A New Family of Ni₄ and Ni₆ Aggregates from the Self-Assembly of [Ni₂] Building Units: Role of Carboxylate and Carbonate Bridges

Abstract

Carboxylato (R = (t)Bu and Et) and carbonato bridges have been utilized for nickel(II)-based aggregates [Ni4(μ-H2L)2(μ3-OH)2(μ1,3-O2CBu(t))2](NO3)2·H2O·2DMF (1·H2O·2DMF), Ni4(μ-(hy)HL)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-(hy)HL)](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-(t)BuCO2(-), 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 Ni(II) ions.

Synthesis, Crystal Structures and Magnetic Properties of Two Heterobridged µ‐Phenoxo‐µ1,1‐Azide/Isocyanate Dinickel(II) Compounds: Experimental and Theoretical Exploration

“…In contrast a very small spin density is observed in the broken‐symmetry state on phenoxido oxygen and azido/isocyanato nitrogen atom (–0.015 e and 0.008 e in 1 ; –0.013 and 0.005 e in 2 ) indicating a polarization competition between the two nickel atoms with α and β spin density, respectively. [28a] It is evident from the values in the Table that the sign of spin density in broken‐symmetry state on the bridging phenoxido atom (O4), in both the complexes, is negative and is the same to the sign to the sign of the Ni2 center. For the bridging azido/isocyanato (N6) atom, in both the complexes, the sign of the spin density of broken‐symmetry state is the same (positive) as that of Ni1.…”

“…This shows that the bridging phenoxido atom is mainly affected by the delocalization from Ni2, while for the bridging azido/isocyanato atom (N6), the delocalization from Ni1 is predominant. [28b] Spin polarization favours ferromagnetic coupling, whereas spin delocalization favors antiferromagnetic interaction. [28b] Obviously, in these dinuclear complexes, the effect of spin polarization competition results in a ferromagnetic interaction.…”

“…[28b] Spin polarization favours ferromagnetic coupling, whereas spin delocalization favors antiferromagnetic interaction. [28b] Obviously, in these dinuclear complexes, the effect of spin polarization competition results in a ferromagnetic interaction. A close inspection of the magnetic orbitals as shown in Figure and Figure for complex 1 and 2 , respectively, reveals that d x ²– y ² orbital of one nickel and d z ² of other nickel atom is involved in the superexchange mechanism with the local orbitals of the ligands.…”

Topological insights in polynuclear Ni/Na coordination clusters derived from a schiff base ligand

“…The interest in polynuclear Ni(II) coordination chemistry was first captured when the first Ni(II)-based SMM, a Ni 12 complex, was reported in 2001 by Cadiou et al [24]. Ever since, there have been a number of homometallic polynuclear Ni II CCs with high nuclearities including, Ni 5 [7,25], Ni 6 [26], Ni 7 [27,28], Ni 8 [29][30][31][32], Ni 9 [33,34], Ni 11 [35], Ni 12 [7], Ni 13 [36], Ni 14 [37], Ni 20 [38], Ni 21 [39], Ni 24 [40] and Ni 26 [41], and many of these display interesting magnetic properties including ferromagnetic, ferrimagnetic coupling, diamagnetism and SMM behaviour.…”

Crystal structure of 1,1′-((1E,1′E)-(((ethane-1,2-diylbis(oxy))bis(2,1-phenylene))bis(azanylylidene))bis(methanylylidene))bis(naphthalen-2-olato-κ3 O,O′,N)zinc(II), C36H26N2O4Zn

“…For a long time, numerous chemists from different disciplines have redirected their efforts to Schiff-base complexes due to their potential application in photocatalysis [4], bioscience [5] and magnetic properties [6]. As part of our work, a novel zinc(II) complex with a Salen-type bisoxime ligand was synthesized and characterized by X-ray diffraction.…”