Construction of a Porous Homochiral Coordination Polymer with Two Types of CunInAlternating Units Linked by Quinine: A Solvothermal and a Mechanochemical Approach

An imidazole-copper(I) metallacycle complex exhibiting thermochromic fluorescence

In this paper, we firstly report the synthesis and structural characterization of a discrete coordination metallacycle complex, [CuI (bipy)]2 (1). The x-ray diffraction structure, temperature-dependent electronic absorption, and photoluminescence spectra have been investigated. The solid-state fluorescence at variable temperatures shows that complex 1 exhibits an obvious thermochromic fluorescence. At low temperature, the dual fluorescence with peaks at 590 and 694 nm was observed. The emission color significantly changes from red at 77 K to yellow at 200 K and blue-green at 330 K. The thermochromic fluorescent molecular materials show great potential as temperature sensing.

Chromium(II)-isophthalate 2D MOF with Redox-Tailorable Gas Adsorption Selectivity

Redox-active metal-organic frameworks (MOFs) are very promising materials due to their potential capabilities for postsynthetic modification aimed at tailoring their application properties. However, the research field related to redox-active MOFs is still relatively underdeveloped, which limits their practical application. We investigated the self-assembly process of Cr(II) ions and isophthalate (m-bdc) linkers, which have been previously demonstrated to yield 0D metal-organic polyhedra. However, using the diffusion-controlled synthetic approach, we demonstrate the selective preparation of a 2D-layered Cr(II)-based MOF material [Cr(m-bdc)]·H2O (1·H2O). Remarkably, the controlled oxidation of the developed 2D MOF using nitric oxide or dry oxygen resulted in modified porous materials with excellent H2/N2 adsorption selectivities.

A Case Study on the Desired Selectivity in Solid-State Mechano- and Slow-Chemistry, Melt, and Solution Methodologies

Solution-based syntheses are omnipresent in chemistry but are often associated with obvious disadvantages, and the search for new mild and green synthetic methods continues to be a hot topic. Here, comparative studies in four different reaction media were conducted, that is, the solid-state mechano- and slow-chemistry synthesis, melted phase, and solution protocols, and the impact of the employed solvent-free solid-state versus liquid-phase synthetic approaches was highlighted on a pool of products. A moderately exothermic model reaction system was chosen based on bis(pentafluorophenyl)zinc, (C₆ F₅ )₂ Zn, and 2,2,6,6-tetramethylpiperidinyl oxide (TEMPO) as a stable nitroxyl radical, anticipating that these reagents may offer a unique landscape for addressing kinetic and thermodynamic aspects of wet and solvent-free solid-state processes. In a toluene solution two distinct paramagnetic Lewis acid-base adducts (C₆ F₅ )₂ Zn(η¹ -TEMPO) (1) and (C₆ F₅ )₂ Zn(η¹ -TEMPO)₂ (2) equilibrated, but only 2 was affordable by crystallization. In turn, crystallization from the melt was the only method yielding single crystals of 1. Moreover, the solid-state approaches were stoichiometry sensitive and allowed for the selective synthesis of both adducts by simple stoichiometric control over the substrates. Density functional theory (DFT) calculations were carried out to examine selected structural and thermodynamic features of the adducts 1 and 2. Compound 2 is a unique non-redox active metal complex supported by two nitroxide radicals, and the magnetic studies revealed weak-to-moderate intramolecular antiferromagnetic interactions between the two coordinated TEMPO molecules.

Copper(i)–iodide cluster structures as functional and processable platform materials

This review provides a complete overview of the progress towards implementation of CuI-nanoclusters in functional materials and devices.

Quantitative Thermal Synthesis of Cu(I) Coordination Polymers That Exhibit Thermally Activated Delayed Fluorescence

As a new environmentally friendly route for synthesizing thermally activated delayed-fluorescence (TADF) Cu(I) complexes, we successfully and quantitatively synthesized strongly emissive Cu(I) coordination polymers [Cu₂I₂(PR₃)₂(n,n'-bpy)]_∞ (CuIR-n, R = Ph, Tol; n = 3, 4; bpy = bipyridine) via the quick thermal reaction of three starting materials (CuI, PR₃, and bpy organic ligands) for 1 h in the absence of a solvent. Powder X-ray diffraction and thermogravimetric analyses revealed that melting of the organic ligands significantly promoted the coordination polymerization reaction, and the stoichiometry of three starting materials was crucial to quantitatively affording CuIR-n. Notably, the photophysical properties of CuIR-n obtained by the thermal reaction were almost the same (emission wavelength, quantum yield, and lifetime) as that obtained by generally used solution reactions, probably because CuIR-n was thermally stable enough to prevent the thermal damage and to improve the crystallinity in the heating process. The emission origin of CuIR-n was assignable to TADF at 298 K and phosphorescence at 77 K originating from the metal-to-ligand charge-transfer excited state effectively mixed with the halide-to-ligand charge transfer ((M+X)LCT) state. Thus, the thermal reaction in the melted ligand could be a promising environmentally friendly method for producing TADF Cu(I) luminophores.

Solvent Templating and Structural Dynamics of Fluorinated 2D Cu-Carboxylate MOFs Derived from the Diffusion-Controlled Process

The layered 2D MOFs, owing to their enhanced flexibility and tunability, have recently emerged as a promising alternative to the 3D microporous MOFs in the quest for novel responsive functional materials. However, maintaining the simultaneous control over self-assembly of molecular building blocks as well as ordered stacking of MOF layers poses a significant synthetic challenge. We report on the controlled 2D MOF formation based on a case study of solvent-templated growth of a series of 2D Cu(II)–carboxylate MOFs varying in stacking modes and distances using a diffusion-controlled MOF deposition approach in various solvent mixtures. Moreover, we demonstrate the structural dynamics of the developed 2D MOFs involving both in-plane and out-of-plane movements of the individual 2D layers triggered by solvent exchange, which allowed for selective postsynthetic transformations between the developed 2D MOFs. We also investigated the gas adsorption properties of the developed MOFs, which demonstrates a remarkable crystal size effect on the N₂ adsorption capacity using a model 2D MOF system.

A room temperature diffusion-based approach has been used to prepare a new family of 2D MOFs based on Cu²⁺ paddlewheel clusters and bifunctional fluorinated carboxylate linkers. The stacking distance and geometry of the MOF layers was depending on the solvent mixture used. Remarkably, the developed 2D materials could be postsynthetically transformed into one another by solvent exchange, which was selectively controlled by the type of guest molecules involved.

Constructing multi-cluster copper(i) halides using conformationally flexible ligands

Conformationally flexible ligands were used to trap various Cu(i)-halide clusters in one system to obtain multi-cluster copper(i)-halides with distinctive temperature-dependent luminescence.

Mechanoperovskites for Photovoltaic Applications: Preparation, Characterization, and Device Fabrication

Hybrid organic-inorganic metal halide perovskites (MHPs) have emerged as excellent absorber materials for next generation solar cells owing to their simple solution-processed synthesis and high efficiency. This breakthrough in photovoltaics along with an accompanying impact in light-emitting applications prompted a renaissance of interest in the broad family of MHPs. Notably, the optoelectronic properties and the photovoltaic parameters of MHPs are highly sensitive to the adopted synthetic strategy. The preparation of MHPs has commonly relied on solution-based methods requiring elevated temperatures for homogeneity of reaction mixtures. While the solution-based approach is relatively versatile, it faces challenges such as limitations in compositional engineering of MHPs or their long-term storage among others. Therefore, there is a continuous great challenge to develop efficient synthetic strategies affording various high-quality MHP materials for numerous technological optoelectronic applications. In the past decade, mechanochemistry has appeared as a green alternative to traditional synthesis. This solid-state, re-emerging efficient synthetic methodology mediated by direct absorption of mechanical energy is growing explosively across organic and inorganic chemistry and materials science. In this Account, we describe our shared interest in the productive use of mechanical force in chemistry of MHPs, as well as assembly of the respective solar cell devices. We highlight the milestones achieved by our groups along with the seminal contributions by other groups. In particular, we demonstrate that mechanochemistry efficiently allows the formation of various phase pure hybrid lead and lead-free halide perovskite compositions (called hereafter "mechanoperovskites"). The progress in solvent-free solid-state synthesis is greatly enhanced by the integration of advanced methods of solid-state analysis like powder X-ray diffraction (pXRD), solid-state nuclear magnetic resonance (ss-NMR) and UV-vis spectroscopies, and we aim to illustrate this ongoing integration through appropriate examples. Furthermore, we show that thin films based on mechanoperovskites have the advantage of providing a higher degree of control of the stoichiometry and higher reproducibility, stability, and material phase purity. The impact of using powdered mechanoperovskite as a precursor for thin film formation on the electrochemical and photovoltaic properties of the solar cells is also discussed. Finally, our view of current challenges and future directions in this emerging interdisciplinary area of research is provided.

Chemoselective mechanochemical route toward a bright TADF-emitting CuI-based coordination polymer

We report a simple and effective mechanochemical synthesis of a strongly-emissive TADF-material based on a CuI-coordination polymer that is unobtainable through traditional wet methods.

Mechanochemical routes for the synthesis of acetyl- and bis-(imino)pyridine ligands and organometallics

Organometallic precatalysts play a pivotal role in organic synthesis. However, their preparation often relies on multiple time, energy, and solvent intensive steps, including the synthesis of supporting organic ligand structures, and finally installation on the desired metal centres. We report the sustainable mechanochemical synthesis of acetyl- and bis-(imino)pyridine pincer complexes, a ubiquitous ligand class for organometallic precatalysts. The approach is extended to the one-pot synthesis of acetyl(imino)pyridine-CoCl₂, where the ligand is formed in situ.

Facile Mechanosynthesis of the Archetypal Zn-Based Metal-Organic Frameworks

Mechanochemical methods have been successful in providing rapid access to a number of inorganic-organic functional materials under mild conditions. Recently, we demonstrated a novel mechanochemical strategy for metal-organic framework (MOF) preparation based on predesigned oxo-centered secondary building units. Herein, we develop this method for the facile preparation of the isoreticular MOF (IRMOF) family members based on a combination of an oxozinc amidate cluster, [Zn₄(μ₄-O)(NHOCPh)₆], and selected ditopic aminoterephthalate and 4,4'-biphenyldicarboxylate as well as tritopic 1,3,5-benzenetribenzoate ligands. The resulting IRMOF-3, IRMOF-10, and MOF-177 crystalline materials were characterized using powder X-ray diffraction, IR spectroscopy, scanning electron microscopy (SEM), and thermogravimetric analysis. We found that the character of the organic linker strongly affects the nature of the resulting MOF crystallites after activation processes. The SEM images demonstrate that IRMOF-3 formed microcrystallites in the range of 400-500 nm, while the two other materials exhibited microstructures of amorphous phases. The porosity of each sample was estimated by N₂ sorption measurements at 77 K. These results provide an efficient and general method for the mechanosynthesis of Zn-based MOF materials using a predesigned oxozinc cluster.

Double helix quinine-based supergelator

10,11-Didehydroquinine is a simple, low molecular weight supergelator which forms, in nonpolar media, stable chiral organogels composed of unique double-helix nano-sized fibers. A novel gelation mechanism involves a hydrogen bonding network formed by an acidic alkyne proton of the Cinchona gelator and the carbonyl group of ethyl acetate used as a solvent.

A mechanochemical strategy for IRMOF assembly based on pre-designed oxo-zinc precursors

We demonstrate a mechanochemical strategy that allowed the first successful mechanosynthesis of IRMOFs based on an oxo-centred secondary building unit (SBU). The presented study indicates that controlling the acid-base relationship between reagents is key to mechanochemical synthesis of IRMOFs, revealing a pre-assembled oxo-zinc amidate cluster as an efficient precursor for IRMOF mechanosynthesis.

An organic-ligand-free thermochromic luminescent cuprous iodide trinuclear cluster: evidence for cluster centered emission and configuration distortion with temperature

An organic-ligand-free cuprous iodide trinuclear cluster with significant temperature-dependent structural distortion shows thermochromic luminescence originating from a single cluster-centered triplet.