Frank De Proft

Vrije Universiteit Brussel, Bruxelles, Brussels Capital, Belgium

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Publications (292)1010.34 Total impact

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    ABSTRACT: The electron density change from reactants towards the transition state of a chemical reaction is expressed as a linear combination of the state-specific dual descriptors (SSDD) of the corresponding reactant complexes. Consequently, the SSDD can be expected to bear important resemblance to the so-called Natural Orbitals for Chemical Valence (NOCV), introduced as the orbitals that diagonalize the deformation density matrix of interacting molecules. This agreement is shown for three case studies: the complexation of a Lewis acid with a Lewis base, a SN2 nucleophilic substitution reaction and a Diels-Alder cycloaddition reaction. As such, the SSDD computed for reactant complexes are shown to provide important information about charge transfer interactions during a chemical reaction.
    Physical Chemistry Chemical Physics 02/2015; · 4.20 Impact Factor
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    ABSTRACT: The contributions of covalent and noncovalent interactions to the formation of classical adducts of bulky Lewis acids and bases and frustrated Lewis pairs (FLPs) were scrutinized by using various conceptual quantum chemical techniques. Significantly negative complexation energies were calculated for fourteen investigated Lewis pairs containing bases and acids with substituents of various sizes. A Ziegler-Rauk-type energy decomposition analysis confirmed that two types of Lewis pairs can be distinguished on the basis of the nature of the primary interactions between reactants; dative-bond formation and concomitant charge transfer from the Lewis base to the acid is the dominant and most stabilizing factor in the formation of Lewis acid-base adducts, whereas weak interactions are the main thermodynamic driving force (>50 %) for FLPs. Moreover, the ease and extent of structural deformation of the monomers appears to be a key component in the formation of the former type of Lewis pairs. A Natural Orbital for Chemical Valence (NOCV) analysis, which was used to visualize and quantify the charge transfer between the base and the acid, clearly showed the importance and lack of this type of interaction for adducts and FLPs, respectively. The Noncovalent Interaction (NCI) method revealed several kinds of weak interactions between the acid and base components, such as dispersion, π-π stacking, CH⋅⋅⋅π interaction, weak hydrogen bonding, halogen bonding, and weak acid-base interactions, whereas the Quantum Theory of Atoms in Molecules (QTAIM) provided further conceptual insight into strong acid-base interactions. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
    Chemistry - A European Journal 02/2015; · 5.93 Impact Factor
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    ABSTRACT: Atomic charges are a key concept to give more insight into the electronic structure and chemical reactivity. The Hirshfeld-I partitioning scheme applied to the model protein human 2-cysteine peroxiredoxin thioredoxin peroxidase B is used to investigate how large a protein fragment needs to be in order to achieve convergence of the atomic charge of both, neutral and negatively charged residues. Convergence in atomic charges is rapidly reached for neutral residues, but not for negatively charged ones. This study pinpoints difficulties on the road towards accurate modeling of negatively charged residues of large biomolecular systems in a multiscale approach.
    Journal of Chemical Information and Modeling 02/2015; · 4.30 Impact Factor
  • Jonathan Furtado, Frank De Proft, Paul Geerlings
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    ABSTRACT: The establishment of an internally consistent scale of noble gas electronegativities is a long standing problem. In the present study the problem is attacked via the Mulliken definition, which in recent years gained widespread use to its natural appearance in the context of conceptual Density Functional Theory. Basic ingredients of this scale are the electron affinity and the ionisation potential. Whereas the latter can be computed routinely, the instability of the anion makes the judicious choice of computational technique for evaluating Electron Affinities much more tricky. We opted for Puiatti's approach extrapolating the energy of high ε solvent stabilised anions to the ε=1 (gas phase) case. The results give negative electron affinity values, monotonically increasing (except for Helium which is an outlier in most of the story) to almost zero at eka-Radon in agreement with high level calculations. Combined with the ionisation energies (in good agreement with experiment), an electronegativity scale is obtained displaying (1) a monotonic decrease of χ when going down the periodic table (2) top values not for the noble gases but for the halogens, as opposed to most (extrapolation) procedures of existing scales, invariably placing the noble gases on top (3) noble gases having electronegativities close to the chalcogens. In the accompanying hardness scale (hardly, if ever, discussed in the literature) the noble gases turn out to be by far the farthest the hardest elements, again with a continuous decrease with increasing Z. Combining χ value of the halogens and the noble gases the Ngδ+F δ- bond polarity emerging from ab initio calculations naturally emerges. In conclusion the chemistry of the noble gases is for a large part determined by their extreme hardness, equivalent to a high resistance to changes in its electronic population coupled to their high electronegativity.
    The Journal of Physical Chemistry A 02/2015; · 2.78 Impact Factor
  • Macromolecular Chemistry and Physics 02/2015; 216(3):334-343. · 2.45 Impact Factor
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    ABSTRACT: doi: 10.1021/om501074m
    Organometallics 01/2015; · 4.25 Impact Factor
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    ABSTRACT: Reactivity of three phosphanes PhP(NHR)2 [R = t-Bu (1), Ph (2)] and PhP(NEt2)(NHDip) (3) (where Dip = 2,6-i-Pr2C6H3) with n-Bu2Mg and MeMgBr is presented. In the case of 1, the reaction with n-Bu2Mg gave [PhP(NHt-Bu)(Nt-Bu)]Mg(n-Bu) (4) and [PhP(NHt-Bu)(Nt-Bu)]2Mg (5) depending on the stoichiometry. The treatment of 1 with MeMgBr led to the phosphinate [Ph(H)P(Nt-Bu)2]2Mg (7) as a result of both the NHPH tautomeric transformation and elimination of MgBr2 from non-isolable intermediate [PhP(NHt-Bu)(Nt-Bu)]MgBr(THF) (6). Phosphane 2 reacted with n-Bu2Mg in 1:1 molar ratio under formation of {[PhP(NPh)2]2Mg(THF)2}2 (8), but analogous reaction in 2:1 molar ratio yielded phosphinate [Ph(H)P(NPh)2]2Mg(THF) (9). Heteroleptic compound [Ph(H)P(NPh)2]MgBr(THF)2 (10) was obtained by the reaction of 2 with MeMgBr. Finally, reaction of 3 with n-Bu2Mg and MeMgBr produced compounds [PhP(NEt2)(NDip)]2Mg (11) and {[PhP(NEt2)(NDip)2]Mg(-Br)(THF)}2 (12), respectively. All products were characterized by the help of 1H, 13C{1H} and 31P NMR spectroscopy and except for 4 and 6 molecular structures were determined using single-crystal X-ray diffraction analysis. In addition, a theoretical study on plausible isomers of 10 was performed to provide additional evidence for the presence of a syn- and anti- isomer in dynamic equilibrium in solution of 10.
    Dalton Transactions 01/2015; · 4.10 Impact Factor
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    ABSTRACT: Novel spiropseudoindoxyls were synthesized in high yields via a fully regioselective Au(III)-catalyzed cycloisomerization of easily obtainable o-nitrophenylpropiolamides, followed by an intramolecular dipolar cycloaddition as key steps. This one-pot cascade reaction resulted in new tetracyclic pseudoindoxyls, which were hydrogenated toward the title compounds as single diastereomers via N-O cleavage. The mechanism of the gold catalyzed cycloisomerization was studied by DFT and suggests a reaction path without the intermediacy of gold carbenoid species in these cases.
    Organic Letters 12/2014; · 6.32 Impact Factor
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    ABSTRACT: Theoretical design can be an important aid in the discovery of valuable stable radical systems. In this study, inverse molecular design was applied to thiadiazinyl radicals to maximize two fundamental electronic properties in chemistry, namely electrophilicity and nucleophilicity. We discovered that the thiadiazinyl structure can be made moderately nucleophilic or highly electrophilic, depending on the electronic character of its substituents. The most electrophilic thiadiazinyl radical displays the highest electrophilic character encountered so far for uncharged radical systems. The accumulated data relating to the influence of different substituents at the various sites has allowed us to propose thiadiazinyl radicals that are intrinsically stable and as electrophilic or nucleophilic as possible. Although the nucleophilicity optimum fulfills the additional requirement of being stable, a significant drop from highly to merely moderately electrophilic is observed for the new electrophilicity optimum.
    European Journal of Organic Chemistry 12/2014; · 3.15 Impact Factor
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    ABSTRACT: Within the context of spin polarized conceptual density functional theory, the spin polarized linear response functions are introduced both in the [N, Ns] and [Nα, Nβ] representations. The mathematical relations between the spin polarized linear response functions in both representations are examined and an analytical expression for the spin polarized linear response functions in the [Nα, Nβ] representation is derived. The spin polarized linear response functions were calculated for all atoms up to and including argon. To simplify the plotting of our results, we integrated χ(r, r') to a quantity χ(r, r(')), circumventing the θ and ϕ dependence. This allows us to plot and to investigate the periodicity throughout the first three rows in the periodic table within the two different representations. For the first time, χαβ(r, r(')), χβα(r, r(')), and χSS(r, r(')) plots have been calculated and discussed. By integration of the spin polarized linear response functions, different components to the polarisability, ααα, ααβ, αβα, and αββ have been calculated.
    The Journal of Chemical Physics 11/2014; 141(18):184107. · 3.12 Impact Factor
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    ABSTRACT: Inspection of the electrostatic potential of C2F3X (X = F, Cl, Br, I) revealed a second electropositive region in the immediate vicinity of the C=C double bond apart from the  hole of chlorine, bromine and iodine, leading to C(sp2)-X…Y halogen bonding, through which complexes stabilized by so-called lone pair…π interactions can be formed. Consequently, the experimental studies for the complexes of dimethyl ether with C2F3X (X = F, Cl, Br, I) not only allowed to experimentally characterize and rationalize the effects of hybridization on halogen bonding but, for the first time, also allowed the competition of C-X…Y halogen bonding and lone pair…π interactions to be studied at thermodynamic equilibrium. Analysis of the infrared and Raman spectra reveals that in the cryosolutions of dimethyl ether and C2F3I, solely the halogen bonded complex is present, whereas C2F3Br and C2F3Cl give rise to a lone pair…π bonded complex as well as a halogen bonded complex. Mixtures of dimethyl ether with C2F4 solely yield a lone pair…π bonded complex. The experimentally derived complexation enthalpies for the halogen bonded complexes are found to be -14.2(5) kJ mol-1 for C2F3I.DME and -9.3(5) kJ mol-1 for C2F3Br.DME. For the complexes of C2F3Cl with dimethyl ether no experimental complexation enthalpy could be obtained, whereas the C2F4.DME complex has a complexation enthalpy of -5.5(3) kJ mol-1. The observed trends have been rationalized with the aid of an interaction energy decomposition analysis (EDA) coupled to a Natural Orbital for Chemical Valence (NOCV) analysis and also using the Non-Covalent Interaction index method.
    The Journal of Physical Chemistry A 11/2014; · 2.78 Impact Factor
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    ABSTRACT: doi: 10.1021/om500873a
    Organometallics 10/2014; · 4.25 Impact Factor
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    ABSTRACT: The interface between donor and acceptor material in organic photovoltaics is of major importance for the function of such devices. In this work, the singlet excitation schemes of six polymers used in organic photovoltaics (P3HT, MDMO-PPV, PCDTBT, PCPDTBT, APFO3 and TBDTTPD) at the interface with a PCBM acceptor were studied using TDDFT in combination with the range-separated CAM-B3LYP exchange-correlation functional. By comparing with the excitations in the pure polymer and analyzing the excitation intensities and a measure for orbital overlap, it was possible to identify excitations as either excitation of the polymer or as a charge transfer between donor and acceptor. By combining orbital overlaps between the molecular orbitals involved in charge transfer and the intensity of the polymer excitation a broad correlation was seen with the record efficiencies found in literature.
    RSC Advances 10/2014; · 3.71 Impact Factor
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    ABSTRACT: The nature and origin of ion-π and ion-σ interactions has been systematically investigated using dispersion-corrected density functional theory and the recently developed noncovalent interaction (NCI) method. A detailed analysis of these interactions is performed with the aim to identify the requirements that have to be fulfilled by the molecular system for strong ion-ligand interactions. Interestingly, our results indicate that aliphatic systems, such as cyclohexane, can interact as strong as aromatic ones with both cations and anions, despite of having a negligible quadrupole moment. In fact, cyclohexane binds anions stronger than benzene itself but slightly weaker that hexafluorobenzene. The NCI method reveals that the interaction between the ions and three C–H bonds of the saturated fragment are responsible for the surprisingly strong ion-σ interaction. A weakening of the ion-σ interactions is observed in the order: Li+ > F− > Na+ > Cl− > Br− ≈ K+. In addition, a complete Ziegler–Rauk type energy decomposition analysis has been carried out in order to reveal the origins of the thermodynamic driving force for complex formations. The electron density deformation upon complex formation has been scrutinized with a complementary NOCV analysis allowing the identification of molecular orbital interaction contributions to the stabilization. Based on these analysis, it is shown that the formally anion-π interaction is rather an anion-σ∗ interaction.
    Computational and Theoretical Chemistry 10/2014; 1053:150-164. · 1.37 Impact Factor
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    ABSTRACT: The reactivity of bis(organoamino)phosphanes PhP(NHR)(NHR′) (1a–1c, in which R, R′ = tBu for 1a; tBu, Dip for 1b; and Ph for 1c; Dip = C6H3–2,6-iPr2) and tBuP(NHDip)2 (1d) with Me3Al was investigated. The reaction of 1a or 1b gave in the first step compounds [PhP(NHR)(NR′)]AlMe2 (in which R, R′ = tBu for 2a; tBu, Dip for 2b) as a result of methane elimination that upon heating underwent nitrogen-to-phosphorus hydrogen-atom migration under the formation of diiminophosphinates [Ph(H)P(NR)(NR′)]AlMe2 (in which R, R′ = tBu for 3a; tBu, Dip for 3b). In contrast, phosphane 1c showed a reversed reaction sequence that yielded an intermediate [Ph(H)P(NHPh)(=NPh)]AlMe3 (2c) first as a consequence of hydrogen-atom migration followed by the methane elimination and formation of diiminophosphinate [Ph(H)P(NPh)2]AlMe2 (3c). The partial deprotonation of 1a,b,d using one molar equivalent of nBuLi followed by the treatment with AlCl3 smoothly produced compounds [Ph(H)P(NR)(NR′)]AlCl2 (in which R, R′ = tBu for 4a; tBu, Dip for 4b) and [tBu(H)P(NDip)2]AlCl2 (4d), in which the hydrogen atom was again shifted from the nitrogen to the phosphorus atom. All studied compounds were characterized with the help of elemental analysis; 1H, 13C{1H}, 31P, and 31P{1H} NMR spectra; and in the case of 3c, 4a, 4b, and 4d by using single-crystal X-ray diffraction analysis. The phenomenon of the hydrogen-atom migration was subjected also to a theoretical survey with particular emphasis on the influence of the phosphane used.
    Berichte der deutschen chemischen Gesellschaft 09/2014; · 2.97 Impact Factor
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    ABSTRACT: Hydrogen peroxide is a natural oxidant that can oxidize protein thiols (\ce{RSH}) via sulfenic acid (\ce{RSOH}) and sulfinic acid (\ce{RSO2H}) to sulfonic acid (\ce{RSO3H}). In this paper, we study the complete anionic and neutral oxidation pathway from thiol to sulfonic acid. Reaction barriers and reaction free energies for all three oxidation steps are computed, both for the isolated substrates and for the substrates in the presence of different model ligands (\ce{CH4}, \ce{H2O}, \ce{NH3}) mimicking the enzymatic environment. We found for all three barriers that the anionic thiolate is more reactive than the neutral thiol. However, the assistance of the environment in the neutral pathway in a Solvent Assisted Proton Exchange mechanism (SAPE) can lower the reaction barrier noticeably. Polar ligands can decrease the reaction barriers, while apolar ligands don't influence the barrier heights. The same holds for the reaction energies: they decrease (become more negative) in the presence of polar ligands while apolar ligands don't have an influence. The consistently negative consecutive reaction energies for the oxidation in the anionic pathway when going from thiolate over sulfenic and sulfinic acid to sulfonic acid are in agreement with biological reversibility.
    The Journal of Physical Chemistry A 07/2014; · 2.78 Impact Factor
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    ABSTRACT: Novel tricyclic tetrahydroazepinones were synthesized via an in situ Diels-Alder reaction of furan with cyclic allenamides. These reactive intermediates are the first examples of cyclic seven-membered allenamides and were prepared starting from N-(2-chloroallyl)-2-allylglycine derivatives via ring-closing metathesis followed by dehydrochlorination. The trapping of the intermediate cycloallene with furan occurred endo- and regioselectively and provided a convenient entry into new building blocks for medicinal chemistry. The diastereoselectivity of the cycloaddition was confirmed using quantum chemical computations.
    ChemInform 07/2014;
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    ABSTRACT: Tuning the band gap of graphene nanoribbons (GNR) by chemical edge functionalization is a promising approach towards future electronic devices based on graphene. The band gap is closely related to the aromaticity distribution and therefore tailoring the aromaticity patterns is a rational way for controlling the band gap. In our work, it is shown how to control the aromaticity distribution and the band-gap in both armchair and zigzag GNRs. We perform periodic density functional theory (DFT) calculations on the electronic structure and the aromaticity distribution, using delocalization and geometry analysis methods like the six-center index (SCI) and the mean bond length (MBL). These results are compared with nonequilibrium Green's function (NEGF) transport property calculations. We also provide a complete description of the relation between band gap, transport properties, and aromaticity distribution along these materials, based on DFT results and Clar's sextet theory.
    Techconnect World 2014, Washington D.C.; 06/2014
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    ABSTRACT: Six palladium(II) complexes bearing three different triazole-based N-heterocyclic carbene (NHC) ligands, [1-tert-butyl-4-{2-[(N,N-dimethylamino)methyl]phenyl}-3-phenyl-1H-1,2,4-triazol-4-ium-5-ide, 1-tert-butyl-4-(2-methoxyphenyl)-3-phenyl-1H-1,2,4-triazol-4-ium-5-ide, and 1-tert-butyl-4-(4-methylphenyl)-3-phenyl-1H-1,2,4-triazol-4-ium-5-ide], were synthesized and fully characterized. NMR spectroscopy and X-ray diffraction analysis revealed that the amino-group-substituted NHC ligand is coordinated in bidentate fashion, forming a monocarbene chelate complex with an additional intramolecular Pd ← N bond with the nitrogen donor atom. The 4-methylphenyl- and 2-methoxyphenyl-substituted NHC ligands coordinate as C-monodentate donors, forming simple biscarbene Pd(II) complexes. The evaluation of the catalytic performance in the Suzuki–Miyaura cross-coupling reaction revealed very promising performance of the intramolecularly coordinated monocarbene complexes under relatively mild conditions even in direct comparison with the commercially available PEPPSI catalyst. In contrast, the biscarbene complexes proved inactive in this catalytic process. According to theoretical calculations (EDA and NOCV analysis), functionalization of the 1,2,4-triazole-based NHC with the 2-[(N,N-dimethylamino)methyl]phenyl group has a significant effect on the stability of the NHC–metal bond.
    Organometallics 06/2014; 33(12):3108–3118. · 4.25 Impact Factor

Publication Stats

5k Citations
1,010.34 Total Impact Points

Institutions

  • 1994–2015
    • Vrije Universiteit Brussel
      • • General Chemistry (ALGC)
      • • Ultrastructure (ULTR)
      • • Faculty of Science and Bio-engineering Sciences
      Bruxelles, Brussels Capital, Belgium
  • 2012
    • Duke University
      • Department of Chemistry
      Durham, NC, United States
  • 2008–2012
    • University of Pardubice
      • Department of General and Inorganic Chemistry
      Pardubice, Pardubicky kraj, Czech Republic
    • University of Oslo
      • Department of Chemistry
      Oslo, Oslo, Norway
    • Universiteit Hasselt
      • Theoretical Physics Research Group (THFY)
      Hasselt, Flanders, Belgium
  • 2011
    • University of Chile
      • Departamento de Física (Ciencias)
      Santiago, Region Metropolitana de Santiago, Chile
    • Ghent University
      • Center for Molecular Modeling
      Gent, VLG, Belgium
  • 2009
    • Bogazici University
      • Department of Chemistry
      İstanbul, Istanbul, Turkey
  • 2007–2008
    • Budapest University of Technology and Economics
      • Department of Inorganic and Analytical Chemistry
      Budapest, Budapest fovaros, Hungary
    • McMaster University
      • Department of Chemistry and Chemical Biology
      Hamilton, Ontario, Canada
    • Durham University
      • Department of Chemistry
      Durham, ENG, United Kingdom
  • 2005–2008
    • Universidad Andrés Bello
      • Department of Chemistry
      Santiago, Region Metropolitana de Santiago, Chile
    • Utrecht University
      • Division of Inorganic Chemistry and Catalysis
      Utrecht, Utrecht, Netherlands
  • 2004–2007
    • Université Libre de Bruxelles
      • Quantum Chemistry and Photophysics Unit
      Bruxelles, Brussels Capital Region, Belgium
    • Vlaams Instituut voor Biotechnologie
      Gand, Flanders, Belgium
  • 2006
    • Sabanci University
      İstanbul, Istanbul, Turkey