Search

The minimum size of a model system to study the peptide bond rupture mechanism in KLK5 is determined using three sequential scale models.

In this research article, we describe a 4H(+)/4e(−) electron-coupled-proton buffer (ECPB) based on Cu and a redox-active ligand. The protonated/reduced ECPB (complex 1: [Cu(8H(+)/14e(−))](1+)), consisting of Cu(I) with 2 equiv of the ligand ((cat)LH(4): 1,1′-(4,5-dimethoxy-1,2-phenylene)bis(3-(tert-butyl)urea)), reacted with H(+)/e(−) acceptors such as O(2) to generate the deprotonated/oxidized ECPB. The resulting compound, (complex 5: [Cu(4H(+)/10e(−))](1+)), was characterized by X-ray diffraction analysis, nuclear magnetic resonance ((1)H-NMR), and density functional theory, and it is electronically described as a cuprous bis(benzoquinonediimine) species. The stoichiometric 4H(+)/4e(−) reduction of 5 was carried out with H(+)/e(−) donors to generate 1 (Cu(I) and 2 equiv of (cat)LH(4)) and the corresponding oxidation products. The 1/5 ECPB system catalyzed the 4H(+)/4e(−) reduction of O(2) to H(2)O and the dehydrogenation of organic substrates in a decoupled (oxidations and reductions are separated in time and space) and a coupled fashion (oxidations and reductions coincide in time and space). Mechanistic analysis revealed that upon reductive protonation of 5 and oxidative deprotonation of 1, fast disproportionation reactions regenerate complexes 5 and 1 in a stoichiometric fashion to maintain the ECPB equilibrium.

The properties of metal/dioxygen species, which are key intermediates in oxidation catalysis, can be modulated by interaction with redox-inactive Lewis acids, but structural information about these adducts is scarce. Here we demonstrate that even mildly Lewis acidic alkali metal ions, which are typically viewed as innocent "spectators", bind strongly to a reactive cis-peroxo dicopper(II) intermediate. Unprecedented structural insight has now been obtained from X-ray crystallographic characterization of the "bare" CuII2(μ-η1:η1-O2) motif and its Li+, Na+, and K+ complexes. UV-vis, Raman, and electrochemical studies show that the binding persists in MeCN solution, growing stronger in proportion to the cation's Lewis acidity. The affinity for Li+ is surprisingly high (∼70 × 104 M-1), leading to Li+ extraction from its crown ether complex. Computational analysis indicates that the alkali ions influence the entire Cu-OO-Cu core, modulating the degree of charge transfer from copper to dioxygen. This induces significant changes in the electronic, magnetic, and electrochemical signatures of the Cu2O2 species. These findings have far-reaching implications for analyses of transient metal/dioxygen intermediates, which are often studied in situ, and they may be relevant to many (bio)chemical oxidation processes when considering the widespread presence of alkali cations in synthetic and natural environments.

S=2 oxoiron(IV) species act as reactive intermediates in the catalytic cycle of nonheme iron oxygenases. The few available synthetic S=2 FeIV=O complexes known to date are often limited to trigonal bipyramidal and very rarely to octahedral geometries. Herein we describe the generation and characterization of an S=2 pseudotetrahedral FeIV=O complex 2 supported by the sterically demanding 1,4,7‐tri‐tert‐butyl‐1,4,7‐triazacyclononane ligand. Complex 2 is a very potent oxidant in hydrogen atom abstraction (HAA) reactions with large non‐classical deuterium kinetic isotope effects, suggesting hydrogen tunneling contributions. For sterically encumbered substrates, direct HAA is impeded and an alternative oxidative asynchronous proton‐coupled electron transfer mechanism prevails, which is unique within the nonheme oxoiron community. The high reactivity and the similar spectroscopic parameters make 2 one of the best electronic and functional models for a biological oxoiron(IV) intermediate of taurine dioxygenase (TauD‐J)., A highly reactive S=2 pseudotetrahedral oxoiron(IV) complex 2 supported by a sterically demanding 1,4,7‐tri‐tert‐butyl‐1,4,7‐triazacyclononane ligand has been synthesized and spectroscopically characterized as one of the best electronic and functional models for a biological oxoiron(IV) intermediate of taurine dioxygenase (TauD‐J).

For many years non-covalently bonded complexes of nucleobases have attracted considerable interest. However, there is a lack of information about the nature of hydrogen bonding between nucleobases when the bonding is affected by metal coordination to one of the nucleobases, and how the individual hydrogen bonds and aromaticity of nucleobases respond to the presence of the metal cation. Here we report a DFT computational study of nucleobase pairs interacting with alkali metal cations. The metal cations contribute to the stabilization of the base pairs to varying degrees depending on their position. The energy decomposition analysis revealed that the nature of bonding between nucleobases does not change much upon metal coordination. The effect of the cations on individual hydrogen bonds were described by changes in VDD charges on frontier atoms, H bond length, bond energy from NBO analysis, and delocalization index from QTAIM calculations. The aromaticity changes were determined by HOMA index M. Solà and O.A.S. are grateful to the Ministerio de Economía y Competitividad (MINECO) of Spain (project CTQ2017-85341-P and Juan de la Cierva formación contract FJCI‐2017‐ 32757 to O.A.S.) and the Generalitat de Catalunya (project 2017SGR39). HS and TMK thank the National Science Centre of Poland for supporting this work under the grant no. UMO2016/23/B/ST4/00082. M. Swart acknowledges MICINN/MINECO (projects CTQ2014 59212 P, CTQ2015-70851-ERC, CTQ2017-87392-P), GenCat (2014SGR1202, 2017SGR1434 and XRQTC network) and European Fund for Regional Development (FEDER, UNGI104E801). C.F.G. thanks the Netherlands Organization for Scientific Research (NWO) for financial support

In soluble methane monooxygenase enzymes (sMMO), dioxygen (O2) is activated at a diiron(II) center to form an oxodiiron(IV) intermediate Q that performs the challenging oxidation of methane to meth...

The biological activity of sulfur and selenium, despite their similarity, shows some remarkable differences that have been recognized in many different scenarios. However, the underlying cause has not been completely clarified yet. The difference in the redox behavior of these two chalcogens has lately been addressed as justification of the presence of selenium in some essential biological systems. In particular, selenium is found in some peroxidases, i.e. glutathione peroxidases (GPx), whose redox activity relies on a fast-reacting selenocysteine and is fundamental in metabolizing harmful peroxides. In this work, a systematic in silico investigation on model systems, i.e. phenylchalcogenides, containing sulfur, selenium and tellurium is presented. Sequential oxidation reactions of these chalcogen-based substrates by hydrogen peroxide are carried out spanning the range of the biologically relevant chalcogen oxidation numbers [Advances in Molecular Toxicology, ed. J. C. Fishbein, Elsevier, 2010, vol. 4, pp. 183–222.] (2−, 0, 2+ and 4+) and analyzed through the calculation of intrinsic reaction coordinate paths and the application of the activation strain model. The results allowed us to highlight the different behaviors of S, Se and Te in highly oxidizing environments.

We disclose a new reactivity mode for electrophilic cyano λ

Copper nitrenes are proposed as reactive intermediates in a number of copper mediated aziridination and amination reactions. However, the isolation and characterization of such intermediates have proved challenging because of their transient nature. One successful approach for the stabilization of the copper-nitrene cores is the employment of a redox innocent Lewis acid (LA) like Sc3+. We herein report the stabilization of two transient copper nitrene species 3 and 4 in the absence of LAs by employing electronegative −CF3 and −NO2 groups in the nitrene substituent. Detailed investigations of the spectroscopic properties of 3 and 4 by theoretical and experimental methods, and a comparison of their reactivities in presence and absence of LAs provide some vital insights into the effect of LAs on the geometric and electronic structures of the copper nitrenes.

In this research article, we describe the structure, spectroscopy, and reactivity of a family of copper complexes bearing bidentate redox-active ligands that contain H-bonding donor groups. Single-crystal X-ray crystallography shows that these tetracoordinate complexes are stabilized by intramolecular H-bonding interactions between the two ligand scaffolds. Interestingly, the Cu complexes undergo multiple reversible oxidation—reduction processes associated with the metal ion (Cu(I), Cu(II), Cu(III)) and/or the o-phenyldiamido ligand (L(2—), L(●—), L). Moreover, some of the Cu(11) complexes catalyze the aerobic oxidation of alcohols to aldehydes (or ketones) at room temperature. Our extensive mechanistic analysis suggests that the dehydrogenation of alcohols occurs via an unusual reaction pathway for galactose oxidase model systems, in which O(2) reduction occurs concurrently with substrate oxidation.

The applications of NMR chemical shift calculations have shown an extraordinary expansion and diversification in the last decade. A significant proportion of these efforts have been devoted to interpreting and reproducing NMR experiments within different solvent environments and in a variety of complexes containing heavy element(s) or molecules of an open-shell nature. Thus, it is the purpose of this chapter to present a broad overview of the state-of-the-art in the field of computational NMR spectroscopy with a particular focus on applications for the prediction of NMR spectra, including NMR chemical shifts of diamagnetic and paramagnetic systems. At the same time, this chapter provides an analysis of the quantitative methodologies developed during recent years, including representative applications to illustrate the historical evolution of this field. Important aspects of the dynamical or solvent effects, and relativistic contributions are also mentioned, highlighting the advantages and limitations of the available methodologies.

The search for evidence of life elsewhere in the universe is hard because it is not obvious what signatures are unique to life. Here we postulate that complex molecules found in high abundance are universal biosignatures as they cannot form by chance. To explore this, we developed the first intrinsic measure of molecular complexity that can be experimentally determined, and this is based upon a new approach called assembly theory which gives the molecular assembly number (MA) of a given molecule. MA allows us to compare the intrinsic complexity of molecules using the minimum number of steps required to construct the molecular graph starting from basic objects, and a probabilistic model shows how the probability of any given molecule forming randomly drops dramatically as its MA increases. To map chemical space, we calculated the MA of ca. 2.5 million compounds, and collected data which showed the complexity of a molecule can be experimentally determined by using three independent techniques including infra-red spectroscopy, nuclear magnetic resonance, and by fragmentation in a mass spectrometer, and this data has an excellent corelation with the values predicted from our assembly theory. We then set out to see if this approach could allow us to identify molecular biosignatures with a set of diverse samples from around the world, outer space, and the laboratory including prebiotic soups. The results show that there is a non-living to living threshold in MA complexity and the higher the MA for a given molecule, the more likely that it had to be produced by a biological process. This work demonstrates it is possible to use this approach to build a life detection instrument that could be deployed on missions to extra-terrestrial locations to detect biosignatures, map the extent of life on Earth, and be used as a molecular complexity scale to quantify the constraints needed to direct prebiotically plausible processes in the laboratory. Such an approach is vital if we are going to find new life elsewhere in the universe or create de-novo life in the lab.

We introduce here the spin-resolved version of the charge displacement function, which is applied to two competing pathways of proton-coupled electron transfer in oxidation catalysis (hydrogen-atom transfer, concerted proton-coupled electron transfer). The difference in charge displacement between the two mechanisms is directly observable and can be translated to electron flow using this new analysis tool.

A new concept of bond order density of shared electron pairs is introduced to study the electronic structure in molecules. This BODSEP analysis is applied to the distortion of benzene toward its building blocks (acetylenes), metalloporphyrins and two recent examples from the literature. The S12g/TZ2P results show the gradual disappearance of the bonds while distorting benzene and strengthening the bonds in acetylene to reach a final triple bond value. A large range of bond orders are observed for the metalloporphyrins, which are consistent with aromaticity indices from the literature [Can. J. Chem. 2009, 87, 1063]; with an ideal value of 1.5 for aromatic molecules (because of resonance), it suggests that (BODSEP) bond orders might be used for aromaticity measures. Finally, the delocalized bonds in porphyrins are localizing in the corrphycenes, and bond order strengths for different spin states of dipyrrolonaphthyridinedione have been assigned, which differ from the original description.

The concepts of nucleophilicity and protophilicity are fundamental and ubiquitous in chemistry. A case in point is bimolecular nucleophilic substitution (SN2) and base‐induced elimination (E2). A Lewis base acting as a strong nucleophile is needed for SN2 reactions, whereas a Lewis base acting as a strong protophile (i.e., base) is required for E2 reactions. A complicating factor is, however, the fact that a good nucleophile is often a strong protophile. Nevertheless, a sound, physical model that explains, in a transparent manner, when an electron‐rich Lewis base acts as a protophile or a nucleophile, which is not just phenomenological, is currently lacking in the literature. To address this fundamental question, the potential energy surfaces of the SN2 and E2 reactions of X−+C2H5Y model systems with X, Y = F, Cl, Br, I, and At, are explored by using relativistic density functional theory at ZORA‐OLYP/TZ2P. These explorations have yielded a consistent overview of reactivity trends over a wide range in reactivity and pathways. Activation strain analyses of these reactions reveal the factors that determine the shape of the potential energy surfaces and hence govern the propensity of the Lewis base to act as a nucleophile or protophile. The concepts of “characteristic distortivity” and “transition state acidity” of a reaction are introduced, which have the potential to enable chemists to better understand and design reactions for synthesis., It's about time! A transparent and physically sound model is proposed to recognize when a Lewis base will react as a nucleophile (SN2) or protophile (E2) and the novel concepts of “characteristic distortivity” and “transition state acidity” are introduced.

In soluble methane monooxygenase enzymes (

Soluble methane monooxygenase (sMMO) carries out methane oxidation at 4 °C and under ambient pressure in a catalytic cycle involving the formation of a peroxodiiron(III) intermediate (P) from the oxygenation of the diiron(II) enzyme and its subsequent conversion to Q, the diiron(IV) oxidant that hydroxylates methane. Synthetic diiron(IV) complexes that can serve as models for Q are rare and have not been generated by a reaction sequence analogous to that of sMMO. In this work, we show that [FeII(Me3NTB)(CH3CN)](CF3SO3)2 (Me3NTB = tris((1-methyl-1H-benzo[d]imidazol-2-yl)methyl)amine) (1) reacts with O2 in the presence of base, generating a (μ-1,2-peroxo)diiron(III) adduct with a low O-O stretching frequency of 825 cm-1 and a short Fe···Fe distance of 3.07 Å. Even more interesting is the observation that the peroxodiiron(III) complex undergoes O-O bond cleavage upon treatment with the Lewis acid Sc3+ and transforms into a bis(μ-oxo)diiron(IV) complex, thus providing a synthetic precedent for the analogous conversion of P to Q in the catalytic cycle of sMMO The authors are thankful for grants from the U.S.National Institutes of Health (R01 GM-38767 and R35 GM-131721 to L.Q.),the U.S. National Science Foundation (CHE1654060 to Y.G.), and MICINN (CTQ2017-87392-P to M.S.) for support of this work. XAS data were collected at the Stanford Synchrotron Radiation Lightsource Beamline 9-3. Use of the Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, is supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences under Contract No.DE-AC02-76SF00515. The SSRL Structural Molecular Biology Program is supported by the DOE Office of Biological and Environmental Research, and by the National Institutes of Health, National Institute of General Medical Sciences (P41GM103393)

A covalently bound flavin cofactor is predominant in the succinate-ubiquinone oxidoreductase (SQR; Complex II), an essential component of aerobic electron transport, and in the menaquinol-fumarate oxidoreductase (QFR), the anaerobic counterpart, although it is only present in approximately 10 % of the known flavoenzymes. This work investigates the role of this 8α-N3-histidyl linkage between the flavin adenine dinucleotide (FAD) cofactor and the respiratory Complex II. After parameterization with DFT calculations, classical molecular-dynamics simulations and quantum-mechanics calculations for Complex II:FAD and Complex II:FADH2, with and without the covalent bond, were performed. It was observed that the covalent bond is essential for the active-center arrangement of the FADH2/FAD cofactor. Removal of this bond causes a displacement of the isoalloxazine group, which influences interactions with the protein, flavin solvation, and possible proton-transfer pathways. Specifically, for the noncovalently bound FADH2cofactor, the N1 atom moves away from the His-A365 and His-A254 residues and the N5 atom moves away from the glutamine-62A residue. Both of the histidine and glutamine residues interact with a chain of water molecules that cross the enzyme, which is most likely involved in proton transfer. Breaking this chain of water molecules could thereby compromise proton transfer across the two active sites of Complex II The following organizations are thanked for financial support: A.T.P.C. is grateful to the Fundação para a Ciência e Tecnologia (FCT) for the grant IF/01272/2015. AGAUR for fellowship 2010 BP_B00238, the Ministerio de Ciencia e Innovación (MICINN, project number CTQ2011‐25086/BQU), and the DIUE of the Generalitat de Catalunya (project number 2009SGR528 and Xarxa de Referència en Química Teòrica i Computacional). Financial support from MICINN (Ministry of Science and Innovation, Spain) and the FEDER fund (European Fund for Regional Development) was provided by grant UNGI08‐4E‐003. With the support of the Secretary for Universities and Research of the Ministry of Economy and Knowledge of the Government of Catalonia and the Cofund programme of the Marie Curie Actions of the 7th R&D Framework Programme of the European Union. D.F.A.R.D. acknowledges the financial support from INVEST NI RD0314092

A. Otero-de-la-Roza acknowledges support from the Spanish government for a Ramón y Cajal fellowship (No. RyC-2016-20301) and for financial support (Project Nos. PGC2018-097520-A-100 and RED2018-102612-T)., Aprà, E., Bylaska, E.J., De Jong, W.A., Govind, N., Kowalski, K., Straatsma, T.P., Valiev, M., Van Dam, H.J.J., Alexeev, Y., Anchell, J., Anisimov, V., Aquino, F.W., Atta-Fynn, R., Autschbach, J., Bauman, N.P., Becca, J.C., Bernholdt, D.E., Bhaskaran-Nair, K., Bogatko, S., Borowski, P., Boschen, J., Brabec, J., Bruner, A., Cauët, E., Chen, Y., Chuev, G.N., Cramer, C.J., Daily, J., Deegan, M.J.O., Dunning, T.H., Jr., Dupuis, M., Dyall, K.G., Fann, G.I., Fischer, S.A., Fonari, A., Früchtl, H., Gagliardi, L., Garza, J., Gawande, N., Ghosh, S., Glaesemann, K., Götz, A.W., Hammond, J., Helms, V., Hermes, E.D., Hirao, K., Hirata, S., Jacquelin, M., Jensen, L., Johnson, B.G., Jónsson, H., Kendall, R.A., Klemm, M., Kobayashi, R., Konkov, V., Krishnamoorthy, S., Krishnan, M., Lin, Z., Lins, R.D., Littlefield, R.J., Logsdail, A.J., Lopata, K., Ma, W., Marenich, A.V., Martin Del Campo, J., Mejia-Rodriguez, D., Moore, J.E., Mullin, J.M., Nakajima, T., Nascimento, D.R., Nichols, J.A., Nichols, P.J., Nieplocha, J., Otero-De-La-Roza, A., Palmer, B., Panyala, A., Pirojsirikul, T., Peng, B., Peverati, R., Pittner, J., Pollack, L., Richard, R.M., Sadayappan, P., Schatz, G.C., Shelton, W.A., Silverstein, D.W., Smith, D.M.A., Soares, T.A., Song, D., Swart, M., Taylor, H.L., Thomas, G.S., Tipparaju, V., Truhlar, D.G., Tsemekhman, K., Van Voorhis, T., Vázquez-Mayagoitia, A., Verma, P., Villa, O., Vishnu, A., Vogiatzis, K.D., Wang, D., Weare, J.H., Williamson, M.J., Windus, T.L., Woliński, K., Wong, A.T., Wu, Q., Yang, C., Yu, Q., Zacharias, M., Zhang, Z., Zhao, Y., Harrison, R.J.

The present chapter gives an overview of the intriguing effects that spin states have on catalysis, and how this can (and cannot) be understood at present. For instance, highly reactive transition-metal complexes are often too fast to be trapped for characterization by spectroscopy and/or crystallography. While significant advances have been made in theory with improved density functional approximations and more efficient wavefunction methods, these have not yet progressed to the point of being robust general-purpose chemical tools. Recent developments in the application of spectroscopy and theory on catalytically (in)active transition- metal complexes are discussed together with future perspectives MINECO (CTQ2014-59212-P, CTQ2017-87392-P), FEDER (UNGI10-4E-801), and the COST Association (CM1305, ECOSTBio) are gratefully thanked for financial support, and CSUC for extensive computer time

The sluggish oxidants, [FeIV(O)(TMC)(CH3CN)]2+ (TMC = 1,4,8,11-tetramethyl-1,4,8,11-tetraazacyclotetradecane) and [FeIV(O)(d12-TMCN)(OTf)]+ (3d; d12-TMCN = 1,4,7,11-tetra-d3-methyl-1,4,7,11-tetraazacyclotetradecane), are transformed into a highly reactive oxidant, [FeIV(O)(TMCO)(OTf)]+ (1; TMCO = 4,8,12-trimethyl-1-oxa-4,8,12-triazacyclotetradecane), upon replacement of a -NMe donor in the TMC and TMCN ligands by an O-atom. A rate enhancement of 5 - 6 orders of magnitude in both H-atom and O-atom transfer reactions is observed upon oxygen incorporation into the macrocyclic ligand and can be explained based upon the higher electrophilicity of the iron center and the higher availability of the more reactive S = 2 state in 1. This rationalizes nature's preference for using O-rich ligand environments for the hydroxylation of strong C-H bonds in enzymatic reactions.

A reactive high-valent dinuclear nickel(IV) oxido bridged complex is reported that can be formed at room temperature by reaction of [(L) 2 Ni(II) 2 (μ-X) 3 ]X (X = Cl or Br) with NaOCl in methanol or acetonitrile (where L = 1,4,7-trimethyl-1,4,7-triazacyclononane). The unusual Ni(IV) oxido species is stabilized within a dinuclear tris-μ-oxido-bridged structure as [(L) 2 Ni(IV) 2 (μ-O) 3 ] 2+ . Its structure and its reactivity with organic substrates are demonstrated through a combination of UV-vis absorption, resonance Raman, 1 H NMR, EPR, and X-ray absorption (near-edge) spectroscopy, ESI mass spectrometry, and DFT methods. The identification of a Ni(IV)-O species opens opportunities to control the reactivity of NaOCl for selective oxidations The Ubbo Emmius fund of the University of Groningen, the European Research Council (StG, no. 279549, W.R.B.), NWO for a VIDI grant (723.014.010, D.J.M. and M.T.), The Netherlands Ministry of Education, Culture and Science (Gravity program 024.001.035, W.R.B.), MINECO (CTQ2014-59212-P and CTQ2015-70851-ERC, M.S.), Gen- Cat (2014SGR1202, M.S.), FEDER (UNGI10-4E-801, M.S.), and COST action CM1305 “ECOSTBio” (W.R.B., COSTSTSM- CM1305-29045) are acknowledged for financial support

Phenolato moieties impart redox flexibility to metal complexes due their accessible (oxidative) redox chemistry and have been proposed as functional ligand moieties in redox non-innocent ligand based transition metal catalysis. Here, the electro- and spectroelectrochemistry of phenolato based μ-oxodiiron(III) complexes [(L1)Fe(μ-O)Fe(L1)]2+ (1) and [(L2)Fe-(μ-O)Fe(L2)]2+ (2), where L1 = 2-(((di(pyridin-2-yl)methyl)-(pyridin-2-ylmethyl)amino)methyl)phenol and L2 = 3, 5-di-tert-butyl-2-(((di(pyridin-2-yl)methyl)(pyridin-2-ylmethyl)amino)-methyl)phenol, is described. The electrochemical oxidation of 1 in dichloromethane results in aryl C-C coupling of phenoxyl radical ligand moieties to form tetra nuclear complexes, which undergo subsequent oxidation to form iron(III) phenolato based polymers (poly-1). The coupling is blocked by placing tert-butyl groups at para and ortho positions of phenol units (i.e., 2). Poly-1 shows two fully reversible redox processes in monomer free solution. Assignment of species observed during the electrochemical and chemical {(NH4)2[CeIV(NO3)6]} oxidation of 1 in acetonitrile is made by comparison with the UV-vis-NIR absorption and resonance micro-Raman spectroelectrochemistry of poly-1, and by DFT calculations, which confirms that oxidative coupling occurs in acetonitrile also. However, in contrast to that observed in dichloromethane, in acetonitrile, the oligomers formed are degraded in terms of a loss of the Fe(III)-O-Fe(III) bridge by protonation. The oxidative redox behavior of 1 and 2 is, therefore, dominated by the formation and reactivity of Fe(III) bound phenoxyl radicals, which considerably holds implications in regard to the design of phenolato based complexes for oxidation catalysis The European Research Council (StG, no. 279549, D.U.,W.R.B.) and the Ministry of Education, Culture and Science(Gravity program 024.001.035, W.R.B.), the Ministerio de Economia y Competitividad (MINECO, projects CTQ2014-59212-P and CTQ2015-70851-ERC, M.S.), the DIUE of the Generalitat de Catalunya (project 2014SGR1202, M.S.), and the European Fund for Regional Development (FEDER, UNGI10-4E-801, M.S.) are acknowledged for financial support. A. van Dam (ERIBA, University of Groningen) is thanked for assistance with a recording of ESI-MS spectra. L. Kortekaas (University of Groningen) is acknowledged for discussion. This work was performed in the framework of the COST action CM1305 “Explicit Control Over Spin-states in Technology and Biochemistry (ECOSTBio)” (with support of an STSM to W.R.B., COST-STSM-CM1305-29045)

The incarceration of o‐benzyne and 27 other guest molecules within hemicarcerand 1, as reported experimentally by Warmuth, and Cram and co‐workers, respectively, has been studied by density functional theory (DFT). 1H‐NMR chemical shifts, rotational mobility and conformational preference of the guests within the supramolecular cage were determined, which showed intriguing correlations of the chemical shifts with structural parameters of the host‐guest system. Furthermore, based on the computed chemical shifts reassignments of some NMR signals are proposed. This affects in particular the putative characterization of the volatile benzyne molecule inside a hemicarcerand, for which our CCSD(T) and KT2 results indicate that the experimentally observed signals are most likely not resulting from an isolated benzyne within the supramolecular host. Instead, we show that the guest reacted with an aromatic ring of the host, and this adduct is responsible for the experimentally observed signals The following organizations are thanked for financial support: MICINN (PhD-scholarship ACC CTQ2011-25086/BQU, projects CTQ2014-59212-P, CTQ2015-70851-ERC, CTQ2017-87392-P), CONACyT project 2014-383560, GenCat (PhD scholarship ARR 2015_FI_B_00165, 2014SGR1202 and XRQTC network) and European Fund for Regional Development (FEDER, UNGI10-4E-801)

We report here a computational study on a series of FeII, FeIIIand FeIVhydroxo/oxo-iron complexes with a broad palette of ligands. We are interested in assessing the robustness of widely used density functionals for their prediction and description of structures and spin states for the examined oxoiron complexes. We have used a variety of density functional approximations (S12g, LDA, BP86-D3, OPBE, SSB-D, B3LYP-D3, S12h and MVS), in all cases including solvation and relativistic effects explicitly. One of the main observations of this detailed study is the excellent performance of S12g for both accurate structures and spin state splittings. Moreover, our results show that in general all density functionals can be used as a reliable computational tool for reproducing and predicting geometries, determining the oxidation state of iron, and most are able as well to providing good descriptions of spin state energetics.

We report a combined experimental-theoretical study on the 31P NMR chemical shift for a number of trans-platinum(ii) complexes. Validity and reliability of the 31P NMR chemical shift calculations are examined by comparing with the experimental data. A successful computational protocol for the accurate prediction of the 31P NMR chemical shifts was established for trans-[PtCl2(dma)PPh3] (dma = dimethylamine) complexes. The reliability of the computed values is shown to be critically dependent on the level of relativistic effects (two-component vs. four component), choice of density functionals, dynamical averaging, and solvation effects. Snapshots obtained from ab initio molecular dynamics simulations were used to identify those solvent molecules which show the largest interactions with the platinum complex, through inspection by using the non-covalent interaction program. We observe satisfactory accuracy from the full four-component matrix Dirac-Kohn-Sham method (mDKS) based on the Dirac-Coulomb Hamiltonian, in conjunction with the KT2 density functional, and dynamical averaging with explicit solvent molecules.

Although the unusual structural, magnetic,electronic, and spin characteristics of manganocene hasintrigued scientists for decades, a unified explanation andrationalization of its properties has not yet been provided.Results obtained by Multideterminantal Density Functional Theory (MD-DFT), Energy Decomposition Analysis (EDA), and Intrinsic Distortion Path (IDP) methodologies indicate how this uniqueness can be traced back tothe manganocene’s peculiar electronic structure, mainly,the degenerate ground state and close-lying electronic andspin states. This is the peer-reviewed, authors’ version of the article: Stepanović, S., Zlatar, M., Swart, M.,& Gruden, M. (2019). The Irony of Manganocene: An Interplay between the Jahn-Teller Effect and Close-Lying Electronic and Spin States. Journal of Chemical Information and Modeling, American Chemical Society (ACS), 59(5), 1806-1810. [https://doi.org/10.1021/acs.jcim.8b00870] This document is the Accepted Manuscript version of a Published Work that appeared in final form in Journal of Chemical Information and Modeling, copyright © American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see [https://doi.org/10.1021/acs.jcim.8b00870] The published version: [http://cer.ihtm.bg.ac.rs/handle/123456789/2894] Supplementary data: [https://cer.ihtm.bg.ac.rs/handle/123456789/4446]

We report a combined experimental-theoretical study on the 31P NMR chemical shift for a number of trans-platinum(ii) complexes. Validity and reliability of the 31P NMR chemical shift calculations are examined by comparing with the experimental data. A successful computational protocol for the accurate prediction of the 31P NMR chemical shifts was established for trans-[PtCl2(dma)PPh3] (dma = dimethylamine) complexes. The reliability of the computed values is shown to be critically dependent on the level of relativistic effects (two-component vs. four component), choice of density functionals, dynamical averaging, and solvation effects. Snapshots obtained from ab initio molecular dynamics simulations were used to identify those solvent molecules which show the largest interactions with the platinum complex, through inspection by using the non-covalent interaction program. We observe satisfactory accuracy from the full four-component matrix Dirac-Kohn-Sham method (mDKS) based on the Dirac-Coulomb Hamiltonian, in conjunction with the KT2 density functional, and dynamical averaging with explicit solvent molecules.