Compartmentalization of Alkaline-Earth Metals in Salen-Type Cu- and Ni-Complexes in Solution and in the Solid State

Abstract

The precise arrangement of metal ions in type and number by a ligand represents an important challenge in biology as well as in materials science. The preorganization of different metal ions such as alkaline-earth and transition-metal ions is of particular interest for the design of catalysts or precursors of oxides. This study is based on a Ω-shaped salen-derived ligand comprising N 2 O 2 and O 2 O 2 coordination sites. The selective binding of Cu(II) and Ni(II) and alkaline-earth-metal ions is influenced by many factors such as the size of the cation, the solvent, or the counterion. UV–vis and 1 H NMR titrations and single-crystal X-ray structures reveal that the obtained complexes tend to adopt different structures in solution compared to the solid state. Mainly discrete motifs with a stoichiometry 1:1 (LM 1 to alkaline-earth-metal ions) have been shown to form in the solid state, whereas in solution, the 2:1 complexes are predominant.

Bimetallic Salen-Based Compounds and Their Potential Applications

“…The formation of 1:1:1 complexes (L:M1:M2) is always observed in the solid state. As already observed previously, 33 LCuM2 with M2, being a third row element, can lead to alternating arrangements of the LCu entities in order to allow interactions of the Cu(II) with anions, but also parallel arrangements with Cu(II)−π interactions are observed. For the heavier cations, packing with a head-to-tail arrangement into coordination polymers along the crystallographic b-axis is found in the case of LCuBi; discrete antiparallel dimer Precursors for Mixed Metal Oxides.…”

“…The silver cation completes its coordination sphere with two O-atoms, O5–O6, from the nitrate counterion. In contrast to 1 , Ni­(II) reaches a bond valence sum of 1.99 solely by the O 2 N 2 donors and hence does not need to complete its coordination sphere through additional coordination, as already observed in previous studies with alkali metal ions . This leads to an offset parallel arrangement of the complex moieties into a 1D coordination polymer along the crystallographic b -axis, governed by Ag1–C6 interactions of 2.690(1) Å.…”

“…Here, we report the study of bimetallic compounds based on a salen-derivative, H 2 L, possessing two distinct coordination sites. We have previously studied the structural trends of LCu and LNi compounds in combination with alkali and alkaline earth metal ions, and found that the Cu-compounds formed mostly chains with alternatingly arranged LCu-moieties, while the Ni-analogues had the LNi entities arranged on the same side of the polymeric chain . Now, the greater interest in the optical, conductive, and catalytic properties of copper–manganese and copper–bismuth oxides, , as well as the efficient antimicrobial properties of silver, copper, zinc, and bismuth ions, encouraged us to combine LCu­(II) with Ag­(I), Mn­(II), Cu­(II), Zn­(II), Bi­(III), and, for comparison, LNi­(II) with Ag­(I) as bimetallic compounds.…”

“…We have previously studied the structural trends of LCu and LNi compounds in combination with alkali and alkaline earth metal ions, and found that the Cu-compounds formed mostly chains with alternatingly arranged LCu-moieties, while the Ni-analogues had the LNi entities arranged on the same side of the polymeric chain. 33 Now, the greater interest in the optical, conductive, and catalytic properties of copper− manganese and copper−bismuth oxides, 34,35 as well as the efficient antimicrobial properties of silver, copper, zinc, and bismuth ions, encouraged us to combine LCu(II) with Ag(I), Mn(II), Cu(II), Zn(II), Bi(III), and, for comparison, LNi(II) with Ag(I) as bimetallic compounds. A structural study of the different compounds was carried out by single crystal X-ray diffraction, and their potential as single-source precursors for the generation of nanoscale, mixed-metal oxides has been investigated together with their potential antimicrobial properties.…”

Chemistry of alkaline earth metals: It is not all ionic and definitely not boring!

“…(pyim = pyim = 2-(2 0 -pyridyl)-imidazole, bipy = 2,2 0 -bipyri dine, dpa = dpa = 2,2 0 -dipyridylamine) [76]. Yet other copper-and nickel-metalloligands obtained with salen-derivatives form coordination polymer, respectively molecular entities depending on the size alkaline earth metal ion [77]. A recent review further highlights the effect of alkali metal ions on organometallic compounds, including the ones of the alkaline earth group [78].…”