Design of organic crystals with lone pairs to study spin resonance and spin-lattice interactions

• Published in: NPG Asia materials 2025-01, Vol.17 (1), p.2-8, Article 2
• Main Authors: Li, Shilin, Lu, Xiangqian, Qin, Wei
• Format: Article
• Language: English
• Subjects: 639/301/119/1001; 639/638/403; Angular momentum; Biomaterials; Carrier transport; Charge transfer; Chemistry and Materials Science; Crystal lattices; Electron paramagnetic resonance; Electron spin; Energy Systems; Lattice design; Lattice vibration; Magnetic properties; Materials Science; Nitrogen; Optical and Electronic Materials; Optical properties; Organic crystals; Photoluminescence; Spin resonance; Spintronics; Structural Materials; Surface and Interface Science; Thin Films; Transport phenomena
• ISSN: 1884-4057; 1884-4049; 1884-4057
• DOI: 10.1038/s41427-024-00583-3

Lone pairs are widely prevalent in various types of molecules and have a significant impact on the band structure, carrier transport, and dielectric response, which are the key factors for exploring the underlying mechanism of phenomena in opto-spintronics. In this work, nitrogen substitutions with nonequivalent hybridization are adopted to obtain different types of organic charge transfer crystals, where lone pairs are generated to weaken the interactions between donors and acceptors, resulting in a blueshift in photoluminescence and a weaker electron-lattice coupling. Moreover, lone pairs could further strengthen the ability to transfer energy and spin angular momentum to the lattice vibration to enhance spin resonance. Additionally, due to the effect of lone pairs, the spin density inside the crystals is redistributed to tune the transition between the singlet and triplet states. Overall, crystals with lone pairs demonstrate a more diverse set of magnetic, optical, and spin-related properties. Lone pairs are essential for exploring the mechanism behind the phenomena in the areas of opto-spintronics. In this paper, the effect of lone pairs on spin resonance and magnetic properties was studied. Using donors with different nitrogen substitutions, three charge transfer crystals were fabricated. In cocrystals, lone pairs could enlarge the distance between donors and acceptors, leading to the shorten of lifetime and the decrease of dielectric constant. Moreover, lone pairs possess the ability to enhance spin-lattice interactions, enabling the three crystals to display diverse and intriguing behaviors under light and magnetic fields, such as light-dependent electron spin resonance.