Dinuclear and Polynuclear Bridged Azido–Nickel(II) Complexes: Synthesis, Structure Determination, and Magnetic Properties

Abstract

Me 6 trien = 1,1,4,7,10,10-hexamethyltriethylene tetramine} were synthesized and structurally characterized by spectroscopic techniques, X-ray crystallography, and variable-temperature magnetic measurements. In the complexes 1-3a, the ClO 4 -groups are counterions and the Ni 2+ centers are bridged by the azido ligands in an end-to-end bonding fashion. The coordination geometry around the Ni II ions is six-coordinate with a distorted octahedral environment achieved by the four N atoms of the tetradentate amines and two terminal N atoms of the azide groups. Complex 1 consists of dinuclear units with doubly bridged azido groups whereas in 2 and 3a, a polymeric 1D chain is formed in which the adjacent azido

Pseudohalide copper(II) complexes derived from polypyridyl ligands: Synthesis and characterization

“…This was synthesized following the published procedures [23] and purified by chromatographing it on silica gel and elution with a 98/2 (v/ v) mixture of ethyl acetate/MeOH. 1 (1 00 -CH 2 ), 54.15 (2 00 -CH 2 ), 35.73 (3 00 -CH 2 ). The purity of pmea and pmap compounds was sufficient for subsequent complex formation.…”

“…Two factors can be considered here to account for this behavior; these include steric and electronic factors. In general in the bridging EO-mode, the azido-and thiocyanato-Cu(II) complexes have Cu...Cu separations in the range of 3.0-3.6 Å [1,17,18] and are >5 Å in the corresponding bridging EE-mode [1,2,16]. Structural analysis of the complexes 2, 6, and 7 where the azide and the thiocyanate anions are terminal ligands showed that the Cu...Cu separations are 4.9141(12), 8.238(2), and 5.7010(14) Å, respectively.…”

“…These anions can act as monodentate ligands and as bridging ligands leading to the formation of mononuclear and polynuclear species with different dimensionality and nuclearity [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19]. Among these, the azide-and thiocyanate-containing metal complexes are considered to be the most investigated systems because of their diverse structures and applications in magnetic materials [20].…”

“…The magnetic exchange interaction in these systems results from the electronic interaction between the paramagnetic metal centers via the bridging N À 3 or NCS À liand(s). Nowadays, it is well established that in azido-bridging Cu(II) or Ni(II) complexes exchange is, with some exceptions [14], generally anti-ferromagnetic in nature for end-to-end (l 1,3 or EE) mode [7][8][9] and ferromagnetic for end-on (l 1,1 or EO) mode [11][12][13]. Moreover, Cu-azide chemistry is of considerable interest in biological systems because copper ions are found in the active sites of a large number of metalloproteins (hemocyanin, ascorbate oxidase, tyrosinase) and the function of these proteins is inhibited by the presence of azide ions [21].…”

Five-coordinate metal(II) complexes based pyrazolyl ligands

“…The ambidentate nature of the thiocyanate anion NCS À , together with the azide ion, N 3 À and the ability of these ligands to bridge and assemble metal ions in extended network structures made these ligands to be among the most extensively studied species [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18]. The interaction of NCS À and N 3 À with divalent metal ions have led to the construction of polynuclear and coordination polymers of diverse topology [1][2][3][4][5]7,[10][11][12][13][14][15][16][17][18] and the development of new magnetic molecular materials of different bridging-azido, and -thiocyanato bonding modes [2,3,4b,5,7,10-17].…”