Role of the coupler to design organic magnetic molecules: LUMO plays an important role in magnetic exchange

Shil, Suranjan; Roy, Moumita; Misra, Anirban

doi:10.1039/c5ra16670e

Cited by 24 publications

(61 citation statements)

References 54 publications

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“…In couple of our recent works, we have studied that the SOMO-SOMO gap is not responsible for the strength of magnetic coupling, rather HOMO-LUMO gap plays a more important role. 39,45,46 If we focus on the energy difference between HOMO and LUMO in this study, it has been found that on going from diradical based allene to its higher homologue ( [5]-and [7]-cumulene) in each series, there is a smooth decrease in HOMO-LUMO energy gap. Hermann et.…”

Section: Mechanism Of Magnetic Interactionmentioning

confidence: 97%

A Perspective on Designing Chiral Organic Magnetic Molecules with Unusual Behavior in Magnetic Exchange Coupling

Sarbadhikary

Shil²,

Panda³

et al. 2016

J. Org. Chem.

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A total of nine diradical-based organic chiral magnetic molecules with allene and cumulene couplers have been theoretically designed, and subsequently, their magnetic property has been studied by density functional theory. It is found that with an increase in length of the coupler, a remarkable increase in spin density within the coupler takes place. An increase in the length of the coupler reduces the energy of LUMO, and a smaller HOMO-LUMO gap facilitates stronger magnetic coupling and thereby a higher magnetic exchange coupling constant (J). This observation is supported by the occupation number of natural orbitals.

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Section: Mechanism Of Magnetic Interactionmentioning

confidence: 97%

A Perspective on Designing Chiral Organic Magnetic Molecules with Unusual Behavior in Magnetic Exchange Coupling

Sarbadhikary

Shil²,

Panda³

et al. 2016

J. Org. Chem.

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“…Thus, the HOMO and LUMO still are popularly utilized to analyze the electronic structures, electronic properties and chemical reactivity of the molecules and chemical systems. On the other hand, although Shil et al . reported that LUMO plays an important role in magnetic exchange, we find that LUMO and other unoccupied orbitals of the bridge would play less roles than its HOMO because HOMOs of the radical groups actually are SOMOs with the LUMO properties and their energy matchings with the bridge HOMO favor the spin coupling interaction between two radical groups through the bridge.…”

Section: Resultsmentioning

confidence: 99%

Tuning the Spin Coupling Interactions in the Nitroxide‐Based Bisphenol‐Like Diradicals

Song

2017

ChemPhysChem

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The intramolecular spin coupling interactions of bisphenol-like trinary-bridged diradicals [nitroxide-(para/meta)phenylene-X-phenylene(para/meta)-nitroxide, X=C=CH , O, BH, NH and SO ] were explored with an emphasis on the tuning role of the X coupler at the (U)B3LYP/6-311++G(d,p) level. Our results indicate that all designed trinary-bridged diradicals featuring a V-type structure with a bending angle of 104-130° and torsional angles of two phenylene rings being 20-90° exhibit different diradical character and magnetism, depending on the structures and properties of the X bridges. More interestingly, although meta/para-phenylene supports a ferromagnetic (FM)/antiferromagnetic (AFM) coupling, their combinations by using X as a trinary bridge can mediate spin coupling, but the coupling magnitude strongly depends on X. In general, a para/para or meta/meta combination with X leads to an open-shell singlet ground state and thus AFM, but the meta/meta combination considerably decreases the spin coupling interaction. In contrast, a para/meta combination with X produces a triplet ground state and FM. Their combination with a single-electron conjugation end coupler (C=CH ) leads to an inverse coupling regularity. All results can be reasonably explained by the spin alternation rule, molecular structures, and properties. In particular, detailed spin coupling mechanisms are suggested to involve cooperative through-space and through-bond pathways with different levels of cooperativity. This is rationalized with the X-induced bending of the diradicals not only modifying the through-bond (extended π conjugation) pathway but also provididng a through-space (face-to-face vs. side-to-side π-π interaction) possibility for spin coupling, in conjunction with twisting of the phenylene rings. Different contributions of the through-space and through-bond couplings are quantitatively distinguished and depend on the structure and property of the X coupler. Clearly, this work reports interesting aspects of the trinary bridged diradicals and also provides important information for the design of molecules for functional magnetic materials and tuning their magnetic properties.

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“…This also confirms the role of LUMO in the magnetic exchange coupling. [64] This might be linked to the fact that the LUMO spans over the entire molecule, whereas the SOMOs are located on the radical units.…”

Section: Molecular Orbitalsmentioning

confidence: 99%

Effect of deprotonation on the magnetic exchange coupling constant of fluorene‐based verdazyl diradical: A computational study

Shil

2017

Int J of Quantum Chemistry

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The magnetic behavior of the fluorene bridged verdazyl diradicals has been studied theoretically in their neutral and deprotonated states. The deprotonation of C9‐H site of the fluorene ring opens a new coupling pathway, which changes the nature of magnetic coupling. The transmission spectra analysis reveals that the transmission through fluorine has also increased due to the opening of a new coupling path after deprotonation.

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Role of the coupler to design organic magnetic molecules: LUMO plays an important role in magnetic exchange

Abstract: The occupation number and spatial position of the LUMO play an important role in magnetic exchange in diradicals.

Cited by 24 publications

References 54 publications

A Perspective on Designing Chiral Organic Magnetic Molecules with Unusual Behavior in Magnetic Exchange Coupling

A Perspective on Designing Chiral Organic Magnetic Molecules with Unusual Behavior in Magnetic Exchange Coupling

Tuning the Spin Coupling Interactions in the Nitroxide‐Based Bisphenol‐Like Diradicals

Effect of deprotonation on the magnetic exchange coupling constant of fluorene‐based verdazyl diradical: A computational study

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