Quasi-1D chains of dinickel lantern complexes and their magnetic properties

摘要

Four new quasi-1D Ni-2-lantern chain complexes of the form [Ni-2(SOCR)(4)(L)](infinity) (R = Ph, L = DABCO (1); R = Ph, L = pyz (2); R = CH3, L = DABCO (3); R = CH3, L = pyz (4)) were prepared from the reaction of [Ni-2(SOCR)(4)(EtOH)], R = CH3 or Ph, with the N,N'-donor bridging ligands pyrazine (pyz) or 1,4diazabicyclo[2.2.2] octane (DABCO). Reaction of [Ni-2(tba)(4)(EtOH)], (tba = thiobenzoate) with the mono-N donor ligand quinuclidine (quin) gave the discrete Ni-2- lantern complex [Ni-2(tba)(4)(quin)] (5), whereas reaction with pyridine led to fragmentation of the lantern and formation of the known [Ni(tba)(2)(py)(2)] (6). Single-crystal X-ray diffraction reveals 2-4 to be 1D chain complexes comprising DABCO or pyz ligands which bridge the Ni2- lantern units. Complex 5 forms dimers through two equivalent Ni. S interactions. The Ni-Ni distances within the Ni2- lanterns are 2.5316(18)- 2.595(2) angstrom for the 1D chain complexes 2-4, and 2.5746(4) angstrom in the dimeric complex 5, respectively. Comparing the solid state magnetism of 5 to precursor [Ni2(tba) 4(EtOH)] demonstrates a change in coupling upon change of capping ligand. Meanwhile, chains 1- 4 exhibit magnetic properties consistent with an S = 1 system, due to a mixed valent system where the two Ni centers differ in spin state, while 5 possesses two S = 1 Ni(II) centers. DFT calculations confirm low-spin S = 0 {NiS4} and high-spin S = 1 {NiO4} centers in each lantern. Fits to the magnetic susceptibility data of the chains suggest a weak antiferromagnetic mean field interaction is present that is largely 1-D in nature, though neither pyrazine nor DABCO promote significant magnetic interaction between neighboring Ni-2-lanterns.