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First principles evaluation of structure and properties of multifunctional materials

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Universitat de Barcelona. Facultat de Química

# metadata.dc.description.abstract[].value
[eng] Organic chemistry is recognized for its ability to arrange a limited set of atoms in numerous
ways, a quality that is crucial in molecular magnetism. This branch benefits from the adaptability
of organic chemistry to conceive a plethora of radicals, i.e., open-shell molecules with unpaired
electrons. These organic radicals are sought for their potential applications in data storage and
spintronics, paving the way towards miniaturized, lightweight and environmentally friendly
solutions. However, challenges remain, particularly regarding the stability and reliability of these
radicals together with their performance and resilience at room temperature. Accordingly, the
successful integration of these radicals into technological innovations requires progress in their
synthesis, characterization, and their property prediction to better suit real-world applications. Yet,
predicting the capabilities of these radicals is far from straightforward. Even minor modifications in
their molecular structure can have significant impact, affecting both their electronic configuration
and their arrangement in crystals. Consequently, there is a high demand for the strategic design of
organic radicals and a more rapid evaluation of their properties to fully harness their potential.
Our research has encompassed three distinct but interrelated topics, all contributing to the
understanding of open-shell molecules and materials. Central to this PhD thesis is the exploration
of magnetic properties of these materials using computational chemistry techniques. A significant
part of the research involves examining how triarylmethyl-based 2D Covalent Organic Radical
Frameworks react to external mechanical stimuli. This investigation has demonstrated the
efficiency of these frameworks in transitioning between various electronic states, each exhibiting
distinct properties and characteristics. In the second study, we make use of quantum mechanical
insights and qualitative models to design and characterize a new set of diradicals displaying a robust
triplet ground state. Notably, we employ pentalene-based couplers as building-blocks, contributing
to pivot the role of pentalene from academic curiosities to potentially viable candidates for high
throughput applications as ferromagnets. Lastly, the third study consists of the development of a
new quantum-informed descriptor for Machine Learning applications in chemistry, referred to as
Molecular Orbital Decomposition and Aggregation (MODA). We prove that MODA excels in
predicting magnetic exchange couplings with respect to other well-established descriptors such as
Bag of Bonds and Smooth Overlap of Atomic Positions.
Overall, the interplay among the three facets provides viable prospects, underscoring the
potential of organic radicals in advancing molecular magnetism and paving the way for innovative
applications in data storage and spintronics.

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[cat] La química orgànica és reconeguda per la seva habilitat en organitzar un conjunt limitat
d'àtoms de nombroses maneres, una qualitat crucial que aprofita el magnetisme molecular.
Aquesta branca es beneficia d’aquesta versatilitat per concebre una gran quantitat de radicals, és a
dir, molècules amb electrons desaparellats. Aquests radicals orgànics són buscats per les seves
potencials aplicacions en emmagatzematge de dades i espintrònica, obrint el camí cap a solucions
miniaturitzades, lleugeres i respectuoses amb el medi ambient. No obstant això, encara hi ha reptes
per resoldre, particularment pel que fa a l'estabilitat i fiabilitat d'aquests radicals. La integració
exitosa d'aquests radicals en innovacions tecnològiques requereix progressos en la seva síntesi,
caracterització i la predicció de les seves propietats per adaptar-se millor a les condicions requerides
en aplicacions reals. Tanmateix, predir les capacitats d'aquests radicals està lluny de ser senzill, ja que
modificacions menors en la seva estructura molecular poden tenir un impacte significatiu, afectant
tant la seva configuració electrònica com la seva disposició en cristalls.
La nostra recerca ha abastat tres temes interrelacionats, tots contribuint al camp de les
molècules i materials amb electró desaparellat. Central en aquesta tesi de doctorat és l'exploració de
propietats magnètiques d'aquests materials utilitzant tècniques de química computacional. Una
part significativa de la recerca implica examinar com els Covalent Organic Radical Frameworks
reaccionen a estímuls mecànics externs. Aquesta investigació ha demostrat l'eficiència d'aquests
materials en transicionar entre diversos estats electrònics. En el segon estudi, s'ha fet ús de conceptes
de la mecànica quàntica per dissenyar un nou conjunt de diradicals que mostren un estat
fonamental triplet. Notablement, emprem acoblaments basats en pentalè com a unitats
fonamentals, contribuint a pivotar el paper del d'aquest des de curiositats acadèmiques cap a
candidats viables per a aplicacions d'alt rendiment. Finalment, el tercer estudi consisteix en el
desenvolupament d'un nou descriptor per a aplicacions d'Aprenentatge automàtic en química,
anomenat Molecular Orbital Decomposition and Aggregation (MODA). Demostrem que MODA
destaca en predir acoblaments d'intercanvi magnètic respecte a altres descriptors ben establerts en la
literatura.

# metadata.dc.title[].value
First principles evaluation of structure and properties of multifunctional materials