Dissertation: Dithiadiazolyl and Diselenadiazolyl Organic radicals as building blocks for next-generation functional materials (Naik)
Scientists are pushing the boundaries of molecular design and exploring sulfur- and selenium-based radicals, 1,2,3,5-dithiadiazolyl (DTDA) and 1,2,3,5-diselenadiazolyl (DSDA) classes, as next-generation building blocks for electronic and magnetic materials. Unlike typical short-lived radicals, these are remarkably stable and electron-rich due to the delocalization of the unpaired electron over the sulfur/selenium and nitrogen atoms.
- Their stability allows them to self-assemble into crystalline materials that exhibit metal- or- magnet-like behavior, despite being composed entirely of non-metal elements. This unique property blurs the line between organic chemistry and materials science, explains Doctoral Researcher Ankita Naik from University of Jyväskylä.
The tunable electronic structure of these radicals opens the door to novel solids with tailored electrical, optical, and magnetic properties. Consequently, they are now key candidates in molecular electronics (e.g. conductors), molecular magnetism (e.g. quantum computing) and fundamental studies of radical interactions.
The power of solvent engineering
Although research began in the late 1970s, improved synthetic methodologies and recent advances in crystallography, spectroscopy, and computational modeling have renewed interest and significantly accelerated progress in this field.
- Our research focuses on organic radical-ion salts, where we discovered that minor structural changes in the crystal lattice, triggered by solvent loss or anion exchange, can dramatically influence the solid-state structure and physical properties. This work further explores how solvent engineering, including trace amounts of water, can govern radical behavior and the resultant crystal lattice environment, says Naik.
Toward stable and controllable radical-based systems
Naik prepared a series of binary organic radical ion salts and investigated their structure-property relationships for various applications. This involved examining solvent inclusion and crystal lattice guest effects, crystal packing motifs (pi‐stacking, chalcogen-chalcogen and sigma-hole interactions), spin coupling.
- A key objective was to achieve bistability for switching or memory applications, where one stable crystalline form corresponds to a distinct ‘on’ or ‘off’ state. We studied these phase transitions in both DTDA and DSDA systems by probing their thermal stability, and reversible/irreversible transformations in response to external stimuli like heat, light and pressure, factors critical for real-world device integration, explains Naik.
Ultimately, the aim was to design robust organic radical‐based materials that are not only stable but also controllably switchable.
- We strive to move these materials beyond laboratory curiosities toward practical applications in memory, sensors, switches, and potentially organic conductors, says Naik.
From stability to switchability
For decades, controlling radicals in the solid state has been a central challenge. While their unpaired electrons make them powerful components for electronics and magnetism, this reactivity also makes them exquisitely sensitive to their environment. Small changes, such as temperature control, solvent loss, or exposure to light or pressure, can trigger structural rearrangements that fundamentally alter their electronic and magnetic properties.
- Yet, it also presents a unique opportunity: the chance to design stimuli-responsive materials whose properties can be deliberately switched, tells Naik.
The research has gained new urgency with the global demand for sustainable, high performance, and miniaturized technologies. Insights from heteroatom-based radicals like DTDA/DSDAs suggest they could rival traditional inorganic materials, offering superior advantages in flexibility, weight, and chemical tunability.
- The goal remains to solve a longstanding problem of harnessing the power of radicals in a stable and controllable way for practical devices, says Naik.
Ankita Naik defends her dissertation “Charge-Transfer Salts Based on Heavy Chalcogen Organic Radicals: The Role of Sulfur vs Selenium and Cyanocarbon Acceptors” on Friday November 7, 2025 at 12.00 o’clock in the lecture hall FYS3 on the Ylistönrinne campus at the University of Jyväskylä. Opponent is Dr. Imma Ratera (Institut de Ciencia de Materials de Barcelona (ICMAB-CSIC)) and custos is Associate Professor Manu Lahtinen (University of Jyväskylä). The public defense is held in English.
The dissertation "Charge-Transfer Salts Based on Heavy Chalcogen Organic Radicals: The Role of Sulfur vs Selenium and Cyanocarbon Acceptors” will be available in the JYX publication archive: https://jyx.jyu.fi/jyx/Record/jyx_123456789_106235?sid=218868657
Further information:
- Doctoral researcher Ankita Naik, ankita.v.naik@jyu.fi
