Transmetalation for Flexible Pendant-Armed Schiff-Base Macrocyclic Complexes Influenced by Halide Effects

Abstract

Three 46-membered [2 + 2] pendant-armed Schiff-base macrocyclic dinuclear Cd and Cu complexes (2a, 2b, and 3b) and one 23-membered [1 + 1] Cu macrocycle 4a were prepared from the template-directed condensation reactions between 1,2-bis(2-aminoethoxy)-ethane and extended Cl-dialdehyde in the presence of CdX and CuX (X = Cl and Br), in which halide effects play important roles in the organization of final macrocyclic complexes in addition to the dominant influence of metal cations. Transmetalation was intensively studied among these Cd and Cu complexes with large and flexible macrocyclic ligands, including two previously synthesized dinuclear Zn macrocycles (1a and 1b). Our results indicate that Zn → Cu and Cd → Cu transmetalation proceeds more quickly than that from Cd to Zn, and all the processes are found to be irreversible. It is noted that a [2 + 2] heterodinuclear CdZn macrocyclic intermediate could be detected by ESI-MS together with [2 + 2] homodinuclear Cd and Zn macrocyclic complexes. Furthermore, distinct halide behavior was observed in the in situ Cd → Cu and Zn → Cu metal-ion exchange. That is to say, [2 + 2] macrocycles (1a and 2a) could be converted to [1 + 1] macrocycles 4a and 4b under the reflux condition in the case of CuCl, accompanied by the configurational transformation from half-folded dinuclear Zn and Cd to unfolded Cu macrocyclic skeleton. In contrast, CuBr leads to a highly efficient transmetalation to corresponding [2 + 2] dinuclear Cu complex 3b from both 1b and 2b no matter the experimental condition used.

Tunable Construction of Sandwich-Type Double-[1 + 1] and Half-Folded [2 + 2] Schiff-Base Complexes Controlled by the Combination of Primary and Secondary Template Effects

“…In this work, the first-row transition-metal divalent cations (Mn 2+ , Fe 2+ , Co 2+ , Ni 2+ , and Cu 2+ ), two extended dialdehydes (H 2 hpdd and H 2 pdd), and a flexible diamine 2,2'-(ethylenedioxy)bis(ethylamine) were selected to construct macrocyclic complexes because our previous results told us neither [1 + 1] nor [2 + 2] Schiff-base macrocycles are not perfect-matching for mono-/dinuclear centers. As for this specific [2 + 2] macrocyclic ligand, the coordination sites are unsaturated, and further transmetalation 67 and even postmodification from dinuclear Zn II to a tetranuclear Na 2 Zn 2 cluster could be allowed, while the corresponding [1 + 1] macrocyclic ligand could coordinate to only one Zn II ion. 61 Herein, our viewpoint lies in the following consideration: the size of this flexible [2 + 2] macrocyclic ligand is believed to be large enough for the first-row transition-metal divalent cations, while the corresponding [1 + 1] macrocyclic ligand seems to be too small for them.…”

“…To date, [1 + 1], [2 + 2], and [4 + 4] macrocycles, a supramolecular box, and a one-dimensional coordination polymer have been elaborately explored, in which Zn II and Pb II ions acted as templates. Moreover, the influences of primary cationic and secondary auxiliary template effects on fabricating diverse macrocyclic structures have been discussed. − The second auxiliary template effect is defined as the influence of non-metal parameters, including anions, pendant arms, and solvent effects.…”

Reversible Macrocycle-to-Macrocycle Interconversion Driven by Solvent Selection

“…Hirao et al showed that interconversion between six discrete states could be controlled by means of appropriate chemical stimuli . In these examples and most, if not all, known macrocycle/cage-to-macrocycle/cage interconversions, the underlying transformations are driven by chemical-, thermal-, or photo-stimuli. ,− Here, we report the reversible interconversion between two imine-based macrocycles, a [1 + 1] system and its [2 + 2] homologue, achieved by simply changing the solvent. In addition, we show that the [1 + 1] macrocycle dissolved in dimethyl sulfoxide (DMSO) (or N , N -dimethylformamide, DMF) is transformed into the [2 + 2] macrocycle via a precipitation-driven process.…”

Design and synthesis of methyl 2-{[4-phenyl-5-(pyridin-2-yl)-4H-1,2,4-triazol-3-yl]sulfanyl}acetate (phpy2NS) as a ligand for complexes of Group 12 elements: structural assessment and hydrogen-bonded supramolecular assembly analysis

“…A value ' = 0 indicates a completely planar dimer, whereas ' = 90 would correspond to a perfect tetrahedral environment around the Cd metal centre (Kapoor et al, 2004). The ' values found up to now in the literature range from 84.91 (Baby Mariyatra et al, 2002) to around 90.00 (Chang et al, 2018), even though the most usual values are 87-88 (Hasselgren et al, 1997;Lo & Ng, 2009;Lee et al, 2016). The anionic moiety in compound 3 presents the second highest ' angle described to date for this class of Cd 2 Br 6 species, taking a value of 89.67 (2) .…”