Unconventional Electron-Deficient Multicenter Bonds in AIO₃ Perovskites

Area of Science:

• Solid-state chemistry
• Materials science
• Crystallography

Background:

• Perovskites (ABX3 and BX3) exhibit exceptional properties for technological applications.
• The nature of B-X bonding in these perovskites remains debated.
• Understanding bonding is crucial for predicting and utilizing material properties.

Purpose of the Study:

• To investigate the pressure-induced polymerization (PIP) of IO3- polyanions in AIO3 compounds.
• To elucidate the resulting changes in crystalline structure and chemical bonding.
• To explore the implications for the formation and properties of main-group element perovskites.

Main Methods:

• Joint experimental and theoretical study of AIO3 compounds (A = K, Rb, Cs, Tl, NH4), focusing on cesium iodate (CsIO3) under compression.
• Analysis of structural symmetrization and changes in chemical bonding.
• Comparison with the unified theory of multicenter bonding.

Main Results:

• Pressure-induced polymerization (PIP) of IO3- leads to 3D structures with IO5+1 and IO6 units.
• PIP induces a transition from delocalized I-O bonds to unconventional electron-deficient multicenter bonds (EDMBs).
• EDMB formation in cubic perovskites aligns with multicenter bonding theory, challenging previous assumptions.

Conclusions:

• PIP is a key mechanism driving the formation of cubic perovskites from main-group elements under pressure.
• Unconventional EDMBs may exist in main-group element perovskites even at room conditions.
• The presence of EDMBs likely explains the extraordinary properties of these perovskite materials.