A single configuration model containing nonorthogonal magnetic orbitals is developed to represent the important features of antiferromagnetic state a transition metal dimer. mixed spin symmetry and lowered space constructed which has both conceptual practical computational value. Either unrestricted Hartree–Fock theory or polarized density functional theory, e.g., Xα can be used generate wave function. The most consequence that Heisenberg exchange coupling constant J calculated simply from...

Huisgen's 1,3-dipolar cycloadditions become nonconcerted when copper(I) acetylides react with azides and nitrile oxides, providing ready access to 1,4-disubstituted 1,2,3-triazoles 3,4-disubstituted isoxazoles, respectively. The process is highly reliable exhibits an unusually wide scope respect both components. Computational studies revealed a stepwise mechanism involving unprecedented metallacycle intermediates, which appear be common for variety of dipoles.

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTElectronic structure, magnetic properties, ESR, and optical spectra for 2-iron ferredoxin models by LCAO-X.alpha. valence bond theoryLouis Noodleman Evert Jan BaerendsCite this: J. Am. Chem. Soc. 1984, 106, 8, 2316–2327Publication Date (Print):April 1, 1984Publication History Published online1 May 2002Published inissue 1 April 1984https://pubs.acs.org/doi/10.1021/ja00320a017https://doi.org/10.1021/ja00320a017research-articleACS PublicationsRequest...

We show that valence bond (VB) concepts can be introduced into Xα theory. The resulting Xα–VB model yields energy states which either are pure multiplets or combined by straightforward projection to give multiplets. new theory should more computationally efficient than Hartree–Fock-based CI models. A preliminary study of the δ→δ* transition in Mo2Cl84− an excitation closer experiment previous theoretical values, including those obtained date from GVB–CI calculations.

The lack of efficient [18F]fluorination processes and target-specific organofluorine chemotypes remains the major challenge fluorine-18 positron emission tomography (PET). We report here an ultrafast isotopic exchange method for radiosynthesis novel PET agent aryl [18F]fluorosulfate enabled by emerging sulfur fluoride (SuFEx) click chemistry. has been applied to fully automated 18F-radiolabeling 25 structurally functionally diverse fluorosulfates with excellent radiochemical yield (83-100%,...

The mechanism by which zinc(II) catalyzes the union of an azide ion with organic nitriles to form tetrazoles is investigated means density functional theory using hybrid B3LYP. calculations indicate that coordination nitrile zinc dominant factor affecting catalysis; this substantially lowers barrier for nucleophilic attack azide. Relative reaction rates catalyzed and uncatalyzed tetrazole formation also provide experimental support conclusion.

It is well-known that azide salts can engage nitriles at elevated temperatures to yield tetrazoles; however, there continued debate as the mechanism of reaction. Density functional theory calculations with hybrid B3LYP have been performed study different mechanisms tetrazole formation, including concerted cycloaddition and stepwise addition neutral or anionic species. The presented here suggest a previously unsuspected nitrile activation step en route an imidoyl azide, which then cyclizes...

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTDensity Functional/Poisson-Boltzmann Calculations of Redox Potentials for Iron-Sulfur ClustersJean-Marie Mouesca, Jun L. Chen, Louis Noodleman, Donald Bashford, and David A. CaseCite this: J. Am. Chem. Soc. 1994, 116, 26, 11898–11914Publication Date (Print):December 1, 1994Publication History Published online1 May 2002Published inissue 1 December 1994https://doi.org/10.1021/ja00105a033RIGHTS & PERMISSIONSArticle Views1210Altmetric-Citations253LEARN...

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTModels for ferredoxins: electronic structures of iron-sulfur clusters with one, two, and four iron atomsLouis Noodleman, Joe G. Norman Jr., Joseph H. Osborne, Arie Aizman, David A. CaseCite this: J. Am. Chem. Soc. 1985, 107, 12, 3418–3426Publication Date (Print):June 1, 1985Publication History Published online1 May 2002Published inissue 1 June 1985https://doi.org/10.1021/ja00298a004RIGHTS & PERMISSIONSArticle Views1055Altmetric-Citations265LEARN...

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTBroken symmetry analysis of spin coupling in iron-sulfur clustersLouis. Noodleman, David A. Case, and Arie. AizmanCite this: J. Am. Chem. Soc. 1988, 110, 4, 1001–1005Publication Date (Print):February 17, 1988Publication History Published online1 May 2002Published inissue 17 February 1988https://pubs.acs.org/doi/10.1021/ja00212a003https://doi.org/10.1021/ja00212a003research-articleACS PublicationsRequest reuse permissionsArticle...

Density functional and continuum dielectric theories have been combined to calculate molecular properties such as hydration enthalpies, redox potentials, absolute pKa values of transition metal cations in solution. The discrete cluster model, which is treated explicitly by density theory, includes six waters the first shell another twelve second shell. solvent reaction field obtained from a finite-difference solution Poisson−Boltzmann equation coupled nonlocal calculation self-consistent...

Density functional theory geometry optimizations and reduction potential calculations are reported for all five known oxidation states of [Fe4S4(SCH3)4]n- (n = 0, 1, 2, 3, 4) clusters that form the active sites iron−sulfur proteins. The geometry-optimized structures tend to be slightly expanded relative experiment, with best comparison found in [Fe4S4(SCH3)4]2- model cluster, having bond lengths 0.03 Å longer on average than experimentally observed. Environmental effects modeled a continuum...

The capability of the density functional broken symmetry approach for calculation various EPR parameters exchange coupled metal clusters is demonstrated by studying experimentally well-investigated [MnIIIMnIV(μ-O)2(μ-OAc)DTNE]2+ complex. Geometry optimizations complex in its and high spin states yielded structures with two distinct manganese sites geometrical good agreement X-ray structure. Exchange coupling constants were calculated from energy differences between using Heisenberg...

Fluorogenic probes, due to their often greater spatial and temporal sensitivity in comparison permanently fluorescent small molecules, represent powerful tools study protein localization function the context of living systems. Herein, we report fluorogenic probe 4, a 1,3,4-oxadiazole designed bind selectively transthyretin (TTR). Probe 4 comprises fluorosulfate group not previously used an environment-sensitive fluorophore. The functional does react covalently with TTR on time scale required...

The M(N) S = (3)/(2) resting state of the FeMo cofactor nitrogenase has been proposed to have metal-ion valencies either Mo(4+)6Fe(2+)Fe(3+) (derived from metal hyperfine interactions) or Mo(4+)4Fe(2+)3Fe(3+) (from Mössbauer isomer shifts). Spin-polarized broken-symmetry (BS) density functional theory (DFT) calculations undertaken determine which oxidation level best represents and provide a framework for understanding its energetics spectroscopy. For state, spin coupling pattern several...

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTIncorporating Solvation Effects into Density Functional Electronic Structure CalculationsJun L. Chen, Louis Noodleman, David A. Case, and Donald BashfordCite this: J. Phys. Chem. 1994, 98, 43, 11059–11068Publication Date (Print):October 1, 1994Publication History Published online1 May 2002Published inissue 1 October 1994https://pubs.acs.org/doi/10.1021/j100094a013https://doi.org/10.1021/j100094a013research-articleACS PublicationsRequest reuse...

Broken symmetry density functional and electrostatics calculations have been used to shed light on which of three proposed atoms, C, N, or O, is most likely be present in the center FeMoco, active site nitrogenase. At Mo4+4Fe2+3Fe3+ oxidation level, a central N3- anion results (1) calculated Fe−N bond distances that are very good agreement with recent high-resolution X-ray data Einsle et al.; (2) redox potential 0.19 eV versus standard hydrogen electrode (SHE) for FeMoco(oxidized) + e- →...

The results of self-consistent field (SCF) nonlocal density functional molecular orbital calculations are presented for the various spin states and tautomeric forms a cobalt complex with two o-quinone-derived ligands. In addition, new variable-temperature solution magnetic susceptibility, EPR, electronic absorption data to characterize low-spin [CoIII(3,5-DTBSQ)(3,5-DTBCat)(phen)] high-spin [CoII(3,5-DTBSQ)2(phen)] valence-tautomeric interconversion, where 3,5-DTBSQ- 3,5-DTBCat2-...

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTA model for the spin states of high-potential iron-sulfur [Fe4S4]3+ proteinsLouis NoodlemanCite this: Inorg. Chem. 1988, 27, 20, 3677–3679Publication Date (Print):October 1, 1988Publication History Published online1 May 2002Published inissue 1 October 1988https://pubs.acs.org/doi/10.1021/ic00293a051https://doi.org/10.1021/ic00293a051research-articleACS PublicationsRequest reuse permissionsArticle Views334Altmetric-Citations104LEARN ABOUT THESE...

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTElectronic structure of 2-Fe ferredoxin models by X.alpha. valence bond theoryJoe G. Norman Jr., P. Barry Ryan, and Louis NoodlemanCite this: J. Am. Chem. Soc. 1980, 102, 12, 4279–4282Publication Date (Print):June 1, 1980Publication History Published online1 May 2002Published inissue 1 June 1980https://pubs.acs.org/doi/10.1021/ja00532a060https://doi.org/10.1021/ja00532a060research-articleACS PublicationsRequest reuse permissionsArticle...