Heterometallic Benzenehexathiolato Coordination Nanosheets: Periodic Structure Improves Crystallinity and Electrical Conductivity

• Published in: Advanced materials (Weinheim) Vol. 34; no. 13; pp. e2106204 - n/a
• Main Authors: Toyoda, Ryojun, Fukui, Naoya, Tjhe, Dionisius H. L., Selezneva, Ekaterina, Maeda, Hiroaki, Bourgès, Cédric, Tan, Choon Meng, Takada, Kenji, Sun, Yuanhui, Jacobs, Ian, Kamiya, Kazuhide, Masunaga, Hiroyasu, Mori, Takao, Sasaki, Sono, Sirringhaus, Henning, Nishihara, Hiroshi
• Format: Journal Article
• Language: English
• Published: Germany Wiley Subscription Services, Inc 01-04-2022
• Subjects: 2D polymers; benzenehexathiolato metal complexes; Bilayers; Coordination; coordination nanosheets; Copper; Crystal structure; Crystallinity; electrical conductivities; Electrical resistivity; heterometallicity; Mixing ratio; Nanosheets; Nickel; Periodic structures; Seebeck effect; Thick films; benzenehexathiolato metal complexes; 2D polymers; electrical conductivities; coordination nanosheets; heterometallicity
• ISSN: 0935-9648; 1521-4095
• DOI: 10.1002/adma.202106204

Coordination nanosheets are an emerging class of 2D, bottom‐up materials having fully π‐conjugated, planar, graphite‐like structures with high electrical conductivities. Since their discovery, great effort has been devoted to expand the variety of coordination nanosheets; however, in most cases, their low crystallinity in thick films hampers practical device applications. In this study, mixtures of nickel and copper ions are employed to fabricate benzenehexathiolato (BHT)‐based coordination nanosheet films, and serendipitously, it is found that this heterometallicity preferentially forms a structural phase with improved film crystallinity. Spectroscopic and scattering measurements provide evidence for a bilayer structure with in‐plane periodic arrangement of copper and nickel ions with the NiCu2BHT formula. Compared with homometallic films, heterometallic films exhibit more crystalline microstructures with larger and more oriented grains, achieving higher electrical conductivities reaching metallic behaviors. Low dependency of Seebeck coefficient on the mixing ratio of nickel and copper ions supports that the large variation in the conductivity data is not caused by change in the intrinsic properties of the films. The findings open new pathways to improve crystallinity and to tune functional properties of 2D coordination nanosheets.
Combination of copper and nickel ions in 2D coordination nanosheets based on benzenehexathiolato‐metal complex motifs induces a periodic in‐plane metal arrangement and a bilayer structure. This heterometallicity affords improved film crystallinity and thus higher electrical conductivities in comparison with the pristine ones, reaching up to 1300 S cm−1. This strategy expands the variation and function of coordination nanomaterials.