Room‐Temperature Ferromagnetism in Perylene Diimide Organic Semiconductor

Abstract

The development of pure organic magnets with high Curie temperatures remains a challenging task in material science. Introducing high‐density free radicals to strongly interacting organic molecules may be an effective method to this end. In this study, a solvothermal approach with excess hydrazine hydrate is used to concurrently reduce and dissolve rigid‐backbone perylene diimide (PDI) crystallites into the soluble dianion species with a remarkably high reduction potential. The as‐prepared PDI powders comprising radical anion aggregates are fabricated by a subsequent self‐assembly and spontaneous oxidation process. The results of magnetic measurements show that the PDI powders exhibit room‐temperature ferromagnetism and a Curie temperature higher than 400 K, with a vast saturation magnetization that reaches ≈1.2 emu g−1. Elemental analysis along with the diamagnetic signal of the ablated residue are used to rule out the possibility that the magnetism is due to metal contamination. The findings suggest that the long‐range ferromagnetic ordering can survive at room‐temperature in organic semiconductors, and offers a new optional way to create room‐temperature magnetic semiconductors.

Magnetic Ordering in a High‐Spin Donor–Acceptor Conjugated Polymer

“…The temperature-independent signal displayed in the M-T curve is reminiscent of perylene diimide dianions, with nearly identical trends in the bifurcation of the ZFC-FC curves at the high-temperature regime. [27] Figure 5c is consistent with this observation, as the paramagnetic-to-diamagnetic transition that occurred ≈75 K in the powder is now replaced with a strong paramagnetic signal with an extraordinarily sharp rise to saturation at low fields (<10 000 Oe) that is also stable at room temperature. The room temperature saturation magnetization of 0.07 emu g −1 exceeds values reported for other modern examples of magnetism from organic, polymer, and framework topologies, [6c,24a,26a,28] low temperatures, these other systems were unable to achieve saturation behavior, even at fields of 10 000 Oe.…”

Comprehending radicals, diradicals and their bondings in aggregates of imide-fused polycyclic aromatic hydrocarbons

“…After dropping into a film, the room-temperature ferromagnetism is observed. 14 It is note-worthy that ferromagnetism is caused by radicals and the candidate groups existing in hydrazine hydrate solution that can provide electrons might be H, H 3 O and NH 4 . Moreover, because the carbonyl groups at both ends of NDI have the trend of strongly attracting electrons, radicals might be generated at these sites.…”

“…13 The temperature effect of magnetism in a fabricated film purely through solution-processed treatment then significantly enable us to comprehend the mechanism. 14 Since the radicals normally delocalize to a few certain πconjugated molecules and even form radical bonds with other radicals, they share similar features with the large polarons, which stem from strong vibronic couplings and hold fermionic statistical properties with spin half. 15 As long as the vibronic couplings are strong enough to suppress the Coulomb repulsion among electrons, there emerge another elementary excitation, which can be named bipolarons or diradicals.…”

“…13 The temperature effect of magnetism in a fabricated film purely through solution-processed treatment then significantly enables us to comprehend the mechanism. 14…”

Development of Tetrameric N‐Annulated Perylene Diimides Using “Click” Chemistry

“…Perylene diimides (PDIs) are a class of organic chromophore renowned for having strong molar absorptivity, high electron affinity, as well as excellent thermal, redox, and photostabilities. [1,2] This combination of desirable chemical and physical properties has made PDI-based materials ideally suited for a number of applications, including: chemical sensing, [3,4] bioimaging, [5,6] magnetics, [7] charge storage, [8,9] charge transport, [10][11][12] charge extraction, [13][14][15] light emission, [16,17] and even small molecule catalysis. [18][19][20][21] Depending on the target application, the proclivity for PDI to π-π stack and form large aggregates in the solid-state may need to be circumvented to enable high performance.…”