Sir Harold Walter Kroto. 7 October 1939 — 30 April 2016

Harry Kroto received the Nobel Prize for Chemistry in 1996 for his discovery of several new allotropes of carbon and in particular the now-famous C 60 , whose atoms are arranged in the spheroidal shape of the truncated icosahedron and which he named as buckminsterfullerene after the architect famous for his design of geodesic domes. Earlier in his career he made important discoveries concerned with the production of small, semi-stable molecules by pyrolysis methods and their characterization, mainly by means of microwave rotational spectroscopy. He was proud to have discovered by this means the compound CH 2 =PH because it contains the first known example of a carbon–phosphorus double bond. He later also made notable contributions to the field of materials chemistry, especially through his work on carbon nanotubes. Harry used his charismatic personality to very good effect in furthering the public understanding of science and was particularly good with children in this context. He also had strong views about science and religion which led him to become a campaigning atheist. He was a loyal and supportive friend and led a very happy family life with his wife Margaret and their two sons. </jats:p

Systematic behaviour of electron redistribution on formation of halogen-bonded complexes B⋯XY, as determined via XY halogen nuclear quadrupole coupling constants

Equilibrium nuclear quadrupole coupling constants associated with the di-halogen molecule XY in each of 60 complexes B⋯XY (where B is one of the Lewis bases N, CO, HCN, HO, HS, HCCH, CH, PH, NH or (CH)N and XY is one of the di-halogens Cl, BrCl, Br, ICl, IBr or I) have been calculated ab initio. The Townes-Dailey model for interpreting the changes in the coupling constants when XY enters the complex was used to describe the electron redistribution in the di-halogen molecule in terms of the fraction δ of an electron transferred from the Lewis base B to atom X and the fraction δ of an electron transferred simultaneously from atom X to atom Y. Systematic relationships between the δ values for the six series are established. It is shown that, in reasonable approximation, δ decays exponentially as the first ionisation energy I of the Lewis base B increases, that is δ = Aexp(-bI). It is concluded from the results for the series B⋯BrCl, B⋯Br, B⋯ICl, B⋯IBr and B⋯I that the coefficients A and b in regression fits to the corresponding logarithmic version ln(δ) = ln(A) - b(I) of the equation are not strongly dependent on either the halogen atom X directly involved in the halogen bond in B⋯XY or, for a given X, on the nature of Y. The behaviour of PH as a Lewis base appears to be anomalous. Values of δ and δ calculated by the quantum theory of atoms-in-molecules and natural bond orbital methodologies are very close to those from application of the Townes-Dailey approach described.IA thanks Ministerio de Ciencia, Innovación y Universidades (Project No. PGC2018-094644-B-C22) and Comunidad Auto´noma de Madrid (P2018/EMT-4329 AIRTEC-CM) for financial support. ACL thanks the University of Bristol for the award of a Senior Research FellowshipPeer Reviewe

H₃P⋯AgI:Generation by laser-ablation and characterization by rotational spectroscopy and: Ab initio calculations

The new compound H(3)P···AgI has been synthesized in the gas phase by means of the reaction of laser-ablated silver metal with a pulse of gas consisting of a dilute mixture of ICF(3) and PH(3) in argon. Ground-state rotational spectra were detected and assigned for the two isotopologues H(3)P···(107)AgI and H(3)P···(109)AgI in their natural abundance by means of a chirped-pulse, Fourier-transform, microwave spectrometer. Both isotopologues exhibit rotational spectra of the symmetric-top type, analysis of which led to accurate values of the rotational constant B (0), the quartic centrifugal distortion constants D (J) and D (JK), and the iodine nuclear quadrupole coupling constant χ (aa)(I) = eQq (aa). Ab initio calculations at the explicitly-correlated level of theory CCSD(T)(F12*)/aug-cc-pVDZ confirmed that the atoms P···Ag–I lie on the C (3) axis in that order. The experimental rotational constants were interpreted to give the bond lengths r (0)(P···Ag) = 2.3488(20) Å and r (0)(Ag–I) = 2.5483(1) Å, in good agreement with the equilibrium lengths of 2.3387 Å and 2.5537 Å, respectively, obtained in the ab initio calculations. Measures of the strength of the interaction of PH(3) and AgI (the dissociation energy D (e) for the process H(3)P···AgI = H(3)P + AgI and the intermolecular stretching force constant F (P···Ag)) are presented and are interpreted to show that the order of binding strength is H(3)P···HI < H(3)P···ICl < H(3)P···AgI for these metal-bonded molecules and their halogen-bonded and hydrogen-bonded analogues

Halogen Bonding with Phosphine: Evidence for Mulliken Inner Complexes and the Importance of Relaxation Energy

Intermolecular halogen bonding in complexes of phosphine and dihalogens has been theoretically investigated using explicitly correlated coupled cluster methods and symmetry adapted perturbation theory. The complexes H3P· · · ClF, H3P· · · BrF and H3P· · ·IF are demonstrated to possess unusually strong interactions that are accompanied by an increase in the induction component of the interaction energy and significant elongation of the X–Y halogen distance on complex formation. The combination of these factors is indicative of Mulliken inner complexes and criteria for identifying this classification are further developed. The importance of choosing an electronic structure method that describes both dispersion and longer range interactions is demonstrated, along with the need to account for the change in geometry on complexation formation via relaxation energy and overall stabilisation energies

Definition of the Chalcogen Bond (IUPAC Recommendations 2019)

This recommendation proposes a definition for the term “chalcogen bond”; it is recommended the term is used to designate the specific subset of inter- and intramolecular interactions formed by chalcogen atoms wherein the Group 16 element is the electrophilic site

Gas phase complexes of H₃N⋯CuF and H₃N⋯CuI studied by rotational spectroscopy and:Ab initio calculations: The effect of X (X = F, Cl, Br, I) in OC⋯CuX and H₃N⋯CuX

Complexes of H3N⋯CuF and H3N⋯CuI have been synthesised in the gas phase and characterized by microwave spectroscopy.</p

Harold Walter Kroto

Bibliograph

An Ab Initio Investigation of the Geometries and Binding Strengths of Tetrel-, Pnictogen-, and Chalcogen-Bonded Complexes of CO2, N2O, and CS2 with Simple Lewis Bases: Some Generalizations

Geometries, equilibrium dissociation energies (De), and intermolecular stretching, quadratic force constants (kσ) are presented for the complexes B· · · CO2, B· · · N2O, and B· · · CS2, where B is one of the following Lewis bases: CO, HCCH, H2S, HCN, H2O, PH3, and NH3. The geometries and force constants were calculated at the CCSD(T)/aug-cc-pVTZ level of theory, while generation of De employed the CCSD(T)/CBS complete basis-set extrapolation. The non-covalent, intermolecular bond in the B· · · CO2 complexes involves the interaction of the electrophilic region around the C atom of CO2 (as revealed by the molecular electrostatic surface potential (MESP) of CO2) with non-bonding or π-bonding electron pairs of B. The conclusions for the B· · · N2O series are similar, but with small geometrical distortions that can be rationalized in terms of secondary interactions. The B· · · CS2 series exhibits a different type of geometry that can be interpreted in terms of the interaction of the electrophilic region near one of the S atoms and centered on the C∞ axis of CS2 (as revealed by the MESP) with the n-pairs or π-pairs of B. The tetrel, pnictogen, and chalcogen bonds so established in B· · · CO2, B· · · N2O, and B· · · CS2, respectively, are rationalized in terms of some simple, electrostatically based rules previously enunciated for hydrogen- and halogen-bonded complexes, B· · · HX and B· · · XY. It is also shown that the dissociation energy De is directly proportional to the force constant kσ, with a constant of proportionality identical within experimental error to that found previously for many B· · · HX and B· · · XY complexes.This work was carried out with financial support from the Ministerio de Economía y Competitividad (Project No. CTQ2015-63997-C2-2-P) and the Comunidad Autónoma de Madrid (S2013/MIT2841, Fotocarbon)

Non-Covalent Interactions Involving Alkaline-Earth Atoms and Lewis Bases B: An ab Initio Investigation of Beryllium and Magnesium Bonds, B···MR2 (M = Be or Mg, and R = H, F or CH3)

Geometries, equilibrium dissociation energies (De), intermolecular stretching, and quadratic force constants (kσ) determined by ab initio calculations conducted at the CCSD(T)/aug-cc-pVTZ level of theory, with De obtained by using the complete basis set (CBS) extrapolation [CCSD(T)/CBS energy], are presented for the B···BeR2 and B···MgR2 complexes, where B is one of the following Lewis bases: CO, H2S, PH3, HCN, H2O or NH3, and R is H, F or CH3. The BeR2 and MgR2 precursor molecules were shown to be linear and non-dipolar. The non-covalent intermolecular bond in the B···BeR2 complexes is shown to result from the interaction of the electrophilic band around the Be atom of BeR2 (as indicated by the molecular electrostatic potential surface) with non-bonding electron pairs of the base, B, and may be described as a beryllium bond by analogy with complexes such as B···CO2, which contain a tetrel bond. The conclusions for the B···MgR2 series are similar and a magnesium bond can be correspondingly invoked. The geometries established for B···BeR2 and B···MgR2 can be rationalized by a simple rule previously enunciated for tetrel-bonded complexes of the type B···CO2. It is also shown that the dissociation energy, De, is directly proportional to the force constant, kσ, in each B···MR2 series, but with a constant of proportionality different from that established for many hydrogen-bonded B···HX complexes and halogen-bonded B···XY complexes. The values of the electrophilicity, EA, determined from the De for B···BeR2 complexes for the individual Lewis acids, A, reveal the order A = BeF2 > BeH2 > Be(CH3)2—a result that is consistent with the −I and +I effects of F and CH3 relative to H. The conclusions for the MgR2 series are similar but, for a given R, they have smaller electrophilicities than those of the BeR2 series. A definition of alkaline-earth non-covalent bonds is presentedThis research was funded by Consejería de Educación e Investigación de la Comunidad de Madrid (P2018/EMT-4329 AIRTEC-CM) and Ministerio de Ciencia, Innovación y Universidades (PGC2018-094644-B-C22).We acknowledge support by the CSIC Open Access Publication Initiative through its Unit of Information Resources for Research (URICI)Peer reviewe