Premium
Intramolecular Spin Alignment in Photomagnetic Molecular Devices: A Theoretical Study
Author(s) -
Ciofini Ilaria,
Lainé Philippe P.,
Zamboni Marta,
Daul Claude A.,
Marvaud Valérie,
Adamo Carlo
Publication year - 2007
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200700015
Subject(s) - density functional theory , intramolecular force , excited state , spin polarization , chemistry , triplet state , ground state , spin (aerodynamics) , anthracene , electron paramagnetic resonance , computational chemistry , chemical physics , molecular physics , condensed matter physics , photochemistry , quantum mechanics , physics , electron , stereochemistry , thermodynamics
Ground‐ and excited‐state magnetic properties of recently characterized π‐conjugated photomagnetic organic molecules are analyzed by the means of density functional theory (DFT). The systems under investigation are made up of an anthracene (An) unit primarily acting as a photosensitizer (P), one or two iminonitroxyl (IN) or oxoverdazyl (OV) stable organic radical(s) as the dangling spin carrier(s) (SC), and intervening phenylene connector(s) (B). The magnetic behavior of these multicomponent systems, represented here by the Heisenberg–Dirac magnetic exchange coupling ( J ), as well as the EPR observables ( g tensors and isotropic A values), are accurately modeled and rationalized by using our DFT approach. As the capability to quantitatively assess intramolecular exchange coupling J in the excited state makes it possible to undertake rational optimization of photomagnetic systems, DFT was subsequently used to model new compounds exhibiting different connection schemes for their functional components (P, B, SC). We show in the present work that it is worthwhile considering the triplet state of anthracene, that is, P when promoted in its lowest photoexcited state, as a full magnetic site in the same capacity as the remote SCs. This framework allows us to accurately account for the interplay between transient ( 3 An) and persistent (IN, OV) spin carriers, which magnetically couple according to a sole polarization mechanism essentially supported by phenyl connector(s). From our theoretical investigations of photoinduced spin alignment, some general rules are proposed and validated. Relying on the analysis of spin‐density maps, they allow us to predict the magnetic behavior of purely organic magnets in both the ground and the excited states. Finally, the notion of photomagnetic molecular devices (PMMDs) is derived and potential application towards molecular spintronics disclosed.