Phase transitions in multifunctional rhodium(i)−semiquinone hybrid materials

Dr. Mercé¨ Deumal Sole
merce.deumal@ub.edu
http://www.ub.edu/gem2/

Details

In recent years, a family of rhodium(I)−semiquinone-based compounds comprising neutral one-dimensional chains of complex molecules has emerged as a switchable material with great potential for technological applications¹, as they exhibit multifunctionality properties such as magnetic, electrical, dielectric, or optical. The [Rh(3,6-DBSQ-4,5-(MeO)2)(CO)2]∞ compound (1a) exhibits bistable multifunctionality with respect to its magnetic and conductive properties in the temperature range 228−207 K. Two other related compounds were prepared with similar semiquinonato ligands: [Rh(3,6-DBSQ-4,5-(PDO)(CO)2]∞ (1b) features also a phase transition that results in changes in the magnetic and conductive properties of the material; in contrast [Rh(3,6-DBSQ-4,5-(N,N’-DEN)(CO)2]∞ (1c) does not exhibit any phase transition and the complex molecules are strongly dimerized in the one-dimensional chain in the whole range of temperatures.1b This PhD project will first focus on rationalizing the magnetic properties of the high-temperature (HT) and low-temperature (LT) phases of 1a-1b. Second, the driving force of the phase transitions are completely unknown and the reason why the first compound exhibits bistability and the second does not is still a mystery. In this sense, it should be mentioned that the large thermal ellipsoids of the Rh+ ions in the HT phases of these materials hint at important dynamic effects, which might play a prime role in driving the phase transition. Finally, the reason why 1c features dimers in the crystalline phase and does not undergo any phase transition is still elusive.

On the basis of all the obtained results, we will explore which chemical modifications should be made to the semiquinone ligand to tune the phase transition temperature and increase the width of the hysteresis loop in order to enhance related technological applications.

¹ (a) M. Mitsumi, et al., J. Am. Chem. Soc. 2014, 136, 7026; (b) M. Mitsumi, et al., Inorg. Chem. 2014, 53, 11710

Job position description

We are seeking a talented student with a high quality Masters degree in Physics, Chemistry or Materials Science. The successful candidate will use computational modeling as a tool to study rhodium(I)−semiquinone hybrid materials, switchable materials with great potential for technological applications, as they exhibit multifunctionality properties such as magnetic, electrical, dielectric, or optical. The research involves a combination of static calculations and ab initio molecular dynamics (AIMD) simulations. The investigation of mechanisms of phase transitions will be carried out using nudged elastic band calculations as implemented in Quantum Espresso and using metadynamics simulations using CP2K. All the simulations of systems in the condensed phase will be based on DFT calculations, whose exchange-correlation functional will be chosen on the basis of benchmark calculations of cluster model systems against wavefunction correlated methods using the MOLCAS and/or ORCA codes.

All computational programs are available at the Molecular Materials Structure Group (GEM2) at Universitat de Barcelona to perform such type of simulations. Day-to-day guidance in Barcelona will be conducted by the experienced scientific staff at GEM2.

Dr. M. Deumal research is framed within the molecular materials field. Specifically, it addresses magnetism and conductivity in multifunctional compounds to elucidate the spin coupling and electron transport mechanisms, and establish structure-property correlations.

The applicant should be a team player, with good two-way communication and presentation skills, highly self-motivated, attention to detail, and able to work independently with excellent time management skills. General programming expertise (UNIX, scripting languages, debugging, etc.), fluency and clarity in oral and written English, commitment and resolution are desirable additional abilities.

Summary of conditions

The project proposal is included in the DOCTORAL INPhINIT FELLOWSHIPS PROGRAMME – INCOMING FRAME, more information at: https://obrasociallacaixa.org/en/investigacion-y-becas/becas-de-la-caixa/doctorado-inphinit/incoming

Contract Length: 3 years

Estimated Incorporation date: From July to September 2020