Charge Equilibration Based on Atomic Ionization in Metal–Organic Frameworks

In this article, two new charge equilibration methods for estimating atomic partial charges are outlined. These methods are based on expanding the Taylor series used to estimate the ionization energy of each atom about either the formal or atomic charge, allowing for accurate charge estimation in both covalent and ionic materials. A new treatment of hydrogen atoms based on molecular hydrogen is also introduced. To demonstrate their general applicability, these new methods have been applied to the simulation of CO₂ adsorption in metal–organic frameworks. Comparisons with other charge equilibration methods and density functional theory (DFT) calculations show that, of the rapid charge-assigning methods, the algorithm based on atomic ionization best replicates the DFT electrostatic potential and provides the most accurate estimation of CO₂ adsorption

Functionalised alkaline earth iodides from Grignard synthons "PhAeI(thf)ₙ" (Ae = Mg‐Ba)

Derivatisation of Grignard synthons "PhAeI(thf)(n)" (Ae = Mg-Ba) prepared in situ from reactions of metal filings and iodobenzene provides a one-pot synthesis of heteroleptic N donor alkaline earth iodide complexes. Protolysis of "PhAeI(thf)(n)" with 3,5-diphenylpyrazole (Ph(2)pzH) yields pyrazolate complexes [Mg-2(mu-Ph(2)pz)(2)(I)(2)(thf)(3)] (1), [Ae(Ph(2)pz)(I)(thf)(4)] (Ae = Ca (2), Sr (3)), and [Ba-2(Ph(2)pz)(2)(mu-I)(2)(thf)(8)] (4). Addition of the Ae-Ph moiety to carbodiimide MesN=C=NMes (Mes = 2,4,6-(CH3)(3)C6H2) gave a series of benzamidinate iodide complexes [Ca-2{(MesN)(2)CPh}(2)(mu-I)(2)(thf)(4)] (6), [Sr{(MesN)(2)CPh}(I)(thf)(4)] (7), and [{Ba{(MesN)(2)CPh}(mu-I)(thf)(3)}(infinity)] (8). By contrast a symmetrical magnesium complex [Mg{(MesN)(2)CPh}(2)(thf)] (5) was obtained by Schlenk redistribution. These syntheses proceed without pre-activation of the metal for strontium and barium, and after activation with 2 mol-% iodine for calcium. The heavy alkaline earth metal complexes are the first examples of heteroleptic halide pyrazolate or amidinate complexes for strontium and barium. Complexes 1, 3, 4 and 6-8 were characterised crystallographically, revealing diverse structural chemistry of heteroleptic amidinate and pyrazolate iodide complexes across the alkaline earth series. A highlight is [Ba{(MesN)(2)CPh}(mu-I)(thf)(3)](infinity) (8) - an iodide bridged infinite 1-D polymer

Kinetic stabilisation of a molecular strontium hydride complex using an extremely bulky amidinate ligand

International audienceTwo extremely bulky amidinate ligands, [RC{N(Dip)}{N(Ar-dagger)}](-) (Dip = 2,6-diisopropylphenyl; Ar-dagger = C6H2{C(H)Ph-2}(2)Pr-i-2,6,4; R = 1-adamantyl (L-Ad), tert-butyl (L-tBu)) have been developed and utilised for the kinetic stabilisation of the strontium and magnesium hydride complexes, [(LSr)-Sr-Ad(mu-H)](2) and [(LMg)-Mg-R(mu-H)](2) (R = Ad or Bu-t). The former represents the missing link in the series of dimeric systems, [LAe(mu-H)](2) (Ae = alkaline earth metal). The structure and bonding of the complexes have been studied by crystallographic, spectroscopic and computational techniques

New, environmentally friendly, rare earth carboxylate corrosion inhibitors for mild steel

Four recently synthesized rare earth 3-(4-methylbenzoyl)propanoate (mbp) compounds (RE = La, Ce, Nd and Y) were evaluated as corrosion inhibitors for mild steel in 0.01 M NaCl. At a concentration of 0.25 mM all the compounds showed some level of inhibition after 30 min immersion, with the Y(mbp)3 complex giving the largest reduction in corrosion current density, from 1.92 mu A/cm(2) for the control sample to 0.25 mu A/cm(2) for the Y based inhibitor. All the RE(mbp)3 inhibitors acted predominantly as anodic inhibitors, showing little effect on the cathodic reaction after 30 min. Surface analysis after 6 h immersion using FTIR and EDS detected the presence of a thin film containing inhibitor components on all surfaces, thus accounting for the reduced corrosion rate, with the Y(mbp)(3) compound having the most significant effect on corrosion and showing the most uniform surface coverage

New, environmentally friendly, rare earth carboxylate corrosion inhibitors for mild steel

Four recently synthesized rare earth 3-(4-methylbenzoyl)propanoate (mbp) compounds (RE = La, Ce, Nd and Y) were evaluated as corrosion inhibitors for mild steel in 0.01 M NaCl. At a concentration of 0.25 mM all the compounds showed some level of inhibition after 30 min immersion, with the Y(mbp)3 complex giving the largest reduction in corrosion current density, from 1.92 mu A/cm(2) for the control sample to 0.25 mu A/cm(2) for the Y based inhibitor. All the RE(mbp)3 inhibitors acted predominantly as anodic inhibitors, showing little effect on the cathodic reaction after 30 min. Surface analysis after 6 h immersion using FTIR and EDS detected the presence of a thin film containing inhibitor components on all surfaces, thus accounting for the reduced corrosion rate, with the Y(mbp)(3) compound having the most significant effect on corrosion and showing the most uniform surface coverage

Synthesis and structures of rare earth 3-(4 '-Methylbenzoyl)-propanoate complexes: new corrosion inhibitors

A series of rare earth 3-(4'-methylbenzoyl)propanoate (mbp(-)) complexes [RE(mbp)(3)(H2O)] (RE = rare earth = Y, La, Ce, Nd, Ho, Er) have been prepared by either metathesis reactions between the corresponding rare earth chloride and Na(mbp) or protolysis of rare earth acetates by the free acid. Single-crystal X-ray diffraction studies of [RE(mbp)(3)(H2O)] (RE = Ce, Nd) and [Ce(mbp)(3)(dmso)] reveal a 1D carboxylate-bridged polymeric structure in the solid state, featuring 9-coordinate rare earth ions. X-ray powder diffraction patterns of the bulk materials indicates that all of the [RE(mbp)(3)(H2O)] complexes except RE = La are isomorphous. Hence, there is no structural change from the complex with RE = Ce to that with RE = Er despite the lanthanoid contraction. The H-1 NMR spectra of the RE = Ho or Er complexes in (CD3)(2)SO show large paramagnetic shifts and broadening of the CH2 resonances, indicating the retention of substantial carboxylate coordination in solution