Luminescent Cs8PbBr64+ Quantum Dots Centered on the Octahedral PbBr64- Cluster within Zeolite LTA: Exploring the Edge of Three-Dimensional Crystal Structure and Its Stability.

The perovskite quantum dots (QDs) of CsPbX3 (X = Cl, Br, I) exhibit exceptional photoluminescent properties, but their sensitivity to moisture and heat poses a challenge. This study presents a solvent-free synthesis approach for incorporating CsPbBr3 perovskite QDs into zeolite A. The introduction of [Cs8PbBr6]4+ perovskite QDs into the zeolite framework resulted in a highly stable configuration, maintaining its initial luminescence properties even after being underwater or exposed to heat. The structure is determined by 3-dimensional single-crystal crystallography. Each octahedral PbBr64- ion is surrounded by Cs+ ions and [Cs8PbBr6]4+ perovskite QDs being formed at the 32% of the center of a large cavity. Further, [Na12CsBr8]5+ QDs are formed at the very center of another 46% large cavities by combining Cs+, Na+, and Br- ions. The peak in the emission spectrum of Pb,Br,Cs,Na-A is similar to those of the CsPbBr3 nanocrystal, Cs4PbBr6 0-dimensional perovskite QDs, and Pb,Br,H,Cs,Na-FAU(X and Y). This work demonstrates that Pb,Br,Cs,Na-A can be produced using a simplified solvent-free synthesis procedure, which exhibits excellent stability against moisture and heat. Moreover, through a straightforward process, various quantum dots (QDs) can be incorporated into zeolite cavities to develop materials with variety photoluminescent properties.

Crystal structure of di-aqua-(3,14-diethyl-2,6,13,17-tetra-aza-tri-cyclo-[16.4.0.07,12]docosa-ne)copper(II) (3,14-diethyl-2,6,13,17-tetra-aza-tri-cyclo[16.4.0.07,12]docosa-ne)copper(II) tetra-bromide dihydrate, [Cu(C22H44N4)(H2O)2][Cu(C22H44N4)]Br4·2H2O.

The crystal structure of the new double CuII complex salt, [Cu(L)(H2O)2][Cu(L)]Br4·2H2O (L = 3,14-diethyl-2,6,13,17-tetra-aza-tri-cyclo-[16.4.0.07,12]docosane, C22H44N4) has been determined using synchrotron radiation. The asymmetric unit contains one half of a [Cu(L)(H2O)2]2+ cation, one half of a [Cu(L)]2+ cation (both completed by crystallographic inversion symmetry), two bromide anions and one water solvent mol-ecule. The CuII atom in the first complex exists in a tetra-gonally distorted octa-hedral environment with the four N atoms of the macrocyclic ligand in equatorial and two aqua ligands in axial positions, whereas the CuII atom in the second complex exists in a square-planar environment defined by the four nitro-gen atoms of the macrocyclic ligand. The two macrocyclic rings adopt the most stable trans-III configuration with normal Cu-N bond lengths from 2.016 (3) to 2.055 (3) Šand an axial Cu-O bond length of 2.658 (4) Å. The crystal structure is stabilized by inter-molecular hydrogen bonds involving the macrocycle N-H or C-H groups and the O-H groups of water mol-ecules as donor groups, and the O atoms of water mol-ecules and bromide anions as acceptor groups, giving rise to a one-dimensional network extending parallel to [100].

Formation mechanism of an Al13 Keggin cluster in hydrated layered polysilicates.

An Al13 ε-Keggin cluster, AlO4Al12(OH)24(H2O)127+, is a predominant intermediate during the hydrolysis and polymerization of aluminum as well as a highly toxic substance to plants and fishes. However, no one could clearly explain why and how a cage-like Al13 ε-Keggin cluster is formed even though it could be readily synthesized by the forced hydrolysis of Al3+. We found that the Al13 ε-Keggin cluster was spontaneously formed not in monocrystalline octosilicate but in polycrystalline magadiite by the cation-exchange reaction with unhydrolyzed Al3+. Furthermore, the Al13 ε-Keggin cluster was hardly detected in disaggregated magadiite crystals whose morphology was changed into monocrystalline crystals like octosilicate. Our findings prove that Al13 formation is necessary to relieve localized inhomogeneity and rationalize that Al13 is formed by the simultaneous co-assembly of four planar trimers and one octahedral monomer. In addition, the spontaneous formation of Al13 in heterogeneous systems could be a vital clue to its evaluation in soils and sediments.

Computational Design of Functional Amyloid Materials with Cesium Binding, Deposition, and Capture Properties.

Amyloid materials are gaining increasing attention as promising materials for applications in numerous fields. Computational methods have been successfully implemented to investigate the structures of short amyloid-forming peptides, yet their application in the design of functional amyloid materials is still elusive. Here, we developed a computational protocol for the design of functional amyloid materials capable of binding to an ion of interest. We applied the protocol in a test case involving the design of amyloid materials with cesium ion deposition and capture properties. As part of the protocol, we used an optimization-based design model to introduce mutations at non-ß-sheet residue positions of an amyloid designable scaffold. The designed amino acids introduced to the scaffold mimic how amino acids bind to cesium ions according to experimentally resolved structures and also aim at energetically stabilizing the bound conformation of the pockets. The optimum designs were computationally validated using a series of simulations and structural analysis to select the top designed peptides, which are predicted to form fibrils with cesium ion binding properties for experimental testing. Experiments verified the amyloid-forming properties of the selected top designed peptides, as well as the cesium ion deposition and capture properties by the amyloid materials formed. This study demonstrates the first, to the best of our knowledge, computational design protocol to functionalize amyloid materials for ion binding properties and suggests that its further advancement can lead to novel, highly promising functional amyloid materials of the future.

Reverse Anti-solvent Crystallization Process for the Facile Synthesis of Zinc Tetra(4-pyridyl)porphyrin Single Crystalline Cubes.

Synthesis of morphologically well-defined crystals of metalloporphyrin by direct crystallization based on conventional anti-solvent crystallization method without using any additives has been rarely reported. Herein, we demonstrate an unconventional and additive-free synthetic method named reverse anti-solvent crystallization method to achieve well-defined zinc-porphyrin cube crystals by reversing the order of the addition of solvents. The extended first solvation shell effect mechanism is therefore suggested to support the synthetic process by providing a novel kinetic route for reaching the local supersaturation environment depending on the order of addition of solvents, which turned out to be critical to achieve clean cube morphology of the crystal. We believe that our work not only extends fundamental knowledge about the kinetic process in binary solvent systems, but also enables great opportunities for shape-directing crystallization of various organic and organometallic compounds.

Mn(2+)-Ion Site Distribution of Zeolite Y (FAU, Si/Al = 1.56) Depending on the Ion-Exchange Ratio.

To investigate the tendency of Mn(2+)-ion exchange into zeolite Y, four single crystals of fully dehydrated Mn2+, Na(+)-exchanged zeolite Y (Si/Al = 1.56) were prepared by the exchange of Na75-Y (INa75I[Si117Al75,O384]-FAU) with aqueous of various concentrations by Mn2+ and Na+ in a total 0.05 M for molar ratios of 1:1 (crystal 1), 1:25 (crystal 2), 1:50 (crystal 3), and 1:100 (crystal 4), respectively, followed by vacuum dehydration at 400 degrees C. Their single-crystal structures were determined by synchrotron X-ray diffraction techniques in the cubic space group Fd3(-)m and were refined to the final error indices R1/wR2 = 0.0440/0.1545, 0.0369/0.1153, 0.0373/0.1091, and 0.0506/0.1667, respectively. Their unit-cell formulas are approximately LMn33.5Na8I[Si117Al75O384]-FAU, IMn20.5Na34I[Si117Al75O384]-FAU, IMn20.5Na34I[Si117Al75O384]-FAU, and IMn16.5Na42I[Si117Al75O384]-FAU, respectively. The degree of Mn2+-ion exchange increases from 44.3% to 89.1% with increasing the initial Mn2+ concentrations as Na+ content and the unit cell constant of the zeolite framework decrease.

Chelation-controlled molecular morphology: aminal to imine rearrangements.

Reactions between the tripodal hydroxytriamine, 2,2-bis(aminomethyl)-3-aminopropan-1-ol, "hytame", and the isomeric pyridine aldehydes generate in all cases the tris(aminal) species based on a 1,3,5-triaza-adamantane skeleton. In all cases also, the product from water under basic conditions consists of an approximately 1:9 mixture of the triequatorial and monoaxial-diequatorial isomers. While all these tripyridyltriaza-adamantanes appear capable of acting as Lewis bases, in particular cases metal ion binding leads to a radical structural rearrangement. These cases involve the pyridine-2-aldehyde derivatives only and certain transition metal ions (notably Fe(II)), and result in the conversion of the tris(aminal) into its isomeric tris(imine) form. This is apparently favoured because it can act as a hexadentate ligand towards a single metal ion, although kinetic influences are clearly important in this chemistry because template reactions of the triamine, pyridine-2-aldehyde and several metal ions give much better yields of the tris(imine) complex than do analogous rearrangement reactions. For the low-spin, kinetically inert Fe(II) complex of the tris(imine), its formation is apparently so favourable that it is generated via aldehyde unit exchange when the aza-adamantanes derived from pyridine-3- and -4-aldehyde are heated with a mixture of Fe(II) and pyridine-2-aldehyde. When the kinetically labile Zn(II) complex is treated with EDTA, the metal ion is extracted but the released ligand does not undergo valence tautomerisation to what would be expected to be the triaxial isomer of the tripyridyltriaza-adamantane but instead rapidly undergoes partial hydrolysis before slowly forming the mixture of triequatorial and monoaxial-diequatorial isomers.

Effect of pH on Fenton and Fenton-like oxidation.

The lifetime of H2O2 is an important factor in the feasibility of Fenton's reaction for soil and groundwater remediation. The lifetime of H2O2 was evaluated in Fenton's reaction and Fenton-like reactions with haematite and magnetite. H2O2 was more stable in the Fenton-like reaction than in the Fenton's reaction. The lifetime of H2O2 was also highly affected by the solution pH, and a pH buffered acidic condition was preferred. Fenton's reaction and Fenton-like reaction were tested for phenanthrene adsorbed on sand. Fenton-like reaction and acidic condition showed better degradation rates in comparing with those of Fenton's reaction and unbuffered systems. The dissolved iron species were measured in the Fenton's reaction, and Fenton-like reaction with haematite as a function of pH. In the presence of H2O2, ferric iron was the major dissolved iron species and the pH buffered to acidic condition maintained relatively high levels of dissolved iron in the aqueous solution. The higher iron concentration in the solution contributed to effective production of hydroxyl radical and degradation of organic contaminants.

Functionalised azetidines as ligands: pyridyl-complemented coordination.

A relatively simple azetidine derivative with 2-aminoethyl and 2-pyridyl substituents functions as a tridentate ligand towards Cu(II), giving species in which the CuN3 unit is essentially planar and that, in the solid state, show a subtle balance between mononuclear and binuclear forms, allowing both to be simultaneously present in some lattices. Displacement of the ligand from Cu(II) by the use of cyanide results in the formation of cyanogen, which appears to slowly react with the free amine to give an oxamidine characterised in its doubly-deprotonated form as its binuclear Ni(II) complex.

Functionalised azetidines as ligands: species derived by selective alkylation at substituent-nitrogen.

Selective functionalisation of the tridentate ligand 1-(2-aminoethyl)-3-methyl-3-(2-pyridyl)azetidine at its terminal amino-nitrogen atom can be readily achieved by both reductive alkylation and simple alkylation reactions to give tri-, quadri-, quinque- and sexi-dentate derivatives. Simple alkylation by 2-picolinyl chloride provides the only example of a second reaction pathway where the azetidine ring of the reactant has undergone activation towards ring opening. Structural characterisation of the Cu(II) complexes of these ligands has revealed several remarkable aspects of their solid-state coordination chemistry, including the formation of infinite helical aggregates through pi-stacking and tetramerisation through carboxylate bridging, as well as further examples of the crystallisation of mixed species found to be rather common with complexes of the parent ligand.

Structural and spectroscopic properties of trans-difluoro(1,4,8,12-tetraazacyclopentadecane)chromium(III) perchlorate hydrate.

The structure of [CrF(2)([15]aneN(4))]ClO(4).H(2)O ([15]aneN(4)=1,4,8,12-tetraazacyclopentadecane) has been determined by a single-crystal X-ray diffraction study at 173 K. The complex crystallizes in the space group P1- of the triclinic system with two mononuclear formula units in a cell of dimensions a=9.6117(7) A, b=10.2882(7) A, c=11.0001(7) A and alpha=99.7570(10) degrees, beta=105.6080(10) degrees and gamma=113.7130(10) degrees. The complex cation unit has its central Cr atom in an octahedral coordination with four nitrogen atoms and two fluorine atoms in a trans position. Three six-membered and one five-membered chelate rings of the [15]aneN(4) ligand are in a chair-twist(skew)-chair-gauche conformation sequence. The gauche five-membered ring is disordered with the twist six-membered ring opposite. The four H atoms in the chiral N atoms have the trans-II (CTCg) type configuration. The mean Cr-N and Cr-F bonds are 2.095(2) and 1.8752(13) A, respectively. The IR and visible spectral properties are consistent with the result of X-ray crystallography. The resolved band maxima of the electronic d-d spectrum are fitted with secular determinant for quartet state energy of d(3) configuration in tetragonal field including configurational but neglecting spin-orbit coupling. It is confirmed that the fluoride has strong sigma- and pi-donor properties toward the chromium(III) ion and the nitrogen atoms of the [15]aneN(4) ligand also have a strong sigma-donor character.

Cis-dinitrito(1,4,8,11-tetraazacyclotetradecane-kappa4N)chromium(III) nitrite.

In the title compound, [Cr(ONO)(2)(cyclam)]NO(2) (cyclam is 1,4,8,11-tetraazacyclotetradecane, C(10)H(24)N(2)), the complex cation is located on a twofold symmetry axis. The central Cr atom has a distorted octahedral coordination, involving two Cr-O bonds, with the monodentate nitrite O atoms adopting a cis configuration, and four Cr-N bonds. The mean Cr-N and Cr-O distances are 2.0895 (14) and 1.9698 (14) A.