Tracking the Multistep Formation of Ln(III) Complexes with in situ Schiff Base Exchange Reaction and its Highly Selective Sensing of Dichloromethane

'Aggregation-Induced Emission' Active Mono-Cyclometalated Iridium(III) Complex Mediated Efficient Vapor-Phase Detection of Dichloromethane

Selective vapor-phase detection of dichloromethane (DCM) is a challenge, it being a well-known hazardous volatile organic solvent in trace amounts. With this in mind, we have developed an 'Aggregation-induced Emission' (AIE) active mono-cyclometalated iridium(III)-based (M1) probe molecule, which detects DCM sensitively and selectively in vapor phase with a response time <30 s. It reveals a turn-on emission (non-emissive to intense yellow) on exposing DCM vapor directly to the solid M1. The recorded detection limit is 4.9 ppm for DCM vapor with pristine M1. The mechanism of DCM detection was explored. Moreover, the detection of DCM vapor by M1 was extended with a low-cost filter paper as the substrate. The DCM is weakly bound with the probe and can be removed with a mild treatment, so, notably, the probe can be reused.

A series of dysprosium clusters assembled by a substitution effect-driven out-to-in growth mechanism

The diacylhydrazone ligands with different substituents were reacted with Dy(NO₃)₃·6H₂O to obtain 16 nuclear (1) and 10 nuclear (2) and pentanuclear (3) dysprosium clusters. Clusters 1–3 are gradually formed through out-to-in growth mechanism.

pH manipulates the assembly of a series of dysprosium clusters with subtle differences

This study is the first to fine-tune a series of lanthanide clusters with the same shape through pH manipulation.

Multifunctional Binuclear Ln(III) Complexes Obtained via In Situ Tandem Reactions: Multiple Photoresponses to Volatile Organic Solvents and Anticounterfeiting and Magnetic Properties

The design and synthesis of simple lanthanide complexes with multiple functions have been widely studied and have faced certain challenges. Herein, we successfully synthesized the series of binuclear lanthanide complexes [Ln₂(L1)₂(NO₃)₄] (HL1 = 2-amino-1,2-bis(pyridin-2-yl)ethanol; Ln = Dy (Dy2), Tb (Tb2), Ho (Ho2) Er (Er2)) via the in situ self-condensation of Ln(NO₃)₃·6H₂O-catalyzed 2-aminomethylpyridine (16 steps) under solvothermal conditions. Dy2 was mixed with different volatile organic solvents, and photoluminescence tests demonstrated that it showed an excellent selective photoresponse to chloroform (CHCl₃). Sensing Tb2 on different organic solvents under the same conditions showed that it exhibited excellent selective photoresponse to methanol (CH₃OH). Even under EtOH conditions, Tb2 could selectively respond to small amounts of CH₃OH. To the best of our knowledge, achieving a selective photoresponse to various volatile organic compounds by changing the metal center of the complex is difficult. Furthermore, we performed anticounterfeiting tests on Tb2, and the results showed significant differences between the anticounterfeiting marks under white light and ultraviolet light conditions. The alternating current susceptibilities of Dy2 suggested that it was a typical single-molecule magnet (SMM) (U_eff = 93.62 K, τ₀ = 1.19 × 10^-5 s) under a 0 Oe dc field. Ab initio calculations on Dy2 indicated that the high degrees of axiality of the constituent mononuclear Dy fragments are the main reasons for the existence of SMM behavior.

Substitution Effects Regulate the Formation of Butterfly-Shaped Tetranuclear Dy(III) Cluster and Dy-Based Hydrogen-Bonded Helix Frameworks: Structure and Magnetic Properties

The generation of two types of complexes with different topological connections and completely different structural types merely via the substitution effect is extremely rare, especially for -CH₃ and -C₂H₅ substituents with similar physical and chemical properties. Herein, we used 3-methoxysalicylaldehyde, 1,2-cyclohexanediamine, and Dy(NO₃)₃·6H₂O to react under solvothermal conditions (CH₃OH:CH₃CN = 1:1) at 80 °C to obtain the butterfly-shaped tetranuclear Dy^III cluster [Dy₄(L¹)₄(μ₃-O)₂(NO₃)₂] (Dy₄, H₂L¹ = 6,6'-((1E,1'E)-(cyclohexane-1,3-diylbis(azanylylidene))bis(methanylylidene))bis(2-methoxyphenol)). The ligand H₂L¹ was obtained by the Schiff base in situ reaction of 3-methoxysalicylaldehyde and 1,2-cyclohexanediamine. In the Dy₄ structure, (L¹)^2- has two different coordination modes: μ₂-η¹:η²:η¹:η¹ and μ₄-η¹:η²:η¹:η¹:η²:η¹. The four Dy^III ions are in two coordination environments: N₂O₆ (Dy1) and O₉ (Dy2). The magnetic testing of cluster Dy₄ without the addition of an external field revealed that it exhibited a clear frequency-dependent behavior. We changed 3-methoxysalicylaldehyde to 3-ethoxysalicylaldehyde and obtained one case of a hydrogen-bonded helix framework, [DyL²(NO₃)₃]_n·2CH₃CN (Dy-HHFs, H₂L² = 6,6'-((1E,1'E)-(cyclohexane-1,3-diylbis(azanylylidene))bis(methanylylidene))bis(2-ethoxyphenol)), under the same reaction conditions. The ligand H₂L² was formed by the Schiff base in situ reaction of 3-ethoxysalicylaldehyde and 1,2-cyclohexanediamine. All Dy^III ions in the Dy-HHFs structure are in the same coordination environment (O₉). The twisted S-shaped (L²)^2- ligand is linked by a Dy(III) ion to form a spiral chain. The spiral chain is one of the independent units that is interconnected to form Dy-HHFs through three strong hydrogen-bonding interactions. Magnetic studies show that Dy-HHFs exhibits single-ion-magnet behavior (U_eff = 68.59 K and τ₀ = 1.10 × 10^-7 s, 0 Oe DC field; U_eff = 131.5 K and τ₀ = 1.22 × 10^-7 s, 800 Oe DC field). Ab initio calculations were performed to interpret the dynamic magnetic performance of Dy-HHFs, and a satisfactory consistency between theory and experiment exists.

Assembly of Dy60 and Dy30 cage-shaped nanoclusters

Rapid kinetics, complex and diverse reaction intermediates, and difficult screening make the study of assembly mechanisms of high-nuclearity lanthanide clusters challenging. Here, we synthesize a double-cage dysprosium cluster [Dy₆₀(H₂L¹)₂₄(OAc)₇₁(O)₅(OH)₃(H₂O)₂₇]·6H₂O·6CH₃OH·7CH₃CN (Dy₆₀) by using a multidentate chelate-coordinated diacylhydrazone ligand. Two Dy₃₀ cages are included in the Dy₆₀ structure, which are connected via an OAc^- moiety. The core of Dy₆₀ is composed of 8 triangular Dy₃ and 12-fold linear Dy₃ units. We further change the alkali added in the reaction system and successfully obtain a single cage-shaped cluster [Dy₃₀(H₂L¹)₁₂(OAc)₃₆(OH)₄(H₂O)₁₂]·2OH·10H₂O·12CH₃OH·13CH₃CN (Dy₃₀) with a perfect spherical cavity, which could be considered an intermediate in Dy₆₀ formation. Time-dependent, high-resolution electrospray ionization mass spectrometry (HRESI-MS) is used to track the formation of Dy₆₀. A possible self-assembly mechanism is proposed. We track the formation of Dy₃₀ and the six intermediate fragments are screened.