A New Family of Ni4 and Ni6 Aggregates from the Self-Assembly of [Ni2] Building Units: Role of Carboxylate and Carbonate Bridges
dataset
posted on 2015-05-18, 00:00 authored by Moumita Pait, Antonio Bauzá, Antonio Frontera, Enrique Colacio, Debashis RayCarboxylato (R = tBu and
Et) and carbonato bridges have been utilized for nickel(II)-based
aggregates [Ni4(μ-H2L)2(μ3-OH)2(μ1,3-O2CBut)2](NO3)2·H2O·2DMF (1·H2O·2DMF), Ni4(μ-hyHL)2(μ3-OMe)2(μ1,1-N3)2(μ1,3-O2CEt)2]·4H2O (2·4H2O), and Ni6(μ4-L)(μ3-L)2(μ6-CO3)(H2O)8](ClO4)·9H2O (3·9H2O). Building blocks [Ni2(μ-H2L)]3+, [Ni2(μ-hyHL)]3+, and [Ni2(μ-L)]+ originating from [Ni2(μ-H2L)]3+ have been trapped in these complexes. The complexes have been characterized
by X-ray crystallography, magnetic measurements, and density functional
theory (DFT) analysis. In 1, the magnetic interactions
are transmitted through the μ3-phenoxido/μ3-hydroxido/syn–syn-tBuCO2–, μ3-phenoxido/μ3- hydroxido, and double μ3-phenoxido/double μ3-hydroxido bridges with J = +11.4 cm–1, J1 = −2.1 cm–1, and J2 = −2.8 cm–1, respectively.
In 2, the interactions are ferromagnetic, with J1 = +27.5 cm–1, J2 = +20.62 cm–1, and J3 = +1.52 cm–1 describing the magnetic
couplings through the μ-phenoxidoo/μ3-methoxido,
μ-azido/μ3-methoxido, and μ3-methoxido/μ3-methoxido exchange pathways, respectively.
Complex 3 gives J1 = −3.30
cm–1, J2 = +1.7 cm–1, and J3 = −12.8
cm–1 for exchange pathways mediated by μ-phenoxido/μ-carbonato,
μ-alkoxido/μ-alkooxido/μ-syn–syn-carbonato, and the μ-phenoxido/μ-carbonato,
respectively. Interestingly, 1 and 3 below
20 K and 35 K, respectively, show an abrupt increase of the χMT product to reach a magnetic-field-dependent
maximum, which is associated with a slightly frequency-dependent out-of-phase
alternating-current peak. DFT calculations have also been performed
on 1–3 to explain the exchange interaction
mechanisms and to support the magnitude and sign of the magnetic coupling
constants between the NiII ions.
