Naslov
High-temperature experimental and theoretical study of magnetic interactions in diamond and pseudo-diamond frameworks built up from hexanuclear tantalum clusters

Autori
Perić, Berislav ; Cordier, Stéphane ; Cuny, Jérôme ; Gautier, Régis ; Guizouarn, Thierry ; Planinić, Pavica

Izvornik
Chemistry : a European journal (0947-6539) 17 (2011), 22; 6263-6271

Vrsta, podvrsta i kategorija rada
Radovi u časopisima, članak, znanstveni

Ključne riječi
cluster compounds; density functional calculations; magnetic properties; tantalum; X-ray diffraction

Sažetak
Magnetic interactions in solid-state tantalum cluster compounds have been evidenced by using magnetic susceptibility measurements and corroborated by broken-symmetry DFT calculations. The three selected compounds are based on [Ta6X12(H2O)6]3+ (X=Cl or/and Br) units with edge-bridged Ta6 octahedral clusters. Although two of them crystallise in the tetragonal space group I41/a, all compounds exhibit a similar arrangement of paramagnetic clusters related to the diamond structural framework (Fd3̄m space group). Magnetic parameters were fitted by using the [5, 4] Padé approximant of high-temperature series expansion of susceptibility for the Heisenberg model (S=1/2) in the diamond framework, assuming only nearest-neighbouring interactions. Such a model appropriately describes magnetic-susceptibility measurements at temperatures T>0.7|J|/k. The magnetic interaction parameter J between two [Ta 6Cl12(H2O)6]3+ clusters is estimated to be -64.28(7) cm-1 ; it has been enhanced by replacing several chlorine inner ligands with bromine ones (J=-123(3) cm-1 for two [Ta6Br7.7(1)Cl4.3(1) (H2O) 6]3+ clusters) and is strongest between two bromine [Ta6Br12(H2O)6]3+ clusters with a value of -155(1) cm-1. Broken-symmetry DFT calculations within spin-dimer analysis confirmed this trend. Those interactions can be explained on the basis of the overlap between singly occupied a 2u orbitals localised on neighbouring clusters.

Izvorni jezik
Engleski

Znanstvena područja
Kemija

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