齐聚噻吩衍生物电致变色性质

合成了四种齐聚噻吩衍生物：5,5"-二氰基-2,2’:5’,2"-三噻吩 (DCN3T), 5,5"’-二氰基-2,2’:5’,2":5",2"’-四噻吩 (DCN4T), 5,5"’-甲氧基-2,2’:5’,2":5",2"’-四噻吩(DMO4T) 和 4,4"-二羧基-5,5"-二丙基-2,2’:5’,2"-三噻吩 (BP3T-DCOOH),研究了它们的电致变色性质,研究结果发现,这四种齐聚噻吩衍生物膜在电场作用下,可以发生可逆的颜色变化。     

A new tetranuclear copper(II) complex containing decameric water clusters bridged by–OH–and pyridine-2,4, 6-tricarboxylate: synthesis and magnetic characterization

Using pyridine-2,4,6-tricarboxylic acid (H₃ptc) and 2,2-bipyridine (2,2-bipy), a tetranuclear copper(II) compound [Cu₄(2,2-bipy)₄(ptc)₂(H₂O)₂(OH)₂] · 12H₂O (1) has been isolated under hydrothermal conditions. Variable temperature magnetic susceptibility of 1 from 2–300 K indicates anti-ferromagnetic interactions. The magnetic exchange coupling constants of J = ?159.4 and J′ = ?18.66 cm^?1 for 1 can be obtained through fit of the magnetic data, corresponding to two kinds of bridges, hydroxyl anions (OH^?) and pyridine carboxylate oxygen of ptc^3?. Moreover, decameric water clusters can also be observed, which are located between these tetranuclear copper(II) entities, forming a series of intricate O-H ··· O hydrogen bonds and stabilizing the resulting three-dimensional (3-D) hydrogen-bonded framework structure.     

Synthesis,Characterization, and Magnetic Behaviour of Dinuclear Nickel(II) Complexes of N,N′‐Substituted Dithiooxamides derived from α‐Amino Acids

New dinuclear complexes of the types [Ni₂(L)(H₂O)₂] and [Ni₂(L)(H₂O)₆] [H₄L = N,N′‐bis(carboxymethyl) dithiooxamide (H₄GLYDTO), N,N′‐bis(1‐carboxyethyl) dithiooxamide (H₄ALADTO), N,N′‐bis(1‐carboxy‐2‐methylpropyl) dithiooxamide (H₄VALDTO) and N,N′‐bis(1‐carboxy‐3‐methylbutyl) dithiooxamide (H₄LEUDTO)] have been prepared and characterized by IR and electronic absorption spectroscopy, and the structure of [Ni₂(ALADTO)(H₂O)₆] crystals has been determined by single crystal X‐ray analysis. This compound is composed of discrete dinuclear units in which two Ni^II atoms with NO₄S kernels are linked by a single [ALADTO]^4– group that coordinates through its carboxylato oxygen, amino nitrogen and thiolato sulphur atoms. In each dimer unit the two nickel(II) ions in distorted octahedral coordination are separated by 5.863(2) Å The temperature dependence of the magnetic susceptibility of the new compounds was measured over the range 2 to 300 K. In the complexes of [GLYDTO]^4– and [ALADTO]^4– the two Ni atoms are antiferromagnetically coupled, with J = –23.51(4) and –20.95(8) cm^–1, respectively. By constrast, [Ni₂(VALDTO)(H₂O)₂], [Ni₂(VALDTO)(H₂O)₆] and [Ni₂(LEUDTO)(H₂O)₂] remain paramagnetic down to 2 K, with magnetic moment values between 2.8 and 3.3 M.B.     

Spin Interactions and Magnetic Anisotropy in a Triangular Nickel(II) Complex with Triaminoguanidine Ligand Framework

The trinuclear nickel(II) complex [Ni₃(saltag^tBu)(bpy)₃(H₂O)₃]Cl (H₅saltag^tBu = 1,2,3-tris[(5-tert-butylsalicylidene)amino]guanidine) was synthesized and characterized by experimental as well as theoretical methods. The complex salt crystallizes with three molecules of dimethylformamide (dmf) and water as [Ni₃(saltag^tBu)(bpy)₃(H₂O)₃]Cl · 3dmf · 3H₂O ( 1 ) in the trigonal space group P3 , with the complex located on a threefold rotation axis, which is consistent with the molecular C₃ symmetry of the complex cation. Magnetic measurements reveal an antiferromagnetic coupling (J = –35.9 cm^–1) between the nickel(II) ions leading to a diamagnetic ground state for the trinuclear complex cation. Theoretical investigations based on broken-symmetry DFT confirm the antiferromagnetic exchange within the complex cation of 1 . Additional single-ion CASSCF ab initio studies reveal that magnetic anisotropy is present in the system. The experimental and theoretical results for 1 are compared with those of a structurally similar nickel(II) complex that is based on the bromo-substituted derivative of the triaminoguanidine ligand. The differences in their magnetic properties can be attributed to the stronger elongation of the pseudo-octahedral coordination sphere at the nickel(II) centers in case of 1 . The analysis of the magnetic properties of 1 clearly shows that for such exchange coupled systems reliable parameters for the magnetic anisotropy cannot be extracted from experimental data alone.     

The Construction of Open GdIII Metal–Organic Frameworks Based on Methanetriacetic Acid: New Objects with an Old Ligand

The preparation, X‐ray crystallography and magnetic investigation of the first examples of methanetriacetate (mta)‐containing lanthanide(III) complexes of formulae [Gd(mta)(H₂O)₃]_n ? 4 n H₂O ( 1 ) [Gd(mta)(H₂O)₃]_n ? 2 n H₂O ( 2 ) and [Gd₂(mta)₂(H₂O)₂]_n ? 2 n H₂O ( 3 ) are described herein. This tripodal ligand promotes the formation of 6³ networks; thus 1 consists of a honeycomb structure, whereas in 2 two of these layers are condensed to form a rare five‐connected two‐dimensional (4⁸6²) network. Compound 3 can be seen as an aggregation of 6³ layers leading to a three‐dimensional (6,6)‐connected binodal (4¹²6³)(4⁹6⁶)‐ nia net, in which the gadolinium(III) ions and the mta ligands act as octahedral and as trigonal prismatic nodes, respectively. The magnetic properties of 1 – 3 were investigated in the temperature range 1.9–300 K. A close fit to the Curie law ( 1 ) and weak either antiferro‐ [J=?0.0063(1) cm^?1 ( 2 )] or ferromagnetic [J=+0.0264(6) cm^?1 ( 3 )] interactions between the Gd^III ions are observed; the different exchange pathways involved [extended tris‐bidentate mta ( 1 ) and μ‐O(1);κ²O(1),O(2) ( 2 and 3 ) plus single syn–syn carboxylate‐mta ( 3 )] accounting for these magnetic features. The nature and magnitude of the magnetic interactions, between the Gd^III ions in 1 – 3 , agree with the small amount of data existing in the literature for these kind of bridges.     

Spin canting and metamagnetism in the first hybrid cobalt-hypoxanthine open framework with umr topology

Hydrothermal reactions generated a cobalt–hypoxanthine framework [Co₃(OH)₄(Hpxt)₂]?2 H₂O (H₂pxt=6‐hydroxypurine, 1 ?2 H₂O), which became a microporous framework [Co₃(OH)₄(Hpxt)₂] ( 1 ) through a single‐crystal‐to‐single‐crystal transformation. Compound 1 ?2 H₂O shows a three‐dimensional umr topological structure with two types of spiral channels constructed by rod‐shaped {Co₃(μ‐OH)₄(N‐C‐N)₂(N‐C‐C‐O)₂} second building units (SBUs). The larger channel is filled by fourfold spiral water chains. An unprecedented μ₅‐O6,N3,N7,N9 coordination mode of the Hpxt anion was observed. Both complexes 1 ?2 H₂O and 1 qualitatively show similar metamagnetism from anti‐parallel to parallel ferromagnetic cobalt‐hydroxide chains. Compared with 1 ?2 H₂O, a smaller Curie constant and more negative Weiss constant in 1 indicate that the helical water chains tend to suppress antiferromagnetic coupling between Co₃(OH)₄ ferromagnetic chains. Detailed magnetic studies of 1 ?2 H₂O revealed that the competitive interactions between interchain antiferromagnetic exchange coupling and single‐ion anisotropy of Co^II resulted in a partly canted antiferromagnetic sate in low fields. Anti‐parallel arrangement of adjacent ferromagnetic chains in middle fields gives 3D antiferromagnetic ordering, and magnetic ground states in high fields are a parallel arrangement of ferromagnetic chains.     

A Pseudorotaxane System Containing γ-Cyclodextrin Formed via Chiral Recognition with an AuI6AgI3CuII3 Molecular Cap

Solvent-mediated crystal-to-crystal transformations of [Au₆Ag₃Cu₃(H₂O)₃(d -pen)₆(tdme)₂]³⁺ (d -[ 1 (H₂O)₃]³⁺; pen²⁻= penicillaminate, tdme=1,1,1-tris(diphenylphosphinomethyl)ethane) to form unique supramolecular species are reported. Soaking crystals of d -[ 1 (H₂O)₃]³⁺ in aqueous Na₂bdc (bdc²⁻=1,4-benzenedicarboxylate) yielded crystals containing d -[ 1 (bdc)(H₂O)₂]⁺ due to the replacement of a terminal aqua ligand in d -[ 1 (H₂O)₃]³⁺ by a monodentate bdc²⁻ ligand. When γ-cyclodextrin (γ-CD) was added to aqueous Na₂bdc, d -[ 1 (H₂O)₃]³⁺ was transformed to d -[ 1 (bdc@γ-CD)(H₂O)₂]⁺, where a γ-CD ring was threaded by a bdc²⁻ molecule to construct a pseudorotaxane structure. While the use of dicarboxylates with an aliphatic carbon chain instead of bdc²⁻ afforded analogous pseudorotaxanes, such pseudorotaxane species were not formed when crystals of [Au₆Ag₃Cu₃(H₂O)₃(l -pen)₆(tdme)₂]³⁺ (l -[ 1 (H₂O)₃]³⁺) enantiomeric to d -[ 1 (H₂O)₃]³⁺ were soaked in aqueous Na₂bdc and γ-CD, affording only crystals containing l -[ 1 (bdc)(H₂O)₂]⁺.     

Synthese,Kristallstruktur und Magnetismus von [(CH3)2NH2][NdCl4(H2O)2]

Preparation, Crystal Structure, and Magnetism of [(CH₃)₂NH₂][NdCl₄(H₂O)₂] The complex water containing chloride [(CH₃)₂NH₂][NdCl₄(H₂O)₂] was prepared for the first time and the crystal structure was determined by X‐ray methods from single crystals. The compound crystallizes in the orthorhombic space group Cmca (Z = 8) with a = 1793.5(2) pm, b = 936.6(2) pm and c = 1232.8(2) pm. The anionic part of the structure is built up by chains of edge connected [NdCl_4/2Cl₂(H₂O)₂]^– trigondodecahedra. In order to study the interactions between the neodymium cation and the ligands magnetic measurements were carried out. The magnetic data were interpreted by ligand field calculations applying the angular overlap model.     

Single‐Molecule Magnetism,Enhanced Magnetocaloric Effect,and Toroidal Magnetic Moments in a Family of Ln4 Squares

Three cationic [Ln₄] squares (Ln=lanthanide) were isolated as single crystals and their structures solved as [Dy₄(μ₄‐OH)(HL)(H₂L)₃(H₂O)₄]Cl₂?(CH₃OH)₄?(H₂O)₈ ( 1 ), [Tb₄(μ₄‐OH)(HL)(H₂L)₃(MeOH)₄]Cl₂?(CH₃OH)₄?(H₂O)₄ ( 2 ) and [Gd₄(μ₄‐OH)(HL)(H₂L)₃(H₂O)₂(MeOH)₂]Br₂?(CH₃OH)₄?(H₂O)₃ ( 3 ). The structures are described as hydroxo‐centered squares of lanthanide ions, with each edge of the square bridged by a doubly deprotonated H₂L^2? ligand. Alternating current magnetic susceptibility measurements show frequency‐dependent out‐of‐phase signals with two different thermally assisted relaxation processes for 1 , whereas no maxima in χ_M“ appears above 2.0 K for complex 2 . For 1 , the estimated effective energy barrier for these two relaxation processes is 29 and 100 K. Detailed ab initio studies reveal that complex 1 possesses a toroidal magnetic moment. The ab initio calculated anisotropies of the metal ions in complex 1 were employed to simulate the magnetic susceptibility by using the Lines model (POLY_ANISO) and this procedure yields J₁=+0.01 and J₂=?0.01 cm^?1 for 1 as the two distinct exchange interactions between the Dy^III ions. Similar parameters are also obtained for complex 1 (and 2 ) from specific heat measurements. A very weak antiferromagnetic super‐exchange interaction (J₁=?0.043 cm^?1 and g=1.99) is observed between the metal centers in 3 . The magnetocaloric effect (MCE) was estimated by using field‐dependent magnetization and temperature‐dependent heat‐capacity measurements. An excellent agreement is found for the ?ΔS_m values extracted from these two measurements for all three complexes. As expected, 3 shows the largest ?ΔS_m variation (23 J Kg^?1 K^?1) among the three complexes. The negligible magnetic anisotropy of Gd indeed ensures near degeneracy in the (2S+1) ground state microstates, and the weak super‐exchange interaction facilitates dense population of low‐lying excited states, all of which are likely to contribute to the MCE, making complex 3 an attractive candidate for cryogenic refrigeration.     

M(H2O)2(4,4′‐bipy)[C6H4(COO)2]·2H2O (M = Mn2+, Co2+) – Zwei isotype Koordinationspolymere mit Schichtstruktur

M(H₂O)₂(4,4′‐bipy)[C₆H₄(COO)₂]·2H₂O (M = Mn²⁺, Co²⁺) – Two Isotypic Coordination Polymers with Layered Structure Monoclinic single crystals of Mn(H₂O)₂(4,4′‐bipy)[C₆H₄(COO)₂]·2H₂O ( 1 ) and Co(H₂O)₂(4,4′‐bipy)[C₆H₄(COO)₂]· 2H₂O ( 2 ) have been prepared in aqueous solution at 80 °C. Space group P2/n (no. 13), Z = 2; 1 : a = 769.20(10), b = 1158.80(10), c = 1075.00(10) pm, β = 92.67(2)°, V = 0.9572(2) nm³; 2 : a = 761.18(9), b = 1135.69(9), c = 1080.89(9) pm, β = 92.276(7)°, V = 0.9337(2) nm³. M²⁺ (M = Mn, Co), which is situated on a twofold crystallographic axis, is coordinated in a moderately distorted octahedral fashion by two water molecules, two oxygen atoms of the phthalate anions and two nitrogen atoms of 4,4′‐biypyridine ( 1 : M–O 219.5(2), 220.1(2) pm, M–N 225.3(2), 227.2(2) pm; 2 : Co–O 212.7(2), 213.7(2) pm, Co–N 213.5(3), 214.9(3) pm). M²⁺ and [C₆H₄(COO)₂)]^2? build up chains, which are linked by 4,4′‐biyridine molecules to yield a two‐dimensional coordination polymer with layers parallel to (001).Thermogravimetric analysis in air of 1 indicated a loss of water of crystallization between 154 and 212 °C and in 2 between 169 and 222 °C.     

Complexes of Co(II), Ni(II), and Cu(II) with 4-(3,4-dichlorophenyl)-1,2,4-triazole

Novel oligonuclear complexes of Co(II), Ni(II), and Cu(II) with 4-(3,4-dichlorophenyl)-1,2,4-triazole (L) of the composition [M₃L₁₀(H₂O)₂](NO₃)₆ (M = Co(II), Ni(II)), [Ni₃L₆(H₂O)₆]Hal₆ (Hal = Cl^?, Br^?), and [Cu₅L₁₆(H₂O)₂](NO₃)₁₀ · 2H₂O were synthesized and studied by magnetic susceptibility, electronic and IR spectroscopy, and powder X-ray diffraction methods. All the above complexes are X-ray amorphous. Antifer-romagnetic exchange interactions between the M²⁺ ions were discovered in the [Co₃L₁₀(H₂O)₂](NO₃)₆ and [Ni₃L₁₀(H₂O)₂](NO₃)₆ complexes, whereas ferromagnetic exchange interactions were observed in the complexes [Ni₃L₆(H₂O)₆]Cl₆, [Ni₃L₆(H₂O)₆]Br₆, and [Cu₅L₁₆(H₂O)₂](NO₃)₁₀ · 2H₂O.     

Synthesis and Crystal Structures of Bis(1‐{(E)‐2‐pyridinylmethylidene}‐semicarbazone)iron(II) and ‐copper(II) Diperchlorate Monohydrates

The pyridine‐2‐carbaldehyde semicarbazone ligand (HL) reacts with iron(II) and copper(II) perchlorates in boiling ethanol to yield red‐violet [Fe^II(HL)₂](ClO₄)₂·H₂O ( 1 ) and light‐green crystals [Cu^II(HL)₂](ClO₄)₂·H₂O ( 2 ). The crystals are triclinic with the metal ions in an octahedral environment, coordinated to two nitrogen and one oxygen‐donor atom from HL. Electronic, magnetic and electrochemical properties are presented as well.     

Kristallstruktur und spektroskopische Daten von Rb2[VOF4(H2O)]

Crystal Structure and Spectroscopic Data of Rb₂[VOF₄(H₂O)] Blue crystals of Rb₂[VOF₄(H₂O)] have been obtained from hydrofluoric acid. The crystal structure (space group Cmcm, a = 969.6(4), b = 780.6(2), c = 835.4(4) pm, Z = 4, d_c = 3.486 gcm^?3, d_m = 3.41 gcm^?3, R_w = 0.032 for 411 independent reflections) shows isolated [VOF₄(H₂O)]^2? anions — with H₂O in trans-position to the relatively long V? O bond (d(V? O) = 166.8(7) pm) — which are connected with each other by hydrogen bonds forming infinite chains. The blue colour of the compound despite of the isotypism to the “green” modification of Cs₂[VOF₄(H₂O)] is discussed on the basis of the structural data, i.r./Raman and u.v./vis reflection spectra. The magnetic moment is 1.72 B.M. at 295 K.     

A DFT study of uranyl hydroxyl complexes: structure and stability of trimers and tetramers

A DFT study of U(VI) hydroxy complexes was performed with special attention paid to the [(UO₂)₃(OH)₅(H₂O)_4–7]⁺ and [(UO₂)₄(OH)₇(H₂O)_5–8]⁺ species. It was established that the ionicity of the U=O bond increased when moving from [(UO₂)(H₂O)₅]²⁺, [(UO₂)₂(OH)(H₂O)₈]³⁺, [(UO₂)₂(OH)₂(H₂O)₆]²⁺, [(UO₂)₃(OH)₅(H₂O)_4–6]⁺ to [(UO₂)₄(OH)₇(H₂O)_5–8]⁺ species. In both [(UO₂)₃(OH)₅(H₂O)_4–6]⁺ and [(UO₂)₄(OH)₇(H₂O)_5–8]⁺ complexes, the U=O bond was observed to have a range of different lengths which depended on the composition of the first coordination sphere of UO₂ ²⁺. The cyclic structures of trimeric complexes were somewhat more stable than their linear structures, which was probably due to the steric effect.

     

Synthesis,Crystal Structure and Magnetic Behaviour of the new Tetrameric Gadolinium Carboxylate [Gd4(OH)4(CF3COO)8(H2O)4] · 2.5 H2O

The novel tetrameric gadolinium(III) compound [Gd₄(OH)₄(CF₃COO)₈(H₂O)₄] · 2.5 H₂O was synthesized and structurally characterized by X‐ray crystallography. The Gd³⁺ ions are bridged by hydroxide ions and carboxylate groups to tetramers with Gd³⁺‐Gd³⁺ distances between 384.2(2) and 388.1(2) pm. The compound crystallizes in the monoclinic space group C2/c (Z = 4). The magnetic behaviour of [Gd₄(OH)₄(CF₃COO)₈(H₂O)₄] · 2.5 H₂O was investigated in the temperature range of 2 to 300 K. The magnetic data of this compound indicate antiferromagnetic interactions (J_ex = ?0.0197 cm^?1).     

Synthesis,characterization, thermal,and antimicrobial studies of binuclear metal complexes of sulfa-guanidine Schiff bases

A series of metal complexes of Schiff bases derived from condensation of sulfa-guanidine with 1-benzoylacetone (H₂L¹), 2-hydroxybenzophenol (H₂L²), dibenzoylmethane (H₂L³), 5-methylisatine (H₂L⁴), and 1-methylisatine (H₂L⁵) have been synthesized. The complexes are characterized by elemental analysis, molar conductance, magnetic moment measurements, IR, UV–Vis, ¹H NMR, and ESR spectra, as well as thermogravimetric analysis. The low molar conductance values indicate the complexes are nonelectrolytes. IR and ¹H NMR spectra show that H₂L¹–H₂L⁵ are coordinated to metal ions by two bidentate centers. Mn(II), Co(II), Ni(II), and Cu(II) complexes display paramagnetic behavior, whereas the Zn(II)-complex was diamagnetic. All studies confirm the formation of an octahedral geometry for [Cu₂L¹(AcO)₂(H₂O)₆] · 3H₂O (1), [Mn₂L⁴(AcO)₂(H₂O)₆] · 2H₂O (6), [Ni₂L⁴(AcO)₂(H₂O)₆] · 2H₂O (8), a tetrahedral geometry for [Cu₂L²(AcO)₂(H₂O)₂] (2), [Cu₂(L⁴)₂] (4), [Co₂(L⁴)₂] · 2H₂O (7) and [ZnHL⁴(AcO)(H₂O)] · 2H₂O (9) and a trigonal bipyramid geometry for [Cu₂L³(AcO)₂(H₂O)₄] (3) and [Cu₂HL⁵(AcO)₃(H₂O)₃] · H₂O (5). H₂L⁴ was most effective on Gram negative, Gram positive bacteria, and fungi (diameters inhibition zone ranged between 10.5–27.5 mm) after 24 and 48 h, respectively. Complex 8 showed moderate antimicrobial activity. Its minimum inhibitory concentration (MIC) against Escherichia coli, Bacillus subtilis, Candida albicans and Aspargllus flavas was 20 mg L^–1. The compound proved to be of moderate toxicity and its LD₅₀ was 20 mg L^–1.     

Synthesis and characterization of CuII and CoII complexes derived from 2,4,6-tri-(2-pyridyl)-1,3,5-triazine (TPT) by chemical and tribochemical reactions

Four Cu^II and Co^II complexes–[Cu(L₁)Cl₂(H₂O)]3/2H₂O · 1/2EtOH, [Cu(L₁)₂Cl₂]6H₂O, [Co(L₁)Cl₂]3H₂O · EtOH, and [Co₂(L₁)(H₂O)Cl₄]1.5H₂O · EtOH (L₁ = 2,4,6-tri(2-pyridyl)-1,3,5-triazine; TPT)–were synthesized by conventional chemical method and used to synthesize another four metal complexes–[Cu(L₁)I₂(H₂O)]6H₂O, [Cu(L₁)₂I₂]6H₂O, [Co(L₁)I(H₂O)₂]I · 2H₂O, and [Co₂(L₁)I₄(H₂O)₃]–using tribochemical reaction, by grinding it with KI. Substitution of chloride by iodide occurred, but no reduction for Cu^II or oxidation of Co^II. Oxidation of Co^II to Co^III complexes was only observed on the dissolution of Co^II complexes in d₆-DMSO in air while warming. The isolated solid complexes (Cu^II and Co^II) have been characterized by elemental analyses, conductivities, spectral (IR, UV-Vis, ¹H-NMR), thermal measurements (TGA), and magnetic measurements. The values of molar conductivities suggest non-electrolytes in DMF. The metal complexes are paramagnetic. IR spectra indicate that TPT is tridentate coordinating via the two pyridyl nitrogens and one triazine nitrogen forming two five-membered rings around the metal in M : L complexes and bidentate via one triazine nitrogen and one pyridyl nitrogen in ML₂ complexes. In binuclear complexes, L is tridentate toward one Co^II and bidentate toward the second Co^II in [Co₂(L₁)Cl₄]2.5H₂O · EtOH and [Co₂(L₁)I₄(H₂O)₃]. Electronic spectra and magnetic measurements suggest a distorted-octahedral around Cu^II and high-spin octahedral and square-pyramidal geometry around Co^II.     

Multi-Step Nucleation of a Crystalline Silicate Framework via a Structurally Precise Prenucleation Cluster

Hierarchical nucleation pathways are ubiquitous in the synthesis of minerals and materials. In the case of zeolites and metal–organic frameworks, pre-organized multi-ion “secondary building units” (SBUs) have been proposed as fundamental building blocks. However, detailing the progress of multi-step reaction mechanisms from monomeric species to stable crystals and defining the structures of the SBUs remains an unmet challenge. Combining in situ nuclear magnetic resonance, small-angle X-ray scattering, and atomic force microscopy, we show that crystallization of the framework silicate, cyclosilicate hydrate, occurs through an assembly of cubic octameric Q³₈ polyanions formed through cross-linking and polymerization of smaller silicate monomers and other oligomers. These Q³₈ are stabilized by hydrogen bonds with surrounding H₂O and tetramethylammonium ions (TMA⁺). When Q³₈ levels reach a threshold of ≈32 % of the total silicate species, nucleation occurs. Further growth proceeds through the incorporation of [(TMA)_x(Q³₈)⋅n H₂O]^(x−8) clathrate complexes into step edges on the crystals.     

Structure and magnetism of a linear trimanganese (III,II, III) complex based on benzoate and Schiff-base ligands

Reaction of [Mn₃O(PhCO₂)₆(py)₂(H₂O)] with a tridentate Schiff-base 2-salicylideneaminoethanol (H₂sae) affords a trinuclear manganese complex [Mn₃(PhCO₂)₄(sae)₂] (1). X-ray structural analysis of 1 reveals that three manganese ions are linear with each pair bridged by two benzoate groups and one μ-alkoxo oxygen of the sae^2? ligand. The central manganese has an octahedral {Mn^IIO₆} configuration and the terminal ones are five-coordinate {Mn^IIINO₄} with a Jahn-Teller elongation axis. The trinuclear complex shows small antiferromagnetic exchange J coupling. The magnetic susceptibility data in the temperature range 2–300 K give the best fitting parameters with J?=??8.44 cm^–1, g?=?2.02, zJ ′?=??0.34 cm^–1, and R ²?=?0.99942. The magnetization versus external magnetic field measurements at 2 K proved that the ground state is S?=?3/2.     

Ligand Exchange Processes on Solvated Beryllium Cations. IV [Be(H2O)2(imidazole‐based Chelate)]1)

The water exchange reaction of [Be(H₂O)₂(1H‐imidazole‐4,5‐dicarboxylate)] and [Be(H₂O)₂(1H‐imidazol‐3‐ium‐4,5‐dicarboxylate)]⁺ in water was studied by DFT calculations (RB3LYP/6‐311+G**) and identified as an associative interchange mechanism. The activation barriers for [Be(H₂O)₂(1H‐imidazole‐4,5‐dicarboxylate)] (16.6 kcal/mol) and [Be(H₂O)₂(1H‐imidazol‐3‐ium‐4,5‐dicarboxylate)]⁺ (13.8 kcal/mol) are similar to the barrier for [Be(H₂O)₄)]²⁺ and independent of the overall charge. NICS calculations show no indication that the aromaticity of the imidazole ring is affected during the water exchange process.