Self-assembly snapshots of a 2 × 2 copper(I) grid

Self-assembled 2 × 2 grids have been characterised as high-fidelity species produced when the correct stoichiometric ratios are met, but rarely are the individual steps leading to and from their formation characterised. Here, we present such a study using equilibrium-restricted factor analysis to model a set of UV–vis spectra starting from a bis-bidentate ligand to the assembly of a 2 × 2 grid complex upon titration with 1 equiv. of [Cu(MeCN)₄](PF₆) and to disassembly upon further titration. Intermediate species [CuL₂]⁺, [Cu₂L₃]²⁺, [Cu₃L₂]³⁺ and [Cu₂L]²⁺ are evidenced along the assembly and disassembly pathways. Complementary ¹H NMR titrations are consistent with the rich set of complexes and equilibria involved. Given the nature of the assembly process, the assembly is entropy driven and likely enthalpy driven as well. The disassembly process is both enthalpy and entropy driven according to the standard free energy values derived from the modelling of the spectrophotometric titration data.     

Synthesis, Solution Equilibria and Antibacterial Activity of Co(II) with 2-(Aminomethyl)-Benzimidazole and Dicarboxylic Acids

Formation equilibria of cobalt(II) complexes of 2-(aminomethyl)-benzimidazole (AMBI) and the ternary complexes Co(AMBI)L (L = aliphatic or aromatic dicarboxylic acids) were investigated in aqueous solutions at 25?°C and 0.1 mol?dm^?3 ionic strength. Stoichiometry and stability constants are reported for the complexes formed. The speciation of the complexes was resolved. Values of $\log_{10}\ (K_{\mathrm{Co(AMBI)L}}^{\mathrm{Co(AMBI)}})$ and Δlog?₁₀ K are calculated and discussed. The effect of chelate ring size of the dicarboxylic acid complexes on their stability constants was examined. The effect of temperature on the dissociation constant of AMBI, CBDCA, and the formation constant of Co(AMBI) and Co(AMBI)-CBDCA complexes was studied and the thermodynamic parameters were calculated. Formation of the metal complexes has been found to be spontaneous, exothermic and entropically favorable. The solid complexes of [Co(AMBI)L] (L = oxalic acid, 1,1-cyclobutanedicarboxylic acid (CBDCAH₂) and malonic acid) have been synthesized and characterized by elemental analysis, infrared, spectra, magnetic and conductance measurements. Electronic spectra and μ _eff values suggest a tetrahedral geometry for Co(II)-complexes. The isolated metal chelates have been screened for their antibacterial activities and the complexes show a significant antibacterial activity against Pseudomonas fluorescence (Gram ?ve) and Bacillus subtilis (Gram +ve). The activity increases at higher concentration of the compounds.     

Preparation, molecular structure, and thermal analyses of a novel coordination compound [Cd(AZT)4(H2O)2](PA)2 · 4H2O (AZT = 3-azido-1,2,4-triazole, PA = picrate)

Abstract  The crystal structure of 3-azido-1,2,4-triazole (AZT) has been determined. A novel coordination compound [Cd(AZT)₄(H₂O)₂](PA)₂ · 4H₂O has been synthesized by using 3-azido-1,2,4-triazole as ligand, and its structure has been characterized by using X-ray single crystal diffraction, elemental analysis, and FT-IR spectroscopy. Each cadmium (II) center is coordinated with four N atoms of four AZT molecules and two O atoms of two H₂O molecules to form a slightly distorted octahedron. The optimized molecular structure and NBO charges of 3-azido-1,2,4-triazole have been obtained from the density functional theory (DFT) with the B3LYP method employing the 6-311 + G** basis sets. Thermal decomposition mechanism of [Cd(AZT)₄(H₂O)₂](PA)₂ · 4H₂O has been predicted based on DSC, TG-DTG, and FT-IR analyses. The kinetic parameters of the first exothermic process of [Cd(AZT)₄(H₂O)₂](PA)₂ · 4H₂O were studied by applying the Kissinger’s and Ozawa-Doyle’s methods. Index Abstract  A novel coordination compound [Cd(AZT)₄(H₂O)₂](PA)₂ · 4H₂O has been synthesized by using 3-azido-1,2,4-triazole as ligand and its structure has been characterized by using X-ray single crystal diffraction, elemental analysis, and FT-IR spectroscopy. Each cadmium (II) center is coordinated to form a slightly distorted octahedron. Thermal decomposition mechanism of [Cd(AZT)₄(H₂O)₂](PA)₂ · 4H₂O has been predicted based on DSC, TG-DTG, and FT-IR analyses.      

Interaction between Glyoxal-bis-(2-hydroxyanil) and Bovine Serum Albumin in Solution

The interaction between glyoxal-bis-(2-hydroxyanil) (GBH) and bovine serum albumin (BSA) was studied by spectroscopic methods including fluorescence spectroscopy, circular dichroism (CD) and UV–visible absorption spectra. The mechanism for quenching the fluorescence of BSA by GBH is discussed. The number of binding sites n and observed binding constant K _b were measured by the fluorescence quenching method. The thermodynamic parameters ΔH ^θ , ΔG ^θ , and ΔS ^θ were calculated at different temperatures and the results indicate that hydrogen bonding and van der Waals forces played major roles in the reaction. The distance r between the donor (BSA) and acceptor (GBH) molecules was obtained according to Förster’s theory of non-radiation energy transfer. Synchronous fluorescence and three-dimensional fluorescence spectra were used to investigate the structural change of BSA molecules that occur upon addition of GBH, and these results indicate that the secondary structure of BSA molecules is changed by the presence of GBH.     

Kinetic Investigation of the Electrochemical Oxidation of Bis(benzene)chromium(0) in Diethyl ketone/N,N-Dimethylformamide

The cyclic voltametric technique utilizing a platinum working electrode was applied for the investigation of the electrochemical oxidation of bis(benzene)chromium(0), (C₆H₆)₂Cr to bis(benzene)chromium(I), (C₆H₆)₂Cr⁺ in diethyl ketone (DEK), N,N-dimethylformamide (DMF), and DEK/DMF binary mixtures containing n-tetrabutylammonium hexafluorophosphate (TBAPF₆) as the supporting electrolyte at T=298.15 K. The half-wave potentials (E _1/2) of the (C₆H₆)₂Cr^+/0 redox couple in DEK, DMF and DEK/DMF binary mixtures, were determined. The variation of E _1/2 with the solvent composition was found to be almost linear. The E _1/2 results were analyzed in terms of the electron-donating power of the solvent medium. The diffusion coefficients, D, were calculated using the Randles-Sevcik equation. The kinetics of the electrode reaction were investigated through the determination of the heterogeneous electron-transfer rate constants, k _s, according to the electrochemical rate equation proposed by Nicholson. Furthermore, the activation Gibbs energies for the electron-transfer process (ΔG ^≠) were also calculated. The results indicate that the redox couple (C₆H₆)₂Cr^+/0 exhibits an electrochemically reversible and diffusion-controlled process in all the investigated solvent media.     

Synthesis, crystal structure and thermal decomposition character of [Zn(CHZ)3][C(NO2)3]2 · (H2O)2 (CHZ = Carbohydrazide)

A new coordination compound [Zn(CHZ)₃][C(NO₂)₃]₂ · (H₂O)₂ was synthesized and characterized by elemental analysis, FTIR and UV spectra, and its crystal structure was determined by X-ray single crystal diffraction. The crystal belongs to the triclinic system, space group . In the asymmetric unit, zinc (II) ion is six-coordinated with three carbonyl oxygen atoms and three terminal nitrogen atoms to form distorted octahedral structure, three CHZ molecules and central metal cation constitute three planar chelate rings which are vertical one to another, and two trinitromethanides are similar to the conformation of C _2v -like. Zinc (II) ions, carbohydrazide ligand molecules, trinitromethanide anions, and lattice water molecules are jointed to a complicated three-dimensional network structure through coordination bonds, electrostatic forces, and extensive hydrogen bonds. The thermal decomposition character and mechanism were tested through DSC, TG–DTG, and FTIR spectra. The results show that the title complex has high energy and good thermal stability.     

Synthesis, crystal structure, and optical properties of a novel rare-earth complex Nd(C2F5COO)3 · Phen

A novel neodymium pentafluoropropionate binuclear complex, Nd(C₂F₅COO)₃ · Phen (Phen: 1,10-phenanthroline), was synthesized and characterized by single-crystal X-ray diffraction, elemental analysis, FT-IR spectra, UV–Vis–NIR absorption, and PL spectra. Single-crystal data show that the complex bears centrosymmetric dinuclear structure with a planar ligand configuration. Four carboxylato groups act as η²-chelate-μ²-carboxylato-k¹O:k¹O′-bridge-ligands, the other two occupy the terminal position as monodentate ligands. At the same time, the C–O distances appear averaged which indicate the three atoms of carboxylato forming electron-conjugate system. Hydrogen bond and π–π-stacking link the binuclear to two-dimensional sheet. Optical spectra exhibit the complex possesses typical Nd(III) ion absorption and photoluminescence emission.     

Density functional study of S(N) 2 substitution reactions for CH(3) Cl + CX(1) X(2•-) (X(1) X(2) = HH, HF, HCl, HBr, HI, FF, ClCl, BrBr, and II)

A systematic investigation on the S_N2 displacement reactions of nine carbene radical anions toward the substrate CH₃Cl has been theoretically carried out using the popular density functional theory functional BHandHLYP level with different basis sets 6‐31+G (d, p)/relativistic effective core potential (RECP), 6‐311++G (d, p)/RECP, and aug‐cc‐pVTZ/RECP. The studied models are CX¹X^2?? + CH₃Cl → X²X¹CH₃C^? + Cl^?, with CX¹X^2?? = CH₂^??, CHF^??, CHCl^??, CHBr^??, CHI^??, CF₂^??, CCl₂^??, CBr₂^??, and CI₂^??. The main results are proposed as follows: (a) Based on natural bond orbital (NBO), proton affinity (PA), and ionization energy (IE) analysis, reactant CH₂^?? should be a strongest base among the anion‐containing species (CX¹X^2??) and so more favorable nucleophile. (b) Regardless of frontside attacking pathway or backside one, the S_N2 reaction starts at an identical precomplex whose formation with no barrier. (c) The back‐S_N2 pathway is much more preferred than the front‐S_N2 one in terms of the energy gaps [ΔE(front)?ΔE(back)], steric demand, NBO population analysis. Thus, the back‐S_N2 reaction was discussed in detail. On the one hand, based on the energy barriers (ΔE and ΔE) analysis, we have strongly affirmed that the stabilization of back attacking transition states (b‐TSs) presents increase in the order: b‐TS‐CI₂ < b‐TS‐CBr₂ < b‐TS‐CCl₂ < b‐TS‐CHI < b‐TS‐CHBr < b‐TS‐CHCl < b‐TS‐CF₂ < b‐TS‐CHF < b‐TS‐CH₂. On the other hand, depended on discussions of the correlations of ΔE with influence factors (PA, IE, bond order, and ΔE), we have explored how and to what extent they affect the reactions. Moreover, we have predicted that the less size of substitution (α‐atom) required for the gas‐phase reaction with α‐nucleophile is related to the α‐effect and estimated that the reaction with the stronger PA nucleophile, holding the lighter substituted atom, corresponds to the greater exothermicity given out from reactants to products. © 2012 Wiley Periodicals, Inc. J Comput Chem, 2012     

Hetero-heptanuclear (Fe–Na) complexes of salicylaldehydes: crystal and molecular structure of [Fe2(3-OCH3-salo)8 · Νa5] · 3OH · 8H2Ο

The reaction of Fe(III) with the substituted salicylaldehydes [X-saloH, where X = 3-OCH₃ (L ¹ ), 5-CH₃ (L ² ), 5-Cl (L ³ ), 5-NO₂ (L ⁴ )] led to the formation of four new iron(III) hetero-heptanuclear complexes (Fe–Na) under the general formula [Fe₂(X-salo)₈Νa₅] · 3OH · zH₂Ο. The two different coordination modes of the ligand, as well as the geometry around the metal ions were deduced by X-ray structure analysis of compound 1, [Fe₂(3-OCH₃-salo)₈Νa₅] · 3OH · 8H₂Ο. The complexes have also been characterized by physicochemical and spectroscopic (IR, UV–Vis, Mössbauer) methods.     

High-resolution observation and analysis of the I(2) (+) A(2)Π(3∕2,u)-X (2)Π(3∕2,g) system

Rotationally resolved absorption spectra of I(2) (+) were recorded in 12 065-13 062 cm(-1) region by employing optical heterodyne velocity modulation absorption spectroscopy. In total, 4054 lines were assigned to 24 bands in the A(2)Π(3∕2,u)-X(2)Π(3∕2,g) system spanning the vibrational levels υ(') = 1-4 and υ(n) (') = 11-19. The assigned lines were globally fitted and an error of 0.003 cm(-1) was obtained. Rotational constants, B(υ), were used to derive equilibrium parameters B(e) (') = 0.03977725(77) cm(-1), a(e) (') = 1.1819(24)×10(-4) cm(-1), r(e) (') = 2.584386(25) A? of the X(2)Π(3∕2,g) state, and B(e) (') = 0.0305787(37) cm(-1), a(e) (') = 1.2353(23)×10(-4) cm(-1), r(e) (') = 2.94758(18) A? of the A(2)Π(3∕2,u) state. Vibrational energies were used to derive ω(e) (') = 239.0397(55) cm(-1), ω(e)x(e) (') = 0.64951(87) cm(-1) of the X(2)Π(3∕2,g) state and ω(e) (') = 138.103(11) cm(-1), ω(e)x(e) (') = 0.45027(34) cm(-1) of the A(2)Π(3∕2,u) state. The A(2)Π(3∕2,u) (υ(n) = 13) state was found to be rotationally perturbed by the a(4)Σ(1/2,u) (-) (υ(n) = 17) state through second-order spin-orbit coupling.     

Facile and Efficient Michael Addition of Indole to Nitroolefins Catalyzed by Zn(OAc)2 · 2H2O

The Zn(OAc)₂2H₂O-catalyed Michael addition reaction of indole to electron-deficient nitroolefins to afford the corresponding adducts in good to excellent yields with high selectivity is reported.     

Stabilities,Electronic Structures,and Bonding Properties of Iron Complexes (E1E2)Fe(CO)2(CNArTripp2)2 (E1E2=BF,CO, N2, CN−, or NO+)**

The coordination of 10-electron diatomic ligands (BF, CO N₂) to iron complexes Fe(CO)₂(CNAr^Tripp2)₂ [Ar^Tripp2=2,6-(2,4,6-(iso-propyl)₃C₆H₂)₂C₆H₃] have been realized in experiments very recently (Science, 2019 , 363, 1203–1205). Herein, the stability, electronic structures, and bonding properties of (E₁E₂)Fe-(CO)₂(CNAr^Tripp2)₂ (E₁E₂=BF, CO, N₂, CN⁻, NO⁺) were studied using density functional (DFT) calculations. The ground state of all those molecules is singlet and the calculated geometries are in excellent agreement with the experimental values. The natural bond orbital analysis revealed that Fe is negatively charged while E₁ possesses positive charges. By employing the energy decomposition analysis, the bonding nature of the E₂E₁–Fe(CO)₂(CNAr^Tripp2)₂ bond was disclosed to be the classic dative bond E₂E₁→Fe(CO)₂(CNAr^Tripp2)₂ rather than the electron-sharing double bond. More interestingly, the bonding strength between BF and Fe(CO)₂(CNAr^Tripp2)₂ is much stronger than that between CO (or N₂) and Fe(CO)₂(CNAr^Tripp2)₂, which is ascribed to the better σ-donation and π back-donations. However, the orbital interactions in CN⁻→Fe(CO)₂(CNAr^Tripp2)₂ and NO⁺→Fe(CO)₂(CNAr^Tripp2)₂ mainly come from σ-donation and π back-donation, respectively. The different contributions from σ donation and π donation for different ligands can be well explained by using the energy levels of E₁E₂ and Fe(CO)₂(CNAr^Tripp2)₂ fragments.     

Speciation of the Vanadium(III) Complexes with 1,10-Phenanthroline, 2,2′-Bipyridine,and 8-Hydroxyquinoline

The complex species formed between vanadium(III) and 1,10-phenanthroline (phen), 2,2′-bipyridine (bipy), and 8-hydroxyquinoline (8hq) were studied in aqueous solution by means of electromotive forces measurements, emf(H), at 25 °C with 3.0 mol⋅dm⁻³ KCl as the ionic medium. The potentiometric data were analyzed using the least-squares computational program LETAGROP, taking into account the hydrolytic vanadium(III) species formed in solution. Analysis of the vanadium(III)–phen system data shows the formation of [VHL]⁴⁺, [V(OH)L]²⁺, [V₂OL₂]⁴⁺ and [V₂OL₄]⁴⁺ complexes. In the vanadium(III)–bipy system the [VHL]⁴⁺, [V(OH)L]²⁺, [V₂OL₂]⁴⁺ and [V₂OL₄]⁴⁺ complexes were observed, and in the vanadium(III)–8hq system the complexes [V(OH)L]⁺, [V(OH)₂L], [VL₂]⁺ and [VL₃] were detected.     

Synthesis,Characterization,and DNA Binding Properties of Dinuclear Copper(Ⅱ)Complex [Cu2(TATP)2(L-Leu)2(CIO4)2]2°2H2O

A dinuclear copper(Ⅱ) complex [Cu2(TATP)2(L-Leu)2(ClO4)2]2.2H2O was synthesized and characterized,where,TATP=1,4,8,9-tetraazatriphenylene,and L-Leu=L-leucinate,The complex was crystallized in the triclinic space group P1,with two independent molecules in a unit cell,Two Cu(Ⅱ) ions in each complex[Cu2(TATP)2(L-Leu)2(ClO4)2]molecule were found to be in different coordination geometries,i.e.,Cu2 or Cu4 of a distorted square-pyramidal geometry coordinated with two nitrogens of TATP,the amino nitrogen and one carboxylate oxygen of L-Leu and one oxygen of perchlorate,and Cul or Cu3 with an octahedral geometry coordinated with the above stated similar coordinated atoms,and another carboxylate oxygen of L-Leu coordinating to Cu2 or Cu4,The complex can interact with CT-DNA by an intercalative mode and cleave pBR322 DNA in the presence of ascorbate.     

Syntheses,crystal structures,and electrochemical studies of Fe2(CO)6(μ-PPh2)(μ-L) (L = OH,OPPh2, PPh2)

Reaction of Fe₃(CO)₁₂ and Ph₂PH in the presence of Et₃N in THF at 0?°C immediately forms Fe₂(CO)₆(μ-PPh₂)(μ-OH) (1), Fe₂(CO)₆(μ-PPh₂)(μ-k²O,P-OPPh₂) (2), and Fe₂(CO)₆(μ-PPh₂)₂ (3) in yields of 25, 14, and 19%, respectively. Experiments confirm that Et₃N shortens the reaction time. The absence of O₂ hinders the formation of 2. The presence of H₂O can increase the yield of 1. Their structures have been determined by X-ray crystallography and the complexes have been completely characterized by EA, IR, and ¹H, ¹³C, ³¹P NMR. Electrochemical studies reveal that they exhibit catalytic H₂-producing activities.     

ZrOCl2 · 8H2O: An Efficient,Ecofriendly, and Recyclable Catalyst for Ultrasound-Accelerated,One-Pot,Solvent-Free Synthesis of 8-Aryl-7,8-dihydro-[1,3]dioxolo[4,5-g]quinolin-6-(5H)-one and 4-Aryl-3,4-dihydroquinolin-2(1 H)-one Derivatives

A convenient, one-pot, solvent-free reaction of amines, aromatic aldehydes, and Meldrum's acid to form 8-aryl-7,8-dihydro-[1,3]dioxolo[4,5-g]quinolin-6-(5H)-one and 4-aryl-3,4-dihydroquinolin-2-(1H)-one in the presence of 10 mol% ZrOCl₂.8H₂O under ultrasonic irradiation is described. This new protocol offers several advantages including low catalyst loading, clean reaction, easy workup, use of recyclable and ecofriendly catalyst, short reaction times, good yields, and solvent-free conditions.

Supplemental materials are available for this article. Go to the publisher's online edition of Synthetic Communications® to view the free supplemental file.     

(Ph3P)2,Co(CO)2Cl和(dppe-P,P)2CO(CO)+的分子轨道研究

本文对(PH3P)2, Co(CO)2Cl和(dppe-P,P)2CO(CO)+(dppe=Ph2CH2CH2PPh2)五配位C2O对称性模型化合物进行了分轨道研究, 结果表明, 钴的3d轨道很少参与成键, 钴的4s, 4P与配体的S,P轨道通过形式上的二电子三中心键和二电子二中心键的相互作用构成五配位, 此外, 还解释了这两种化合物不同稳定性的原因。     

Buffer Standards for pH Measurement of N-(2-Hydroxyethyl)piperazine-N′-2-ethanesulfonic Acid (HEPES) for I=0.16 mol⋅kg−1 from 5 to 55 °C

The values of the second dissociation constant, pK ₂, of N-(2-hydroxyethyl) piperazine-N′-2-ethanesulfonic acid (HEPES) have been reported at twelve temperatures over the temperature range 5 to 55 °C, including 37 °C. This paper reports the results for the pa _H of eight isotonic saline buffer solutions with an I=0.16 mol⋅kg⁻¹ including compositions: (a) HEPES (0.01 mol⋅kg⁻¹) + NaHEPES (0.01 mol⋅kg⁻¹) + NaCl (0.15 mol⋅kg⁻¹); (b) HEPES (0.02 mol⋅kg⁻¹) + NaHEPES (0.02 mol⋅kg⁻¹) + NaCl (0.14 mol⋅kg⁻¹); (c) HEPES (0.03 mol⋅kg⁻¹) + NaHEPES (0.03 mol⋅kg⁻¹) + NaCl (0.13 mol⋅kg⁻¹); (d) HEPES (0.04 mol⋅kg⁻¹) + NaHEPES (0.04 mol⋅kg⁻¹) + NaCl (0.12 mol⋅kg⁻¹); (e) HEPES (0.05 mol⋅kg⁻¹) + NaHEPES (0.05 mol⋅kg⁻¹) + NaCl (0.11 mol⋅kg⁻¹); (f) HEPES (0.06 mol⋅kg⁻¹) + NaHEPES (0.06 mol⋅kg⁻¹) + NaCl (0.10 mol⋅kg⁻¹); (g) HEPES (0.07 mol⋅kg⁻¹) + NaHEPES (0.07 mol⋅kg⁻¹) + NaCl (0.09 mol⋅kg⁻¹); and (h) HEPES (0.08 mol⋅kg⁻¹) + NaHEPES (0.08 mol⋅kg⁻¹) + NaCl (0.08 mol⋅kg⁻¹). Conventional pa _H values, for all eight buffer solutions from 5 to 55 °C, have been calculated. The operational pH values with liquid junction corrections, at 25 and 37 °C have been determined based on the NBS/NIST standard between the physiological phosphate standard and four buffer solutions. These are recommended as pH standards for physiological fluids in the range of pH = 7.3 to 7.5 at I=0.16 mol⋅kg⁻¹.