A novel metallo‐organically templated pentaborate: acetato[N,N′‐bis(2‐aminoethyl)ethane‐1,2‐diamine]zinc(II) 4,4′,6,6′‐tetrahydroxy‐2,2′‐spirobi[cyclotriboroxane](1−)

The title compound, [Zn(C₂H₃O₂)(C₆H₁₈N₄)][B₅O₆(OH)₄], contains mixed‐ligand [Zn(CH₃COO)(teta)]⁺ complex cations (teta is triethylenetetramine) and pentaborate [B₅O₆(OH)₄]⁻ anions. The [B₅O₆(OH)₄]⁻ anions are connected to one another through hydrogen bonds, forming a three‐dimensional supramolecular network, in which the [Zn(CH₃COO)(teta)]⁺ cations are located.     

Acetate-Functionalized Zirconium-Substituted Tungstogermanate, [Zr4O2(OH)2(CH3COO)2(α-GeW10O37)2]12−

The two acetate-functionalized zirconium(IV)-substituted tungstogermanates, Na₈K₄[Zr₄O₂(OH)₂(CH₃COO)₂(α-GeW₁₀O₃₇)₂] · 33H₂O and Na₈Cs₄[Zr₄O₂(OH)₂(CH₃COO)₂(α-GeW₁₀O₃₇)₂] · 32H₂O, were synthesized by the reaction of ZrOCl₂ with [A-α-GeW₉O₃₄]¹⁰⁻ in pH = 4.8 buffer and their structures were determined by single-crystal X-ray analysis. Both of them contain a centrosymmetric polyanion [Zr₄O₂(OH)₂(CH₃COO)₂(α-GeW₁₀O₃₇)₂]¹²⁻ consisting of two {α-GeW₁₀O₃₇} units sandwiching an inorganic–organic hybrid {Zr₄O₂(OH)₂(CH₃COO)₂} cluster. The polyanion contains a mixing of seven- and eight-coordinate Zr centres. The two compounds were also characterized by elemental analysis, IR spectroscopy, UV–vis and TG–DSC analysis.     

Porous Salts Containing Cationic Al24-Hydroxide-Acetate Clusters from Scalable,Green and Aqueous Synthesis Routes

The solution chemistry of aluminum is highly complex and various polyoxocations are known. Here we report on the facile synthesis of a cationic Al₂₄ cluster that forms porous salts of composition [Al₂₄(OH)₅₆(CH₃COO)₁₂]X₄, denoted CAU-55-X, with X=Cl⁻, Br⁻, I⁻, HSO₄⁻. Three-dimensional electron diffraction was employed to determine the crystal structures. Various robust and mild synthesis routes for the chloride salt [Al₂₄(OH)₅₆(CH₃COO)₁₂]Cl₄ in water were established resulting in high yields (>95 %, 215 g per batch) within minutes. Specific surface areas and H₂O capacities with maximum values of up to 930 m² g⁻¹ and 430 mg g⁻¹ are observed. The particle size of CAU-55-X can be tuned between 140 nm and 1250 nm, permitting its synthesis as stable dispersions or as highly crystalline powders. The positive surface charge of the particles, allow fast and effective adsorption of anionic dye molecules and adsorption of poly- and perfluoroalkyl substances (PFAS).     

Characterization of tetra,dodeca and tetradeca MoV polyoxometalate wheels structured by etidronate ligands

The reactivity of the [Mo^V₂O₄]²⁺ dinuclear unit with the [O₃P(C(CH₃)(OH))PO₃]^4? etidronate ligand has been investigated. Three complexes have been isolated and characterized by IR spectroscopy, elemental analysis and single crystal X-Ray diffraction studies. Structural determination of the tetranuclear compound (CN₃H₆)₆[(Mo^V₂O₄)₂(O₃P(C(CH₃)O)PO₃)₂]·12H₂O (1) revealed that the hydroxo group of the etidronate ligand can be deprotonated in presence of Mo^V even in acidic media. It follows that its coordination mode thus differs from that of the methylenediphosphonate ligand [O₃P(CH₂)PO3]4?, which reactivity with Mo^V has been previously widely studied. In contrast, no such deprotonation of the hydroxo group is observed in the (NH₄)₁₈[(Mo^V₂O₄)₆(OH)₆(O₃P(C(CH₃)(OH))PO₃)₆]·35H₂O complex 2. This species contains a dodecanuclear core analogous to the one previously found in the [(Mo^V₂O₄)₆(OH)₆(O₃PCH₂PO₃)₆]^18? methylenediphosphonato polyanion. In 2, six interconnected {(Mo^V₂O₄)(O₃P(C(CH₃)(OH))PO₃)} units form a cyclohexane-like ring in a chair conformation. In the (CN₃H₆)₁₈Na₃[(Mo^V₂O₄)₇(O₃P(C(CH₃)(OH))PO₃)₇(CH₃COO)₇]·5CH₃COONa 52H₂O compound 3, seven {(Mo^V₂O₄)(O₃P(C(CH₃)(OH))PO₃)(CH₃COO)} units are connected, forming an almost planar tetradecanuclear wheel. This compound represents the largest homometallic Mo^V polyoxometalate cyclic system reported to date. Finally, ³¹P NMR studies revealed that only complex 1 is stable in aqueous solution.     

Ternäre Acetate der Lanthanide mit Caesium: Dimere und Trimere in CsLu(CH3COO)4 bzw. Cs2[Lu3(CH3COO)10(OH)(H2O)]. Synthese,Kristallstrukturen und Thermolyse

Ternary Acetates of the Lanthanides with Cesium: Dimers in CsLu(CH₃COO)₄ and Trimers in Cs₂[Lu₃(CH₃COO)₁₀(OH)(H₂O)]. Synthesis, Crystal Structures, Thermolysis Single crystals of CsLu(CH₃COO)₄ and Cs₂[Lu₃(CH₃COO)₁₀(OH)(H₂O)] were obtained from an aqueous solution of lutetium and cesium acetate in a 1:1 molar ratio. The crystal structures (CsLu(CH₃COO)₄: monoclinic, P2₁/n (no. 14), Z = 8, a = 1 293.1(2), b = 1 323.8(2), c = 1 622.5(3) pm, β = 92.01(2)°, V_m = 208.97(6) cm³/mol, R = 0.056, R_w = 0.034; Cs₂[Lu₃(CH₃COO)₁₀(OH)(H₂O)]: monoclinic, C2/c (no.15), Z = 4, a = 2 138.5(6), b = 1 378.0(3), C = 1 482.9(4) pm, β = 106.15(2)°, V_m = 632.0(3) cm³/mol, R = 0.049, R_w = 0.036) were determined from four-circle-diffractometer data. The structures consist of dimers and trimers, respectively, that are built by bridging acetate groups. These units are fragments of the infinite chains of the Ho(CH₃COO)₃ type of structure. The isotypic compounds CsM(CH₃COO)₄ with M=Eu? Lu were synthesized and characterized by the X-ray Guinier technique. The thermal decomposition of CsLu(CH₃COO)₄ was examined with thermoanalytical methods (TG/DSC with coupled gas analysis) and the Guinier-Simon technique: it decomposes at 260°C in an endothermic reaction to Lu₂O₃ and Cs₂CO₃.     

Low Bandgap 2D Perovskite Single Crystal with Anomalous-large Charges/ions Collection Ratio for Ultra-sensitive and Stable X-ray Detectors

The low-dimensional halide perovskites have attracted increasing attention due to their improved moisture stability, reduced defects, and suppressed ions migration in many optoelectronic devices such as solar cells, light-emitting diodes, X-ray detectors, and so on. However, they are still limited by their large band gap and short charge carriers’ diffusion length. Here, we demonstrate that the introduction of metal ions into organic interlayers of two-dimensional (2D) perovskite by cross-linking the copper paddle-wheel cluster-based lead bromide ([Cu(O₂C−(CH₂)₃−NH₃)₂]PbBr₄) perovskite single crystals with coordination bonds can not only significantly reduce the perovskite band gap to 0.96 eV to boost the X-ray induced charge carriers, but can also selectively improve the charge carriers’ transport along the out-of-plane direction and blocking the ions motion paths. The [Cu(O₂C−(CH₂)₃−NH₃)₂]PbBr₄ single-crystal device can reach a record charges/ions collection ratio of 1.69×10¹⁸±4.7 % μGy_air⁻¹ s, and exhibit a large sensitivity of 1.14×10⁵±7% μC Gy_air⁻¹ cm⁻² with the lowest detectable dose rate of 56 nGy_air s⁻¹ under 120 keV X-rays irradiation. In addition, [Cu(O₂C−(CH₂)₃−NH₃)₂]PbBr₄ single-crystal detector exposed to the air without any encapsulation shows excellent X-ray imaging capability with long-term operational stability without any attenuation of 120 days.     

The hydroxyl radical reaction rate constants and atmospheric reaction products of three siloxanes

The relative rate technique has been used to measure the hydroxyl radical (OH) reaction rate constant of hexamethyldisiloxane (MM, (CH₃)₃Si-O-Si(CH₃)₃), octamethyltrisiloxane (MDM, (CH₃)₃Si-O-Si(CH₃)₂-O-Si(CH₃)₃), and decamethyltetrasiloxane (MD₂M, (CH₃)₃Si-O-Si(CH₃)₂-O-Si(CH₃)₂-O-Si(Ch₃)₃). Hexamethyldisiloxane, octamethyltrisiloxane, and decamethyltetrasiloxane react with OH with bimolecular rate constants of 1.32 ± 0.05 × 10⁻¹² cm³molecule⁻¹s⁻¹, 1.83 ± 0.09 × 10⁻¹² cm³ molecule⁻¹s⁻¹, and 2.66 ± 0.13 × 10⁻¹² cm³molecule⁻¹s⁻¹, respectively. Investigation of the OH + siloxane reaction products yielded trimethylsilanol, pentamethyldisiloxanol, heptamethyltetrasiloxanol, hexamethylcyclotrisiloxane, octamethylcyclotetrasiloxane, and other compounds. Several of these products have not been reported before because these siloxanes and the proposed reaction mechanisms yielding these products are complicated. Some unusual cyclic siloxane products were observed and their formation pathways are discussed in light of current understanding of siloxane atmospheric chemistry. © 1997 John Wiley & Sons, Inc. Int J Chem Kinet 29: 445–451, 1997.     

Kinetic studies of the self‐reaction and reaction with HO2 of a tertiary β‐brominated peroxy radical between 298 and 393 K

The kinetics of reactions of the tertiary β‐brominated peroxy radical BrC(CH₃)₂C(CH₃)₂O₂ (2‐bromo‐1,1,2‐trimethylpropylperoxy) have been studied using the laser flash photolysis technique, photolysing HBr at 248 nm in the presence of O₂ and 2,3‐dimethylbut‐2‐ene. At room temperature, a rate constant of (2.0 ± 0.8) × 10⁻¹⁴ cm³ molecule⁻¹ s⁻¹ was determined for the BrC(CH₃)₂C(CH₃)₂O₂ self‐reaction. The reaction of BrC(CH₃)₂C(CH₃)₂O₂ with HO₂ was investigated in the temperature range 306–393 K, yielding the following Arrhenius expression: k(BrC(CH₃)₂C(CH₃)₂O₂ + HO₂) = (2.04 ± 0.25) × 10⁻¹² exp[(501 ± 36)K/T] cm³ molecule⁻¹ s⁻¹, giving by extrapolation (1.10 ± 0.13) × 10⁻¹¹ cm³ molecule⁻¹ s⁻¹ at 298 K. These results confirm the enhancement of the peroxy radical self‐reaction reactivity upon β‐substitution, which is similar for Br and OH substituents. In contrast, no significant effect of substituent has been observed on the rate constant for the reactions of peroxy radicals with HO₂. The global uncertainty factors on rate constants are equal to nearly 2 for the self‐reaction and to 1.35 for the reaction with HO₂. © 2000 John Wiley & Sons, Inc. Int J Chem Kinet 33: 41–48, 2001     

Neutralization-reionization mass spectrometry (NRMS). Structural information from vertical neutralization and reionization efficiencies

The neutralization-reionization mass spectra of alkane radical ions indicate significant differences between the structures and geometries of alkane molecules and their molecular ions, confirming recent ab initio predictions. Ionic isomers that are indistinguishable by collisionally-activated dissociation because of easy interconversion can be characterized by neutralization-reionization if the corresponding neutrals show different reactivities, as is demonstrated for the [C₂H₅]⁺/C₂H₅˙ system and for [C₂H₄O₂]⁺˙ isomers. For identification of mixtures of more than one neutral species, the relative efficiency for reionizing each neutral must be determined; e.g. the O₂ reionization efficiency of ˙CH₂OH radicals is ～4 times greater than that of CH₃O˙. This information and reference reionization spectra of CH₃O˙ and ˙CH₂OH show that metastable or collisionally activated methyl acetate cations lose CH₃O˙, not ˙CH₂OH as previously reported; the newly-formed CH₃O˙ undergoes partial (～20%) isomerization to ˙CH₂OH in the ～10^?6s before reionization. Similar results are obtained for [B(OCH₃)₃]⁺˙.     

Structures of an infinite helical water chain and discrete lattice water in metal–organic framework structures

Two supramolecular complexes Ni[(Py)₂C(OH)₂]₂·(CH₃COO)₂·4H₂O 1 and Co[(Py)₂C(OH)₂]₂·(CH₃COO)₂·2H₂O 2 have been synthesized under hydrothermal conditions and structurally characterized by elemental analysis, IR spectra, and X-ray single-crystal diffraction. The X-ray diffraction analysis indicates that the center metal (Ni²⁺ and Co²⁺) ions having the same coordination environments are chelated by two pyridyl N atoms and a hydroxyl O atom of the gem-diol ligand in an octahedral geometry. In 1, the lattice water molecules form infinite single helical chains, while in 2, two lattice water molecules are discrete. In their crystal structures, intermolecular O–H···O and C–H···O hydrogen bonds form an extensive three-dimensional network, which consolidates the crystal packing.     

Das wasserfreie Lanthanacetat,La(CH3COO)3, und sein Precursor,NH4)3[La(CH3COO)6] · 1/2 H2O: Synthese,Strukturen, thermisches Verhalten

Anhydrous Lanthanum Acetate, La(CH₃COO)₃, and its Precursor, ·NH₄)₃[La(CH₃COO)₆] · 1/2 H₂O: Synthesis, Structures, Thermal Behaviour Single crystals of (NH₄)₃[La(CH₃COO)₆] · ½ H₂O are obtained by refluxing La₂O₃in (CH₃COO)₃ · 1.5 H₂O with an excess of NH₄CH₃COO in methanol. The crystal structure (trigonal, R3 , Z = 6, a = 1 365.0(3) pm, c = 2 360(1) pm, R = 0.088, R_w = 0.061 exhibits the coordination number of nine for La³⁺, which is surrounded by three chelating-type bidentate and three unidentate acetate groups. Characteristic are monomeric units of [La(CH₃COO)₆]^3? which are connected to a three-dimensional network by hydrogen bonds with the NH ions. Thermal decomposition consists of four steps with La(CH₃COO)₃, La₂(CO₃)₃ and La₂O₂CO₃ as intermediates and La₂O₃ as the final Product. Single crystals of La(CH₃COO)₃ are obtained from La₂O₃ in a melt of NH₄CH₃COO (molar ratio 1:12) in a sealed glass ampoule. The crystal structure (trigonal, R3 , Z = 18, a = 2 203.0(5) pm; c = 987.1(3) pm, R = 0.027, R_w = 0.023) shows the coordination number of ten for La³⁺. These are three-dimensionally connected by oxygen atoms of the acetate groups with two tetradentate double-bridging and one Z,Z-type-bridging bidentate acetate group.     

A kinetic and product study of the gas-phase reaction of ozone with vinylcyclohexane and methylene cyclohexane

The gas-phase reaction of ozone with vinylcyclohexane and methylene cyclohexane has been investigated at ambient T and p=1 atm of air in the presence of sufficient cyclo-hexane or 2-propanol added to scavenge OH. The reaction rate constants, in units of 10⁻¹⁸ cm³ molecule⁻¹ s⁻¹, are 7.52±0.97 for vinylcyclohexane (T=292±2 K) and 10.6±1.9 for methylene cyclohexane (T=293±2 K). Carbonyl reaction products were cyclohexyl meth-anal (0.62±0.03) and formaldehyde (0.47±0.04) from vinylcyclohexane and cyclohexanone (0.55±0.10) and formaldehyde (0.60±0.05) from methylene cyclohexane, where the yields given in parentheses are expressed as carbonyl formed, ppb/reacted ozone, ppb. The sum of the yields of the primary carbonyls is close to the value of 1.0 that is consistent with the simple mechanisms: O₃+cyclo(C₆H₁₁)−CH(DOUBLEBOND)CH₂→α(HCHO+cyclo(C₆H₁₁)CHOO)+(1−α)(HCHOO+cyclo(C₆H₁₁)CHO) for vinylcyclohexane and O₃+(CH₂)₅C(DOUBLEBOND)CH₂→α(HCHO +(CH₂)₅COO)+(1−α)(HCHOO+(CH₂)₅C(DOUBLEBOND)O) for methylene cyclohexane. The coefficients α are 0.43±0.10 for vinylcyclohexane and 0.52±0.05 for methylene cyclohexane, i.e., (formaldehyde+the substituted biradical) and (HCHOO+cyclohexyl methanal or cyclo-hexanone) are formed in ca. equal yields. Reaction rate constants, carbonyl yields, and reaction mechanisms are compared to those for alkene structural homologues. © 1997 John Wiley & Sons, Inc. Int J Chem Kinet 29: 855–860, 1997     

The hydroxyl radical reaction rate constant and atmospheric transformation products of 2-butanol and 2-pentanol

The relative rate technique has been used to measure the hydroxyl radical (OH) reaction rate constant of +2-butanol (2BU, CH₃CH₂CH(OH)CH₃) and 2-pentanol (2PE, CH₃CH₂CH₂CH(OH)CH₃). 2BU and 2PE react with OH yielding bimolecular rate constants of (8.1±2.0)×10⁻¹² cm³molecule⁻¹s⁻¹ and (11.9±3.0)×10⁻¹² cm³molecule⁻¹s⁻¹, respectively, at 297±3 K and 1 atmosphere total pressure. Both 2BU and 2PE OH rate constants reported here are in agreement with previously reported values [1–4]. In order to more clearly define these alcohols' atmospheric reaction mechanisms, an investigation into the OH+alcohol reaction products was also conducted. The OH+2BU reaction products and yields observed were: methyl ethyl ketone (MEK, (60±2)%, CH₃CH₂C((DOUBLEBOND)O)CH₃) and acetaldehyde ((29±4)% HC((DOUBLEBOND)O)CH₃). The OH+2PE reaction products and yields observed were: 2-pentanone (2PO, (41±4)%, CH₃C((DOUBLEBOND)O)CH₂CH₂CH₃), propionaldehyde ((14±2)% HC((DOUBLEBOND)O)CH₂CH₃), and acetaldehyde ((40±4)%, HC((DOUBLEBOND)O)CH₃). The alcohols' reaction mechanisms are discussed in light of current understanding of oxygenated hydrocarbon atmospheric chemistry. Labeled (¹⁸O) 2BU/OH reactions were conducted to investigate 2BU's atmospheric transformation mechanism details. The findings reported here can be related to other structurally similar alcohols and may impact regulatory tools such as ground level ozone-forming potential calculations (incremental reactivity) [5]. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet 30: 745–752, 1998     

Hydration of medium reactive magnesium oxide using hydration agents

Water, magnesium acetate, magnesium chloride, acetic acid and hydrochloric acid were used as hydrating agents for an industrially obtained MgO sample. The influence of these different hydrating agents on the pH of the hydrating solution, degree of hydration to Mg(OH)₂, and product surface area was studied as a function of the temperature of hydration. When compared to the hydration in water, all hydrating agents improved the degree of hydration between 5 and 50% at all temperatures. MgCl₂ and a mixture of HCl and Mg(CH₃COO)₂ seemed to be the most effective hydrating agents below 60°C, while at temperatures above 60°C Mg(CH₃COO)₂ formed the largest percentage Mg(OH)₂. Mg(CH₃COO)₂ was the hydrating agent that showed the strongest temperature dependence. The mechanism of the hydration reaction seems to be dependent of the availability of Mg²⁺ ions and the increased formation of Mg(OH)₂ as temperature increases.     

Mechanism for hydrolysis of double six-membered ring tetraborate anion

[B₄O₅(OH)₄²⁻] is a representative borate anion with a double six-membered ring structure, but there is limited knowledge about the hydrolysis mechanisms of [B₄O₅(OH)₄²⁻]. Density functional theory-based calculations show that the tetraborate ion undergoes three-step hydrolysis to form [B(OH)₄⁻] and an ring intermediate, [B₃O₂(OH)₆⁻]. Other new structures, such as linear trimer, branched tetraborate, analogous linear tetraborate, are observed, but they are not stable in neutral systems and change to ring structures. [B₃O₂(OH)₆⁻] hydrolyzes to [B(OH)₄⁻] and [B(OH)₃] in the last two steps. The structure of borate anion and the coordination environment of the bridge oxygen atom control the hydrolysis process. [B₄O₅(OH)₄²⁻] always participates in the hydrolysis reaction, even with a decrease in concentration. [B₃O₃(OH)₄⁻], [B(OH)₄⁻], and [B(OH)₃] have different roles in “water-poor” and “water-rich” zones. Concentration and pH of solution are the key factors that affect the distribution of borate ions.     

Study on the equilibrium in the M(CH3COO)2 ? CH3OH ? H2O system (M  Mg2+, Ca2+, Ba2+) at 25°C

The complex formation and dehydration processes in the system M(CH₃COO)₂? CH₃OH? H₂O have been studied by the methods of the physico-chemical analysis at 25°C; (M = Mg²⁺, Ca²⁺ and Ba²⁺). In the Mg(CH₃COO)₂? CH₃OH? H₂O system. methanol was found to behave as a solvent in which complex formation reactions take place, including also methanolation of Mg²⁺. The fields of equilibrium existence of two new compounds have been found: Mg(CH₃COO)₂ · 3H₂O · CH₃OH and Mg(CH₃COO)₂ · 1,5 CH₃OH. In the systems M(CH₃COO)₂? CH₃OH? H₂O (M = Ca²⁺, Ba²⁺), methanol was found to react as a dehydrating reagent.     

Positive and negative methanol cluster ions using a direct fast atom bombardment technique

Positive and negative cluster ions in methanol have been examined using a direct fast atom bombardment (FAB) probe technique. Positive ion (CH₃OH)_IIH ⁺ clusters with n = 1-28 have been observed and their clusters are the dominant ions in the low-mass region. Cluster-ion reaction products (CH₃OH)_II(H₂O)H⁺ and (CH₃OH)_II(CH₃OCH₃)H⁺ are observed for a wide range of n and the abundances of these ions decrease with increasing n. The negative ion (CH₃OH)_II(CH₃O)^? clusters are also readily observed with n = 0-24 and these form the most-abundant negative ion series at low n. The (CH₃OH)_II(CH₂O)^?, (CH₃OH)_II(H_IIO)(CH₂O)^? and (CH₃OH)_II(H₂OXCH₃O)^? cluster ions are formed and the abundances of these ions approach those of the (CH₃OH)_II(CH₃O)^? ion series at high n. Cluster-ion structures and energetics have been examined using semi-empirical molecular orbital methods.     

SIFT studies of the reactions of H3O+, NO+ and O+2 with a series of volatile carboxylic acids and esters

We report the results of a selected ion flow tube (SIFT) study of the reactions of H₃O⁺, NO⁺ and O⁺₂ with some nine carboxylic acids and eight esters. We assume that all the exothermic proton transfer reactions of H₃O⁺ with all the acid and esters molecules occur at the collisional rate, i.e. the rate coefficients, k, are equal to k_c; then it is seen that k values for most of the NO⁺ and O⁺₂ reactions also are equal to or close to k_c. The major ionic products of the H₃O⁺ reactions with both the acids and esters are the protonated parent molecules, MH⁺, but minor channels are also evident, these being the result of H₂O elimination from the excited (MH⁺)1 in some of the acid reactions and an alcohol molecule elimination (CH₃OH or C₂H₅OH) in some of the ester reactions. The NO⁺ reactions with the acids and esters result in both ion-molecule association producing NO⁺M in parallel with hydroxide ion (OH⁻) transfer with some of the acids, and parallel methoxide ion (CH₃O⁻) and ethoxide ion (C₂H₅O⁻) transfer as appropriate with some of the esters. The O⁺₂ reactions proceed by dissociative charge transfer with the production of two or more ionic fragments of the parent molecules, the different isomeric forms of both the acid and the ester molecules resulting in different product ions.     

A Lead Mixed Halide with Three Different Coordinated Anions and Strong Second-Harmonic Generation Response

Nonlinear optical (NLO) crystals are widely applied in information technology, micro-manufacturing and medical treatment. Herein, a new lead mixed halide with strong second-harmonic generation (SHG) response, Cs₃Pb₂(CH₃COO)₂Br₃I₂, has been designed and rationally synthesized. Cs₃Pb₂(CH₃COO)₂Br₃I₂ represents the rare NLO crystal featuring that three different anions (I⁻, Br⁻ and O²⁻) simultaneously coordinate the Pb(II) atom to form a severely distorted [PbBr₂I₂O₂] polyhedron with a large polarizability. Remarkably, Cs₃Pb₂(CH₃COO)₂Br₃I₂ not only exhibits a very strong phase-matching SHG response of 9×KH₂PO₄ (KDP), but also possesses a large birefringence (0.27@1064 nm) and high laser damage threshold (LDT). The strong SHG effect of Cs₃Pb₂(CH₃COO)₂Br₃I₂ mainly originates from the oriented arrangement of [Pb₂Br₃I₂] chains. This study points out an effective strategy to develop new NLO crystals with strong SHG response.     

Morphology and Temperature Phase Transitions in α,ω-Alkanediols with Different Chain Lengths

A comparative analysis of phase transitions in diols with various chain lengths [(CH₂)₄₄(OH)₂ and (CH₂)₂₂(OH)₂] and changes in their absorption spectra with temperature have been investigated by DSC and FTIR. Analysis of the DSC data has led to the conclusion that the low-temperature phase transition of (CH₂)₂₂(OH)₂ in a solid state (T_s-s = 367.1 K) is a phase transition of the first order, while the high-temperature phase transition (T_m = 376.3 K) is of the second order, i.e., a transition of the order-disorder type. Splitting of the IR absorption bands into doublets at 720-730 cm⁻¹ and 1463-1473 cm⁻¹ indicates that crystalline subcells in the lamellae of both diols are orthorhombic lattices with the parameters typical of hydrocarbons. IR spectra showed that at the phase transition temperature T_s-s transformation of an orthorhombic subcell into a hexagonal one occurs. This type of molecular chain packing remains the same up to the melting temperature T_m. In a (CH₂)₄₄(OH)₂ diol, the ortho-hexagonal subcell transition occurs only at the melting temperature (390.0 K). The wide IR band in the region from 3000 cm⁻¹ to 3600 cm⁻¹ shows that end hydroxyl groups of diol molecules form, on the surfaces of lamellar crystals, long (polymer) regular sequences consisting of intermolecular hydrogen bonds.