Transformation of Perovskite BaBiO3 into Layered BaBiO2.5 Crystals Featuring Unusual Chemical Bonding and Luminescence

• Published in: Chemistry : a European journal 2018-06, Vol.24 (35), p.8875-8882
• Main Authors: Li, Hong, Zhao, Qing, Liu, Bo‐Mei, Zhang, Jun‐Ying, Li, Zhi‐Yong, Guo, Shao‐Qiang, Ma, Ju‐Ping, Kuroiwa, Yoshihiro, Moriyoshi, Chikako, Zheng, Li‐Rong, Sun, Hong‐Tao
• Format: Article
• Language: English
• Subjects: bismuth; Cations; Chemical bonds; Chemistry; Covalent bonds; Crystals; Entropy; layered structures; Luminescence; Maximum entropy; Organic chemistry; Oxides; Oxygen; Oxygen atoms; Perovskites; Phase transitions; solid-state structures; X-ray diffraction
• ISSN: 0947-6539; 1521-3765
• DOI: 10.1002/chem.201801257

Engineering oxygen coordination environments of cations in oxides has received intense interest thanks to the opportunities for the discovery of novel oxides with unusual properties. Herein, the synthesis of stoichiometric layered BaBiO2.5 by a nontopotactic phase transformation of perovskite BaBiO3 is presented. By analyzing the synchrotron X‐ray diffraction data by the maximum‐entropy method/Rietveld technique, it was found that Bi is involved in an unusual chemical bonding situation with four oxygen atoms featuring one ionic bond and three covalent bonds, which results in an asymmetric coordination geometry. Photophysical characterization revealed that this peculiar structure shows near‐infrared luminescence differing from that of conventional Bi‐containing compounds. Experimental and theoretical results led to the proposal of an excitonic nature of the luminescence. This work highlights that synthesizing materials with uncommon Bi−O bonding and Bi coordination geometry provides a pathway to the discovery of systems with new functionalities. This could inspire interest in the exploration of a range of materials containing heavier p‐block elements with prospects for finding systems with unusual properties. Coordination environment engineering: Layered stoichiometric BaBiO2.5, synthesized by nontopotactic transformation of perovskite BaBiO3, features an unusual electron‐density distribution and Bi−O bonding situation featuring one ionic and three covalent bonds, which give rise to peculiar near‐infrared luminescence never seen before in any Bi‐containing system (see figure).