The first lead cobalt phosphite, PbCo₂(HPO₃)₃

Area of Science:

• Inorganic Chemistry
• Solid-State Chemistry
• Materials Science

Background:

• Phosphite materials offer diverse structural and magnetic properties.
• Non-centrosymmetric (NCS) compounds are crucial for nonlinear optical applications.
• Understanding structure-property relationships in metal phosphites is an active research area.

Purpose of the Study:

• To synthesize and characterize a novel lead cobalt phosphite, PbCo2(HPO3)3.
• To elucidate the crystal structure and magnetic behavior of the new compound.
• To investigate the origin of its non-centrosymmetric nature.

Main Methods:

• Mild hydrothermal synthesis for single crystal growth.
• X-ray diffraction for crystal structure determination.
• SQUID magnetometry, IR, UV/vis spectroscopy, TGA, and SEM for characterization.

Main Results:

• PbCo2(HPO3)3 was successfully synthesized and crystallized in the NCS R3m space group.
• The structure features 2D heteropolyhedral blocks with Co2O9 dimers and HPO3 groups, with Pb2+ cations in interlayer spaces.
• Weak antiferromagnetic interactions were observed between cobalt ions within the Co2O9 dimers.

Conclusions:

• The NCS character of PbCo2(HPO3)3 is attributed to cooperative Pb2+ lone pair arrangements.
• Structural distortions, including HPO3 group twisting, are influenced by short HH contacts.
• The magnetic behavior aligns with expectations for phosphite-bridged cobalt dimers.