Discrete Coordination Compound Research Articles

Synthesis, characterization, and density functional theory investigation of (CH6N3)2[NpO2Cl3] and Rb[NpO2Cl2(H2O)] chain structures.

The actinyl tetrachloro complex [An(V/VI)O2Cl4]2-/3- tends to form discrete molecular units in both solution and solid state materials, but related aquachloro complexes have been observed as both discrete coordination compounds and 1-D chain topologies. Subtle differences in the inner sphere coordination significantly influence the formation of structural topologies in the actinyl chloride system, but the exact reasoning for these variations has not been delineated. In the current study, we present the synthesis, structural characterization, and vibrational analysis of two 1-D neptunyl(V) chain compounds: (CH6N3)2[NpO2Cl3] (Np-Gua) and Rb[NpO2Cl2(H2O)] (Np-Rb). Bonding and non-covalent interactions (NCIs) in the systems were evaluated using periodic Density Functional Theory (DFT) to link these properties to related phases. We observed ∼6.5% and ∼3.9% weakening of NpO bonds in Np-Gua and Np-Rb compared to the reference Cs3[NpO2Cl4]. NCI analysis distinguished specific assembly modes, where Np-Gua was connected via hydrogen bonding (N-H⋯Cleq and N-H⋯Oyl) and Np-Rb contained both cation interactions (Rb+⋯Oyl and Rb+⋯Cleq) and hydrogen bonding (Oeq-H⋯Oyl) networks. Thermodynamically viable formation pathways for both compounds were explored using DFT methodology. The [NpO2Cl4](aq)3- and [NpO2Cl3(H2O)](aq)2- substructures were identified as precursors to Np-Gua and [NpO2Cl3(H2O)](aq)2- and [NpO2Cl2(H2O)2](aq)- were isolated as the primary building units of Np-Rb. Finally, we utilized DFT to analyze the vibrational modes for Np-Gua and Np-Rb, where we found evidence of the NpO bond weakening within the Np(V) chain structures compared to [NpO2Cl4]3-.

The role of anion in supramolecular aggregation and energetic properties in a series of Cd picolinamide complexes

A novel group of energetic compounds, known as energetic coordination polymers (ECPs), can be rationally designed by introducing of highly energetic ions like ClO4-, N3–, NO3– and NO2– into a polymeric framework. Herein we report the preparation of four novel cadmium(II) complexes with picolinamide (pia) as ligand and different ions: [Cd(pia)3](ClO4)2·2H2O (1), [Cd(NO3)(ac)(pia)2] (2), [Cd(NO2)2(pia)2] (3), [Cd2(μ1,1-N3)4(pia)2]n [Cd(μ1,1-N3)2(pia)]n (4). The presence of different anions from starting Cd(II) salts caused the formation of discrete coordination compounds(1, 2 and 3), and coordination polymer (4). In 2, 3 and 4 anions are coordinated to Cd(II), while in 1 perchlorate anions act as a counterion. The molecular and crystal structure analysis has shown that in all compounds pia acts as N,O-chelator in various coordination arrangements depending on the present anion (1, 2 and 4 - distorted octahedral, 3- distorted square antiprismatic). In the crystal structures, the dominant mode of intermolecular interaction is a strong head−to−head amide hydrogen bond, with exception of 1. Structural analysis of herein-reported compounds and previously described Cd(pia)A (A – anion) compounds has shown that bulky tetrahedral anions (ClO4- and SO42-) inhibit the formation of the strong head−to−head amide hydrogen bonds. The investigations of energetic properties and sensitivity indicate a possible application of compound 4 as a secondary explosive material with energetic properties like those of LA (lead azide), mercury fulminate, or ammonium nitrate.

Lithium-, Sodium-, and Potassium-ion Conduction in Polymeric and Discrete Coordination Systems

Abstract Coordination compounds have been increasingly studied as a new class of promising candidates for the matrix of ionic conducting materials because of their designability and high crystallinity. The ionic conduction of light alkali metal ions (Li+ and Na+) has been developed in polymeric coordination systems, which are commonly used under nonaqueous conditions. Recent studies have shown that discrete coordination compounds, as well as hydrated polymeric coordination compounds, can function as excellent ionic conductors even for heavier K+.

Coordination compounds in lithium storage and lithium-ion transport.

Lithium-ion batteries (LIBs) have enabled wireless revolution of portable digital products. However, for high-performance applications such as large-scale energy storage and next-generation portable devices, the energy and power densities as well as the cycle life of LIBs still need to be further enhanced. This can be realized by improving the electrochemical performance of the three main components of LIBs: cathode, anode, and electrolyte. In addition to LIBs, lithium-metal batteries (LMBs) have also attracted considerable attention owing to their ultra-high energy density arising from the lithium-metal anode. However, LMB performance is currently limited by dendrite formation and poor interfacial contact between electrode and electrolyte. Herein we highlight the applications of coordination chemistry in LIBs and LMBs, especially for realization of promising next-generation electrode and electrolyte materials based on coordination compounds with well-defined molecular structures. We start by introducing the development of coordination chemistry from discrete coordination compounds to coordination polymers and metal-organic frameworks. Then, we present the design strategies of coordination compounds for lithium storage and lithium-ion transport. Approaches to enhance the electrochemical properties, working potential, capacity, cycling stability, and rate capability of coordination compound-based electrodes are discussed in detail. The reticular chemistry endowing metal-organic frameworks with desired structures and pore metrics as electrolytes for lithium-ion transmission is also summarized. Finally, the current challenges and promising research directions of coordination chemistry for LIBs and LMBs are presented.

A novel self-assembled Na{Cu12Zn4} multifunctional material: first report of a discrete coordination compound for detection of Ca2+ ions and selective adsorption of cationic dyes in water.

A novel metal directed discrete self-assembled compound, Na2O[Cu12Zn4(μ-OH)8(H4btp)8](ClO4)8·26H2O (1), was synthesized employing a flexible aminoalcohol ligand, 2,2'-(propane-1,3-diyldiimino)bis-[2-(hydroxylmethyl)propane-1,3-diol] (H6btp), and mixed metal ions (CuII and ZnII) in order to explore it as a multifunctional material. The molecular cluster is characterized by spectral and analytical techniques, single crystal X-ray diffraction and magnetic studies. Crystallography reveals the presence of eight peripheral CuII centers in octahedral environments, while four interior CuII and ZnII centers are present in tetrahedral systems. The ligand is coordinated in the dianionic form (H4btp2-) with copper and zinc metal ions through various bridging modes. Magnetic data suggest the presence of strong antiferromagnetic coupling between the twelve Cu(ii) centers (C = 4.31 cm3 K mol-1 and θ = -120.44 K). Interestingly, the eight ligands present in the system have eight free hydroxyl groups at the periphery of the cluster, which could be employed in molecular recognition for the analytes under investigation. One of the sodium cations of the lattice sodium oxide [Na2O or Na+(Na+O2-)] is encapsulated in the {Cu12Zn4} cavity and held through electrostatic interactions with the oxygen atoms, forming a Na{Cu12Zn4} core. Taking advantage of this entrapped cation, we have used the present assembly in the sensing of various s-block cations. Interestingly, the cluster shows a sensitive and selective sensing ability towards Ca2+ ions through cation exchange. The selectivity towards Ca2+ can be rationalized in terms of the identical size of the sodium and calcium ions and the HSAB principle. Hard sodium is exchanged with the hard Ca2+ ion, which effectively interacts with the hard oxygen donor, giving rise to a stable hard-hard interaction. Moreover the Na{Cu12Zn4} cluster shows excellent selectivity towards the adsorption of cationic dyes, specifically methylene blue (MB), via non-covalent interactions. An abundance of free O-H groups in the cluster gives rise to the existence of O-Hπ interactions with the dye for enhanced adsorption. Thus, the present report is the first example of any heterometallic coordination compound (in contrast to complex systems like polymeric frameworks/nanocomposites) with discriminating sensing of Ca2+ ions with ultra-low detection limit (4 nM) and with high efficiency in the selective adsorption and separation of methylene blue.

A novel nano-structured three-dimensional supramolecular metal-organic framework for cadmium (II): A new precursor for producing nano cadmium oxide

Abstract A novel sonochemical method was utilized for synthesizing the nano-rods of cadmium coordination systems {{Cd(L1)2(NO3)2(H2O)2}n, (A)} (L=(2-hydroxybenzylidene) isonicotinohydrazide). Thermogravimetric analysis (TGA), elemental analysis and X-ray powder diffraction (XRD) as well as scanning electron microscopy (SEM) were applied to characterize this new nanostructure. The X-ray structure of a single-crystal type suggests that (A) is a discrete coordination compound, which is self-assembled by a weak directional intermolecular interaction into a three-dimensional supramolecular structure. The Cd(II) ions coordination number equals six (CdO4N2). Oleic acid used as the surfactant for the thermolysis of (A) at 180 °C yielded cadmium oxide nanoparticles. In addition, SEM was used to observe the size and morphology of the Cadmium oxide samples obtained.

Enhancing the Lithium Storage Capacities of Coordination Compounds for Advanced Lithium-Ion Battery Anodes via a Coordination Chemistry Approach.

The influence of the water molecule on both the structural dimensionality and the lithium storage capacities of four coordination compounds was studied. Increasing the reaction temperature to remove the terminal water ligand of discrete coordination compounds [M(HNA)2(H2O)4] (H2NA = 5-hydroxynicotinic acid, M = Co for 1 and Ni for 2) led to forming three-dimensional (3D) coordination polymers [M(NA)] n (M = Co for 3 and Ni for 4). When 1-4 were investigated as active anode materials for lithium storage at 100 mA g-1, the relatively low capacities of 455 and 411 mA h g-1 were obtained after 60 cycles with discrete 1 and 2, while that of 3 and 4 showed high capacities of 618 and 610 mA h g-1 after 100 cycles. Detailed mechanism studies by powder X-ray diffraction, X-ray photoelectron spectroscopy, and scanning electron microscopy showed that the structural dimensionality change induced by water molecules can greatly contribute the cyclability and rate performance for coordination compounds as anode material for lithium storage.

Recent Advances of Single-Crystal to Single-Crystal Transformation for Discrete Coordination Compounds

In this short review we highlight the diversity of single-crystal to single-crystal transformations that has been discovered in the last few years in the field of coordination cluster chemistry. In particular, we focus on phase transformations which involve a chemical change such as bond formation, oxidation–reduction, electron-transfer, and ligand exchange, which will, for example, cause spin-crossover or switch non-linear optical activity. We first deal with crystals without guests followed by those losing guest or exchange ligands during the transformations and discuss how guests are involved before focusing on the rare occurrence of chemical reactions that take place on molecular components within crystalline solids without destroying the long-range crystalline state. Finally, a perspective following these advances made in the field is developed.

Coordination behavior of 1-(3,2′:6′,3″-terpyridin-4′-yl)ferrocene: Structure and magnetic and electrochemical properties of a tetracopper dimetallomacrocycle

The discrete coordination compound [Cu4Cl8(3)4(MeOH)2] is obtained from the reaction of a chloroform solution of 1-(3,2′:6′,3″-terpyridin-4′-yl)ferrocene (3) with a methanol solution of CuCl2; the single crystal structure of [{Cu4Cl8(3)4(MeOH)2}·0.7CHCl3·1.8MeOH] is described. Two {Cu2Cl4(3)2(MeOH)} units are connected by bridging chlorido ligands to generate a centrosymmetric tetranuclear molecule featuring face-to-face π-interactions between ferrocene units and between tpy domains. Intermolecular π-stacking of ferrocene and tpy units lead to quadruple-decker stacking motifs in the solid-state. The tetranuclear compound represents a pair of μ-Cl bridged Cu(II) dimers exhibiting a weak antiferromagnetic coupling via the bridging chlorido ligands. The redox behavior of 3 has been investigated by cyclic voltammetry and spectroelectrochemistry; a ferrocenyl oxidation process is observed for [Cu4Cl8(3)4(MeOH)2].

Development of hybrid diblock copolypeptide amphiphile/magnetic metal complexes and their spin crossover with lower-critical-solution-temperature(LCST)-type transition

Diblock copolypeptide amphiphiles have been attracting much interest as motifs for self-assembly in the production of nanostructures such as nanoparticles, nanosheets, and nanofibers. In this study, we first focus on the self-assembly of magnetic metal complexes in water using diblock copolypeptides. In addition, not only were nanocomposites formed, but also observed were the development of lower critical solution temperature (LCST) and LCST-induced spin crossover phenomenon, which are discussed. Three composites composed of the iron complex [FeII(ppi)2(NCS)2] (ppi = N-phenyl-2-pyridinalimine) and the diblock copolypeptide amphiphiles 1 and 2 or the polypeptide 3 (containing glutamic acid and leucine) were prepared. Supramolecular structures such as sheets and rectangular morphologies were obtained from composites. A perfectly reversible spin crossover with LCST was successfully generated in the case of composites made with 1. The technique of combining polypeptide molecules and discrete coordination compounds thus makes it possible to design flexible, reversible, and spin-controllable metastable systems.

Synthesis, structural characterization, thermal analysis, and DFT calculation of a novel zinc (II)-trifluoro-β-diketonate 3D supramolecular nano organic-inorganic compound with 1,3,5-triazine derivative

A sonochemical method was used to synthesize a novel nano-structure of a zinc(II) organic-inorganic compound [Zn(dapt)2(ttfa)2] (1) [dapt = 2,4-diamino-6-phenyl-1,3,5-triazine and ttfa = 2-thenoyltrifluoroacetonate]. The new nanostructure was characterized by scanning electron microscopy, X-ray powder diffraction, elemental analysis, and thermal analysis. The single-crystal X-ray structure shows that 1 is a discrete coordination compound. Strong intra- and intermolecular hydrogen bonds are observed in the structure with the latter forming chains of molecules running parallel to (110). The chains are further extended into a three-dimensional supramolecular structure by intermolecular CF⋯π interactions between trifluoromethyl and triazine moieties. The coordination number of the zinc(II) ion is six (ZnN2O4), and the coordination sphere is tetragonally elongated octahedral. The structure of the title complex was optimized by DFT calculations.

Thermolysis Synthesis of Pure Phase Nano-Sized Cobalt(II) Oxide from Novel Cobalt(II)-Pyrazole Discrete Nano Coordination Compound

Nano-structures of a new discrete coordination compound of divalent cobalt with the pyrazol (pzH) containing the terminal isothiocyanate anions, [Co(pzH)2(NCS)2] (1), with discrete molecular architecture in solid state was synthesized by a sonochemical method. The new nanostructure was characterized by scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, X-ray powder diffraction, IR, and elemental analysis. The supramolecular features in these complexes are guided and controlled by weak directional intermolecular interactions. The discrete molecules interact with each other through labile interactions creating a 3D supramolecular framework. The CoO nanoparticles were obtained by thermolysis of 1 at 180 °C with oleic acid as a surfactant.

Further Insights into the Role of Temperature in the Synthesis of the Lanthanide(III)‐Pyrazine‐Octacyanotungstate(V) System: an Example of Discrete Materials

AbstractSlow diffusion reactions of Ln3+ (Ln = Ce, Eu, Tb) ions, pyrazine, and the [W(CN)8]3– unit at 0 °C produced three discrete coordination compounds [Ln(H2O)5(CH3CN)2][W(CN)8]·0.5pyrazine·CH3CN·2H2O [Ln = Ce (1), Eu (2)] and [Tb(H2O)6(CH3CN)2][W(CN)8]·pyrazine·2CH3CN·3H2O (3). Single crystal X‐ray diffraction analysis revealed that compounds 1 and 2 are isomorphous and adopt a rare centrosymmetric tetranuclear square unit, while compound 3 exhibits an ion‐pair moiety, in which unique tetramer water clusters (H2O)4 are involved. The presence of different types of hydrogen‐bonding interactions is responsible for the formation of three‐dimensional supramolecular networks. The isolations of compounds 1–3 provide a further insight into the effect of temperatures on constructions and structures of the lanthanide(III)‐pyrazine‐octacyanotungstate(V) system.

Self-assembly of discrete metal complexes in aqueous solution via block copolypeptide amphiphiles.

The integration of discrete metal complexes has been attracting significant interest due to the potential of these materials for soft metal-metal interactions and supramolecular assembly. Additionally, block copolypeptide amphiphiles have been investigated concerning their capacity for self-assembly into structures such as nanoparticles, nanosheets and nanofibers. In this study, we combined these two concepts by investigating the self-assembly of discrete metal complexes in aqueous solution using block copolypeptides. Normally, discrete metal complexes such as [Au(CN)2]−, when molecularly dispersed in water, cannot interact with one another. Our results demonstrated, however, that the addition of block copolypeptide amphiphiles such as K183L19 to [Au(CN)2]− solutions induced one-dimensional integration of the discrete metal complex, resulting in photoluminescence originating from multinuclear complexes with metal-metal interactions. Transmission electron microscopy (TEM) showed a fibrous nanostructure with lengths and widths of approximately 100 and 20 nm, respectively, which grew to form advanced nanoarchitectures, including those resembling the weave patterns of Waraji (traditional Japanese straw sandals). This concept of combining block copolypeptide amphiphiles with discrete coordination compounds allows the design of flexible and functional supramolecular coordination systems in water.

Effect of ionic radius on the assemblies of first row transition metal–5-tert-butylisophthalates–(2,2′-bipyridine or phenanthroline) coordination compounds

18 coordination compounds of Mn2+, Fe2+, Co2+, Ni2+, Cu2+ and Zn2+, with mixed organic ligands 5-tert-butylisophthalic acid, 2,2′-bipyridine or phenanthroline, have been hydrothermally synthesized and characterized. Structure analysis shows that the ionic radius of a metal ion determines the form of the metal centre and the structure of the product. Large metal ions tend to have higher coordination numbers, connect to more bridging ligands and form multinuclear metal centres. On the contrary, small metal ions tend to connect to fewer bridging ligands, and act as mononuclear metal centres for discrete coordination compounds or low dimensional coordination polymers. The influences of other factors such as molar ratio of reactants, pH and temperature, have also been discussed. The magnetic properties of the temperature dependent cobalt compounds have been investigated.

Cis-2,2′-Bipyrimidine-Bridged Polynuclear Complex: A Stairway-like Mixed-Valent {Fe4} Cluster

We report the first example of a polynuclear discrete coordination compound exhibiting only bpym bridges and containing a first-row d transition metal. A smooth self-assembly one-pot synthetic route, starting from simply FeCl(2) and FeCl(3) hydrates, allowed us to prepare a tetranuclear Fe(4) cluster with a stairway-like structure and the formula cis-{[(H(2)O)Cl(3)Fe(III)-μ(bpym)Fe(II)Cl(2)]}(2)-μ(bpym) (1) . All spectroscopic data suggest that complex 1 is a valence-localized mixed-valent Fe(II)-Fe(III) cluster with typical Mössbauer lines for both sites, which do not change with temperature. Reflectance spectroscopy did not allow one to distinguish an intervalence charge-transfer band. However, time-dependent density functional theory (DFT) calculations predict a weak high-energy Fe(II) → Fe(III) transition. Regarding the magnetic properties, the high-spin Fe(II) and Fe(III) ions interact in a weakly antiferromagnetic way with isotropic J constants of only a few wavenumbers as derived from direct-current susceptibility and magnetization data. Broken-symmetry DFT calculations support these observations.

General principles of biochemistry of the elements

Discrete coordination compounds and coordination polymers are topical research fields in inorganic chemistry, crystal engineering, solid-state chemistry, and materials science, due to their potential applications in adsorption, separation, catalysis, electrical, magnetic, and optical applications. Beginning with the basic concepts of coordination compounds and coordination polymers, this chapter briefly describes the synthetic methods and rational synthesis of coordination compounds, and the frequently used strategies for the molecular design, the important factors (such temperature, pH, template, additive, solvent, and counter-ion) that have influences on the self-assembly and crystallization, as well as solvothermal/hydrothermal in situ metal/ligand reactions for coordination compounds and coordination polymers, as well as postsynthetic modifications for porous coordination polymers, through selected examples in the literature.