectroscopic techniques.

Main Methods:

• Synthesis and single-crystal X-ray diffraction of antimony borosulfate compounds.
• 121Sb Mössbauer spectroscopy and Density Functional Theory (DFT) calculations.
• Infrared spectroscopy, thermal analysis, and temperature-programmed X-ray diffraction.

Main Results:

• Discovery of SbX[B(SO4)2]4 compounds crystallizing in space groups I4̄, P4̄, and C2, influenced by antimony's lone pair and cation size.
• Identification of a new borosulfate structure type, SbX[B4O2(SO4)6], featuring a 1D anion with B-O-B bridges.
• Observation of unprecedented negative isomer shifts (~ -22 mm·s-1) in 121Sb Mössbauer spectra, indicating weak borosulfate anion coordination.

Conclusions:

• The study expands the known structural diversity within borosulfate chemistry.
• New antimony borosulfates exhibit unique structural motifs and electronic properties.
• The findings provide insights into the coordination chemistry of borosulfate anions and antimony's behavior.