Receptor versus Counterion: Capability of N,N′‐Bis(2‐aminobenzyl)‐diazacrowns for Giving Endo‐ and/or Exocyclic Coordination of Zn^II

Anion Coordination Effect on the Nuclearity of CoII, NiII, CuII, and ZnII Complexes with a Benzimidazole Pendant‐Armed Crown

“…In the case of the Co II complex, the presence of a hydroxido bridge allows antiferromagnetic exchange in this compound. However, this receptor only forms mononuclear complexes with Zn II [10] and Mn II in acetonitrile, [11] but not binuclear ones. We showed that the presence of a poorly coordinating anion such as perchlorate results in endocyclic coordination of Zn II , whereas the presence of a more-coordinating anion such as nitrate gives rise to exocyclic coordination of this metal ion.…”

“…On the grounds of our previous experience, [6,7,10] full geometry optimizations of the [Zn(L 4 )] 2+ system were performed in vacuo by using the standard 6-31G(d) basis on the ligand atoms and Ahlrichs' valence triple-ζ (VTC) on Zn. The latter basis was shown to provide accurate molecular structures for several firstrow transition-metal complexes.…”

A merged experimental and theoretical conformational study on alkaline-earth complexes with lariat ethers derived from 4,13-diaza-18-crown-6

“…We have carried out studies to asses their different complexation capabilities towards post-transitional divalent metal ions such as Zn(II) [17], Pb(II) and Cd(II) [18][19][20][21] as well as transition metal ions. With first-row transition metal ions such as Ni(II), Co(II) and Cu(II), L 2 and L 4 are able to form binuclear complexes [22,23], whereas the related receptors L 1 and L 3 only form mononuclear complexes [24][25][26].…”

Evolution of the Coordination‐Sphere Symmetry in Copper(II), Nickel(II), and Zinc(II) Complexes with N,N′‐Double‐Armed Diaza‐Crown Ethers: Experimental and Theoretical Approaches

“…The [15]crown-5-based ligands usually lead to heptacoordinated complexes with metal ions, the most common polyhedron being the pentagonal bipyramid [19] with either O 7 , [11,12] N 2 O 5 , [10,20] or N 4 O 3 [6,8,9,14] coordination spheres. The pentagonal equatorial plane is probably imposed by the rigid structure of the [15]crown-5 ligand.…”

“…In previous works, it has been shown that the diaza [18]crown-6 ether is a versatile receptor that is able to adapt to the coordination preferences of the particular metal cation, [4][5][6][7][8][9] whereas the diaza [15]crown-5 ether has been revealed to be a receptor that imposes seven-coordination around the metal ion. [8,[10][11][12][13][14] The size of chelate rings formed upon coordination of the pendant arms to the metal ion influences the nuclearity of the complexes. For instance, in the case of disubstituted diaza [18]crown-6 ethers, the six-membered chelate rings (and beyond) tend to form binuclear complexes, [6,7] whereas the five-membered chelate rings lead to mononuclear complexes in the presence of non-coordinating counterion.…”