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In this study, two polymorphs of the [1,1′-dibutyl-4,4′-bipyridinium][Ni(mnt)2] salt (1) were synthesized. The dark-green polymorph (designated as 1-g) was prepared under ambient conditions by the rapid precipitation method in aqueous solutions. Subsequently, the red polymorph (labeled as 1-r) was obtained by subjecting 1-g to ultrasonication in MeOH at room temperature. Microanalysis, infrared spectroscopy, thermogravimetry (TG), differential scanning calorimetry (DSC), and powder X-ray diffraction (PXRD) techniques were used to characterize the two polymorphs. Both 1-g and 1-r exhibit structural phase transitions: a reversible phase transition at ∼403 K (∼268 K) upon heating and 384 K (∼252 K) upon cooling for 1-g (1-r) within the temperature range below 473 K. Interestingly, on heating 1-r to 523 K, an irreversible phase transition occurred at about 494 K, resulting in the conversion of 1-r into 1-g. Relative to 1-r, 1-g represents a thermodynamically metastable phase wherein numerous high-energy conformations in butyl chains of cations are confined within the lattice owing to quick precipitation or rapid annealing from higher temperatures. Through variable-temperature single crystal and powder X-ray diffractions, UV-visible spectroscopy, dielectric spectroscopy, and DSC analyses, this study delves into the mechanism underlying phase transitions for each polymorph and the manual transformation between 1-g and 1-r as well. [ABSTRACT FROM AUTHOR]

The supramolecular crystals, Mn(15-crown-5)(MnCl4)(DMF), (1; 15-crown-5 = 1,4,7,10,13-pentaoxacyclopentadecane), were synthesized via a self-assembly strategy under ambient conditions. Comprehensive characterization of the crystals involved microanalysis for C, H, and N elements, thermogravimetric (TG) analysis, differential scanning calorimetry (DSC) and single-crystal X-ray diffraction techniques. The results reveal that 1 undergoes a two-step thermotropic and isostructural phase transition at around 217 K and 351 K upon heating. All three phases belong to the same space group (P212121) with analogous cell parameters. These two phase transitions primarily involve the thermally activated ring rotational dynamics of the 15-crown-5 molecule, with only the transition at ca. 351 K being associated with a dielectric anomaly. 1 exhibits intense luminescence with a peak at ∼600 nm and a high quantum yield of 68%. The mechanisms underlying this intense luminescence are likely linked to low-symmetry ligand fields. Additionally, 1 displays phase transition-induced luminescence enhancement behavior, and the possible mechanism is further discussed. [ABSTRACT FROM AUTHOR]

Two sets of 1D/2D lanthanide coordination polymers with formulas of Ln(oqa)3·2H2O [Hoqa = 2-(4-oxoquinolin-1(4H)-yl) acetic acid, Ln = Dy (1), Yb (2)] and Ln(oaa)2(HCOO)(H2O) [Hoaa = 2-(9-oxoacridin-10(9H)-yl) acetic acid, Ln = Dy (3), Yb (4)] have been synthesized and their physical properties were investigated. All four complexes are constructed from seven-coordinate lanthanide ions and corresponding organic linkers. The lanthanide ions in 1 and 2 adopt a pentagonal bipyramid coordination geometry, whereas the coordination geometry of lanthanide ions in 3 and 4 can be described as a capped octahedron. Slow magnetic relaxation behaviors were observed in these four products at a zero/non-zero static magnetic field. Complexes 1, 2 and 4 exhibit the characteristic emission of Ln(III) ions, whereas complex 3 shows ligand-based emission. Bright yellow light emission was also observed when a voltage was applied, demonstrating the potential of 1 for application in light-emitting diodes (LEDs). Compounds 3 and 4 are the first examples of lanthanide complexes based on Hoaa ligands. [ABSTRACT FROM AUTHOR]

Two haloargentate hybrids, [Me-dabco]Ag2X3 (Me-dabco = 1-methyl-1,4-diazabicyclo-[2.2.2]octan-1-ium, X = I (1) or Br (2)), with the same formula but different structures have been synthesized by a slow evaporation method and characterized by microanalysis, infrared spectroscopy, thermogravimetric, and powder X-ray diffraction techniques. Hybrid 1 consists of completely isolated [Ag4I6]2− clusters, while hybrid 2 exhibits a complicated one-dimensional (1D) chain structure formed by four different configurations of neutral chains and two dissimilar configurations of anionic chains. Hybrid 2 undergoes two reversible order–disorder phase transitions, while hybrid 1 displays one reversible and one irreversible structural phase transition. Both 1 and 2 displayed step-like dielectric anomalies in the vicinity of the phase transition temperature. The corresponding dielectric constants in the high dielectric states are approximately 13 and 6 times higher than those in the low dielectric states for 1 and 2, respectively. Interestingly, the subtle change of halides from I− to Br− significantly affects the aggregated structure of haloargentate, the phase transition, and dielectric behaviors, revealing the typical 'butterfly effect' with the ion radii of halides in these two haloargentate hybrids. [ABSTRACT FROM AUTHOR]

A thermochromic or mechanochromic material can switch between at least two stable states in response to changes in temperature or static pressure/strain. In this study, we investigated a Ni-dithiolene dianion salt, 1,1′-diheptyl-4,4′-bipyridinium bis(maleonitriledithiolato)nickelate (1), and found that its cations and anions stack alternately to form a uniform mixed stack. These mixed stacks then combine to form a molecular solid through Coulomb and van der Waals interactions. Upon heating, 1 undergoes a reversible phase transition at around 340/320 K during the first heating/cooling cycle, resulting in rapid thermochromism with a color change from green (stable state) to red (metastable state) within a few seconds. This is the first report of a crystal of bis(maleonitriledithiolato)nickelate(II) salt with green color. Additionally, 1 exhibits irreversible mechanochromism, intense near-IR absorbance, and a dielectric anomaly. The structural phase transition is responsible for these properties, as it induces alterations in the π-orbital overlap between the anion and cation within a mixed stack. The intense near-IR absorbance arises from the ion-pair charge transfer transition from [Ni(mnt)2]2− to 4,4′-bipyridinium. [ABSTRACT FROM AUTHOR]

Stimuli-responsive smart materials have applications in a range of technologies. Herein, we present a hybrid (1), built from Me3EtN+ organic cations and {Cu2I3−}∞ inorganic chains with Cu⋯Cu metal⋯metal interactions. The two-step phase transition undergone in 1 on the first heating and the phase transition at a lower temperature show symmetry-broken features, leading to switchable dielectrics; the one at a higher temperature displays isomorphic characteristics. Besides the switchable dielectrics, 1 exhibited other multi-stimuli-responsive functionalities, including thermochromism and piezochromism. Combining temperature-dependent powder and single crystal X-ray diffraction, as well as variable-temperature UV-visible absorption spectrum and EPR spectrum analyses, it is demonstrated that the thermochromism is due to the synergy of anharmonic fluctuations with electron–phonon couplings, and the piezochromism arises from compression inducing a lattice distortion in 1. Our study provides insight into understanding the thermochromic and piezochromic mechanisms of cuprous halide-based hybrids, and paves a pathway for designing new multi-stimuli-responsive hybrid materials. [ABSTRACT FROM AUTHOR]

Kaolinite possesses a structure with asymmetrically layered 1 : 1 dioctahedral aluminum silicate, and this structural property provides a useful platform for creating new cost-efficient functional materials that require noncentrosymmetric crystal packing. In this study, we prepared three covalently grafted kaolinites of propanediol (PD)/butanediol (BD)/glycerol (GL) by forming Al−O−C bonds between the OH groups of PD/BD/GL and the surface of kaolinite (K). Three covalently grafted kaolinites (K-PD, K-BD and K-GL) were characterized by X-ray diffraction, infrared spectroscopy, thermogravimetric analysis, scanning electron microscopy and microanalysis for C, H and N elements. The test of K-PD, K-BD and K-GL stirred with water at ambient conditions for 3 days demonstrated these hybrids showing extra high chemical stability to water. The dielectric spectra of three hybrids show two-step dielectric relaxation in the range of 1–107 Hz, and the P−E measurements revealed the existence of ferroelectricity at room temperature with the spontaneous polarization, the remanent polarization and the coercive field of ∼0.014 μC cm−2, ∼0.008 μC cm−2 and ∼0.426 kV cm−1 for K-PD, ∼0.017 μC cm−2, ∼0.011 μC cm−2 and ∼0.645 kV cm−1 for K-BD, and ∼0.018 μC cm−2, ∼0.011 μC cm−2 and ∼0.141 kV cm−1 for K-GL, respectively. [ABSTRACT FROM AUTHOR]

The supramolecular lead iodide perovskite crystals, {[NH4(18-crown-6)]PbI3}∞ (1), (18-crown-6 = 1,4,7,10,13,16-hexaoxacyclooctadecane), was successfully achieved by a facile solvent evaporation strategy using a DMF solution containing equal molar quantities of PbI2, NH4I and 18-crown-6. The supramolecular perovskite was characterized by microanalysis for C, H and N elements, thermogravimetric (TG) analysis, differential scanning calorimetry (DSC), powder X-ray diffraction (PXRD) and single crystal X-ray diffraction techniques. DSC measurements demonstrated that 1 experiences a two-step thermotropic phase transition around 333 K and 383 K, respectively. The phase transition is relevant to the disorder–order transformation of the 18-crown-6 molecule at ∼333 K, while both breaking-symmetry and ordered-disordered transformation of the 18-crown-6 molecule occurred at ∼383 K. In addition, the sharp change of the PbI6 coordination octahedron distortion degree plays a synergistic role in the two-step phase transition. The dielectric relaxation occurs above 243 K in 1 and is mainly attributed to the displacement of the NH4+ ions relative to the ring of the 18-crown-6 molecule and {PbI3}∞ chain induced by an AC electrical field. [ABSTRACT FROM AUTHOR]

A series of tetranuclear coordination clusters [Ln4L2(HL)2(μ3-OH)2(NO3)2](NO3)2 [Ln = Dy (1·3CH3CN·5H2O), Gd (2·4CH3CN·5H2O), H2L = 6,6′-dimethoxy-2,2′-[2,2-dimethylpropane-1,3-diylbis-(nitrilomethylidyne)] diphenol] and dinuclear complexes [LnZnL(NO3)3(H2O)]·2CH3CN [Ln = Dy (3), Er (4), Yb (5), Lu (6)] were prepared and characterized. Static magnetic measurements revealed the presence of ferromagnetic interactions between the Dy(III) ions and weak antiferromagnetic couplings between the Gd(III) ions in 1 and 2. Dynamic magnetic studies showed that complexes 1 and 3 exhibit slow magnetic relaxation under a zero static field as expected for single molecule magnet (SMM) behavior, whereas complex 4 is a field-induced SMM. Clear hysteresis loops were observed for 1 and 3 at 2 K, verifying their SMM behavior. Luminescence investigations demonstrated that complexes 1 and 2 show ligand-based emission and can act as luminescence thermometers below 100 K, whereas complexes 3 and 5 display the characteristic emission of lanthanide ions. From the high-resolution emission spectra of 3 and 5, the energy gaps between the ground state and excited states of Dy(III) and Yb(III) ions were determined. [ABSTRACT FROM AUTHOR]

Correction for 'Single molecule magnet features in luminescent lanthanide coordination polymers with heptacoordinate Dy/Yb(III) ions as nodes' by Xiang-Tao Dong et al., Dalton Trans., 2023, 52, 12686–12694, https://doi.org/10.1039/D3DT02106H. [ABSTRACT FROM AUTHOR]

Three mononuclear Co(II) complexes with the compositions of [Co(L1)2] (1), [Co(L2)2(CH3CN)] (2) and [Co(L3)2] (3) (HL1 = 2-((E)-(2-fluorobenzylimino)methyl)-4,6-dibromophenol, HL2 = 2-((E)-(3-fluorobenzylimino)methyl)-4,6-dibromophenol and HL3 = 2-((E)-(4-fluorobenzylimino)methyl)-4,6-dibromophenol) were prepared and structurally determined. The changes in the F-positions in the ligands and solvents led to the formation of these products with various coordination geometries. Both complexes 1 and 3 are four-coordinated and their coordination geometries can be described as tetrahedron and seesaw, whereas complex 2 is five coordinated with a coordination configuration in between trigonal bipyramid and square pyramid. Static magnetic studies reveal that all these complexes exhibit considerable easy-axis magnetic anisotropy. The easy-axis magnetic anisotropy of 1 and 3 mainly derives from the first quartet excited state, whereas that of 2 primarily originates from the first, third and fourth quartet excited states established by theoretical calculations. All the resulting complexes display field-induced slow magnetic relaxation. Complex 3 represents the first Co(II) single ion magnet with a seesaw coordination geometry. Ab initio calculations predict that the magnetic anisotropy will enhance when the seesaw coordination geometry varies from distortion to regulation. [ABSTRACT FROM AUTHOR]

Open-framework zinc phosphate (NMe4)(ZnP2O8H3) undergoes irreversible phase transformation. Structural transformation with α (NMe4·Zn[HPO4][H2PO4] the low-temperature phase) and β (NMe4·ZnH3[PO4]2 the high-temperature phase) (Tc = 149 °C) and conduction properties were investigated by single-crystal X-ray diffraction, differential scanning calorimetry, and alternating current (ac) impedance. The open-framework material was sensitive to humidity and β proton conductivity was higher than 10−2 S cm−1 at room temperature and 98% relative humidity (RH). Given that the high proton conductivity of the open-framework material can compete with that of many advanced proton conductors based on metal–organic frameworks (MOFs), it has broad application prospects in various electrochemical devices. [ABSTRACT FROM AUTHOR]

Two rare earth metal–organic frameworks (MOFs), [Y2(PTC)2(H2O)2]·3H2O (Y-PTC) and [Eu2(PTC)2(H2O)5]·H2O (Eu-PTC) together with the solid solutions [Eu2xY2(1−x)(PTC)2(H2O)5]·H2O (EuxY1−x-PTC, x = 0.013–0.82), were synthesized hydrothermally, and characterized by microanalysis, IR spectroscopy, TG, powder, and single crystal X-ray diffraction techniques. Eu-PTC and Y-PTC showed different crystal structures; however, all solid solutions were isomorphic to Eu-PTC even at x = 0.013, leading to the IR spectra and TG plots of the solid solutions to be similar to those of Eu-PTC but distinct from those of Y-PTC. DFT calculations for the crystal lattice energy demonstrated that the procedure for the crystallizing nucleation of Eu-PTC occurred prior to that of Y-PTC in the reaction solution, leading to the all solid solutions being isomorphic to Eu-PTC. The solid emission spectra at ambient condition showed that Y-PTC emitted ligand-based phosphorescence at 433 nm with a quantum yield (QY) of 27.02%, while Eu-PTC and EuxY1−x-PTC (x = 0.013–0.82) emitted the characteristic luminescence of Eu3+ ions, and most solid solutions showed higher QYs than Eu-PTC; in particular, the QY of Eu0.195Y0.805-PTC was up to 29.48%, i.e., increased by 10% regarding Eu-PTC (19.86%). Interestingly, solid solutions with x = 0.013–0.395 showed excitation-wavelength-dependent luminescence, and such type of luminescence MOFs have promising applications including the areas of precise temperature, gas sensing and information encryption or anti-counterfeiting materials. [ABSTRACT FROM AUTHOR]

The zero/negative thermal expansion (ZTE/NTE), which is an intriguing physical property of solids, has been observed in a few families of materials. ZTE materials possess practical applications in specific circumstances such as space-related applications, engineering structures and precision instrument. Generally, NTE materials are used as additives to form a composite of the ZTE material with positive thermal expansion material. It is still a tremendous challenge to design new families of ZTE/NTE materials. Herein, we presented a temperature-dependent single crystal structure analysis in 110–300 K for a layered (NH4)2V3O8, which crystallizes in a tetragonal space group P4bm and comprises mixed valence [V3O82−]∞ monolayers and NH4+ residual in the interlayer spaces. Along the c-axis, (NH4)2V3O8 demonstrated uniaxial expansion behaviors, i.e., ZTE with αc = −1.10 × 10−6 K−1 in 110–170 K and NTE with αc = −16.25 × 10−6 K−1 in 170–220 K. Along the a-axis, (NH4)2V3O8 exhibited ZTE with αa = + 2.06 × 10−6 K−1 in 240–300 K. The mechanisms of ZTE and NTE were explored using structural analysis. The conduction of NH4+ ions in the interlayer space was studied, indicating that the conductivity rapidly rises with the expansion of interlayer space at temperatures of >293 K. This study discloses that layered vanadates are promising ZTE/NTE materials. [ABSTRACT FROM AUTHOR]

Two mononuclear Co(II) complexes with tetrahedral coordination geometry have been constructed from different bulky Schiff-base ligands. Both complexes exhibit slow magnetic relaxation without a static field and their relaxation behaviors can be tuned by ligand substitution. Clear magnetic hysteresis loops were observed for both complexes at 2 K. [ABSTRACT FROM AUTHOR]

As a class of anionic oxoclusters of early transition metals in their highest oxidation states, polyoxometalates (POMs) show considerable structural versatility and unique chemical and physical properties, making them promising multifunctional materials. In this study, a Keggin-type POM has been achieved, with a formula of [(H2O)0.3@K6(H2O)12]H4.45[PV7.45Mo4.55O40]·11H2O (1), and its microcrystals and nanocrystals have been obtained, respectively. This POM was characterized by elemental analysis for C, H and N, ICP-MS, TG, PXRD, SEM, X-band EPR and XPS techniques. Single crystal X-ray diffraction analysis demonstrated that 1 shows a rare extended structure with a high-connected three-dimensional (3D) all inorganic network of a Keggin-type POM, built from {Mo4.55V7.45PO40}10.45− polyoxoanions and {(H2O)0.3@K6(H2O)12}6+ clusters with CsCl-type crystal structure. In addition, to the best of our knowledge, 1 shows the highest ratio of vanadium to molybdenum among Keggin-type POMs reported thus far. Most interestingly, 1 exhibits intrinsic proton conduction below the freezing point of water, with a proton conductivity of 6.90 × 10−7 S cm−1 at 249 K and further reaching 3.36 × 10−6 S cm−1 at 272 K and Ea = 0.44 eV at 249–272 K. [ABSTRACT FROM AUTHOR]

New luminescent Pb(II)-coordination polymers (Pb(II)-CPs), [Pb(2-anc)2]n (1) and [Pb(3-qlc)2(H2O)2]n (2) (2-anc = 2-aminonicotinate, 3-qlc = 3-quinolinecarboxylate), were synthesized by a solvothermal reaction and characterized using microanalysis, IR spectrometry and thermogravimetric analysis. Single crystal structure analysis revealed that the Pb2+ ion displays a hemi-directed coordination geometry in 1 and a holo-directed coordination geometry in 2. The difference between the coordination spheres of 1 and 2 is related to the steric hindrance effect of the ligands. A two-dimensional (2D) corrugated layer structure is formed in 1, and the neighboring layers are further extended into a three-dimensional (3D) van der Waals crystal by π⋯π interactions between the pyridyl rings in the neighboring layers. In contrast, a one-dimensional (1D) coordination polymeric chain is formed in 2, and the adjacent chains are connected in a 2D network by hydrogen bonds. The photophysical properties of 1 and 2 were studied at ambient conditions, disclosing that 1 emits phosphorescence at 548 nm with a millisecond-scale emission lifetime and an absolute quantum yield of 2.2%; 2 emits only blue fluorescence with an absolute quantum yield of 3.5% and nanosecond-scale emission lifetime. The reasons for the difference in the photophysical nature of 1 and 2 are discussed in regards to the electron band structure and density of states analysis. [ABSTRACT FROM AUTHOR]

A multifunctional material, with two or more types of functionalities in a single material, might give new phenomena and novel applications. Metal–organic frameworks (MOFs) or porous coordination polymers (PCPs) can be utilized as a highly versatile and tunable platform for exploring multifunctional materials. In this study, an extra thermally stable indium–MOF (1) was synthesized via self-assembly of 1,1′-ethynebenzene-3,3′,5,5′-tetracarboxylic acid (H4EBTC) with an indium salt under solvothermal conditions. MOF 1 crystallizes in a tetragonal space group P4/mmm and shows a three-dimensional (3D) anionic framework with one-dimensional (1D) channels along the c-axis direction, and charge-balancing [(CH3)2NH2]+ cations together with lattice DMF and water molecules are accommodated in channels. This multifunctional MOF emits pure blue luminescence under ambient conditions, arising from the π* → π electron transition in EBTC4−, with CIE coordinates of (0.16, 0.07), and shows the highest quantum yield of 61.4% among indium–MOFs. Alternatively, 1 features fast proton conductivity with σ = 3.49 × 10−3 S cm−1 at 25 °C and 99% RH, attributed to the efficiently synergistic proton transfer in the H-bond networks constructed by [NH2(CH3)2]+ cations, lattice water molecules in channels and carboxylate groups in the framework. The notable level of performance of 1, combined with good hydrolytic and extra thermal stability, offers great opportunities for its future applications, and it may behave as a kind of promising multifunctional MOF material. [ABSTRACT FROM AUTHOR]

A supramolecular crystal, built from a 1 : 1 molar ratio of potassium tetraphenylboron (KBPh4) with 1,4,7,10,13,16-hexaoxacyclooctadecane (18-Crown-6), contains an organometallic half-sandwich superstructure unit {K(18-Crown-6)(ηn-C6H5B(C6H5)3)} (1 with n = 1–6), and shows a reversible phase transition at ∼211 K. The analysis of crystal structures at 173 K in the low-temperature phase, and 293 and 423 K in the high-temperature phase revealed that the breaking-symmetry phase transition is associated with the order–disorder transformation of [K(18-Crown-6)]+ and the change of the coordination mode of the phenyl ring to K+. A dielectric anomaly appears at ca. 212 K and dielectric relaxation occurs above 375 K in 1. The dielectric and thermal anomaly temperatures are close to each other, and the dielectric relaxation is relevant to the relative displacement of [K(18-Crown-6)]+ and the tetraphenylboron anion. [ABSTRACT FROM AUTHOR]

A new 1D phosphorescence coordination polymer (CP) [Pb2O(C6H4NO2)2]n (1; C6H4NO2 = nicotinate) was synthesized by a solvothermal reaction and PbO was used as a Pb(ii) source instead of traditional Pb(ii) salts. This remarkably thermal-stable CP crystallizes in the space group I41/a. In the crystal structure of 1, two different Pb(ii) ions show a five-coordinated and hemidirected coordination geometry, two nonequivalent nicotinate ligands link to Pb(ii) ions in μ2–η1:η1 and μ4–η2:η2 modes, and the hemidirected coordination polyhedra of Pb(ii) form a helical lead-oxide chain via an edge-sharing fashion along the c-axis. Under ambient conditions, 1 emits cyan ligand-based phosphorescence with an absolute quantum yield as high as 59.4% and a lifetime of 9.86 ms under UV-light irradiation. Under the same conditions, nicotinic acid emits simultaneously fluorescence and phosphorescence with a total absolute quantum yield of 4.8%. The great enhancement of phosphorescence quantum yield in 1, regarding nicotinic acid, is assigned to the heavy atom effect of Pb(ii) and negligible π…π interaction between pyridyl rings. Noticeably, the vibronic fine structure is observed in the emission spectrum of 1 at room temperature. Additionally, 1 shows thermochromic behavior, and such functionality probably has realistic application in the field of temperature detection. [ABSTRACT FROM AUTHOR]

Two pairs of MOF-based hybrid enantiomorphs, [NH2(CH3)2]3[Pb2X3(BDC)2] (H2BDC = 1,4-benzenedicarboxylic acid, X = Br or I), have been synthesized using the solvothermal reaction and then manually separated, which are labeled as 1a/1b (X = Br) and 2a/2b (X = I). The isomorphic 1a and 2a crystallize in tetragonal space group P43212, and the isomorphic 1b and 2b in the enantiomorphic space group P41212. Twofold interpenetrated three-dimensional (3-D) networks were built from two sets of equivalent I1O2 type hybrid inorganic–organic frameworks in 1a/1b and 2a/2b. Each I1O2 type hybrid inorganic–organic framework constructs by the inorganic pentagonal bipyramid-shape PbX3O4 (X = Br or I) polyhedral chains along the c-axis, which are further connected though bridged BDC2− ligands in the directions perpendicular to the c-axis. Hybrids 1a/1b and 2a/2b have been characterized by elemental analysis (C, H and N elements), thermogravimetric and powder X-ray diffraction techniques, and UV-visible absorption spectroscopy in the solid state. These hybrids show dual emissions at ambient conditions, which arise from the π–π* electron transition within the aromatic rings in the BDC2− ligands and the electron transition in the inorganic polyhedral semiconducting chains, as well as thermochromic luminescence behavior from 10 to 300 K owing to two emission bands displaying different responses to the temperature change. [ABSTRACT FROM AUTHOR]

Under solvothermal conditions, a robust Pb2+-based coordination polymer (CP), [Pb(TDC)]n (1), where H2TDC is thiophenedicarboxylic acid, has been achieved. Structural analysis reveals that 1 crystallizes in the monoclinic space group C2/c, where the Pb2+ ions show quadrangular prism coordination geometry. CP 1 represents a 3D coordination network based on a TDC2− ligand as bridges and quadrangular prismatic PbO8 units as nodes, among which the PbO8 units are extended through edge-sharing to form a 2D layer in the bc plane. Interestingly, CP 1 emitted intense and long-lived orange phosphorescence in the solid state at room temperature, with a quantum yield of 6.7% and a phosphorescence lifetime of 1.78 ms. A fine structure is clearly observed in the phosphorescence emission spectra at temperatures below 55 K. The emission mainly arose from the electron transition within the π-type orbitals of the TDC2− ligand. This study gives a fresh impetus to achieve CP-based long-lived phosphorescent materials under ambient conditions. [ABSTRACT FROM AUTHOR]

A two-dimensional coordination polymer, [Mn3(HEBTC)2(DMSO)6] (1), has been achieved by a solvothermal reaction of Mn2+ with 1,1′-ethynebenzene-3,3′,5,5′-tetracarboxylic acid (H4EBTC). The layer of a coordination polymer is composed of trinuclear Mn2+ clusters linked by HEBTC3− ligands to form a (3,6)-connected topological net. CP 1 with paramagnetic Mn2+ ions shows dual emissions centered at 397 and 468 nm in the solid state under ambient conditions with respectable quantum yields of 15.3% (397 nm) and 12.3% (468 nm). The dual emissions arise from n ←π* transition in HEBTC3− and MLCT between HEBTC3− and Mn2+ centers. [ABSTRACT FROM AUTHOR]

The solid state electrolytes show a wide range of practical applications in a variety of all-solid-state electrochemical devices, and it is highly in demand to explore new types of solid state electrolyte materials. In this study, we have designed and prepared a fluorite-type coordination compound, [Mn(en)3]I2, which has been characterized by microanalysis for C, H and N elements, infrared spectrum in the wavenumber range of 4000–400 cm−1, thermogravimetric analysis and differential scanning calorimetry. The single crystal X-ray diffraction revealed that the bigger size [Mn(en)3]2+ cations build three-dimensional network in the crystal of [Mn(en)3]I2 and the smaller size iodide ions occupy the tetrahedral or octahedral cavities surrounded by the [Mn(en)3]2+ cations, featuring as the fluorite-type compound. The impedance spectra were investigated to reveal the ionic conductivity σ = 3.45 × 10−11 S cm−1 at 303 K, while σ = 1.37 × 10−6 S cm−1 at 423 K, sharply increasing by five orders of magnitude regarding to that at 303 K. The electric modulus analysis further confirmed the conductance contributed from the migration of iodide ions. This study opens a way to design and achieve new coordination compound-based ion conductors. [ABSTRACT FROM AUTHOR]

In this study, a new two-dimensional Pb2+-based coordination polymer (CP), [Pb2(EBTC)(DMSO)3] (1), where H4EBTC is 1,1′-ethynebenzene 3,3′,5,5′-tetracarboxylic acid, was synthesized under solvothermal conditions. Structural analysis reveals that 1 crystallizes in the monoclinic space group C2/m, where two crystallographically different Pb2+ ions show a coordination geometry of bicapped trigonal prisms that are connected to a double-chain by the EBTC4− ligands through carboxylate groups along the b-axis direction, and where successive double chains are held together to form a 2D layer via the Pb1 and Pb2 bicapped trigonal prisms sharing one edge or a triangle face along the c-axis direction. Interestingly, CP 1 emitted intense and long-lived greenish phosphorescence in the solid state at ambient conditions, with a quantum yield of 1.5% and a phosphorescence lifetime of 4.17 ms, and the emission mainly arose from the electron transition within the π-type orbitals of the EBTC4− ligand. The emission bands assignment and photophysical process were further discussed according to the calculation of both the electronic band structures and density of states. This study gives a fresh impetus to achieve coordination polymer-based long-lived phosphorescence materials under ambient conditions. [ABSTRACT FROM AUTHOR]

Proton conducting materials have important technological applications as key components in electrochemical devices, including fuel cells, electrochemical sensors, electrochemical reactors and electrochromic displays. And the exploration of novel proton conducting materials is significant for the development of efficient electrochemical devices. In this study, we have investigated the proton conductance of an open-framework manganese(ii) phosphite, (NH4)0.59(H3O)1.41Mn5(HPO3)6 (1). The open-framework manganese(ii) phosphate shows superior water-stability and excellent thermal stability. There was intrinsic water-assisted proton conductivity with σ = 3.94 × 10−4 S cm−1 at 328 K and 98% RH. Furthermore, composite membranes have further been fabricated using polyvinylidene fluoride (PVDF) and 1, labeled as 1@PVDF-X, where the symbol X represents the mass percentage of 1 (as X%) in the composite membrane and X = 10–55%. The composite membranes display good mechanical performance and durability for practical applications, and the proton conductivity of 1@PVDF-55 reaches 3.32 × 10−5 S cm−1 in deionized water at 336 K. [ABSTRACT FROM AUTHOR]

Proton-conducting materials show important technological applications as key components in energy conversion, electrochemical sensing and electrochromic devices; the exploration for new types of proton-conducting materials is crucial for the development of efficient electrochemical devices. In this study, we investigated the proton transport nature of an inorganic–organic hybrid crystal of open-framework cobalt phosphate, (C2N2H10)0.5CoPO4. The structure of the hybrid crystal consists of the [CoPO4]−∞ anionic framework, and the proton carriers, H2en2+ cations (en = ethylenediamine), are located in the pores to compensate the negative charges of the inorganic framework. The open-framework is thermally stable up to 653 K (380 °C) at least, and also shows superior water stability. The open-framework exhibits negligible conductance in an anhydrous environment even at 473 K; however, there is evident water-assisted proton conduction. The conductivity reaches 2.05 × 10−3 S cm−1 at 329 K and 98% RH. Such high proton conductivity can compete with numerous state-of-the-art MOFs/PCPs-based proton conductors, and this material has promising applications in diverse electrochemical devices. [ABSTRACT FROM AUTHOR]

A highly thermally stable CP/MOF, comprised of Mg2+ and H2EBTC2− with the formula of [Mg(H2EBTC)(DMF)2], emits dual band luminescence centered at 376 and 555 nm. The former is assigned to the fluorescence of H2EBTC2− and the latter with 1.63 μs decay lifetime and large Stokes shifts corresponds to the phosphorescence of H2EBTC2−. To the best of our knowledge, this is the first time the ligand-based phosphorescence in a CP/MOF without any heavy atom at room temperature has been observed. [ABSTRACT FROM AUTHOR]

Films of Prussian blue analogue (PBA) Co3[Co(CN)6]2 were fabricated on porous α-alumina, ITO glass, silicon wafer and non-woven fabric substrates via a facile self-assembly method, and were characterized using infrared spectroscopy, X-ray powder diffraction and scanning electron microscope techniques. The films composed of truncated cube-shaped PBA particles are highly oriented with a preferred (100) plane on the glossy and smooth surfaces of ITO glass and silicon wafer, but crystallographically isotropic on the rough surface of porous α-alumina and non-woven fabric substrates. Compact films were achieved on porous α-alumina and surface-functionalized ITO glass. Reversible solvatochromism/vapochromism was discovered and investigated for the powdered and thin-film PBA samples. Such peculiar solvatochromism/vapochromism is related to the process of the adsorbed solvent molecules replacing the coordinated water molecules in octahedral Co2+–(N)4(H2O)2. The change of the Co2+ ion’s coordination atmosphere leads to the variation of crystal field strength, as a result, the d–d transitions within the Co2+ ions are altered to give rise to a color change. [ABSTRACT FROM AUTHOR]

A clathrate NH4Br@HKUST-1 has been prepared by means of soaking the metal–organic-framework, HKUST-1, in ammonium bromide saturated ethanol solution at ambient temperature. Both NH4Br@HKUST-1 and HKUST-1 show the same framework structure. The formula of the clathrate is approximately expressed as Cu3(BTC)2(NH4Br)1.15. The thermal stability of the metal–organic framework is not affected by incorporating ammonium bromide into its pores. The impedance spectra measurements were performed for both NH4Br@HKUST-1 and HKUST-1 in anhydrous and selected relative humidity environments, disclosing that the conductivity of NH4Br@HKUST-1 is enhanced by three/four orders of magnitude under the same conditions with respect to HKUST-1. This study provided an efficient strategy to achieve new high conductivity proton transport materials. [ABSTRACT FROM AUTHOR]

An iodoplumbate-based hybrid, [C7-Apy][PbI3] (1), where C7-Apy+ = 1-heptyl-4-aminopyridinium, was prepared using a simple solution process. Three sequential phase transitions occur in the range of 402–443 K. In both the lowest and highest temperature phases, hybrid crystal 1 is composed of discrete [Pb2I6]∞ twin chains surrounded by C7-Apy+ cations. The connectivity between PbI6 octahedra within a [Pb2I6]∞ twin chain and the arrangement of cations are quite difference between the lowest and highest temperature phases. Hybrid crystal 1 shows switchable ion conductivity due to the structural phase transition and white light emission attributed to the broad band semiconductor emission of the twin chain. The former functionality has potential application in ion conductor devices; the single-phase white light emitter is a useful material in low-cost, easily-made, high-efficiency white light-emitting diodes. [ABSTRACT FROM AUTHOR]

A coordination polymer (CP) of Mg2+ with 1,3,5-benzenetricarboxylate (BTC3−) was synthesized using a solvothermal method. The Mg-CP, with a formula of Mg3(BTC)(HCOO)3(DMF)3, crystallizes in the trigonal space group P3̅, with cell parameters of a = b = 13.972(5) Å, c = 8.090(5) Å and V = 1367.6(11) Å3, and shows a lamella structure built from planar rosette-type hexanuclear architectures. The Mg-CP emits intense blue fluorescence arising from π* →π transition of intra-ligand of BTC3− with 21.69% quantum yield, yet it exhibits poor stability to water. The composites of Mg-CP with hydrophobic polyvinylidene fluoride (PVDF) were sequentially prepared by mechanically mixed, tableted and annealed processes, which showed good compatibility between Mg-CP and PVDF, high hydrostability, and intense blue emission. This study suggests a simple but efficient method to solve the drawbacks of some functional CPs unstable to water and to promote them as practical applications in the field of functional materials. [ABSTRACT FROM AUTHOR]

Organic–inorganic hybrid crystals, [1,5-bis(1-methylimidazolium)pentane][PbBr3]2 (1), were achieved through the mutual diffusion of a bi-imidazolium based ionic liquid and PbBr2 solution of DMF in a glass tube. The hybrid solid crystallizes in the orthorhombic space group Fdd2 at room temperature; and is composed of one-dimensional [PbBr3]∞ chains where the neighbouring PbBr6 coordination octahedra are linked together via the face-sharing mode and the inorganic chains are surrounded by organic cations. The hybrid solid exhibits a dielectric anomaly around 443 K and dielectric relaxation above 400 K, the dielectric response mechanism was investigated using variable-temperature X-ray single crystal and powder diffraction as well as DSC techniques. Fascinatingly, this hybrid solid shows dual band emissions, moreover, the fluorescence nature of the two emission bands exhibits a distinct response to temperature, leading to a temperature-dependent fluorescence color, this feature has promising application in the emission temperature-sensing field. [ABSTRACT FROM AUTHOR]

A family of novel lanthanide metal–organic frameworks (MOFs) with formula [Ln2(EBTC)1.5(CH3OH)4]·6H2O [EBTC4− = 1,1′-ethynebenzene-3,3′,5,5′-tetracarboxylate, Ln = La (1), Ce (2), Pr (3), Nd (4), Sm (5), Eu (6), Gd (7), Tb (8) and Dy (9)], have been synthesized via solvothermal reaction. All compounds are isostructural, crystallized in the monoclinic space group P21/n, and show a three-dimensional (4,6)-connected network with Schläfli symbol of {310}. Photoluminescent measurements indicated that 1 and 7 emit the luminescence originating from the intraligand π←π* transition, 2 shows the broadband emission due to allowed 4f–5d transitions, and 4–9 show the emission of typical lanthanide f–f transition via the ligand “antenna effect” in the solid state at ambient temperature. Interestingly, compounds 6 and 8 showed microsecond time-scale fluorescence lifetimes with 0.84 ms for 6 and 0.39 ms for 8, respectively. Such unique spectroscopy features may have applications in biomacromolecule research. [ABSTRACT FROM AUTHOR]

Since carrier doping of two-leg spin ladders can theoretically induce a superconductive state, investigation of such systems is of great use in the study of superconductivity. In this paper, we report the successful creation of a non-magnetic impurity doped into a two-leg molecular spin ladder and the characterization of its magnetic properties. [ABSTRACT FROM AUTHOR]

Herein we report the synthesis of α-Dawson type POM, Li6[α-P2W18O62]·28H2O, directly from the use of Li2WO4 as the tungstate source. The salt obtained was soluble not only in water but also in a range of polar and non-polar organic solvents, such as benzene. [ABSTRACT FROM AUTHOR]

Two novel lanthanide coordination polymers, [Eu2(EBTC)(DMF)5(NO3)2]·DMF (1) and [Eu2(BBTC)1.5(CH3OH)2(H2O)2]·7DMF·HNO3(2) (EBTC4−= 1,1′-ethynebenzene-3,3′,5,5′-tetracarboxylate; BBTC4−= 1,1′-butadiynebenzene-3,3′,5,5′-tetracarboxylate), were successfully synthesized from conjugated ligands of EBTC4−and BBTC4−. Although the two tetracarboxylate ligands have similar structures, their different rigidity/flexibility results in quite different networks upon complexation. Complex 1has a two-dimensional (2-D) layered structure with two crystallographically independent Eu3+ions, one in a distorted monocapped square-antiprism and the other in a distorted square-antiprism coordination geometry. Complex 2exhibits a three-dimensional (3-D) porous framework, with one type of Eu3+in a distorted square-antiprism and the other in a trigondodecahedron environment. Both 1and 2emit the intensely red characteristic luminescence of Eu3+ion at room temperature, with a long lifetime of up to 1.3 and 0.7 ms, respectively, during which the ligand emission of EBTC4−/BBTC4−was quenched by the Eu3+ion, indicating the existence of efficient energy transfer between the conjugated ligand of EBTC4−/BBTC4−and the Eu3+ion. Thus, both EBTC4−and BBTC4−are ideal ligands with an “antenna” effect for the Eu3+ion. The two complexes show the single-ion magnetic behaviors of Eu3+with strong spin–orbit coupling interactions even if there are shorter distances (5.714 Å for 1versus4.275 and 5.360 Å for 2) between the neighboring Eu3+ions connected by oxygen atoms of the tetracarboxylates. [ABSTRACT FROM AUTHOR]

A low-dimensional compound [C6-Apy][Ni(mnt)2] (1, where mnt2−= maleonitriledithiolate, C6-Apy+= 4-amino-1-hexylpyridinium) has been designed and synthesized, which has layer arrangement of anions and cations and shows two steps of magnetic transitions. The low temperature magnetic transition has an uncommon hysteresis loop, while the crystal structure investigations disclosed no structural transition with the magnetic transition. The high temperature magnetic transition exhibits two remarkable features: (1) it synchronously occurs with a crystalline-to-mesophase transition in the first heating process and (2) the structural changes that accompany the solid-mesophase transition are irreversible. A diamagnetic and isostructural compound, [C6-Apy][Cu(mnt)2], is further characterized by structure, DSC and POM techniques, which revealed also the existence of an irreversible crystalline-to-mesophase transition in the same temperature interval of [C6-Apy][Ni(mnt)2]. Therefore, the high-temperature magnetic transition in 1is driven by release of the structural strains, but not magnetoelastic interactions. The mesophase exhibits the characteristic of smectic A phase, and the alkyl chain melting in the cation layers probably lead to the formation of mesophase. It is noticeable that the finding of a mesophase occurring in a hexyl hydrocarbon chain molecular system is in contrast to a suggested rule that at least a dodecyl chain is required. Our results will shed a light on the design and preparation of a new low-dimensional molecular system combining magnetic transition and liquid crystal properties. [ABSTRACT FROM AUTHOR]

Eight inorganic–organic hybrid compounds with a formula of [R-Bz-1-APy][PbI3] (R-Bz-1-APy+= mono-substituted benzylidene-1-aminopyridinium Schiff base derivative; R = m-CN (1), m-CH3(2), H (3), p-F (4), p-Cl (5), p-Br (6), o-Cl (7), o-Br (8)) have been synthesized and characterized structurally. The common characteristic of the crystal structures of 1–8is that the inorganic components form straight and face-sharing octahedral [PbI3]∞chains and the Schiff base cations surround the [PbI3]∞chains to form molecular stacks. The substituent (R) on the phenyl ring of the Schiff base cation clearly influences the packing structures of 1–8, and the hybrid compound crystallizes in the space group P63when R = CN (1) in the meta-position of the phenyl ring, and in a central symmetric space group when R is in the ortho- or para-position of the phenyl ring. The conformation of the Schiff base cation is related to the R position, and the dihedral angle between the phenyl and pyridyl rings increases in the order of para- < meta- < ortho-position substitution of the phenyl ring. The long molecular axis of the Schiff base cation adopts a manner approximately parallel to the straight inorganic [PbI3]∞chain in the para-substituted hybrid compounds, and perpendicular to the straight inorganic [PbI3]∞chain in the ortho-substituted hybrid compounds. 1is second harmonic generation (SHG) active with a comparable response as that of urea and also exhibits ferroelectricity with larger Psand Prvalues; 1–8emit multi-band luminescence in the 300–650 nm regions under the excitation of ultraviolet light. [ABSTRACT FROM AUTHOR]

The supramolecular lead iodide perovskite crystals, {[NH4(18-crown-6)]PbI3}∞ (1), (18-crown-6 = 1,4,7,10,13,16-hexaoxacyclooctadecane), was successfully achieved by a facile solvent evaporation strategy using a DMF solution containing equal molar quantities of PbI2, NH4I and 18-crown-6. The supramolecular perovskite was characterized by microanalysis for C, H and N elements, thermogravimetric (TG) analysis, differential scanning calorimetry (DSC), powder X-ray diffraction (PXRD) and single crystal X-ray diffraction techniques. DSC measurements demonstrated that 1 experiences a two-step thermotropic phase transition around 333 K and 383 K, respectively. The phase transition is relevant to the disorder–order transformation of the 18-crown-6 molecule at ∼333 K, while both breaking-symmetry and ordered-disordered transformation of the 18-crown-6 molecule occurred at ∼383 K. In addition, the sharp change of the PbI6 coordination octahedron distortion degree plays a synergistic role in the two-step phase transition. The dielectric relaxation occurs above 243 K in 1 and is mainly attributed to the displacement of the NH4+ ions relative to the ring of the 18-crown-6 molecule and {PbI3}∞ chain induced by an AC electrical field. [ABSTRACT FROM AUTHOR]

The zero/negative thermal expansion (ZTE/NTE), which is an intriguing physical property of solids, has been observed in a few families of materials. ZTE materials possess practical applications in specific circumstances such as space-related applications, engineering structures and precision instrument. Generally, NTE materials are used as additives to form a composite of the ZTE material with positive thermal expansion material. It is still a tremendous challenge to design new families of ZTE/NTE materials. Herein, we presented a temperature-dependent single crystal structure analysis in 110–300 K for a layered (NH4)2V3O8, which crystallizes in a tetragonal space group P4bm and comprises mixed valence [V3O82−]∞ monolayers and NH4+ residual in the interlayer spaces. Along the c-axis, (NH4)2V3O8 demonstrated uniaxial expansion behaviors, i.e., ZTE with αc = −1.10 × 10−6 K−1 in 110–170 K and NTE with αc = −16.25 × 10−6 K−1 in 170–220 K. Along the a-axis, (NH4)2V3O8 exhibited ZTE with αa = + 2.06 × 10−6 K−1 in 240–300 K. The mechanisms of ZTE and NTE were explored using structural analysis. The conduction of NH4+ ions in the interlayer space was studied, indicating that the conductivity rapidly rises with the expansion of interlayer space at temperatures of >293 K. This study discloses that layered vanadates are promising ZTE/NTE materials. [ABSTRACT FROM AUTHOR]