Spacer Ligands Research Articles

Construction of Pillared-Layer Metal-Organic Frameworks as an All-Visible-Light Switchable Photocatalyst for Aqueous Cr(VI) Reduction.

Recently, two-dimensional metal-organic frameworks that are photoactive have shown great potential for efficiently converting solar energy into chemical energy. In this work, we successfully synthesized and designed two M2-MOFs ([Cu(L1)((CH3)2NH)]n (Cu-MOF) and [Zn(L1)(CH3)2NH)]n (Zn-MOF), H2L1 = 4,4'-(benzo[c][1,2,5]thiadiazole-4,7-diyl)dibenzoic acid). Structural analysis suggests that the five-coordinated M(II) ion is surrounded by four oxygen ions from two ligands and one nitrogen atom from one dimethylamine molecule. The ligand spacer acts as a bridge between two SBUs and forms a 2D layer with rhomboid windows. These moieties are arranged in a staggered ABAB pattern, which likely aids in exfoliation. The UV-vis diffuse reflectance spectra (DRS) test shows that when the metal center in the MOF framework is replaced with Cu(II) ions, the light absorption range covers 200-1100 nm, which is much larger than the light absorption range of Zn-MOF. Moreover, the photoelectric current, electrochemical impedance spectra (EIS), and Mott-Schottky tests all indicate that Cu-MOF has better photoelectric properties. When applied to the photocatalytic reduction of Cr(VI), Cu-MOF and Zn-MOF can completely reduce Cr(VI) within 100 min under 450 nm LED light irradiation. Under sunlight irradiation, Cu-MOF can completely reduce Cr(VI) within 40 min, achieving the removal of Cr(VI) ions, which is much faster than the rate of Cr(VI) removal by Zn-MOF.

Design and photophysical characterization of dinuclear lanthanide complexes incorporating spacer ligands along with their mononuclear analogues: A comparative study

Two heteroleptic homo-dinuclear complexes of Dy(III) and Sm(III) with pyrazine (pyz) as spacer ligand [Ln(TFPB)3(μ-pyz)Ln(TFPB)3], along with their mononuclear analogue [Ln(TFPB)3(pyz)2] were synthesized and characterized. Diketone TFPB (4,4,4-trifluoro-1-phenyl-1,3-butanedione) was incorporated as main ligand. NMR analysis depicted single peak for pyz protons for dinuclear complexes and two for mononuclear ones, which confirmed the bridging nature of pyz in former complexes. UV spectra revealed two absorption bands despite of the different metal ion and nuclearity of complex, suggesting the absorption of UV-radiation by coordinated moieties inspite of the metal ion involved. The emission spectra exhibited significant intensity of yellow and orange-red peaks for Dy(III) and Sm(III) complexes, respectively, indicating effective sensitization of metal center. The enhanced emission intensity observed in dinuclear Sm-complexes, compared to their mononuclear counterparts, indicates a synergistic effect of the two metal ions on the overall emission properties, rather than a mere additive effect that would be expected from two independent mononuclear units. The photoluminescent properties of synthesized complexes were examined and discussed, suggesting potential applications in display devices. The Correlated Color Temperature (CCT) of these complexes falls within a range suitable for warm light sources and the highest branching ratio observed for 4G5/2 → 6H9/2 (for Sm3+ ion) and 4F9/2 → 6H13/2 (for Dy3+ ion) transitions suggests potential application in laser amplification. The alignment between band gap measurements obtained from UV and CV analyses highlight the possibility of employing these complexes in semiconductor technologies.

Topological investigation on the structural diversity of Co(II) coordination polymers with mixed ligands: Effect of ligand isomerism and substituent

Co(II) coordination polymers constructed from the isomeric N,N’-bis(3-pyridylmethyl)oxalamide (L1) and N,N’-bis(4-pyridylmethyl)oxalamide (L2) and polycarboxylic acids with different substituents at the 5th positions of the phenyl rings are reported, including {[Co(L1)(1,3,5-HBTC)]·H2O}n (1,3,5-H3BTC = benzene-1,3,5-tricarboxylic acid), 1, {[Co(L1)(5‑tert-IPA)(H2O)2]·H2O}n (5‑tert-H2IPA = 5‑tert-butylbenzene-1,3-dicarboxylic acid), 2, [Co(L1)0.5(5-NH2-IPA)(H2O)]n (5-NH2H2IPA = 5-aminoisophthalic acid), 3, {[Co2(L2)2(1,3,5-HBTC)2]·(L2)·5H2O}n, 4, {[Co(L2)1.5(1,3,5-HBTC)]·2H2O}n, 5, {[Co(L2)(5‑tert-IPA)]·H2O}n, 6, {[Co(L2)(5-NH2-IPA)(H2O)]·2·5H2O}n, 7, {[Co(L2)(5-NH2-IPA)]·4H2O}n, 8. Complexes 1, 3, 5 and 6 are 2D nets with the 3,5L2, bey, bey, 3,5L2 topologies, and 2 is a 3-fold interpenetrated 2D net with the hcb topology, whereas 4 is a 3D framework with the pcu topology, 7 is a self-catenated 3D net with the 3,5T48 topology and 8 is a 3-fold interpenetrated 3D net with the 3,5T1 topology, respectively. While the solvent system and energy are important in the preparation of Co(II) coordination polymers, the ligand isomerism of the neutral spacer ligand and the identity of the substituent group of the polycarboxylate ligand govern the structural diversity.

Halide Ion Mobility in Paired 2D Halide Perovskites: Ruddlesden–Popper Versus Dion–Jacobson Phases

Abstract2D lead halide perovskites with tunable optoelectronic properties through modulating inorganic components and organic spacer ligands represent a promising candidate in perovskite optoelectronics. However, an intrinsic soft lattice of perovskites gives rise to a vacancy‐mediated halide ion migration, which further affects the long‐term stability of materials as well as devices. Here, halide ion mobility is evaluated using two different 2D perovskites yielded with butylammonium (BA) for the Ruddlesden–Popper (RP) phase and butane‐1,4‐diamine (BDA) for the Dion–Jacobson (DJ) phase, respectively. By probing the halide ion migration kinetics in the physically paired 2D bromide and iodide perovskite films, the softer lattice (RP) shows a lower activation energy of 50.9 kJ mol−1 as compared to that of more rigid lattice (DJ) of 60.8 kJ mol−1. Given similar halide diffusion pathlength and halide mixing chemical potential, the binding mode (RP and DJ) can indeed dictate the overall halide ion stability. Understanding such halide ion mobility is important in designing perovskites with increased stability and performances at material and device levels.

Cu(II) Coordination Polymers Containing Mixed Ligands with Different Flexibilities: Structural Diversity and Iodine Adsorption.

Reactions of N,N'-bis(3-methylpyridyl)oxalamide (L1), N,N'-bis(3-methylpyridyl)adipoamide (L2) and N,N'-bis(3-methylpyridyl)sebacoamide (L3) with tricarboxylic acids and Cu(II) salts afforded {[Cu(L1)(1,3,5-HBTC)]·H2O}n (1,3,5-H3BTC = 1,3,5-benzenetricarboxylic acid), 1, {[Cu1.5(L2)1.5(1,3,5-BTC)(H2O)2]·6.5H2O}n, 2, [Cu(L2)0.5(1,3,5-HBTB)]n (1,3,5-H3BTB = 1,3,5-tri(4-carboxyphenyl)benzene), 3, [Cu4(L3)(OH)2(1,3,5-BTC)2]n, 4, {[Cu3(L3)2(1,3,5-BTB)2]·2.5MeOH·2H2O}n, 5, and {[Cu3(L3)2(1,3,5-BTB)2 ]·DMF·2H2O}n, 6, which have been structurally characterized by using single crystal X-ray crystallography. Complexes 1-4 form a 2D layer with the {44.62}-sql topology, a 2D layer with the (4.62)2(42.62.82)-bex topology, a three-fold interpenetrated 3D net with the (412·63)-pcu topology and a 3D framework with the (410·632·83)(42·6)2(43·63) topology, respectively, whereas 5 and 6 are 3D frameworks with the (63)2(64·82)(68·85·102) topology. Complex 5 shows a better iodine adsorption factor of 290.0 mg g-1 at 60 °C for 360 min than the other ones, revealing that the flexibility of the spacer ligand governs the structural diversity and the adsorption capacity.

Mononuclear or Coordination Polymer Complexes? Both Are Possible for 3,6,9-Trioxaundecanedioic Acid

Investigating the driving forces leading to the formation of a specific supramolecular architecture among a wide spectrum of all the possibly obtainable structures is not an easy task. The contemporary literature provides several models for correctly predicting the thermodynamically accessible structures that can originate from a library of building blocks. Definitions are rigid by their very nature, so their application may sometimes require a shift in perspective. In the study presented herein, we describe the crystal structures of three metallo-supramolecular architectures assembled from deprotonated derivatives of 3,6,9-trioxaundecanedioic acid and Mn(II), Co(II) and Zn(II). In the Mn(II) case, the complexation resulted in a complex of a discrete/heptacoordinated nature, whereas the other two structures appeared as helical polymers. To explain such an anomaly, in this work, we describe how the interplay between the flexibility of the ligand spacer and the number of coordinating atoms involved determines the divergent or convergent organisation of the final coordination architecture.

Electronic Devices Made from Chitin: NAND Gates Made from Chitin Sorbates and Unsaturated Bridging Ligands—Possible Integration Levels and Kinetics of Operation

Chitin (usually derived from aq. arthropods like shrimp Pandalus borealis) acts as a potent metal sorbent in both environmental monitoring and retention applications such as wastewater purification or nuclear fuel reprocessing. Given this established (starting in the 1970s) use of chitin and the fact that adsorption of metal ions/complexes to chitin does increase the currents observed in metal-centered redox couples by a factor of about 10, it is straightforward to conceive self-organized (by adsorption modified by adding certain ligands bridging M and chitin) surface films which exert electrical information processing by means of inner-sphere redox processes. Preliminary work is shown concerning the influence of ligands—including some possibly acting as inner-sphere-transfer agents, like caffeic acid—on metal ion retention by chitin. Another ligand is reported to enhance current flow into electrodes (i.e., electron injection from some reducing cation). These inner-sphere redox processes, in turn, can be controlled by creating or removing a chain of conjugated double bonds, e.g., by Diels–Alder reactions. Devices admitting corresponding reagents in a controlled manner and appropriate array then act as NAND gates, thus being components capable of performing each kind of classical computation. Applications in environmental analysis and “green” computing for simple purposes like electronic keys are suggested. The empirical basis for these conclusions includes studies on the influences of ligand additions on M adsorption (Mn, Ni, several REEs…) on chitin; some of these bridging ligands, like caffeinate and ferulate, can reversibly react with appropriate dienes. At the employed concentrations, distances among adsorbed metal ions are 1–3 nm, meaning that the charge-flow control takes spacer ligands like carotenoids. Practical setups are pointed to, using evidence from ligand-augmented metal ion–chitin interactions, which might combine oxidizing (Ce) and optically address reducing (Eu) metal ions into a framework for coligand-controlled charge flow.

Nanoplatelet Superlattices by Tin-Induced Transformation of FAPbI3 Nanocrystals.

The transition from 3D to 2D lead halide perovskites is traditionally led by the lattice incorporation of bulky organic cations. However, the transformation into a coveted 2D superlattice-like structure by cationic substitution at the Pb2+ site of 3D perovskite is unfamiliar. It is demonstrated that the gradual increment of [Sn2+ ] alters the FASnx Pb1- x I3 nanocrystals into the Ruddlesden-Popper-like nanoplatelets (NPLs), with surface-absorbed oleic acid (OA) and oleylamine (OAm) spacer ligand at 80°C (FA+ : formamidinium cation). These NPLs are stacked either by a perfect alignment to form the superlattice or by offsetting the NPL edges because of their lateral displacements. The phase transition occurs from the Sn/Pb ratio ≥0.011, with 0.64 wt% of Sn2+ species. At and above Sn/Pb = 0.022, the NPL superlattice stacks start to grow along [00l] with a repeating length of 4.37(3) nm, comprising the organic bilayer and the inorganic block having two octahedral layers (n = 2). Besides, a photoluminescence quantum yield of 98.4% is obtained with Sn/Pb = 0.011 (n ≥ 4), after surface passivation by trioctylphosphine (TOP).

Halide Ion Mixing across Colloidal 2D Ruddlesden-Popper Perovskites: Implication of Spacer Ligand on Mixing Kinetics.

Halide ion exchange seen in metal halide perovskites provide a substantial opportunity to control their halide composition and corresponding optoelectronic properties. Halide ion mixing across colloidal 3D perovskite nanocrystals have been extensively studied while the mixing within colloidal 2D counterparts remain underexplored. In this study, the halide ion exchange kinetics across colloidally stable 2D Ruddlesden-Popper layered bromide (Br) and iodide (I) perovskites using two different spacer ligands such as aromatic phenethylammonium (PEA) versus linear butyammonium (BA) is demonstrated. The halide exchange kinetic rate constant (k), as determined by tracking time-dependent absorbance changes, indicates that Br/I halide mixing in 2D PEA-based perovskites (2.7 × 10-3 min-1 ) occurs at an order of magnitude slower than in 2D BA-based perovskites (3.3 × 10-2 min-1 ). Concentration (≈1mM to 100mM) and temperature-dependent (50 to 80 °C) kinetic studies further allow for the determination of activation barrier for halide ion mixing across the 2D layered perovskites with 75.2 ± 4.4kJ mol-1 (2D PEA) and 57.8 ± 7.8kJ mol-1 (2D BA), respectively. The activation energy reveals that the type of spacer cations plays a crucial role in controlling the halide ion mobility and halide stability due mainly to the internal ligand chemical interaction within 2D structures.

Zn(II) Metal–Organic Frameworks with a Long Spacer Ligand and a Tricarboxylate Coligand

The preparations and structural characteristics of three-dimensional Zn(II) metal-organic frameworks (MOFs) with dipyridyl-olefin and tricarboxylate are reported. The solvothermal reactions of zinc(II) nitrate hexahydrate, 1,4-bis [2-(4-pyridyl)ethenyl]benzene (bpeb), and 4,4′,4″,-benzene-1,3,5-triyl-tris(benzoic acid) (H3btb) furnished three Zn(II) MOFs (1–3) with new topologies. Depending on the temperature or mole-ratio variations, self-interpenetrated [Zn2(bpeb)(btb)(OH)]·DMF·H2O (1), noninterpenetrated [Zn3(btb)2(bpeb)]·xSolvent (2), and fourfold interpenetrated [Zn2(Hbtb)2(bpeb)][Zn2(Hbtb)2(bpeb)][Zn4(Hbtb)4(bpeb)2] (3) structures were generated with different molecular building blocks. It is interesting that although all three MOFs contain the same metal cation, anion, and spacer ligand, they show different emissions due to structure and connectivity.

Trefoil-shaped metallacycle and metallacage via heteroleptic self-assembly

Template-oriented multi-component synthesis method has been proven to be an exceedingly reasonable and excellent method for the synthesis of giant two-dimensional (2D) and three-dimensional (3D) supramolecules, but designing and constructing heteroleptic and controllable self-assembly without unexpected by-products remains a challenge. Here we report two discrete trefoil-shaped metallacycle S1 and metallacage S2 by heteroleptic self-assembly using one hexaphenylbenzene core ligand and two capping ligands. The 2D trefoil-shaped metallacycle S1 could resemble the emblem of the classic ‘Mitsubishi’ motif. The use of template-oriented ligand and bent spacer ligand promotes the quantitative formation of the desired 3D trefoil-shaped metallacage S2. The formed metallacage S2 possesses a molecular weight up to 36 kDa, diameter 6.6 nm and height 3.0 nm. All supramolecular coordination complexes were fully characterized by NMR spectroscopy (1H NMR, 2D COSY, 2D NOESY, 2D DOSY), high-resolution electrospray ionization mass spectrometry ESI-MS, ESI-TWIM-MS, TEM and AFM.

Modulating the Schottky barriers of metal-2D perovskite junctions through molecular engineering of spacer ligands.

The crucial role of spacer ligands in affecting the contact properties of metal-2D perovskite junctions, which can severely affect device performance, is revealed in this work. We studied the contact properties of Ag, Au, and Pt with 2D perovskites that possess ligands with different sizes and functional groups. It is found that the interface binding energy, Schottky barrier height (SBH), and tunneling property depend strongly on the ligand size and functional group type. Small-size ligands can induce effective interface coupling and result in perturbed perovskite electronic properties and a high tunneling probability. In addition, high work-function metals and more electronegative functional groups can induce more severe band shifts at the interface. The features of diverse ligands ensure a widely tunable SBH ranging from 0-1.07 eV. This study provides guidance for developing more effective 2D perovskite-based electric nanodevices by tuning the contact properties through molecular engineering of spacer ligands.

Green Preparation of Antimicrobial 1D-Coordination Polymers: [Zn(4,4'-bipy)Cl2]∞ and [Zn(4,4'-bipy)2(OAc)2]∞ by Ultrasonication of Zn(II) Salts and 4,4'-Bipyridine.

We report on the green preparation of one-dimensional metal coordination polymers by sonochemical approach. The spacer ligand 4,4′-bipyridine was ultrasonicated with chloride or acetate zinc salts to obtain [Zn(4,4′-bipy)Cl2]∞ and [Zn(4,4′-bipy)2(OAc)2]∞, respectively. Benign solvents such as ethanol and water were selected as reaction media, and the synthesis took place in a few minutes—a very short time compared to conventional methods where some days’ synthesis is required. X-ray powder diffraction, Fourier transform infrared spectroscopy, thermal analysis (thermogravimetric and differential scanning calorimetry), and CHN techniques investigated the influence of using different reaction solvents on the chemical, structural, and thermal properties of the final products. The 1D [Zn(4,4′-bipy)Cl2]∞ and [Zn(4,4′-bipy)2(OAc)2]∞ polymers, in agreement with the structures reported in the literature, were obtained in the form of nanocrystals with an average crystal size around 100 nm. As a proof of concept, a set of Gram-positive (Staphylococcus aureus) and Gram-negative bacteria (Klebsiella pneumoniae), and three yeast strains (Candida albicans, Candida krusei, Candida glabrata) were tested to evaluate the antimicrobial activity of the coordination polymers, following the Kirby–Bauer procedure and microplate dilution method. Thus, minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC), and minimal biofilm inhibitory concentration (MBIC) were evaluated. Except for Candida krusei, the compounds showed an appreciable antimicrobial and antibiofilm activity against these strains grown in the liquid medium.

Elongation of a Trigonal-Prismatic Copper Cluster by Diphosphine Ligands with Longer Spacers.

A pair of alkynyl-diphosphine-coprotected copper(I) clusters, namely, [Cu6(4-MeO-PhC≡C)5(dppe)3](ClO4) [Cu6; dppe = 1,2-bis(diphenylphosphino)ethane] and [Cu11(H)(4-MeO-PhC≡C)8(dpppe)3](ClO4)2 [Cu11; dpppe = 1,5-bis(diphenylphosphino)pentane], featuring trigonal-prismatic frameworks have been synthesized by a reduction method. Their molecular structures are determined by X-ray crystallography and characterized by multiple techniques. The length of the spacer of the diphosphine ligand can directly affect the aspect ratio of the clusters. Cu6 with dppe as ligands has a trigonal-prismatic core. The longer alkyl spacer of dpppe helps to elongate the trigonal-prismatic framework to form Cu11, with its trigonal-prismatic framework encapsulating a Cu5H unit. Electrospray ionization mass spectrometry, 2H NMR, and liberations of hydrogen further verify the presence of a hydride in the cluster. Density functional theory calculations help to locate the position of the hydride and understand the electronic structures of the clusters. Cu11 is the first alkynyl-phosphine-coprotected copper hydride cluster. These two clusters show distinct luminescence properties. The compact Cu6 is phosphorescent upon radiation, while the longer Cu11 with more flexibility is nonluminous. This work enriches the family of copper hydrides and demonstrates the ligand effects in the extension of the length and structural complexity of clusters.

Endohedrally Functionalized Metal–Organic Cage-Cross-Linked Polymer Gels as Modular Heterogeneous Catalysts

The immobilization of homogeneous catalysts onto supports to improve recyclability while maintaining catalytic efficiency is often a trial-and-error process limited by poor control of the local catalyst environment and few strategies to append catalysts to support materials. Here, we introduce a modular heterogenous catalysis platform that addresses these challenges. Our approach leverages the well-defined interiors of self-assembled Pd12L24 metal-organic cages/polyhedra (MOCs): simple mixing of a catalyst-ligand of choice with a polymeric ligand, spacer ligands, and a Pd salt induces self-assembly of Pd12L24-cross-linked polymer gels featuring endohedrally catalyst-functionalized junctions. Semi-empirical calculations show that catalyst incorporation into the MOC junctions of these materials has minimal affect on the MOC geometry, giving rise to well-defined nanoconfined catalyst domains as confirmed experimentally using several techniques. Given the unique network topology of these freestanding gels, they are mechanically robust regardless of their endohedral catalyst composition, allowing them to be physically manipulated and transferred from one reaction to another to achieve multiple rounds of catalysis. Moreover, by decoupling the catalyst environment (interior of MOC junctions) from the physical properties of the support (the polymer matrix), this strategy enables catalysis in environments where homogeneous catalyst analogues are not viable, as demonstrated for the Au(I)-catalyzed cyclization of 4-pentynoic acid in aqueous media.

Synthesis of Triple‐Stranded Diruthenium(II) Compounds

AbstractA series of ligands containing a 1,4‐disubstituted 1,2,3‐triazole unit have been used for the formation of triple‐stranded dinuclear Ru(II) complexes. In contrast to the previously reported complexes of labile metals, the use of inert Ru(II) enabled stereoisomeric mixtures of triple‐stranded diruthenium(II) complexes to be accessed. The chromatographic resolution of the enantiomers of a reported helicate containing a more rigid 1,4‐xylyl spacer was carried out on cellulose. The ligand spacer was modified and as the flexibility increased the production of isomeric mixtures was detected; the mesocate and helicate forms were separated when an n‐propyl spacer was used. This pair of diastereomers was found to exhibit photoconversion, a unique observation for Ru(II) compounds of this type. Partial separation via chromatographic resolution was achieved for compounds containing an n‐butyl spacer, and the presence of a mesocate/helicate pair confirmed.

Subtle Ligand Spacer Change in 2D Metal-Organic Framework Sheets for Dual Turn-On/Turn-Off Sensing of Acetylacetone and Turn-On Sensing of Water in Organic Solvents.

Metal-organic framework (MOF)-based sensors for the detection of various analyte molecules has been a subject of absolute importance. However, most of these sensors rely on the turn-off (quenching) transduction response, while those reporting turn-on response are very rare. In this article, we have synthesized two new MOF-based sensors, {[Zn2(oxdz)2(tpbn)]·14H2O}n (1) and {[Zn2(oxdz)2(tpxn)]·10H2O·2C2H5OH}n (2), via the self-assembly of Zn(II) metal ions, a fluorogenic oxdz2- linker, and bis(tridentate) ligands (tpbn and tpxn) under ambient conditions. Their formation from such a self-assembly process has been evaluated on the basis of the geometry around the five-coordinated Zn(II), preferential meridional binding of the bis(tridentate) ligands, and diverse binding of the carboxylate groups in oxdz2-. Although 1 and 2 are isostructural, a difference in the transduction mechanism for the sensing of acetylacetone in organic solvents (turn-on for 1 and turn-off for 2) is observed and can be attributed to the spacer in the bis(tridentate) ligands. We have demonstrated the competing effect of the nonradiative interactions and photoinduced electron transfer toward the sensing mechanism. The results are well-supported by the Fourier transform infrared spectroscopy study, intensity versus concentration plots, spectral overlap measurements, time-resolved fluorescence studies, and MM2 and density functional theory calculations. Furthermore, we have showcased the utilization of 1 for the sensing of trace amounts of water in organic solvents.

Nickel(II) Coordination Polymers Supported by Bis-pyridyl-bis-amide and Angular Dicarboxylate Ligands: Role of Ligand Flexibility in Iodine Adsorption.

Reactions of N‚N’-bis(3-pyridylmethyl)oxalamide (L1), N‚N’-bis(4-pyridylmethyl)oxalamide (L2), or N,N’-bis(3-pyridylmethyl)adipoamide) (L3) with angular dicarboxylic acids and Ni(II) salts under hydro(solvo)thermal conditions afforded a series of coordination polymers: {[Ni(L1)(OBA)(H2O)]·H2O}n (H2OBA = 4,4-oxydibenzoic acid), 1, {[Ni(L1)(SDA)(H2O)2]·H2O·CH3OH}n (H2SDA = 4,4-sulfonyldibenzoic acid), 2, {[Ni(L2)(OBA)]·C2H5OH}n, 3, {[Ni(L2)(OBA)]·CH3OH}n, 4, {[Ni2(L2)(SDA)2(H2O)3]·5H2O}n, 5, {[Ni2(L2)(SDA)2(H2O)3]·H2O·2C2H5OH}n, 6, {[Ni(L3)(OBA)(H2O)2]·2H2O}n, 7, {[Ni(L3)(SDA)(H2O)2]·2H2O}n, 8, and {[Ni(L3)0.5(SDA)(H2O)2]·0.5C2H5OH}n, 9, which have been structurally characterized by using single-crystal X-ray crystallography. Complex 1 exhibits an interdigitated 2D layer with the 2,4L2 topology and 2 is a 2D layer with the sql topology, while 3 and 4 are 3D frameworks resulting from polycatenated 2D nets with the sql topology and 5 and 6 are 2-fold interpenetrated 3D frameworks with the dia topology. Complexes 7 and 8 are 1D looped chains and 9 is a 2D layer with the 3,4L13 topology. The various structural types in 1–9 indicate that the structural diversity is subject to the flexibility and donor atom position of the neutral spacer ligands and the identity of the angular dicarboxylate ligands, while the role of the solvent is uncertain. The iodine adsorption of 1–9 was also investigated, demonstrating that that the flexibility of the spacer L1–L3 ligands can be an important factor that governs the feasibility of the iodine adsorption. Moreover, complex 9 shows a better iodine adsorption and encapsulates 166.55 mg g−1 iodine in the vapor phase at 60 °C, which corresponded to 0.38 molecules of iodine per formula unit.

Role of ligand spacer length of a tripodal amide on uranium(vi) and plutonium(iv) complexation: synthesis, solvent extraction, liquid membrane transport and theoretical studies

Liquid–liquid extraction of several actinide and lanthanide ions,viz., U(vi), Pu(iv), Am(iii) and Eu(iii) was investigated from nitric acid feed solutions employingN,N,N′,N′,N′′,N′′-hexa-n-octyl nitrilotripropamide (HONTP) in 90%n-dodecane + 10% isodecanol.

Organic Spacer Cation Assisted Modulation of the Structure and Properties of Bismuth Halide Perovskites

ConspectusLead halide perovskites are under the spotlight of current research due to their potential for efficient and cost-effective next-generation optoelectronic devices. The unique photonic and electronic properties of these solution-processable materials brought them to the forefront of materials science. However, the toxicity and instability of lead-based perovskites are the major hurdles for their commercialization. These issues initiated an effort towards the development of environmentally friendly, lead-free perovskites. In this context, bismuth halide perovskites (BHPs) were ideal rivals for lead-based congeners due to their excellent chemical stability, lower toxicity, and structural versatility. Understanding the crystal structure and optoelectronic properties of BHPs is crucial for designing them for specific, tailor-made applications. This Account aims to review our recent research progress on the role of functional organic spacer cations in modulating the electronic confinements, optical properties, and photoconductivity of BHPs. We have employed a comprehensive experimental and theoretical investigation to probe the intriguing optical and electronic properties of these materials. Our findings on the structure-optoelectronic property correlations will be valuable guidelines for the rational selection of organic spacer cations in designing BHPs featuring low exciton binding energy, narrow optical bandgap, enhanced visible light absorption, and high photoconductivity. One of our key findings is that by increasing the electron affinity of the organic spacer ligands, photoconductivity and visible light absorption of BHPs could be significantly enhanced. We hope that the fundamental level understanding of the photophysical properties discussed in this Account will lead to new design rules for developing high-performance BHP materials.