Theoretical design of magnetic wires from acene and nanocorone derivatives

Cano, Joan; Lloret, Francesc; Julve, Miguel

doi:10.1039/c6dt02406h

Cited by 9 publications

(4 citation statements)

References 82 publications

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“…Cano et al have shown the effect of increasing open shell character of acenes escalating the spin contamination in both the triplet and BS states with dinuclear copper(II) systems. [74] Applying ab initio calculations here we have quantified the radicaloid characters (y-value) of the pristine polyacene as well as for polyacene in diradicals 1-10 where it acts as a coupler between -NO radical sites and tabulated in Table 3. This has been calculated following the work of Yamaguchi et al [75].…”

Section: Hubbard-u Corrected Gga + U Functionalmentioning

confidence: 99%

First principle investigations of long‐range magnetic exchange interactions via polyacene couplers

Kaur¹,

Ali²

2021

Int J of Quantum Chemistry

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The electronic and magnetic properties of polyacenes become quite fascinating as the number of linearly conjugated benzene rings increases. Higher-order conjugated polyacenes develop radicaloid characters due to the transition of electronic structures from closed-shell to the open-shell system. Here we have investigated the role of such polyacenes as the magnetic coupler when placed between the two spinsources based on nitroxy radicals. To do so, the magnetic exchange interactions (2J) are computed employing broken-symmetry (BS) approach within the density functional theory (DFT). In this approach, various genre of exchange-correlation (XC) functionals such as generalized gradient approximation (GGA), meta-GGA, hybrid functional, constrained spin density (i.e. CDFT) and on-site Coulomb correlation corrected GGA + U functionals are adopted. All DFT based calculations estimate an exponential increase in 2J values with the length of the couplers. This observation has been understood in terms of increase in number of near-degenerate or quasidegenerate molecular orbitals (MOs), reduction of HOMO-LUMO energy gap and descend of low-lying excited states as the number of fused benzene rings are increased. K E Y W O R D SDFT, intramolecular exchange interactions, long-range interactions, organic diradicals, polyacene | INTRODUCTIONMolecular magnets based on the stable organic radicals have attracted enormous attention due to their potential applications in spintronics, [1] magnetic logic devices, [2] and quantum computers. [3] The non-magnetic spacer between the radical centers control the nature and strength of intramolecular magnetic exchange interactions. [4][5][6] The seamless π-conjugations between the radical centers and spacer play a vital role in magnetic couplings. [7][8][9] Strong magnetic exchange interactions are reported mostly for couplers with smaller lengths. [10] However, the fascinating long-range couplers desired [11,12] for magnetic and spintronic applications are relatively less explored. On the top of it accomplishment of long range strong magnetic exchange interactions in molecular system is another challenge. The exchange interactions through the larger molecular spacers were investigated by Matsuda et al. for various π-conjugated couplers and established a correspondence between electrical conductance and the magnetic exchange interaction. [13] Both the molecular conductance and the exchange interactions decay exponentially with an increase in distance between radical centers. They observed that the increased π-conjugations slow down the decay process. [14,15] The strength of the magnetic exchange coupling constants (2J), mediated through π-conjugated molecular spacers was found to decay exponentially with the length of the couplers. [13] Essentially, the conductance and magnetic coupling (2J) between two spin sources are related through the molecular bridge properties. [16-18] However, in recent years interest has increased in designing and finding molecular candidates that would show an increase in

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Section: Hubbard-u Corrected Gga + U Functionalmentioning

confidence: 99%

First principle investigations of long‐range magnetic exchange interactions via polyacene couplers

Kaur¹,

Ali²

2021

Int J of Quantum Chemistry

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“…Cano et al have shown the effect of increasing open shell character of acenes escalating the spin contamination in both the triplet and BS states with dinuclear copper(II) systems. 70 Applying ab initio calculations here we have quantified the radicaloid characters (y-value) of the pristine polyacene as well as for polyacene in diradicals 1-10 where it acts as a coupler between -NO radical sites and tabulated in Table 3. This has been calculated following the work of Yamagucghi et al 71 and details of calculations could be found in SI.…”

Section: Magnetic Exchange Interactions Vs Length Of the Couplersmentioning

confidence: 99%

First Principle Investigations of Long-range Magnetic Exchange Interactions via Polyacene Coupler

Kaur¹,

Ali²

2021

Preprint

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The polyacene tend to transition from closed-shell to open-shell singlet systems with increase in the number of linearly fused benzene rings thus, enriching it's electronic as well as magnetic properties. Here, we have probed the role of such a polyacene couplers in mediating the magnetic exchange coupling between nitroxy radicals. For this, magnetic exchange coupling constants (2J) are computed employing broken-symmetry approach within density functional theory (DFT) as well as symmetry-adopted wave function based multi-configuration approach. Within DFT approach, apart from most commonly used exchange-correlation functional (generalized gradient approximation (GGA), meta-GGA, and hybrid) constrained spin density (CDFT) and on-site Coulomb correlation corrected GGA+U functionals have also been used to evaluate the exchange coupling constants in the diradicals. All DFT based methods approximate an exponential increase in the coupling constant values with increase in the length of the coupler. This is indeed an unexpected observation with no experimental report available to such an outcome by DFT calculations. Therefore, the electronic structures for these diradical systems with the increase in number of benzene rings were looked upon thoroughly. The properties like increase in number of degenerate or quasi-degenerate molecular orbitals (MOs), the lowering in energy of low-lying excited states and the development of intrinsic radical character of the coupler add to the complexity in evaluation of 2J values for such diradical systems with DFT approach. Consequently, wave function based multi-reference approach (CAASCF/NEVPT2) has been adopted. The active space has been limited to π-orbitals which are found to play an important role in the magnetic exchange interactions. With increase in the coupler size, the active space even with only π obitals would increase enormously which could not be taken into account even in the CASSCF study. The limited active space calculations also indicate quite strong exchange interaction, thus in principle, supporting the DFT observations of long-range magnetic exchange interactions but not an exponential increase in 2J with length of couplers.

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“…The basic components of a molecular spintronic circuit are molecular magnetic wires (MWs), which would facilitate the magnetic communication between the spin carriers along the circuit [100,101]. MWs offer a new design concept for the transfer of information over long distances based on EE interactions and without current flow [102][103][104][105][106][107][108][109][110][111][112][113][114][115], in contrast to conventional charge transport-based electronic wires [116][117][118][119][120][121][122], as stated by Lloret [100]. Indeed, setting a long-range magnetic coupling between two distant spin centers connected by a long organic spacer that ultimately extends over infinite distances ("wire-like magnetic coupling") is the cornerstone.…”

Section: Dinuclear Copper(ii) Metallacyclophanes In the Proof-of-concmentioning

confidence: 99%

When Molecular Magnetism Meets Supramolecular Chemistry: Multifunctional and Multiresponsive Dicopper(II) Metallacyclophanes as Proof-of-Concept for Single-Molecule Spintronics and Quantum Computing Technologies?

et al. 2020

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Molecular magnetism has made a long journey, from the fundamental studies on through-ligand electron exchange magnetic interactions in dinuclear metal complexes with extended organic bridges to the more recent exploration of their electron spin transport and quantum coherence properties. Such a field has witnessed a renaissance of dinuclear metallacyclic systems as new experimental and theoretical models for single-molecule spintronics and quantum computing, due to the intercrossing between molecular magnetism and metallosupramolecular chemistry. The present review reports a state-of-the-art overview as well as future perspectives on the use of oxamato-based dicopper(II) metallacyclophanes as promising candidates to make multifunctional and multiresponsive, single-molecule magnetic (nano)devices for the physical implementation of quantum information processing (QIP). They incorporate molecular magnetic couplers, transformers, and wires, controlling and facilitating the spin communication, as well as molecular magnetic rectifiers, transistors, and switches, exhibiting a bistable (ON/OFF) spin behavior under external stimuli (chemical, electronic, or photonic). Special focus is placed on the extensive research work done by Professor Francesc Lloret, an outstanding chemist, excellent teacher, best friend, and colleague, in recognition of his invaluable contributions to molecular magnetism on the occasion of his 65th birthday.

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Theoretical design of magnetic wires from acene and nanocorone derivatives

Cited by 9 publications

References 82 publications

First principle investigations of long‐range magnetic exchange interactions via polyacene couplers

First principle investigations of long‐range magnetic exchange interactions via polyacene couplers

First Principle Investigations of Long-range Magnetic Exchange Interactions via Polyacene Coupler

When Molecular Magnetism Meets Supramolecular Chemistry: Multifunctional and Multiresponsive Dicopper(II) Metallacyclophanes as Proof-of-Concept for Single-Molecule Spintronics and Quantum Computing Technologies?

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