Despite enormous synthetic effort expended in making novel examples of MNMs, clear understanding of the origin of the slow relaxation of the magnetisation and the mechanisms of the Quantum Tunnelling of the Magnetisation (QTM) still remains scarce.Although numerous experimental tools such as Inelastic Neutron scattering (INS), multifrequency high-field EPR, field and orientation dependent magnetic susceptibility have been used to investigate the magnetic anisotropy, none of them are suffice to resolve the directions of local anisotropy axes accurately. Here, we (“Computational Chemists”) can find out the remedy using our computational tools. The only straightforward way to attain quantitative information about magnetic networks is via fragment quantum chemistry calculations taking into account the spin-orbit coupling non-perturbatively.
Being computational chemists our main goal is to investigate the structure and properties of metal complexes/clusters possessing unpaired electrons (open shell systems). We and other computational chemists are using Gaussian09, ORCA,MOLCAS suite to calculate the spin Hamiltonian parameters zero-field splitting, EPR spectroscopic parameters(g tensors), inter- and intra- molecular exchange interactions to corroborate experimental observations. Using computational tools we also have succeeded to gain deeper insights into the magnetization blockade , energy barrier and relaxation dynamics. We have also attempted to compare experimental magnetic susceptibility and magnetization data using our computed results which have been proved to be compatible for most of the complexes. All of our comparisons have been performed using experimentally synthesises crystal structures. Apart from these, we have modelled some of the structures to make predictions out of our calculations for promoting synthetic chemists towards preparing better SMMs.
Our group is the first to report theoretical studies on {3d-4f} clusters whereby we have proposed a protocol to compute exchange and general mechanism of coupling and have employed DFT for prediction and for developing Magneto-structural correlations.
Radical-4f complexes added another dimension to our research efforts. Our first report on {2p-4f} rationalize the strong coupling observed and offers way to enhance the exchange interaction further. We have also for the first time investigated the importance of dihedral angle in regulating magnetic coupling.
Magnetic coupling in GdIII-GdIII dimers been reported by us along with the mechanism of coupling and magneto-correlations. Some clues into how to enhance magneto-calorie effect (important for realization of molecular refrigerants) on this class has been proposed.
Underlying different magnetic exchange coupling within the wheels have been computed by us in compliance with the experimental observations. Besides,we have attempted to predict the possible ground state of the wheels. We have also tried to explain the spin frustration observed in some of the complexes through model calculations.
We have probed the origin of large magnetocaloric effect (MCE) in large clusters. Moreover, magnitude of the MCE has been examined as a function of the exchange interactions, and clues to increase the MCE has been investigated in detail.
Using DFT methods,we have shown that for a dinuclear Mn(III) possessing bis-μ-alkoxo bridge, strong ferromagnetic exchange and anisotropy would not co-exist. Our studies on dinuclear {MnCu} dimer unfold the origin of positive zero-field splitting in this unusual {MnCu} dinuclear complex possessing Jahn-Teller compressed Mn(III) ions.
Using DFT methods,we have shown that for a dinuclear Mn(III) possessing bis-μ-alkoxo bridge, strong ferromagnetic exchange and anisotropy would not co-exist. Our studies on dinuclear {MnCu} dimer unfold the origin of positive zero-field splitting in this unusual {MnCu} dinuclear complex possessing Jahn-Teller compressed Mn(III) ions.