Frank De Proft

University of Pardubice, Pardubitz, Pardubický, Czech Republic

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Publications (303)1062.56 Total impact

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    ABSTRACT: The reduction of N,C,N-chelated bismuth chlorides [C6 H3 -2,6-(CHNR)2 ]BiCl2 [where R=tBu (1), 2',6'-Me2 C6 H3 (2), or 4'-Me2 NC6 H4 (3)] or N,C-chelated analogues [C6 H2 -2-(CHN-2',6'-iPr2 C6 H3 )-4,6-(tBu)2 ]BiCl2 (4) and [C6 H2 -2-(CH2 NEt2 )-4,6-(tBu)2 ]BiCl2 (5) is reported. Reduction of compounds 1-3 gave monomeric N,C,N-chelated bismuthinidenes [C6 H3 -2,6-(CHNR)2 ]Bi [where R=tBu (6), 2',6'-Me2 C6 H3 (7) or 4'-Me2 NC6 H4 (8)]. Similarly, the reduction of 4 led to the isolation of the compound [C6 H2 -2-(CHN-2',6'-iPr2 C6 H3 )-4,6-(tBu)2 ]Bi (9) as an unprecedented two-coordinated bismuthinidene that has been structurally characterized. In contrast, the dibismuthene {[C6 H2 -2-(CH2 NEt2 )-4,6-(tBu)2 ]Bi}2 (10) was obtained by the reduction of 5. Compounds 6-10 were characterized by using (1) H and (13) C NMR spectroscopy and their structures, except for 7, were determined with the help of single-crystal X-ray diffraction analysis. It is clear that the structure of the reduced products (bismuthinidene versus dibismuthene) is ligand-dependent and particularly influenced by the strength of the N→Bi intramolecular interaction(s). Therefore, a theoretical survey describing the bonding situation in the studied compounds and related bismuth(I) systems is included. Importantly, we found that the C3 NBi chelating ring in the two-coordinated bismuthinidene 9 exhibits significant aromatic character by delocalization of the bismuth lone pair.
    Chemistry - A European Journal 10/2015; DOI:10.1002/chem.201502724 · 5.73 Impact Factor
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    ABSTRACT: Two ethylene-bridged methylaluminium amidinates and one aluminium amidinate containing three terminal trimethylstannyl-ethynyl groups interconnected by π-coordinated potassium ions were prepared in situ. The re-oxidation of the ethylene-bridged compound by iodine followed by further reduction using the same activation procedure demonstrated the versatility of the approach. The reactivity of an ethylene-bridged methylaluminum amidinate towards HCl was examined to demonstrate the building block concept. DFT calculations were performed to gain insight into the mechanism of the in situ activation of diphenylacetylene.
    Dalton Transactions 09/2015; DOI:10.1039/c5dt03128a · 4.20 Impact Factor
  • T. Stuyver · S. Fias · F. De Proft · P. Geerlings
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    ABSTRACT: Pauling long bond orders have previously been used to obtain qualitative insight in the transmission through nanographenes. Here we show that this long bond order, the atom–atom polarizability (a mea- sure for delocalization) and the transmission probability are intimately linked and that their relationships are valid for all alternant hydrocarbons. These relationships allow a simple rationalization of the transport properties of a variety of molecules considered in molecular electronics. As an example, some molecular wires such as oligo(p-phenylene) are studied, leading to a simple explanation for the experimentally observed exponential decay of the transmission probability with the number of phenyl units.
    Chemical Physics Letters 06/2015; 630:51-56. DOI:10.1016/j.cplett.2015.04.043 · 1.90 Impact Factor
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    Gabriella Skara · Balazs Pinter · Paul Geerlings · Frank De Proft
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    ABSTRACT: Metal and ligand-based reductions have been modeled in octahedral ruthenium complexes revealing metal-ligand interactions as the profound driving force for the redox-active behaviour of orthoquinoid-type of ligands. Through an extensive investigation of redox-active ligands we revealed the most critical factors that facilitate or supress redox-activity of ligands in metal complexes, from which basic rules for designing non-innocent/redox-active ligands can be put forward. These rules also allow the rational redox-leveling, i.e. moderating redox potentials of ligand-centred electron transfer processes potentially leading to catalysts with low overpotential in multielectron activation processes.
    Chemical Science 05/2015; 6(7). DOI:10.1039/C5SC01140J · 9.21 Impact Factor
  • Yannick Geboes · Frank De Proft · Wouter A Herrebout
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    ABSTRACT: The molecular electrostatic potential surface of unsaturated, locally electron deficient molecules shows a positive region perpendicular to (a part of) the molecular framework. In recent years it has been shown both theoretically and experimentally that molecules are able to form noncovalent interactions with Lewis bases through this π-hole. When studying unsaturated perfluorohalogenated molecules containing a higher halogen atom, a second electropositive region is also observed near the halogen atom. This region, often denoted as a σ-hole, allows the molecules to interact with Lewis bases and form a halogen bond. To experimentally characterize the competition between both these noncovalent interactions, Fourier transform infrared and Raman spectra of liquefied noble gas solutions containing perfluorohalogenated ethylene derivatives (C2F3X; X= F, Cl, Br or I) and trimethylamine(-d9) were investigated. Analysis of the spectra shows that in mixed solutions of trimethylamine(-d9) and C2F4 or C2F3Cl lone pair···π complex is present, while evidence for halogen bonded complex is found in solutions containing TMA(-d9) and C2F3Cl, C2F3Br or C2F3I. For all species observed, complexation enthalpies were determined, the values varying between -4.9(1) and -24.4 kJ mol(-1).
    The Journal of Physical Chemistry A 04/2015; 119(22). DOI:10.1021/acs.jpca.5b02283 · 2.69 Impact Factor
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    ABSTRACT: We investigate the local polarisability or polarisability density using both a conceptual density functional theory approach based on the linear response function and time-dependent density functional theory. Using a zero frequency in the latter, we can immediately compare both approaches. Using an analytical expression for the linear response kernel, we are able to systematically analyse α(r) throughout the periodic table. An extension to molecules is also made with a study of the CO molecule retrieving the connection between local softness and local polarisability.
    Molecular Physics 03/2015; 113(13). DOI:10.1080/00268976.2015.1021110 · 1.72 Impact Factor
  • T Stuyver · S Fias · F De Proft · P W Fowler · P Geerlings
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    ABSTRACT: The atom-atom polarizability and the transmission probability at the Fermi level, as obtained through the source-and-sink-potential method for every possible configuration of contacts simultaneously, are compared for polycyclic aromatic compounds. This comparison leads to the conjecture that a positive atom-atom polarizability is a necessary condition for transmission to take place in alternant hydrocarbons without non-bonding orbitals and that the relative transmission probability for different configurations of the contacts can be predicted by analyzing the corresponding atom-atom polarizability. A theoretical link between the two considered properties is derived, leading to a mathematical explanation for the observed trends for transmission based on the atom-atom polarizability.
    The Journal of Chemical Physics 03/2015; 142(9):094103. DOI:10.1063/1.4913415 · 2.95 Impact Factor
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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; 17(14). DOI:10.1039/C4CP05454G · 4.49 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; 21(14). DOI:10.1002/chem.201405891 · 5.73 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; 55(3). DOI:10.1021/ci5006417 · 3.74 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; 119(8). DOI:10.1021/jp5098876 · 2.69 Impact Factor
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    ABSTRACT: In this study, the rate of photopolymerization (Rp) of 21 alkyl methacrylates is correlated with the chemical properties of their monomeric radicals by making use of the enthalpic and polar effects of these radicals. Based on these properties, a general non-linear expression is derived by optimizing the radicals and evaluating both their stability and polar effects, via the radical electrophilicity, using density functional theory. The expression performs quite well in predicting Rp for 16 of the 21 methacrylates with an R2 value of 0.9384, but does not hold for too unstable and/or too nucleophilic radicals. Increasing the stability or decreasing the nucleophilicity of the monomeric radical results in a higher polymerization rate; in addition, the influence of the polar effects becomes larger for more stable radicals. Methacrylates containing a pendant phenyl, where π–π stacking plays an important role, are experimentally found to have a higher polymerization rate than predicted.
    Macromolecular Chemistry and Physics 02/2015; 216(3):334-343. DOI:10.1002/macp.201400484 · 2.62 Impact Factor
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    ABSTRACT: Seven tin(IV) amidinates were prepared and isolated from the reactions of tin(II) bisamidinate [Cy-NC(nBu)N-Cy]2Sn with a series of various 1,2-diones ((4 + 1) oxidative cycloaddition mechanism) and chlorine/oxygen molecules, respectively. The ligand substitution effect of (non)symmetric 1,3-diones to starting stannylene as well as intermolecular CO2 activation via prepared dimeric stannoxane is also reported. All the prepared tin containing compounds as well as ligand substitution reactions were investigated by the multinuclear NMR (1H, 13C, and 119Sn) spectroscopic techniques. Molecular structures of one tin(II) and seven tin(IV) amidinates investigated were determined by X-ray diffractions and also evaluated by DFT methods. The UV-vis absorption spectra of all desired colored tin(IV) diolates and its diketo precursors were recorded and simulated by TD-DFT methods.
    Organometallics 01/2015; 34(3). DOI:10.1021/om501074m · 4.13 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; 44(10). DOI:10.1039/C4DT03929G · 4.20 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; 17(2). DOI:10.1021/ol503364w · 6.36 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; 2015(3). DOI:10.1002/ejoc.201403198 · 3.07 Impact Factor
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    Stijn Fias · Zino Boisdenghien · Frank De Proft · Paul Geerlings
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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. DOI:10.1063/1.4900513 · 2.95 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; 119(11). DOI:10.1021/jp5087812 · 2.69 Impact Factor
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    ABSTRACT: A series of tin(IV) guanidinates were prepared by a (4+1) oxidative cycloaddition of four 1,2-diones (3,5-di-tert-butyl-o-benzoquinone, 3,4,5,6-tetrachloro-1,2-benzoquinone, 9,10-phenanthrenedione, 1,2-diphenylethanedione) or by an oxidative addition of a C–Br bond (from 2-bromo-1,3-diphenylpropane-1,3-dione followed by rearrangement) and a Cl–Cl bond (Cl2 generated from (dichloro-λ3-iodanyl)benzene) with {pTol-NC[N(SiMe3)2]N-pTol}2Sn (1). The reactivity of five pentane-1,3-diones and dimethyl malonate with compound 1 was assessed on the basis of the effect of 1,3-diones on the reaction mechanism in comparison with 1,2-diones. In contrast with oxidation reactions observed for compounds containing conjugated C═O bonds, the reactions of the tin(II) guanidinate with 1,3-diones revealed a high ability for ligand substitution. All the tin compounds prepared were characterized, and ligand substitution reactions were monitored using 1H, 13C, and 119Sn NMR spectroscopy. The molecular structures of one tin(II) and five tin(IV) guanidinato complexes investigated were determined by X-ray diffraction. All tin(IV) compounds display six- or seven-coordination. The UV–vis absorption spectra were recorded and simulated by TDDFT methods in order to get insight into the origin of the nontypical colors of the target tin(IV) diolato-guanidinates and their keto-functionalized precursors.
    Organometallics 10/2014; 34(11). DOI:10.1021/om500873a · 4.13 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; 4(95). DOI:10.1039/C4RA12053A · 3.84 Impact Factor

Publication Stats

7k Citations
1,062.56 Total Impact Points


  • 2007–2015
    • University of Pardubice
      • Department of General and Inorganic Chemistry
      Pardubitz, Pardubický, Czech Republic
  • 1993–2015
    • Vrije Universiteit Brussel
      • • Ultrastructure (ULTR)
      • • General Chemistry (ALGC)
      Bruxelles, Brussels Capital, Belgium
  • 2003
    • University of Exeter
      Exeter, England, United Kingdom