On November 15th, a research paper titled “Effect of Strong Intermolecular Interaction in 2D Inorganic Molecular Crystals” was published online in the Journal of the American Chemical Society and was selected as the front cover. The paper was jointly written by Prof. Zhai Tianyou of the School of Materials Science and Engineering and Prof. Shuai Zhigang from Tsinghua University. This paper reveals the effect of strong intermolecular interactions in 2D inorganic molecular crystals and provides new theoretic insights into the intermolecular interactions of inorganic molecular crystals, which play a key role in promoting the development of molecular physics and optoelectronics.

Since graphene was discovered in 2004, two-dimensional materials have become a research hotspot throughout the world. Different from traditional two-dimensional materials (such as graphene, black phosphorous, etc.), which have strong in-plane chemical bonds and weak van der Waals forces between the planes, two-dimensional inorganic molecular crystals are combined through weak van der Waals forces in all three dimensions. In 2019, professor Tianyou Zhai’s group, proposed the world first concept of two-dimensional inorganic molecular crystals (2DIMCs). The team developed a passivator-assisted gas phase synthesis method, and successfully realized the precise synthesis of two-dimensional Sb₂O₃ inorganic molecular crystals (Nat. Commun. 2019, 10, 4728), and explored the microscopic processes and mechanisms of its phase transition. In 2020, this team again designed a vertical microspacing sublimation strategy and prepared two-dimensional inorganic bimolecular crystals (SbI₃·3S₈), breaking the center-inversion symmetry of inorganic molecular crystal and demonstrated its application potentials in nonlinear optics (Adv. Mater. 2020, 32, 2003146).

The microstructure-properties relationship of molecular crystals is the key of self-assembly into 2D morphology, achieving high mobility and high thermal stability, and exciting new physical properties (Nat. Mater. 2020, 19, 491; Nat. Phy. 2019, 15, 814). Recently, Prof. Zhai Tianyou of the School of Materials Science and Engineering and Prof. Shuai Zhigang from Tsinghua University systematically revealed the effect of strong intermolecular interaction in 2D inorganic molecular crystals. In this paper, the authors first demonstrated the strong intermolecular interaction in 2D α-P₄Se₃ induced by unusually short intermolecular Se-Se and P-Se atomic contacts with X-ray photoelectron spectroscopy and other spectroscopy experimental methods. Subsequently, the authors compared the experimental phenomenon of spectroscopy with theoretical calculation results based on the quantum nuclear tunneling model, and proposed that a physical picture of strong intermolecular interactions could be elucidated as a higher charge density between adjacent P₄Se₃ molecules. Besides, the significant impact of the higher charge density on intermolecular charge transport was clearly revealed. Last, but not least, the authors further investigated the temperature and phase transition dependence of the strong intermolecular interaction in α-P₄Se₃ and concluded that unusually short intermolecular Se−Se and P−Se contacts are caused by an orderly and close packing of P₄Se₃ molecules, primarily arising from steric effects produced by the intermolecular repulsive forces. This work provides new insights into the nature and origin of strong intermolecular interactions in inorganic molecular crystals, which lays the foundation of property control and design of inorganic molecular crystal and will promote the potential applications of 2DIMCs in electronics and optoelectronics.

The work was supported by the National Natural Science Foundation of China, the Hubei Provincial Natural Science Foundation of China and the Fundamental Research Funds for the Central University. Professor Zhai Tianyou of HUST and Professor Shuai Zhigang from Tsinghua University were co-corresponding authors. Doctoral student Feng Xin from HUST and postdoctoral fellow Peng Xingliang of Tsinghua University were both first authors. Meanwhile, Professor Li Huiqiao of HUST and Professor Huang Fuqiang from Peking University also participated in this work.

Paper link: https://pubs.acs.org/doi/abs/10.1021/jacs.1c08030

Group link: http://zml.mat.hust.edu.cn/index.htm

Written by: Feng Xin

Edited by: Scott, Peng Yumeng