Maochun Hong

Lanthanide–transition metal coordination polymers based on multiple N- and O-donor ligands

Lanthanide-transition metal (Ln-M) coordination polymers have attracted extensive interest because they exhibit novel physical properties originating from the interactions between distinct metal ions. This review mainly describes our recent work in the design of Ln-M coordination polymers through the assembly of different metal ions and organic ligands, especially the ligands with multiple N- and O-donor atoms. Many of these crystalline Ln-M materials exhibit intriguing structural motifs and interesting magnetic properties.

Copper-catalyzed direct alkynylation of electron-deficient polyfluoroarenes with terminal alkynes using O2 as an oxidant.

A copper-catalyzed direct alkynylation of electron-deficient polyfluoroarenes with a wide range of terminal alkynes is realized for the first time. The reaction proceeds under mild conditions with O(2) as an oxidant.

Beryllium-free Li4Sr(BO3)(2) for deep-ultraviolet nonlinear optical applications

Nonlinear optical (NLO) materials are of great importance in laser science and technology, as they can expand the wavelength range provided by common laser sources. Few NLO materials, except KBe2BO3F2 (KBBF), can practically generate deep-ultraviolet coherent light by direct second-harmonic generation process, limited by the fundamental requirements on the structure-directing optical properties. However, KBBF suffers a strong layering tendency and high toxicity of the containing beryllium, which hinder the commercial availability of KBBF. Here we report a new beryllium-free borate, Li4Sr(BO3)2, which preserves the structural merits of KBBF, resulting in the desirable optical properties. Furthermore, Li4Sr(BO3)2 mitigates the layering tendency greatly and enhances the efficiency of second-harmonic generation by more than half that of KBBF. These results suggest that Li4Sr(BO3)2 is an attractive candidate for the next generation of deep-ultraviolet NLO materials. This beryllium-free borate represents a new research direction in the development of deep-ultraviolet NLO materials.

A new type of three-dimensional framework constructed from dodecanuclear cadmium(ii) macrocyclesElectronic supplementary information (ESI) available: Synthesis of 1 Figures S1‒S4. See http://www.rsc.org/suppdata/cc/b2/b212425d/This work was supported by the National Nature Science Foundation of China, Nature Science Foundation of Fujian Province and the Key Project of Chinese Academy of Science.

A new type of three-dimensional framework based on dodecanuclear Cd(II) macrocycles [[Cd2(dpa)(pya)]6(pya)6(dpe)3]n (1) (H2dpa = diphenic acid; Hpya = isonicotinic acid, dpe = 1,2-di(4-pyridyl)ethylene) was prepared by the hydrothermal reaction and in situ synthesis of pya from dpe precursor.

Pd(O2CCF3)2/Benzoquinone: A Versatile Catalyst System for the Decarboxylative Olefination of Arene Carboxylic Acids

A versatile palladium catalyst system was developed to effect the decarboxylative Heck coupling of a variety of arenecarboxylic acids with a wide range of olefins. The key to obtaining the efficient catalyst system is the use of 1-adamatanecarboxylic acid as additive. Alkyl-substituted olefins with coordinating groups were observed to provide significantly improved regioselectivity compared with other alkyl-substituted olefins lacking coordinating groups, and the acetate group of allylic ester was also tolerated in this reaction.

Controllable Coordination-Driven Self-Assembly: From Discrete Metallocages to Infinite Cage-Based Frameworks

CONSPECTUS: Nanosized supramolecular metallocages have a unique self-assembly process that allows chemists to both understand and control it. In addition, well-defined cavities of such supramolecular aggregates have various attractive applications including storage, separation, catalysis, recognition, drug delivery, and many others. Coordination-driven self-assembly of nanosized supramolecular metallocages is a powerful methodology to construct supramolecular metallocages with considerable size and desirable shapes. In this Account, we summarize our recent research on controllable coordination-driven assembly of supramolecular metallocages and infinite cage-based frameworks. To this end, we have chosen flexible ligands that can adopt various conformations and metal ions with suitable coordination sites for the rational design and assembly of metal-organic supramolecular ensembles. This has resulted in various types of metallocages including M3L2, M6L8, M6L4, and M12L8 with different sizes and shapes. Because the kinds of metal geometries are limited, we have found that we can replace single metal ions with metal clusters to alternatively increase molecular diversity and complexity. There are two clear-cut merits of this strategy. First, metal clusters are much bigger than single metal ions, which helps in the construction and stabilization of large metallocages, especially nanosized cages. Second, metal clusters can generate diverse assembly modes that chemists could not synthesize with single metal ions. This allows us to obtain a series of unprecedented supramolecular metallocages. The large cavities and potential unsaturated coordination sites of these discrete supramolecular cages offer opportunities to construct infinite cage-based frameworks. This in turn can offer us a new avenue to understand self-assembly and realize certain various functionalities. We introduce two types of infinite cage-based frameworks here: cage-based coordination polymers and cage-based polycatenanes, which we can construct through coordination bonds and mechanical bonds, respectively. Through either directly linking the unsaturated coordination sites of metallocages or replacing the labile terminal ligands with bridging ligands, we can produce infinite cage-based frameworks based on coordination bonds. We introduce several interesting cage-based coordination polymers, including a single-crystal-to-single-crystal transformation from a M6L8 cage to an infinite cage-based chain. Compared with discrete metallocages, these kinds of materials can give us higher structural stability and complexity, favoring the applications of metallocages. In addition, we discuss how we can use mechanical bonds, such as interlocking and interpenetrating, to construct extended cage-based frameworks. So far, study in this field has focused on polycatenanes constructed from M6L4 and M12L8 cages, as well as a controllable and dynamic self-assembly based on M6L4 metallocages. We also discuss cage-based polycatenanes, which can give dynamic properties to discrete metallocages. We hope that our investigations will bring new insights to the world of the supramolecular metallocages by enlarging its breadth and encourage us to devote more effort to this blossoming field in the future.

Cobalt–Lanthanide Coordination Polymers Constructed with Metalloligands: A Ferromagnetic Coupled Quasi‐1D Dy3+ Chain Showing Slow Relaxation

Four types of cobalt-lanthanide heterometallic compounds based on metalloligand Co(2,5-pydc)(3) (3-) (2,5-H(2)pydc=pyridine-2,5-dicarboxylate acid), [Ln(2)Co(2)(2,5-pydc)(6)(H(2)O)(4)](n) 2n H(2)O (1) (Ln=Tb, Dy for 1 a, 1 b respectively), [Tb(2)Co(2)(2,5-pydc)(6)(H(2)O)(4)](n)3n H(2)O (2), [Tb(2)Co(2)(2,5-pydc)(6)(H(2)O)(9)](n)4n H(2)O (3), and [LaCo(2,5-pydc)(3)(H(2)O)(2)](n)2n H(2)O (4) have been synthesized. Compound 1 has a layer structure with well-isolated carboxylate-bridged Ln(3+) chains, compound 2 is a three-dimensional (3D) porous network with Tb(3+) chains that are also well isolated and carboxylate bridged, 3 is a layer structure based on dinuclear units, and 4 is a 3D network with boron nitride (BN) topology. DC magnetic studies reveal ferromagnetic coupling in all the carboxylate-bridged Ln(3+) chains in 1 a, 1 b, and 2. Compared to the silence of the out-of-phase ac susceptibility of 2, above 1.9 K the magnetic relaxation behavior of both 1 a and 1 b is slow like that of a single-chain magnet.

Solvothermal syntheses and crystal structures of two metal coordination polymers with double-chain structures

Two polymeric complexes, [Cu2(btec)(phen)2]n·(H2O)n (1) and [Cd4(btec)2(phen)4(H2O)4]n (2 )( H 4btec = 1,2,4,5-benzenetetracarboxylic acid; phen =1,10-phenanthroline), were synthesized by solvothermal reactions at 140 °C. Both complex 1 and 2 possess infinite double-chain structures, in which each Cu(II) center has a tetrahedral configuration and the Cd(II) centers adopt triangular prismatic and square-based pyramidal configurations simultaneously. The inter-chain face to face – interactions among the aromatic rings of phen and the hydrogen bond interactions between aqua molecules and carboxyl O atoms result in 3-D networks in the two complexes. The ESR spectra study of complex 1 shows that there is negligibly small long-range super-exchange interactions between the Cu(II) atoms via benzenecarboxylate bridging.

A multi-metal-cluster MOF with Cu4I4 and Cu6S6 as functional groups exhibiting dual emission with both thermochromic and near-IR character

Two classical metal clusters, CuI4I4 and CuI6S6, are introduced as functional connecting nodes to construct a novel multi-metal-cluster MOF [(CuI4I4)3(CuI6)2(3-ptt)12]n·24nDEF·12nH2O (1) that incorporate their inherent luminescent properties, induced by their respective metal–metal interactions. These two distinct clusters are combined together for the first time to perform as functional luminophores that display unusual dual emission with both thermochromic luminescence and near-infrared (NIR) character.

Pd-Catalyzed Dearboxylative Heck Coupling with Dioxygen as the Terminal Oxidant

A Pd-catalyzed desulfitative Heck-type reaction of aromatic sulfinic acid sodium salts with various olefins is developed with O(2) as the terminal oxidant under mild conditions. The presence of phosphane ligand DPEphos in anisole can significantly enhance the reaction selectivity.