Magnetic coupling in oximato bridged {MnIII6} clusters bridged by diamagnetic dicyano-metallato linkers: A theoretical perspective

Oximato bridged {Mn-6(III)} clusters are among the best known SMMs for transition metal clusters that exhibit a very large barrier height for magnetization reversal and decent blocking temperatures. Several attempts were made to improve the magnetic properties of this family, among others, employing dicyano-metallo linkers such as [Au/Ag(CN)(2)](-) to link two {Mn-6(III)} clusters gained attention as this paves the way forward to construct supramolecular architecture based on {Mn-6(III)} units and also facilitate a way to control the intercluster exchange coupling - a parameter vital to Qubit application. In this work, we have employed DFT calculations to estimate various exchange coupling constants within the {Mn-6(III)} clusters ([Mn-6(III)(mu(3)-O)(2)(Et-sao)(6)(3-py)(2)(MeOH)(2) (M (CN)(2))(2)] M = Au (1), Ag (2) here sao(2-) is the dianion of salicylaldoxime or 2-hydroxybenzaldeyhyde oxime). We have identified four different Js within the cluster based on the orientation of the Jahn-Teller axes and the Mn-N-O-M dihedral angles. The computed J values within the clusters are in the borderline of ferro and antiferromagnetic coupling, leading to a competing interaction within the cluster, and for this reason, several spin states are found to lie close to each other. The computed Js reproduce the experimental susceptibility data and yield very small/negligible {Mn-6(III)-M-I-Mn-6(III)} intercluster interaction. The reason for such weak couplings was analysed, and a search for stronger exchange coupling was undertaken by studying in detail the J values in [{Mn(salen)(EtOH)}(3){M(CN)(6)}] (here M = Fe-III (3), Cr-III (4); Salen = N,N'-bis(salicylidene)ethylenediamine) clusters. This predictive strategy suggests that incorporating a metal ion such as Cr-III could be a game-changer as this promotes a very strong ferromagnetic coupling between two Mn-III centers. If this prediction is attempted for oximato bridged {Mn-6(III)} clusters, it could be very rewarding.

Automated summary

In this study, density functional theory calculations were used to estimate the exchange coupling constants within oximato bridged {Mn-6(III)} clusters, revealing a competing interaction within the cluster and closely spaced spin states. Experimental data supported the computed results, showing negligible intercluster interaction. By studying other metal ion clusters, it was suggested that introducing Cr-III could potentially alter the magnetic coupling, which could be significant for oximato bridged {Mn-6(III)} clusters.