A Versatile Series of Nickel(II) Complexes Derived from Tetradentate Imine/Pyridyl Ligands and Various Pseudohalides: Azide and Cyanate Compared

Abstract

The chemical reactions of a family of tetradentate pyridyl/imine ligands, L1, L2, and L3 (L1=[ N, N'-bis(2-pyridinylmethylene)]ethane-1,2-diamine; L2=[ N, N'-bis(pyridin-2-yl)benzylidene]ethane-1,2-diamine; L3=[ N, N'-bis(2-pyridinylmethylene)]propane-1,3-diamine), with Ni (II) in the presence of various pseudohalides (N3(-), SCN(-), and NCO(-)) have served to prepare six different complexes, [Ni 2(L1)2(N3)2](ClO4)2.H2O (1), [Ni 2(L2)2(N3)2](ClO4)2 (2), [Ni2(L2)2(NCS)4] (3), [Ni2(L2)2(NCO) 2](ClO4)2 (4), [Ni2(L3)2(NCO)2](ClO4)2 (5), and [Ni(L3)(N 3)2] (6), which have been characterized by X-ray crystallography. Interestingly, four of these complexes are dinuclear and exhibit end-on (EO) pseudohalide bridges (1, 2, 4, and 5), one is dinuclear and bridged exclusively by the tetradentate ligand (3), and one is mononuclear (6). The bulk magnetization of the complexes bridged by EO pseudohalides has been studied, revealing these ligands to mediate ferromagnetic coupling between the Ni(II) ions, with modeled coupling constants, J, of +31.62 (1), +28.42 (2), +2.81 (4), and +1.72 (5) cm(-1) (where the convention H=-2JS1S2 was used). The striking difference in the coupling intensity between N3(-) and NCO(-) has prompted an investigation by means of density functional theory calculations, which has confirmed the experimental results and provided insight into the reasons for this observation.

Synthesis, characterization and molecular structures of Ni(II) complexes derived from Schiff base pyridylimine ligands

“…The NiL1 (15) Å] is close to those observed in other aqua nickel complexes [17,18,[25][26][27][28][29][30][31], lengths for Ni-N imine and Ni-N pyridyl bonds are in accordance with other structurally similar complexes [15,[17][18][19]32,33].…”

“…Whilst group 10 transition metal complexes based on pyridylimine ligands have been synthetized being important those of nickel [15,[17][18][19] for their potential as models for the mimicking of active centers of metalloenzymes. Thus, in this report we would like to report our findings on the synthesis, characterization and supramolecular studies in the solid state of a series of Ni(II) complexes derived from pyridylimine ligands.…”

Syntheses, crystal structures, and DNA-binding of some nickel(II) complexes of 1,3-bis(2-pyridylmethylthio)propane and pseudohalides

“…Intense bands at 2027 cm -1 for 1, 2182 cm -1 for 2 and 2082 cm -1 for 3 are assignable to N3 , NCO and NCS , respectively [12]. These IR data confirm the presence of endon N-bonded terminal pseudohalides [13,14].…”

Double azido-bridged and mixed-bridged binuclear copper(II) and nickel(II) compounds with N,N,O-donor Schiff bases: Synthesis, structure, magnetic and DFT study

“…In addition, the dinuclear Ni(II) complexes also possess interesting magnetic properties. The exchange interactions of such complexes changes dramatically in the presence of exogenous bridging group, e.g., chloro and azido ions, in their close proximity as these groups show diverse magnetic properties depending on their orientation with respect to the magnetic center [24][25][26][27][28][29]. Therefore, these systems still remain interesting for further investigations.…”