Structural characterization of a new samarium–sodium heterometallic coordination polymer

Post-synthetic modification of metal-organic frameworks (MOFs) facilitates a strategic transformation of potentially inert frameworks into functionalized materials, tailoring them for specific applications. In particular, the post-synthetic incorporation of transition-metal complexes within MOFs, a process known as 'metalation', is a particularly promising avenue towards functionalizing MOFs. Herein, we describe the post-synthetic metalation of a microporous MOF with various transition-metal nitrates. The parent framework, 1: , contains free-nitrogen donor chelation sites, which readily coordinate metal complexes in a single-crystal to single-crystal transformation which, remarkably, can be readily monitored by X-ray crystallography. The presence of an open void surrounding the chelation site in 1: prompted us to investigate the effect of the MOF pore environment on included metal complexes, particularly examining whether void space would induce changes in the coordination sphere of chelated complexes reminiscent of those found in the solution state. To test this hypothesis, we systematically metalated 1: with first-row transition-metal nitrates and elucidated the coordination environment of the respective transition-metal complexes using X-ray crystallography. Comparison of the coordination sphere parameters of coordinated transition-metal complexes in 1: against equivalent solid- and solution-state species suggests that the void space in 1: does not markedly influence the coordination sphere of chelated species but we show notably different post-synthetic metalation outcomes when different solvents are used.This article is part of the themed issue 'Coordination polymers and metal-organic frameworks: materials by design'.

Burning of fossil fuels in this and the last century lead to global warming and the climate crisis. It is utmost important to prevent further global warming and reverse the increases of the past few decades. A reasonable approach is to replace fossil fuel burning power plants with renewable energy producing technologies. The most promising renewable energy source is the sun. The sun delivers 23 000 TW of sun-light energy every year to the earth, which is a ~1000 times more than the energy consumption of the earth. One technology to harvest sun light energy and produce electricity is the solar cell. Different solar cell technologies exist, and the approach presented in this thesis is concerning dye-sensitized solar cells. Dye-sensitized solar cells (DSSCs) have the advantage of a relatively easy fabrication and the incorporation of cheap light harvesting materials is possible. In DSSCs a metal oxide (TiO2) semiconductor is sensitized with an organic or inorganic dye, enabling photon absorption and electron injection into the semiconductor, which generates electric current. The dyes presented in this thesis are based on the relatively cheap and abundant metal copper. Copper in its +1 oxidation state can form heteroleptic complexes with two bisdiimine ligands. One of these ligands (the anchoring ligand) bears anchoring groups, that allow attachment of the complex on TiO2. The emergence of new anchoring ligands for heteroleptic bisdiimine copper(I) dyes was the aim of my PhD studies and the results are presented in this thesis. In four chapters a systematic investigation of bisdiimine ligands as anchors and capping ligand is described. Various spacers and anchoring groups were incorporated into the anchoring ligand and the performance of these compounds was investigated in solar cell devices. In the last chapter of the main part the synthesis of compound with potential application in p-type DSSCs is presented. ------------------------------------------------------------ The careful choice of building blocks, the consideration of their geometry, topology and their influence on the crystal packing interactions enables control of the self-assembly processes in coordination polymer synthesis. When these aspects are well understood the specific construction of various multidimensional motifs, by self-assembly of building blocks can be achieved. The building blocks are often easily accessible in the form of metal salts and organic ligands, that often require few synthetic steps to synthesize. Screening of building blocks for the creation of multidimensional motifs on the nano to micro scale is an important research field. The building blocks self-assemble and form these structures without further influence of the scientist. With the right selection of building blocks and by careful consideration of conditions, like temperature and concentration it is possible to predefine the outcome of the self-assembly process. Organic ligands based on 4,2':6',4''- and 3,2':6',3''-terpyridine were synthesized and the control of the self-assembly process of these linkers with various metal centres was investigated. Rigid ditopic 4,2':6',4''-terpyridines proved to be the most reliable ligand in this respect. In combination with linear two-connecting metal centres, 1D zig-zag chains were the dominant motif. With metal centres, like Co(II) (and to some extent Cd(II)), that have a connectivity of four, the dominant motif was the formation of 2D (4,4) nets. Tetratopic bis(4,2':6',4''-terpyridines) and bis(3,2':6',3''-terpyridines) were used to assemble 2D networks, 3D frameworks and MOFs. 3D frameworks are known for their potential applications in gas-sorption, guest exchange, drug-delivery etc. Their formation was not predictable, but the change from ditopic linkers to tetratopic linkers increased the probability to obtain these 3D motifs. A 2-fold interpenetrating MOF with ~65% void space, relative to the total volume, was obtained with a tetratopic bis(4,2':6',4''-terpyridine) ligand in combination with ZnBr2, which highlights the great potential of this ligand class. A collection of ~30 multidimensional structures is presented in this thesis and should give an indication how one might be able to control self-assembly processes in coordination polymers with 4,2':6',4''- and 3,2':6',3''-terpyridines as linkers.

Nanoparticles (NP) with optical properties embedded silica particles have been widely used in various fields because of their unique properties. The surfaces of optical NPs have been modified with various organic ligands to maintain their unique optical properties and colloidal stability. Among the surface modification methods, silica encapsulation of optical NPs is widely used to enhance their biocompatibility and stability. However, in the case of NPs with hydrophobic ligands on the surface, the ligands that determine the optical properties of the NPs may detach from the NPs, thereby changing the optical properties during silica encapsulation. Herein, we report a generally applicable silica encapsulation method using trimethoxy(2-phenylethyl)silane (TMPS) for non-hydrophilic optical NPs, such as quantum dots (QDs) and gold NPs. This silica encapsulation method was applied to fabricate multiple silica-encapsulated QD-embedded silica NPs (SiO2@QD@SiO2 NPs; QD2) and multiple silica-encapsulated gold NP-embedded silica NPs labeled with 2-naphthalene thiol (SiO2@Au2-NT@SiO2). The fabricated silica-encapsulated NPs exhibited optical properties without significant changes in the quantum yield or Raman signal intensity.

Xylitol pentanitrate (XPN) is a little‐studied nitrate ester of similar molecular structure to the military energetic materials pentaerythritol tetranitrate (PETN) and nitroglycerin (NG). XPN was crystallised from a mixture of ethanol and water by slow evaporation and studied by single crystal X‐ray diffraction. XPN crystallises in the centrosymmetric monoclinic space group P21/n, with a calculated density of 1.852 g cm−3. Sensitiveness analysis of the energetic material revealed it to be a primary explosive, significantly more sensitive than PETN to friction and impact. The calculated heat of formation of XPN, −500.48 kJ mol−1, and the density were exploited utilising the Cheetah 7.0 suite of programs to predict explosive performance parameters. The theoretical explosive performance of XPN was comparable to the calculated explosive parameters of erythritol tetranitrate (ETN), PETN and cyclotrimethylene trinitramine (RDX).

By using a new flexible tetracarboxylic acid, bis(3,5-dicarboxyphenyl) adipoamide, H4L1, and its isomer, bis(2,5-dicarboxyphenyl)adipoamide, H4L2, three Mg(II) coordination polymers, {[Mg2(L1)(H2O)2]·2EtOH·3H2O}n, 1, [Mg2(L1)(H2O)8]n, 2, and {[Mg2(L2)(H2O)6]·H2O}n, 3, have been hydrothermally synthesized and structurally characterized by single-crystal X-ray diffraction. Complexes 1 and 2 are the solvent ratio-dependent hydrothermally stable products. The tetracarboxylate ligand of complex 1 connects eight Mg(II) ions through nine oxygen atoms, resulting in a three-dimensional (3D) 5-connected uninodal net with a rare non-interpenetrating (44.66)-pcu-5-Pmna topology, whereas those of 2 and 3 link four Mg(II) ions through four oxygen atoms and six Mg(II) ions through six oxygen atoms, forming a 1D linear chain and a 3,6-connected 2-nodal 3D net having {4.62}2{42.610.83}-rtl topology, respectively. Complex 1 shows a series of structural transformations on heating to 200 °C and almost reversible structural transformation when the activated products were immersed in a mixture of ethanol and water or on hydrothermal. Likewise, complex 2 exhibits a reversible structural transformation on heating/hydrothermal, while 3 exhibits irreversible structural transformations. All three complexes exhibit blue light emissions, with that of complex 3 being much more intense.

Owing to the unique catalytic, optical and magnetic properties, lanthanides (Ln) as multicomponent biomarkers, are widely used in the field of optical sensing, mass spectrometry and magnetic resonance imaging. As ligands, DNA molecules have good biocompatibility, high stability, cost efficiency, programmability and biodegradability. Based on the coordination-driven self-assembly between Ln ions (Ln3+ ) and DNA molecules, a multifunctional Ln3+ -DNA hybrid coordination polymers (CPs) were synthesized. Not only a series of different Ln3+ (single Ln3+ ) and DNA hybrid CPs were synthesized, but one hybrid CP contains two kinds of Ln3+ was obtained. Besides, the synthetic CPs in cell fluorescence imaging and miRNA sensing also exhibited high performance. This work provides a novel idea for the synthesis of DNA based nanomaterials, which is promising for biologically-related applications.

The morphological transformation of soot particles via condensation of low-volatility materials constitutes a dominant atmospheric process with serious implications for the optical and hygroscopic properties, and atmospheric lifetime of the soot. We consider the morphological transformation of soot aggregates under the influence of condensation of vapors of sulfuric acid, and/or limonene ozonolysis products. This influence was systematically investigated using a Differential Mobility Analyzer-Aerosol Particle Mass Analyzer (DMA-APM) and the Tandem DMA techniques integrated with a laminar flow-tube system. We hypothesize that the morphology transformation of soot results (in general) from a two-step process, i.e., (i) filling of void space within the aggregate; (ii) growth of the particle diameter. Initially, the transformation was dominated by the filling process followed by growth, which led to the accumulation of sufficient material that exerted surface forces, which eventually facilitating further filling. The filling of void space was constrained by the initial morphology of the fresh soot as well as the nature and the amount of condensed material. This process continued in several sequential steps until all void space within the soot aggregate was filled. And then “growth” of a spherical particle continued as long as vapors condensed on it. We developed a framework for quantifying the microphysical transformation of soot upon the condensation of various materials. This framework used experimental data and the hypothesis of “ideal sphere growth” and void filling to quantify the distribution of condensed materials in the complementary filling and growth processes. Using this framework, we quantified the percentage of material consumed by these processes at each step of the transformation. For the largest coating experiments, 6%, 10%, 24% and 58% of condensed material went to filling process, while 94%, 90%, 76% and 42% of condensed material went to growth process for 75 nm, 100 nm, 150 nm and 200 nm soot particles, respectively. We also used the framework to estimate the fraction of internal voids and open voids. This information was then used to estimate the volume equivalent diameter of the soot aggregate containing internal voids and to calculate the dynamic shape factor, accounting for internal voids. The dynamic shape factor estimated based on the traditional assumption (of no internal voids) differed significantly from the value obtained in this study. Internal voids are accounted for in the experimentally derived dynamic shape factor determined in the present study. In fact, the dynamic shape factor adjusted for internal voids was close to 1 for the fresh soot particles considered in this study, indicating the particles were largely spherical. The effective density was strongly correlated with the morphological transformation responses to the condensed material on the soot particle and the resultant effective density was determined by the (i) nature of the condensed material; (ii) morphology and size of the fresh soot. In this work we quantitatively tracked in-situ microphysical changes in soot morphology, providing details of both fresh and coated soot particles at each step of the transformation. This framework can be applied to model development with significant implications for quantifying the morphological transformation (from the viewpoint of hygroscopic and optical properties) of soot in the atmosphere.

Core/shell nanoparticles were first reported in the early 1990s with a simple spherical core and shell structure, but the area is gradually diversifying in multiple directions such as different shapes, multishells, yolk/shell etc., because of the development of different new properties of the materials, which are useful for several advanced applications. Among different sub-areas of core/shell nanoparticles, yolk/shell nanoparticles (YS NPs) have drawn significant attention in recent years because of their unique properties such as low density, large surface area, ease of interior core functionalization, a good molecular loading capacity in the void space, tunable interstitial void space, and a hollow outer shell. The YS NPs have better properties over simple core/shell or hollow NPs in various fields including biomedical, catalysis, sensors, lithium batteries, adsorbents, DSSCs, microwave absorbers etc., mainly because of the presence of free void space, porous hollow shell, and free core surface. This review presents an extensive classification of YS NPs based on their structures and types of materials, along with synthesis strategies, properties, and applications with which one would be able to draw a complete picture of this area.

Luminescent lanthanide coordination polymer as a platform for DNA colorimetric detection

A series of microporous coordination polymers of adipic (H2ad) and pimelic acids (H2pim) with rare earth metals have been synthesized and structurally characterized. In the case of adipic acid, two distinct structure types were isolated: structure type I with formula [Ln2(ad)3(H2O)4]6H2O, Ln = Ce3+, Pr3+, Nd3+, and strucure type II with formula [Ln2(ad)3(H2O)4]xH2O, Ln = Nd3+, Sm3+, Gd3+, Er3+, Yb3+. Type I compounds are isostructural to lanthanum adipate (Inorg. Chem. 1998, 37, 3407) and contain interconnected channels filled with hydrogen-bonded water molecules. The structure of type II polymers consists of interpenetrated (4,4) metal−organic networks. Channels along one crystallographic direction are created by the interpenetration. The minimum width of the channels depends on the nature of the metal incorporated in the framework. The passage from type I to type II structure is ascribed to the well-known effect of lanthanide contraction. In the case of H2pim, one compound of formula [La(pim)(Hpim)(H2O)]H2O was isolated. Channels, filled with water molecules, are formed along one crystallographic direction. In all compounds, the water molecules can be reversibly removed.

Liquid crystal, as a condensed matter, is a phase state between crystal and isotropic liquid. On the one hand, it has mobility and continuity as a liquid, and on the other hand, it has arranging ordering as a crystal, then it has many unique properties. Because the factors, such as heat, electric field, magnetic field, pressure, and so on, will easily influence the arranging of liquid crystal molecular, so once it is excited externally, its optical properties will be changed. At present, most research on the theory and application of liquid crystal mainly focus on the display. Thermo-optic effect is defined as the phenomenon that the optical properties of liquid crystal change with the changing of temperature. At the phase transition point, the thermo-optic effect of liquid crystal is very obvious. In this paper, non-electric readout infrared thermal imaging detection technology based on the optical rotation property of the cholesteric liquid crystals is mainly researched. Through the research, the cholesteric liquid crystals’ light curves, gray value curves and CCD image were obtained under different temperatures; it proved that using the optical rotation property of cholesteric liquid crystals to achieve the infrared imaging of hot objects is possible.

The Zinc oxide (ZnO) and cadmium sulfide (CdS) nanostructures and ZnO/CdS nanocomposite were prepared by a solvothermal method using acetate precursors using 1:1 volume mixture of water and ethanol as solvent. The structural characterization of the synthesized samples was carried by X-ray diffraction (XRD) technique and the results showed hexagonal and cubic phases for ZnO and CdS, respectively. The surface morphology and elemental compositions were analyzed using FESEM and EDX spectroscopy. The optical absorption and photoluminescence properties were characterized by UV-Visible absorption spectroscopy and photoluminescence spectrometer (PL), respectively. ZnO/CdS nanocomposite shows an enhanced optical absorption with respect to the ZnO and CdS nanostructures. ZnO nanostructures show an intense band edge luminescence.

A new class of lanthanide mixed-carboxylate ligands compounds with formula {[Ln2 (phthgly)4 (bdc)(H2 O)6 ]·(H2 O)4 }∞ , labelled as Ln3+ : Eu (1) and Gd (2) coordination polymers (CP) were synthesized under mild reaction conditions between lanthanide nitrate salts and a solution of N-phthaloylglycine (phthgly) and terephthalic (bdc) ligands. The (1) and (2) coordination polymers were formed by symmetric binuclear units, in which phthgly and bdc carboxylate ligands are coordinated to the lanthanide ions by different coordination modes. Surprisingly, all organic ligands participate in hydrogen bonding interactions, forming an extremally rigid crystalline structure. The red narrow emission bands from the 5 D0 →7 FJ transitions of the Eu3+ ion show a high colour purity. The intramolecular energy transfer process from L→Eu3+ ion has been discussed. The experimental intensity parameters (Ω2,4 ) reflect lower angular distortion and polarizability of the chemical environment around the metal ion compared with other Eu3+ compounds reported in the literature. This novel class of coordination polymer offers a more attractive platform for developing luminescent functional materials for different applications.

Due to the unique electronic, optical, catalytic and biological properties, well ordered nanostructures have attracted enormous interest. They have potential applications in photonic crystal devices (Yablonovitch, 1987), large-density magnetic recording devices (Chou et al., 1994), novel electronic devices (Schmidt & Eberl, 2001), synthesis of DNA electrophoresis mediate (Volkmuth & Austin, 1992),nanocontainers (Chen et al., 2008), surface-plasmon resonance biosensors (Brolo et al., 2004), antireflective coatings for solar cells (Yae et al., 2005), and etc. Such broad applications of nanostructures were intimately associated with their unique properties, which are sensitively dependent on their size and/or shape. It is well-established that magnetic (Shi et al., 1996; Zhu et al.,2004), optical (Aizpurua et al., 2003; Larsson et al. 2007), electrocatalytic (Bratlie et al., 2007; Narayanan & El-Sayed, 2004), optoelectronic (Chovin et al., 2004), data storage (Ma, 2008), thermodynamic (Volokitin et al., 1996; Wang et al., 1998) and electrical transport (Andres et al., 1996; Bezryadin et al., 1997) properties of the nanostructures are affected by the shape and the size, as well as the interfeature spacing. In general, there are two approaches to realize ordered nanostructures with desired size, shape and arrangement. One is the “bottom up” approach on pre-patterned substrates (Zhong et al, 2007; Zhong et al., 2008). The other is the “top-down” approach (Ito & Okazaki, 2000). Both of these two approaches are always based on lithographic technology. In the first approach, lithographic techniques were employed to fabricate various patterned substrates, on which ordered nanostructures can then be realized by subsequent growth of desired materials. The main reason for this approach is to suppress defects in the nanostructures. In the second approach, ordered nanostructures can be directly fabricated by lithographic techniques. Several standard lithographic techniques are frequently exploited to fabricate desired surface nanostructures, including holographic lithography, electron-beam lithography (EBL) and ion-beam lithography (IBL) (Arshak et al., 2004;Ebbesen et al., 1998; Ito & Okazaki, 2000). Recently, a new extreme ultraviolet (EUV) lithography was developed, which is a potential candidate for achieving critical dimensions below 100 nm (Service, 2001). In addition, there are some other lithographic techniques applied in the fabrication of nanostructures (Haynes & Van Duyne, 2001). However, fabrication of nanostructures in a regular arrangement over large areas is still a major challenge in modern nanotechnologies. There is substantial interest in developing new technologies to facilitate pattern fabrication.

Gold nanostars (GNSs) have received considerable attention in surface-enhanced spectroscopies, catalysis, biosensing, photothermal therapy, and photovoltaics because of their unique optical properties arising from the anisotropic structure. GNSs typically consisting of a central core and several protruding tips are usually synthesized by a seed-mediated growth approach, but the growth mechanism and optical properties have yet to be fully understood. Here, we systematically investigate the seed-mediated growth process of GNSs to gain an insight into the growth mechanism and evolution of their optical and photothermal properties. By tailoring the core size, tip length and tip angle, the main localized surface plasmon resonance (LSPR) peak wavelength can be broadly tuned from the visible to near-infrared (NIR) region. Our observations show that the protruding tips grow rapidly away from the central core at the initial growth stage, leading to a red-shift of the main LSPR peak. The preferential deposition of gold atoms onto the gold core takes place at the later growth stage, gradually blue-shifting the main LSPR peak. GNSs exhibit a large molar extinction coefficient ranging from 4.0 × 108 M-1 cm-1 to 4.5 × 1010 M-1 cm-1, the log value of which correlates linearly with the main LSPR peak wavelength and accordingly allows for facile determination of the GNS concentration in a suspension. In addition, GNSs are excellent NIR photothermal materials with the LSPR-dependent photothermal conversion efficiency. The maximum photothermal conversion efficiency of GNSs occurs at a LSPR wavelength of 740 nm, blue-shifted from the incident laser wavelength. Our present work suggests that GNSs exhibit excellent optical and photothermal properties that can be optimized by tailoring the dimensional parameters.