Oligometallic Template Strategy for Synthesis of a Macrocyclic Dimer-Type Octaoxime Ligand for Its Cooperative Complexation

Abstract

The new acyclic tetraoxime ligand H(4)L(1), having two allyl groups at the terminal benzene rings, was designed and synthesized. The ligand H(4)L(1) was converted to five kinds of the trinuclear complexes, [L(1)Zn(3)(OAc)(2)], [L(1)Zn(2)La(OAc)(3)], [L(1)Zn(2)Ca(OAc)(2)], [L(1)Zn(2)Sr(OAc)(2)], and [L(1)Zn(2)Ba(OAc)(2)]. The terminal allyl groups were introduced so that the olefin metathesis could convert the metal complexes into the dimeric macrocyclic ligand H(8)L(3). The X-ray crystallographic analysis of the trinuclear complexes [L(1)Zn(3)(OAc)(2)(H(2)O)], [L(1)Zn(2)La(OAc)(3)(MeOH)], [L(1)Zn(2)Ca(OAc)(2)], and [L(1)Zn(2)Sr(OAc)(2)] revealed that the distances between the two allyl groups are 11-12 Å, which should be sufficient to suppress the intramolecular reaction leading to the monomeric macrocycle H(4)L(2). Indeed, the olefin metathesis of the [L(1)Zn(2)Ca(OAc)(2)] and [L(1)Zn(2)Sr(OAc)(2)] followed by demetalation with dilute hydrochloric acid afforded the dimeric macrocycle H(8)L(3) as the major product, while the reaction of the uncomplexed ligand H(4)L(1) gave the monomeric macrocycle H(4)L(2) as the major product. The complexation behavior of H(8)L(3) at the two tetraoxime sites was investigated. Although the formation process of the hexanuclear zinc(II) complex [L(3)Zn(6)](4+) was complicated, the metal exchange of the two trinuclear zinc(II) units proceeded in a two-step fashion. The analysis of the spectral changes indicated the positive and negative cooperative effects on the double metal exchange with Ca(2+) and Ba(2+), respectively. The first metal exchange reactions with Ca(2+) made the second metal exchange more favorable. Thus, the obtained dimeric macrocycle H(8)L(3) has two tetraoxime coordination sites, whose complexation behavior is remotely affected by each other.

Heterometallic SrII‐MII (M=Co, Ni, Zn and Cu) Coordination Polymers: Synthesis, Temperature‐Dependent Structural Transformation, and Luminescent and Magnetic Properties

“…Heterometallic coordination polymers containing alkaline earth (AE) metals have attracted increasing attention owing to their fascinating architectures along with their potential applications in the fields of catalysis,1 materials science,2, 3 and biochemistry 4. However, these types of complexes are very scarce and only a limited number of complexes, namely AE‐Zn,5, 6 AE‐Cu,7–10 AE‐Ni,11, 12 AE‐Co,13 AE‐Fe,14 AE‐Mn,10, 15 and AE‐Ln16–22 have been reported. The inclusion of alkaline earth metals into the heterometallic coordination polymers remains a great challenge for the following two important reasons: 1) the large and variable coordination numbers and versatile coordination behavior of alkaline earth metals make the coordination architectures of the coordination polymers uncontrollable and 2) the alkaline earth metal ions are oxophilic, while the transition metal ions have a strong tendency to coordinate N ‐donors as well as O ‐donors; it is quite possible that the competition reaction between the alkaline earth metals and the transition metals in coordinating to the same ligand gives rise to homometallic coordination polymers rather than heterometallic ones.…”

Dynamic Helicity Control of Oligo(salamo)-Based Metal Helicates

“…We have already demonstrated that a binding selectivity trend of alkali metal << Zn 2+ < alkaline earth < rare earth metal ions was observed in the shorter L 1 Zn2M system [57] and related complexes [79][80][81][82][83] without chiral auxiliary. If the longer L 4 Zn3M system having a chiral auxiliary also shows a similar selectivity trend, Ba 2+ in the L 4 Zn3Ba can be efficiently replaced by La 3+ .…”

Syntheses, structures and catecholase activities of homo‐ and hetero‐trinuclear cobalt(II) complexes constructed from an acyclic naphthalenediol‐based bis(Salamo)‐type ligand

“…The synthetic route to H 4 L is shown in Scheme . The 2,3‐dihydroxynaphthalene‐1,4‐dicarbaldehyde was synthesized by the standard method according to the literature . The 1 H NMR spectrum of the ligand obtained shows clearly that it was highly symmetrical.…”

“…The coordination chemistry of transition metal complexes with Salen‐type N 2 O 2 tetradentate ligands (N,N′‐disalicylideneethylenediamine) have achieved a considerable attention in the past decades due to their potential application in catalysts, biological fields, electrochemical conducts, nonlinear optical materials, magnetic materials, luminescence properties and supramolecular architecture . Chemical modifications of substituent or functional groups in the Salen N 2 O 2 ligands are effective in exchanging the structures or the main functions of the complexes, such as Salamo ligand, a Salen's analogue, (R‐CH = N‐O‐(CH) n ‐O‐N = CH‐R) is one of the most versatile ligand . Noticeably, a number of works have been devoted to synthesize and characterize mono‐, di‐ and multinuclear transition metal(II) complexes bearing mono(Salamo)‐type ligand orits derivatives .…”