Static Retention of Dynamic Chiral Arrangements for Achiral Shear Thinning Metal-Organic Colloids

Chiral compounds are known to be important not only because they are the fundamental components of living organisms, but also for their unique chiroptical properties. In recent years, scientists have fabricated several chiral organic supramolecular aggregates by using chiral physical fields, such as vortex flow. Herein, the relationship between dynamic chiroptical properties and rheological nature is discussed, suggesting the shear thinning properties of non-Newtonian fluids might help colloidal particles adopt a chiral arrangement in vortices. Furthermore, the storage modulus of colloids could be increased by adding a linking agent, which successfully kept the dynamic chiroptical properties in the static state. Moreover, the salt effect on the host-guest interaction involved in the colloids was studied, the results suggested a significant enhancement of the transferred dynamic circular dichroism for the achiral guest molecule.

Circularly Polarized Luminescence of Achiral Metal-Organic Colloids and Guest Molecules in a Vortex Field

Recently, scientists have reported a range of chiral fluorescence materials or chiral composites that can emit circularly polarized luminescence. Herein, two achiral metal-organic colloidal solutions were studied, showing active circularly polarized luminescence, which is observed in vortex stirring. The absolute values for g_lum are 0.05 and 0.03 and the plus or minus sign of g_lum depends on the colloidal structure and stirring direction, which make the property easy to manipulate. Further, the host-guest interaction study suggests both electrostatic interactions and coordination bonding may influence the chiroptical property from the colloidal solution to the guest molecule. Rhodamine 6G and its carboxylic acid derivative exhibit good quantum yields and acceptable g_lum values in the colloidal solution.

Beyond the Simple Copper(II) Coordination Chemistry with Quinaldinate and Secondary Amines

Copper(II) acetate has reacted in methanol with quinaldinic acid (quinoline-2-carboxylic acid) to form [Cu(quin)₂(CH₃OH)]∙CH₃OH (1) (quin⁻ = an anionic form of the acid) with quinaldinates bound in a bidentate chelating manner. In the air, complex 1 gives off methanol and binds water. The conversion was monitored by IR spectroscopy. The aqua complex has shown a facile substitution chemistry with alicyclic secondary amines, pyrrolidine (pyro), and morpholine (morph). trans-[Cu(quin)₂(pyro)₂] (2) and trans-[Cu(quin)₂(morph)₂] (4) were obtained in good yields. The morpholine system has produced a by-product, trans-[Cu(en)₂(H₂O)₂](morphCOO)₂ (5) (morphCOO⁻ = morphylcarbamate), a result of the copper(II) quinaldinate reaction with ethylenediamine (en), an inherent impurity in morpholine, and the amine reaction with carbon dioxide. (pyroH)[Cu(quin)₂Cl] (3) forms on the recrystallization of [Cu(quin)₂(pyro)₂] from dichloromethane, confirming a reaction between amine and the solvent. Similarly, a homologous amine, piperidine (pipe), and dichloromethane produced (pipeH)[Cu(quin)₂Cl] (11). The piperidine system has afforded both mono- and bis-amine complexes, [Cu(quin)₂(pipe)] (6) and trans-[Cu(quin)₂(pipe)₂] (7). The latter also exists in solvated forms, [Cu(quin)₂(pipe)₂]∙CH₃CN (8) and [Cu(quin)₂(pipe)₂]∙CH₃CH₂CN (9). Interestingly, only the piperidine system has experienced a reduction of copper(II). The involvement of amine in the reduction was undoubtedly confirmed by identification of a polycyclic piperidine compound 10, 6,13-di(piperidin-1-yl)dodecahydro-2H,6H-7,14-methanodipyrido[1,2-a:1′,2′-e][1,5]diazocine.

A family of 3d metal clusters based on N–N single bonds bridged quasi-linear trinuclear cores: the Mn analogue displaying single-molecule magnet behavior

The reactions of the diacylhydrazine ligands N,N′-bisalicyl-2,6-pyridine dicarbohydrazide (H₆sphz) and N,N′-bis(3-methoxysalicyl)-2,6-pyridine dicarbohydrazide (H₆msphz) with various 3d metal salts, afforded a series of coordination clusters, namely, [Mn^III₂Mn^II(sphz)(acac)₂(CH₃OH)₄] (1, acac⁻ = acetylacetone anions), [Ni^II₃(msphz)(Py)₄] (2, Py = pyridine), [Cu^II₆(sphz)₂(Py)₄] (3) and [Cu^II₆(msphz)₂(Py)₄]·2DMF·2H₂O (4). Cluster 1 and 2 are single ligand assembled quasi-linear trinuclear structures. Both 3 and 4 consist a pair of quasi-linear {Cu₃} cores, which are linked together by two crossed ligands. The adjacent 3d metal ions in all trinuclear cores of 1–4 are bridged by N–N single bonds of ligands, which convey ferromagnetic (FM) interactions between 3d metal centers of 1, and antiferromagnetic (AFM) interactions between those of 2–4. In particular, the FM interactions and linear arrangement of mixed-valence Mn centers in 1 result in a large spin ground states value (S_T) of 13/2, as well as single-molecule magnet (SMM) behavior of slow relaxation and hysteresis of magnetization.

A family of 3d metal clusters featuring N–N single bonds bridged quasi-linear trinuclear cores were designed and synthesized. The Mn analogue represents a very rare case of quasi-linear 3d SMM using N–N single bonds as magnetic coupling pathways.

Coordination ability of amino acid hydrazide ligands and their influence on magnetic properties in copper(ii) coordination polymers

Copper(ii) coordination polymers constructed from newly synthesized amino acid hydrazides and 4,4′-bipyridine exhibit antiferromagnetic ordering mediated through hydrazide bridges.

Ammonia-modulated reversible gel–solution phase transition and fluorescence switch for a salicylhydrazide-based metal–organic gel

A fluorescence metal–organic gel was studied with its reversible gel–solution phase transition and fluorescence switch by the modulation of ammonia.