Air-oxidation from sulfur to sulfone-bridged Schiff-base macrocyclic complexes showing enhanced antimicrobial activities

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

The first-row transition-metal ions Mn²⁺-Cu²⁺ could serve as effective templates to construct three types of double-[1 + 1], [2 + 2], and [1 + 1] Schiff-base dinuclear macrocyclic complexes in the presence of dialdehydes with different pendant arms and a common 1,8-diamine. The extremely flexible nature of macrocyclic ligands allows for the multiple template-directed syntheses, but the final products could be finely tuned by the subtle variations of Mn²⁺-Cu²⁺ ions in a 3d-electronic configuration, radius, and coordination number/geometry as well as the auxiliary (pendant-armed and anionic) template effect at the same time. Two borderlines are observed at the Co²⁺ ion for forming double-[1 + 1] and [2 + 2] metallacycles involving the H₂pdd precursor and the [1 + 1] Cu²⁺ complex for double-[1 + 1] and [2 + 2] macrocycles containing the H₂hpdd unit, respectively. The structural diversity is originated from the non-perfect match between [1 + 1]/[2 + 2] Schiff-base macrocycles and dinuclear metal centers; hence, a compromise between the metal coordination modes and alterations of the ligand conformation takes place.

Synthetic approaches to metal-coordination-directed macrocyclic complexes

Metal-coordination-directed macrocyclic complexes, in which macrocyclic architectures are formed by metal-ligand coordination interactions, have emerged as attractive supramolecular scaffolds for the creation of materials for applications in biosensing and therapeutics. Despite recent progress, uncontrolled multicyclic cages and linear oligomers/polymers is the most likely outcome from metal-ligands assembly, representing a challenge to current synthetic methods. Herein we outlined the state-of-art synthetic approaches to the metal-coordination-directed macrocyclic complexes by using foldable ligands or through assembly of amphiphilic ligands. This mini-review offers a guideline for the efficient preparation of metal-coordination-directed macrocyclic complexes with predictable and controllable structures, which may find applications in many biology-related areas.

A systematic investigation on the impact of the level of oxidation at sulfur and the configuration of R/S-sulfoxide on the solid structure

In this work, the two aspects, different oxidation states of sulfur and diastereomeric sulfoxides, were combined to comprehend the role of crystal packing and different weak intermolecular interactions in the solid state.

Formation of a four-bladed waterwheel-type chloro-bridged dicopper(ii) complex with dithiamacrocycle via double exo-coordination

A four-bladed waterwheel-like chloro-bridged dicopper(ii) complex! The self-assembly of O₃S₂-macrocycle (L) with copper(ii) nitrate afforded a chloro-bridged tetra(macrocycle) dicopper(ii) complex.

Construction and Photoluminescent Properties of Schiff-Base Macrocyclic Mono-/Di-/Trinuclear ZnII Complexes with the Common 2-Ethylthiophene Pendant Arm

A new flexible 2-ethylthiophene pendant-armed dialdehyde (H₂tdd) was reacted with 1,3-propanediamine, [( S, S),( R, R),(±)]-1,2-diaminocyclohexane, and 1,2-bis(2-aminoethoxy)ethane, giving birth to 36-membered [2 + 2] Schiff-base macrocyclic trinuclear Zn^II complex 1, 18-membered [1 + 1] mononuclear Zn^II macrocycles 2-4, chiral/racemic 34-membered [2 + 2] dinuclear Zn^II complexes 5-9, and 46-membered [2 + 2] dinuclear Zn^II macrocycles 10-12 via Zn^II ion template-assisted Schiff-base condensation. It is worth mentioning that the secondary template effects for nitrate and halide counterions have been observed in the 1,3-propanediamine involved imine condensation. In all [2 + 2] Zn^II macrocycles, dinuclear complexes 5-9 display a full-folded molecular conformation, while trinuclear complex 1 and dinuclear complexes 10-12 exhibit distinct half-folded structures in the presence or absence of intramolecular π-π stacking interactions between two phenolic rings of the dialdehyde component. Interestingly, a solvent-induced single-crystal-to-single-crystal transformation was first achieved for two types of solvated mononuclear macrocycles 3a and 3b (H₂O vs CH₃CN) with folded and unfolded ligand conformations. In addition, the photoluminescent properties were studied for this family of Schiff-base macrocyclic Zn^II complexes as well as the dialdehyde precursor H₂tdd.

Schiff-base macrocyclic ZnII complexes based upon flexible pendant-armed extended dialdehydes

This Frontier article reviews diverse structures of Schiff-base macrocyclic ZnII complexes derived from a family of flexible pendant-armed extended dialdehydes via a preorganized synthetic strategy and the corresponding structure-determining factors, including primary cationic template effects and secondary complementary template effects. In addition, further post-modification and supramolecular self-assembly of Schiff-base ZnII macrocycles and their possible applications in a variety of areas have been discussed.