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The gas-phase molecular structure of iso-propyl(tert-butyl)(trichlorosilyl)phosphine has been determined using a combination of gas electron diffraction and computational methods. The structure presents a conformational challenge that required use of the SARACEN method to combine theoretical observations into the least-squares refinement process, a great advance on the techniques used to solve the structure of the parent trisilyl phosphine. Five conformers were found on the potential-energy surface for iso-propyl(tert-butyl)(trichlorosilyl)phosphine using the UCONGA program, and following a series of individual structure refinements a combined model with the two most abundant confirmers was evaluated. Key structural parameters (ra) include rP–Si [225.5(6) pm], rSi–Clmean [204.0(1) pm] and rP–Cmean [204.0(1) pm], ∠P–C–H 101.5(5)°, ∠C–C–C (iPr) 110.5(5)°, ∠C–C–C (tBu) 109.2(5)° and ∠C–P–C 105.4(5)°.

In the series of silatranes XSi(OCH2CH2)3N, 1 (X = Me, 1a; H, 1b; F, 1c) with the known gas electron diffraction (GED) structures, the problematic geometry of 1-methylsilatrane 1a has been revised. In particular, the new value of the SiN distance (dSiN) in 1a turned out to be ∼0.06 A longer than the generally accepted one. This dSiN resolves the long-standing contradiction between the data of the structural and spectral experiments regarding the sensitivity of 1 to the medium effect. We also performed the ab initio and DFT study of the combined series of silatranes 1a-c, silylalkylamines H3Si(CH2)3NMe2 (2a) and F3SiCH2NMe2 (2b), silylhydrazines F3SiN(Me)NMe2 (2c) and F3SiN(SiMe3)NMe2 (2d), and silyloxyamines ClH2SiONMe2 (2e,f), (F3C)F2SiONMe2 (2g,h) and F3SiONMe2 (2i), in which the GED dSiN values are in a wide range of 2-3 A. None of the involved quantum chemical methods has succeeded in reproducing all the experimental gas-phase dSiN values in 1a-c, 2a-i with an acceptable accuracy (0.01-0.03 A). The problems of the used methods, primarily CCSD with the Pople basis sets, are caused by four molecules with the geminal SiNN and SiON fragments (2d,f-i) and dSiN 2.3 A: MP2 < PBE0 ∼ B3PW91 ∼ SCS-MP2 < CCSD < CCSD(T).

9-Br-closo-1,2-C2 B10 H11 has been prepared and its gas-phase structure has been examined by means of gas electron diffraction. The structure of the carbaborane core is similar to the structure of the parent compound, which is of C2v symmetry. A DFT-based search for the corresponding reaction pathway of the bromination of closo-1,2-C2 B10 H12 revealed that the catalytic amount of aluminum reduces the barrier of the initial attack of the bromination agent toward the negatively charged part of the icosahedral carbaborane, i. e., the first transition state, from about 40 to about 27 kcalmol-1 . The Br-Br bond is weakened by an intermediate binding to the large π-hole on the aluminum atom of AlBr3 , which is the driving force for the AlBr3 -catalyzed bromination.

Difluorothiophosphoryl isocyanate, F2P(S)NCO was characterized with UV/vis, NMR, IR (gas and Ar‐matrix), and Raman (liquid) spectroscopy. Its molecular structure was also established by means of gas electron diffraction (GED) and single crystal X‐ray diffraction (XRD) in the gas phase and solid state, respectively. The analysis of the spectroscopic data and molecular structures is complemented by extensive quantum‐chemical calculations. Theoretically, the C s symmetric syn‐conformer is predicted to be the most stable conformation. Rotation about the P−N bond requires about 9 kJ mol−1 and the predicted existence of an anti‐conformer is dependent on the quantum‐chemical method used. This syn‐orientation of the isocyanate group is the only one found in the gas phase and contained likewise in the crystal. The overall molecular structure is very similar in gas and solid, despite in the solid state the molecules arrange through intramolecular O⋅⋅⋅F contacts into layers, which are further interconnected by S⋅⋅⋅N, S⋅⋅⋅C and C⋅⋅⋅F contacts. Additionally, the photodecomposition of F2P(S)NCO to form CO, F2P(S)N, and F2PNCO is observed in the solid Ar‐matrix., All about isocyanates: Difluorothiophosphoryl isocyanate, F2P(S)NCO, was investigated using an experimental multimethod approach in the gaseous, liquid and solid state to elucidate its structure, vibrational behaviour and photodecomposition: spectroscopy (UV/Vis, NMR, IR, Raman) and gas electron as well as single‐crystal X‐ray diffraction and in addition quantum‐chemical calculations.

Conformational composition and molecular structure of sulfanilamide (para-aminobenzenesulfonamide, SA) has been investigated by means of gas electron diffraction (GED) and quantum chemical (QC) calculations. Conformations with eclipsed orientation of the S=O and the N–H bonds in the sulfonamide moiety have been found to be predominant in vapor at the average temperature of the GED experiment of 184(5) °C. The structural parameters of the most stable conformer are the following (rh1 in A and ∠h1 in ° with 3σ in parenthesis): r(C=C) av = 1.410(4), r(S=O)av = 1.433(4), r(C–S) = 1.763(6), r(S–N) = 1.649(6), ∠CSN = 104.7(15), (∠CSO)av = 109.0(8). The orientation of the S–N bond of the sulfonamide group about the anilinic ring plane has been found to be different from orthogonal by about 13°. It has been shown that QC calculations tend to overestimate the values the S=O bond lengths as well as are not always accurate in the prediction of mutual orientation of the sulfonamide group and the anilinic ring plane. While in the gas phase, low energy conformations are found to be the most abundant; the molecular structure of SA in the crystal phase resembles a high energy conformation with staggered orientation of the N–H and the S=O bonds for all polymorph modifications. The mechanisms of mutual transformations of different SA conformers into each other have also been considered and discussed.

Two new silicon/phosphorus-based frustrated Lewis pairs (FLP), F3SiCH2PtBu2 (1) and Cl3SiCH2PtBu2 (2) were prepared from lithiated di-tert-butylmethylphosphane, LiCH2PtBu2, and the corresponding silicon tetrahalides. They were characterised by NMR spectroscopy and by single-crystal X-ray diffraction. A gas phase electron diffraction study of 1 identified two conformers of similar energy in the vapor. The reactivity of both, 1 and 2, towards a series of small molecules was investigated. Phenyl isocyanate was found to undergo addition reactions of its C-N unit to afford five-membered SiCPC(O)N-ring structures. Cl3SiCH2PtBu2 (2) was converted with perfluorophenyllithium and 3,5-bis(trifluoromethyl)phenyllithium. The reaction with LiC6F5 resulted in the ortho-fluoride substitution product (C6F5)(2)SiCH2(C6F4)PtBu2 (5), while the aryl reagent without ortho-fluoride groups, leads to the intramolecular Lewis pair (C8H3F6)(3)SiCH2PtBu2 (6). The FLP reactivity of 6 was tested.

Molecular structure and conformational equilibria of 1-methoxy- 1 and 1-hydroxy-1-phenylsilacyclohexanes 2 were studied by quantum chemical (QC) calculations and combined gas electron diffraction/mass spectrometry (GED/MS). Both molecules may exist in 5 or 6 forms, differing from each other by the substituents' position: (i) axial or equatorial and (ii) rotational orientation relative to the six-membered ring frame. The contribution of axial forms of both compounds varies from 35 to 60% depending on the theoretical method applied. From the GED data, the summarized molar fractions of the conformers were found to be Phax:Pheq = 70(15):30(20) and 50(20):50(20)% which corresponds to ΔG = Gax–Geq = −0.55(46) and 0.00(56) kcal/mol, for compound 1 and 2, respectively. The concentration of the Phax forms of 1-phenyl-1-(X)-silacyclohexanes (X = H, HO, Me, MeO and Me2N) increases with the size of the second substituent at the silicon atom: 38(10)

Several ethylenedioxy‐bridged bisarenes with a variety of type and number of aryl groups were synthesized to study non‐covalent dispersion‐driven inter‐ and intramolecular aryl–aryl interactions in the solid state and gas phase. Intramolecular interactions are preferably found in the gas phase. DFT calculations with and without dispersion correction show larger interacting aromatic groups increase the stabilization energy of folded conformers and decrease the intermolecular centroid–centroid distance. Single‐molecule structures generally adopt folded conformations with short intramolecular aryl–aryl contacts. Gas electron diffraction experiments were performed exemplarily for 1‐(pentafluorophenoxy)‐2‐(phenoxy)ethane. A new procedure for structure refinement was developed to deal with the conformational complexity of such molecules. The results are an experimental confirmation of the existence of folded conformations of this molecule with short intramolecular aryl–aryl distances in the gas phase. Solid‐state structures are dominated by stretched structures without intramolecular aryl–aryl interactions but interactions with neighboring molecules., London calling: London dispersion driven interactions between two aryl groups, separated by ethylenedioxy‐bridged linkers, lead to different conformations, dependent on the size and nature of the aryl groups and the phase, as studied by X‐ray (solid) and electron diffraction (gas).

The synthesis and results of gas electron diffraction (GED), temperature-dependent Raman spectroscopy, along with detailed quantum chemical (QC) study of 1-methoxy-1-silacyclohexane 1 are reported. Within the series of the QC results, DFT(B3LYP, PBE0, M06, M062X), and MP2, the conformational preference predictions are rather contradictive. From the both GED and Raman experimental methods applied, the vapour and liquid phases of 1 were found to exist as a mixture of two conformers, gauche- axial and gauche -equatorial, with almost equal contributions, while the trans -forms are much less stable. In addition, theoretical calculations on the cyclohexane analog, methoxycyclohexane 2 , are performed in order to compare with the conformational properties of 1 . The latter is predicted not to diminish the axial/equatorial ratio, as contrasted to the expectations at switching the point of the substituent attachment from Si to C.

The molecular structure and intramolecular inversions of N-cyanopiperidine (CNP) were studied by various quantum chemical methods and using synchronous gas electron diffraction/mass spectrometry (GED/MS) and IR spectroscopy. The contribution of the equatorial conformer was found GED 52(6), IR 60(6), B3LYP 77, B3LYP-D3 67, M062X 59, MP2 54%. Interpolation using CCSD(T)-F12/CBS predicts Eax–Eeq = 0.26 kcal/mol. The NBO analysis shows a strong conjugation of the nitrogen atom lone pair with the triple bond making the r(N–CCN) = 1.355(3) A distance as short as a typical sesquilateral bond. A low energy barrier for the Eq→Ax transition of 1.0–2.3 kcal/mol in CNP leads to difficulties in NMR conformational ratio studies. This leaves the GED method almost as the only experimental method to study both structural and conformational properties. Conformational properties of the related compounds are found to depend on the X–CCN bond distance and conjugation between the CN group and the lone pair on the heteroatom. The contribution of the axial form of 1-cyano-heterocyclohexanes increases in the series of heteroatoms X in the cyclohexane ring: N→C→Si→P.

The crystal structure and disorder phenomena of Al4B2O9, an aluminum borate from the mullite-type family, were studied using automated diffraction tomography (ADT), a recently established method for collection and analysis of electron diffraction data. Al4B2O9, prepared by sol-gel approach, crystallizes in the monoclinic space group C2/m. The ab initio structure determination based on three-dimensional electron diffraction data from single ordered crystals reveals that edge-connected AlO6 octahedra expanding along the b axis constitute the backbone. The ordered structure (A) was confirmed by TEM and HAADF-STEM images. Furthermore, disordered crystals with diffuse scattering along the b axis are observed. Analysis of the modulation pattern implies a mean superstructure (AAB) with a threefold b axis, where B corresponds to an A layer shifted by ½a and ½c. Diffraction patterns simulated for the AAB sequence including additional stacking disorder are in good agreement with experimental electron diffraction patterns.

The conformational preference of the cyano group of the 1-cyano-1-silacyclohexane was studied experimentally by means of gas electron diffraction (GED) and dynamic nuclear magnetic resonance (DNMR) as well as by quantum chemical (QC) calculations applying high-level coupled cluster methods as well as DFT methods. According to the GED experiment, the compound exists in the gas-phase as a mixture of two conformers possessing the chair conformation of the six-membered ring and Cs symmetry while differing in the axial or equatorial position of the substituent (axial = 84(12) mol %/equatorial = 16(12) mol %) at T = 279(3) K, corresponding to an A value (Gax – Geq) of −1.0(4) kcal mol−1. Gas-phase CCSD(T) calculations predict an A value of −0.72 kcal mol−1 at 279 K. In contrast, the low-temperature 13C NMR experiments resulted in an axial/equatorial ratio of 35/65 mol % at 120 K corresponding to an A value of 0.14 kcal mol−1. An average value for ΔG#e→a = 5.6 ± 0.1 kcal mol−1 was obtained for the temperature range 110–145 K. The dramatically different conformational behaviour in the gas-phase (GED) compared to the liquid phase (DNMR) suggests a strong solvation effect. According to natural bond orbital analysis the axial conformer of the title compound is an example of stabilization of a form, which is not favored by electrostatic effects and is favored predominantly by steric and conjugation effects., A.V.B. and Yu.F.S. are grateful to the Ministry of Education and Science of Russia (State Contracts N 14.B25.31.0013) for financial support. S.A.Sh. thanks the Russian Foundation for Basic Research (Grant 14-03-0023-a). I.A., S.O.W., and N.R.J. thank the Icelandic Centre for Research (RANNIS) for financial support, Grants No 080038021 and 100040022. R.B. acknowledges support from the Icelandic Research Fund, grant no. 141218051.

Molecular structure and conformational behavior of N -phenylpiperidine ( NPhP ) were investigated by synchronous gas-phase electron diffraction/mass spectrometry (GED/MS) and quantum chemistry. Due to influence of steric repulsion and hyperconjugation, NPhP may exist in two conformers, equatorial and axial chair forms. Both experiment and theoretical calculations suggest a C 1 symmetry of the conformers, with the plane perpendicular to the phenyl group turned by ca. 30–40° (equatorial) and 0–20° (axial) about the plane perpendicular to the piperidine ring symmetry plane. According to the QC calculations, NPhP may exist as two conformers, equatorial and axial, with a ratio of Eq:Ax = 92:8 (B3LYP), 87:13 (B3LYP-GD3), 84:16 (M06-2X), 83:17 (MP2/6-311G**) and 76:24% (MP2/cc-pVTZ). Except for the latter, these values are in good agreement with the experimental GED data of 90(10):10(10)%. A comparative analysis of similar compounds, phenylcyclohexane and 1-phenylheterocyclohexanes, was performed. Conformational properties depend on the C Ph X bond distance and hyperconjugation between the phenyl ring and the lone pair on the heteroatom. The contribution of the axial form of 1-phenylcyclohexane derivatives increases in the series of the heteroatom X in the cyclohexane ring: C → N → Si → P.

The tautomeric and structural properties of 5-hydroxy-2,2,6,6-tetramethyl-3-heptanone, (dipivaloylmethane, C(CH3)3C(O)CH2C(O)C(CH3)3) have been studied by means of gas-phase electron diffraction (GED) and quantum chemical calculations (B3LYP and MP2 approximation with different basis sets up to aug-cc-pVTZ). Both, quantum chemistry and GED analyses resulted in the presence of 100(5)% enol tautomer at 296(3)K. Quantum chemical calculations predict the existence of two enol conformers in about equal amounts. In both conformers the enol ring possesses Cs symmetry and they possess different torsional orientations of the two tert-butyl groups. The experimental data refinement results in an enol tautomer, in which the tert-butyl group adjacent to the carbonyl group possesses an intermediate orientation between those in “enol1” and “enol 2” forms (torsional angle is about 30°), and the tert-butyl group adjacent to the hydroxyl group slightly deviates from orientation in the theoretical conformers (by about 10°). The enol ring possesses CS symmetry with a strongly asymmetric hydrogen bond. The experimental geometric parameters are reproduced very closely by the B3LYP/aug-cc-pVTZ method.

Non-covalent aryl–aryl interactions for the molecular structures of three 1,2-diaryltetramethyldisilanes X5C6–(SiMe2)2–C6Y5 (X ≠ Y; X, Y = H, F, Cl) were studied by single crystal X-ray and gas electron diffraction as well as by SAPT calculations. Aryl–aryl interactions cause all to adopt exclusively rather untypical eclipsed syn-conformers in the gas phase, and C6F5–(SiMe2)2–C6Cl5 also in the solid state.

Conformational properties and molecular structure of 1-methyl-1-phenylsilacyclohexane 1 were studied by quantum chemical (QC) calculations, combined gas electron diffraction/mass spectrometry (GED/MS) and IR spectroscopy. Molecule 1 may exist in four forms that differ by axial or equatorial positions of the substituents and by relative orientation of the two rings. Two of these conformers were found to dominate in the gas phase: 1 -Ph eq -orth conformer with the phenyl ring plane bisecting the CSiC endocyclic angle, and 1 -Ph ax -twist with the phenyl ring and the CSiC exocyclic angle oriented nearly perpendicularly to each other. From the GED data, the summarized molar fractions of the conformers were found to be Ph eq :Ph ax = 42(15):58(15)% which corresponds to Δ G = G eq – G ax = 0.19(37) kcal/mol. Experimental and calculated IR spectra provides an evidence of existence of both conformers in the liquid phase. The QC calculations yielded the Δ G = G (Ph eq –orth)– G (Ph ax –twist) values of 0.18–0.36 DFT and 0.82 MP2 kcal/mol.

1-dimethylamino-1,3,5-trisilacyclohexane was synthesized and its structure and conformational properties have been determined by gas electron diffraction (GED) and quantum chemical (QC) calculations. The molecule may exist in 3 or 4 forms differing from each other by the substituents' position. QC results shows that the equatorial conformers are more stable than axial forms with ratio Eq:Ax=(75–58):(25–42)% (depending on method and basis set). From the GED data, the molar fractions of the conformers were found to be g-Eq:tr-Eq:tr-Ax=40(4):31(8):29(9)% at 272(3) K. In the liquid phase, as follows from IR measurements, the molecule may also exist in equatorial and axial forms.

The Cu–Zr–Ag ternary system belongs to the Cu-based bulk amorphisable alloy systems. The solidification of the amorphisable alloy is still not well-understood. The identification and characterization of the crystal structure of the solidified phases are essential for describing the ternary system. A typical Cu-rich solidified phase in the Cu–Zr–Ag ternary system is the so-called m-phase. The structure of this phase was not known before. Another typical phase is the Ag-containing Cu 10 Zr 7 phase. We determined and refined the crystal structures of single crystals of these two phases by transmission electron microscopyusing precession electron diffraction technique and diffraction tomography (performed by ADT3D software). The determination and refinement procedure was achieved in SIR2008, SIR2011 and SHELXL software packages. In conclusion, precession electron diffraction technique combined with diffraction tomography makes it possible to determine the crystal structure of materials with sub-micrometer sized crystals such as alloys when single crystal X-ray diffraction based structure determination fails.

The equilibrium structure of the 2-chloro-3-nitrothiophene molecule and the internal rotation of the nitro group have been studied in gas phase using electron diffraction data and quantum chemical calculations in the framework of the large-amplitude motion model for internal rotation. Quantum chemical calculations at the MP2 and B3LYP levels of theory with various Pople and Dunning basis sets predict the planar minimum energy molecular conformation, with the internal rotation barrier height in the interval 1140–1560 cm −1 . The experimental GED data are consistent with the dynamic model governed by the twofold cosine potential energy function with the barrier height in the range from 600 to 1400 cm −1 . The main equilibrium structure parameters are as follows (values in parentheses correspond to 3 times standard deviations): r e (N O) = 1.225/1.227(3) A, r e (C − C)/ r e (C − N) = 1.362/1.376/1.403/1.438(3) A, r e (C − Cl)/ r e (C − S) = 1.700/1.712/1.715(2) A, ∠ e C2SC5 = 92.2 (5)°, ∠ e C3C2S = 110.8 (6)°, ∠ e C4C5S = 111.3 (5)°, ∠ e C3C4C5 = 113.0 (7)°, ∠ e C2C3C4 = 112.7 (8)°, ∠ e C3NO11 = 116.9(6)°, ∠ e C3NO10 = 118.5 (6)°, ∠ e SCCl = 118.6 (5)°, ∠ e C4C3N = 121.8 (7)°, ∠ e ONO = 124.6(6)°, ∠ e C2C3N = 125.1 (6)°, ∠ e C3C2Cl = 130.7 (6)°. Thermally averaged parameters are provided for comparison with the results of traditional studies.

The molecular structure of chloropropanone oxime [ClCH2C(CH3)=NOH] has been determined by gas electron diffraction (GED), microwave spectroscopy (MW) and quantum chemical calculations. Potential energy curves for the internal rotation of CH2Cl group in (E)- and (Z)-isomers as well as the optimized geometries and force constants for four conformations have been calculated by the quantum chemical calculations. Combined data analysis of the GED and MW data revealed the conformational mixture of 68(4) % (E)-anticlinal and 32 % (Z)-synclinal conformers. The principal values of geometrical parameters of the E-anticlinal conformer are: r g(ClH2C–C) = 1.499(2) A, r g(C–CH3) = 1.503(2) A, r g(C=N) = 1.276(4) A, r g(C–Cl) = 1.805(3) A, r g(N–O) = 1.398(4) A, ∠αC–C=N = 113.2(16)°, ∠αC–C–Cl = 111.1°(5), ∠αH3C–C=N = 127.0°(13), ϕ(NCCCl) = 121.1°(21). Numbers in parentheses are three times standard deviations of the data fit.

The gas electron diffraction (GED) study of succinic anhydride (dihydro-2,5-furandione) is used as a benchmark example for the reliable determination of the structure of floppy molecules with saturated non-rigid ring. According to results of B3LYP calculations, the molecule has a planar skeleton (C2v total symmetry), whereas the MP2 optimized structure has a non-planar ring with the torsional angle φ(C–C–C–C) of up to 11° (C2 symmetry). It has been revealed that the increase in the quality of ab initio calculations up to CCSD(T) level and the enlargement of basis set up to quadruple-ζ size decrease the non-planarity of the molecular skeleton, which is approximated to be planar in the best-estimated ab initio structure. The semiexperimental equilibrium structure ( $$r_{\text{e}}^{\text{se}}$$ ) has been determined from the GED data with the application of the so-called dynamic (pseudo-conformer) model describing the large-amplitude ring-twisting motion. Vibrational corrections Δ(r a − r e) to the experimental internuclear distances have been calculated from the B3LYP/cc-pVTZ quadratic and cubic force constants. The best-estimated ab initio structure agrees well with the $$r_{\text{e}}^{\text{se}}$$ structure. This fact points to the reliability and a high accuracy of both experimental data and applied theory.

A brief description of a solution of the problem on electron diffraction analysis using the potential procedure for nonrigid molecules with large-amplitude motions along several symmetric internal coordinates was given. The efficiency of the approach was demonstrated for determination of the equilibrium geometry of the 1,3,5-trinitrobenzene molecule with three equivalent internal rotation coordinates of NO2 groups. The results of the electron diffraction experiment and quantum-chemical calculation at the MP2(full)/cc-pVTZ level were considered along with the vibrational spectra of 1,3,5-trinitrobenzene and a planar equilibrium D 3h symmetry conformation for the molecule was found reliably for the first time. The geometrical parameters of the molecule were determined (r e , the bond lengths are given in A, the angles in deg): CC 1.387(2), CN 1.474(4), NO 1.220(1), CH 1.072(31), ONO 125.8(2), CC(H)C 116.6(3), HCC* 121.7(1), CC(N)C* 123.4(3), NCC* 118.3(1), and CNO* 117.1(1); the asterisk marks the dependent parameters.

Molecular structure of copper(II) etioporphyrin-II (CuEP-II) has been studied by a combined gas-phase electron diffraction and mass spectrometry (GED/MS) method in synchronous mode. The experimental results were complemented by DFT calculations using the B3LYP and PBE functionals with pVTZ basis sets for describing H, C, N atoms and cc-pVTZ for describing Cu atom. The CuEP-II molecule was found to possess quasiplanar geometry of macroheterocycle. DFT calculations predict six conformers for the molecule, which differ by the orientation of the ethyl groups with respect to the macrocycle. Energy differences of five conformers are less, than 0.1 kJ/mol (UPBE) or 0.3 kJ/mol (UB3LYP). Rotation barriers of single ethyl-group are 14.6 and 19.8 kJ/mol (UPBE), 15.7 and 21.6 kJ/mol (UB3LYP). Sixth conformer has relatively high energy. Structural parameters of the CuEP-II molecule yielded by DFT calculations are, in general, in a good agreement with the GED data. Structural analysis indicated that the gas-phase electron diffraction method is robust for determination of the macroheterocyclic fragment, but is not enough sensitive to conformational composition of CuEP-II. Substitution effect in pyrrole fragments of CuP, CuOFP, CuOMP and CuEP-II complexes has been analyzed.

The structure of molecules using gas electron diffraction (GED) was my graduate study. However, I was making a new apparatus for precise measurements by GED and formulated a scheme for the least-squares analysis for a smooth continuous curve of scattering intensity. My research was completely shifted to the solid surface after moving to Gakushuin University, where I briefly studied the liquid structure of CCl4 molecules, and I then moved to the Institute for Solid State Physics, the University of Tokyo. My studies of surface science were focused on the electronic properties and related phenomena, and various experimental methods were developed. The plasmon dispersions elucidated the initial oxidation of aluminum and one-dimensional metal on Si(001)2 × 1-K. Irreversible phase transition was discovered on MgO(001) using the LEED Kikuchi pattern. The electronic structure of the dislocation was observed on MgO(001) by the electron time-of-flight method. The phase transition on Si(001) and the rotational epitaxy in a K monoatomic layer on Cu(001) were found. Next, I changed to studies of the dynamical phenomena on the surface, where very low energy reactive ion scattering on metal surfaces and laser-induced desorption caused by electronic transition of NO and CO molecules from metal surfaces were observed, and the hydrogen atom location at the surface and interface was measured with a high depth resolution using a resonance nuclear reaction of (1) H + (15) N(2+) at 6.385 MeV. Finally, I moved to the University of Electro-Communications and studied thin single-crystal oxide layers on transition metals, in which the band-gap narrowing was found, and then a Pt monoatomic layer was prepared on the α-Al(2)O(3) film.

We report on ultrafast electron diffraction on high quality single crystal silicon. The ultrafast dynamics of the Bragg peaks exhibits a giant photo-induced response which can only be explained in the framework of dynamical diffraction theory, taking into account multiple scattering of the probing electrons in the sample. In particular, we show that lattice heating following photo-excitation can cause an unexpected increase of the Bragg peak intensities, in contradiction with the well-known Debye-Waller effect. We anticipate that multiple scattering should be systematically considered in ultrafast electron diffraction on high quality crystals as it dominates the Bragg peak dynamics. In addition, taking into account multiple scattering effects opens the way to quantitative studies of non-equilibrium dynamics of defects in quasi-perfect crystals., Comment: 11 pages, 7 figures (including supplementary information)

Disulfuryl dichloride ClSO 2 OSO 2 Cl was characterized byvibrational spectroscopy in the gaseous and liquid phase as well asin the Ar-matrix. By varying the temperature, certain bands could beassigned to several conformers. Gas-phase electron diffractionrevealed a dominance of the anti-conformer at ambient temperature.The same conformation was found in the solid state. Via the in situtechnique for crystallization, not less than four different modificationswere identified. Among these different modifications, the structuralparameters of the molecules remain relatively constant, but theaggregation pattern changes. Although the molecules aggregate bychlorine···oxygen contacts in each modification, the geometricalparameters of these interaction show significant differences andwere evaluated and are in part inconsistent with the halogen bondingconcept. Fil: Moreno Betancourt, Angelica. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Química Inorgánica "Dr. Pedro J. Aymonino". Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Centro de Química Inorgánica "Dr. Pedro J. Aymonino"; Argentina Fil: Schwabedissen, Jan. Universitat Bielefeld; Alemania Fil: Romano, Rosana Mariel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Química Inorgánica "Dr. Pedro J. Aymonino". Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Centro de Química Inorgánica "Dr. Pedro J. Aymonino"; Argentina Fil: Della Védova, Carlos Omar. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Química Inorgánica "Dr. Pedro J. Aymonino". Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Centro de Química Inorgánica "Dr. Pedro J. Aymonino"; Argentina Fil: Beckers, Helmut. Bergische Universität Wuppertal; Alemania Fil: Willner, Helge. Bergische Universität Wuppertal; Alemania Fil: Stammler, Hans Georg. Universitat Bielefeld; Alemania Fil: Mitzel, Norbert Werner. Universitat Bielefeld; Alemania

Dynamic structural analysis of the molecules possessing large-amplitude degrees of freedom has been attempted by many researchers; however, so far, electron diffraction investigations involved only one large-amplitude coordinate (internal rotation or bending). The current state of computational facilities allows extending of the general dynamic approach to the systems possessing two or more large-amplitude motions. This paper presents the first practical implementation of the theoretical method developed previously by the authors for solving the dynamic-structural problem with two or more large-amplitude coordinates; the procedure is applied to a molecule of 3-nitrostyrene. The molecule is represented as a set of pseudoconformers built on a two-dimensional grid corresponding to both internal rotation coordinates present in the molecule (with 10-30° steps by each angle); altogether, up to 342 pseudoconformers were used. Structural analysis was based on the experimental electron diffraction data supported by quantum chemical calculations (at the MP2 and B3LYP levels of theory) and molecular spectroscopy data. Quantum chemistry predicts the planar structure of both syn- and anti- stable conformations with close energies and weak interaction between internal rotations of nitro and vinyl groups. The gas-phase electron diffraction experimental data are compatible with the quantum chemical predictions. The principal equilibrium geometry parameters of the molecule (syn- conformation) have been determined as follows: r(e)(C-C)(ring, avg.) = 1.391(1) Å, r(e)(C-C) = 1.477(5) Å, r(e)(C═C) = 1.333(7) Å, r(e)(C-N) = 1.463(5) Å, r(e)(N═O) = 1.227(3) Å, ∠e(O═N═O) = 124.3 (4)°. Experimental data for this molecule are insufficient to make estimates of the barrier heights of internal rotation; the population ratio of syn- and anti- conformations is evaluated as 50 ± 20%. Results of our investigation confirm the presence of significant internal rotations in the 3-nitrostyrene molecule.

The earlier reported Al–Ti–Pt phases τ 5 and τ 6 were studied using Precession Electron Diffraction (PED) and Convergent Beam Electron Diffraction (CBED). Their atomic models were proposed applying Direct Methods to the PED zonal data. The τ 5 -phase (FeCr-type, P 4 2 / mnm , a = 9.702 and c = 5.023 A) can be described by the formula Al 2 Ti 5 Pt 3 , positioning 18 Ti, eight Pt and four Al atoms at five unique atomic positions in the unit cell. The τ 6 -phase ( P 2 1 3, a = 6.8477 A) can be described by the formula Al 3 Ti 5 Pt 2 . Its unit cell consists of 20 atoms at 12 b and two 4 a atomic positions occupied by Ti, Pt and Al atoms, respectively. Due to deviation from the stoichiometry, the τ 6 -phase can be related to a defect variant of the Au 4 Al-type structure. The structures of the studied phases are presented as the stacking of coordination polyhedra.

To further investigate the alpha-effect in silanes bearing a geminal donor atom, the model compounds (C2F5)(3)SiCH2NMe2, (C2F5)(3)SiCH2OMe and (C2F5)(3)SiONMe2 were prepared by introduction of pentafluoroethyl groups via nucleophilic substitution of the corresponding chloro-derivatives with pentafluoroethyl lithium. The substances were characterised by NMR spectroscopy and X-ray diffraction via in situ crystallization techniques. The solid state structures of these highly electronegatively substituted a-silanes contain monomeric molecules. The Si-C-N angle in (C2F5)(3)SiCH2NMe2 shows a value of 115.3(2)degrees and the Si-C-O angle in (C2F5)(3)SiCH2OMe a value of 105.4(1)degrees. Both values are smaller than the Si-C-C angle of the reference compound (C2F5)(3)SiCH2CH3 with a value of 118.6(2)degrees indicating attractive interaction between the silicon atom and the respective donor atoms. The Si-O-N angle in (C2F5)(3)SiONMe2 is extremely narrow at 82.0(1)degrees. This behaviour was further investigated by gas electron diffraction and by quantum-chemical calculations. The NBO method finds no significant orbital interactions between Si and N/O atoms in the Si-C-N, Si-C-O and Si-O-N units. The IQA model describes the compounds as strongly stabilised by electrostatic interactions between formally non-bonded silicon and donor atoms.

After numerous attempts over the last seven decades to obtain a structure for the simple, highly symmetric molecule tetranitromethane (C(NO2 )4 , TNM) that is consistent with results from diffraction experiments and spectroscopic analysis, the structure has now been determined in the gas phase and the solid state. For the gas phase, a new approach based on a four-dimensional dynamic model for describing the correlated torsional dynamics of the four C-NO2 units was necessary to describe the experimental gas-phase electron diffraction intensities. A model describing a highly disordered high-temperature crystalline phase was also established, and the structure of an ordered low-temperature phase was determined by X-ray diffraction. TNM is a prime example of molecular flexibility, bringing structural methods to the limits of their applicability.

The structures of the molecules C(SiXMe2)4 (X=H, F, Cl, Br) have been determined by gas electron diffraction (GED). Ab initio calculations revealed nine potential minima for each species, with significant ranges of energies. For the H, F, Cl, and Br derivatives nine, seven, two, and two conformers were modelled, respectively, as they were quantum-chemically predicted to be present in measurable quantities. Variable-temperature 1H and 29Si solution-phase NMR studies and, where applicable, 13C NMR, 1H/29Si NMR shift-correlation, and 1H NMR saturation-transfer experiments are reported for C(SiXMe2)4 (X=H, Cl, Br, and also I). At low temperature in solution two conformers (one C1-symmetric and one C2-symmetric) are observed for each of C(SiXMe2)4 (X=Cl, Br, I), in agreement with the isolated molecule ab initio calculations carried out as part of this work for X=Cl, Br. C(SiHMe2)4 is present as a single C1-symmetric conformer in solution at the temperatures at which the NMR experiments were performed.

Symmetrically independent geometrical parameters of six molecules, viz. benzene C6H6 (D6h), pyridine C5H5N (C2v), diphenyl C6H5–C6H5 (D2), 2,2′-dipyridine C5H4N–C5H4N (C2), naphthalene C10H8 (D2h), ferrocene (C5H5)2Fe (D5), and substituted (η5-C5H5)FeCp′ molecular fragment, were calculated from crystal structures deposited in the Cambridge Structural Database (CSD). Average CSD interatomic distances from low-temperature (LT) studies are systematically shortened by 0.01–0.02 A in comparison with gas electron diffraction results for free molecules; room temperature CSD bond lengths are further reduced relative to LT ones. Bicyclic diphenyl and 2,2′-dipyridine display a similar distribution of planar (mostly in special positions) and nonplanar molecules with the interring dihedral angle varying up to 49.6° and 46.0°, respectively. A strong positive correlation between C–C and Fe–C bond lengths was observed in (η5-C5H5)Fe fragments. Bond angle values at neighboring atoms in planar cycles are negatively correl...

The molecular structure of 1,3,5-tris(trifluoromethyl)benzene (1,3,5-TTFB) was studied by gas-phase electron diffraction (GED) and quantum chemical calculations (B3LYP method with 6-31G(d,p) basis set and MP2 method with cc-pVTZ basis set). The best fit of the experimental scattering intensities (RG = 4.0%) was obtained for the structure of CS symmetry. The differences between some geometric parameters were constrained at the values calculated at the MP2/cc-pVTZ level. The principal structural parameters rh1(∠h1) determined by GED are (bond lengths in Angstroms and bond angles in degrees with 3σ in parentheses): r(C C) = 1.392(4), r(C C)=1.512(4), r(C F)av = 1.346(2), ∠C C(CF3) C = 120.9(2), ∠C C(H) C = 119.1(2), ∠(C C F)av = 111.6(2). The structure of the carbon ring deviates from a regular hexagon due to the σ-electronegative effect of the CF3 groups. The geometric parameters of the trifluoromethyl groups deviate considerably from regular tetrahedron arrangement. The experimental structural parameters agree well with the results of B3LYP/6-31G(d,p) and MP2/cc-pVTZ calculations. The electron diffraction data are in agreement with nearly free rotation of the CF3 groups around Cmethyl Cphenyl axis.

Single crystal X-ray diffraction and powder X-ray diffraction (PXRD) are powerful methods for determination of unknown crystal structures including zeolites. However, these techniques have some limitations. For instance, single crystal X-ray diffraction requires large enough crystals which are often difficult to synthesize. For powder X-ray diffraction, peak indexing and intensity extraction become difficult if there exist peak broadening caused by small crystal sizes and peak overlap due to large unit cell and high symmetry. This becomes even more complicated for samples that contain more than one phase. We developed a new rotation electron diffraction (RED) method that can overcome these limitations. Almost complete three-dimensional electron diffraction datasets can be collected from micron- or nano-sized single crystals in a transmission electron microscope by combining electron beam tilt and goniometer tilt. Here, we demonstrate the power and limitations of the RED method for ab initio structure determination of four sub-micron sized zeolites, including a calcined silicalite-1, an EUO-type germanosilicate, an FER-type aluminogermanosilicate and an AST-type aluminogermanosilicate. The latter three zeolites were found in multiphasic samples. We show how the tilt range, tilt step and resolution affect the unit cell determination, structure solution and structure refinement. The EUO-, FER- and AST-type zeolites were found in two multiphasic samples in the Al–Ge–Si system, which were also characterized by PXRD and N2 sorption.

The equilibrium structure of the urotropine molecule is characterized by means of gas electron diffraction (GED) with the involvement of quantum chemistry and vibrational spectroscopy. A structural analysis of the GED data is performed based on the parameters of the intramolecular potential function using of the program complex SYMM/DISP/ELDIFF/LARGE. The quadratic and cubic force constants of the urotropine molecule were obtained earlier on the basis of calculations at the MP2(full)/cc-pVTZ level and assuming molecular symmetry Td. The values of the equilibrium geometric parameters re of the urotropine molecule are found. The experimental structural parameters are in good agreement with those calculated at the MP2(full)/cc-pVTZ level.

The equilibrium structures and force fields of the twelve simplest silyl- and alkyl-pseudo halides are calculated by means of B3LYP and MP2(full) quantum-chemical methods with the use of the aug-cc-pVTZ basis. Some regularities in their structure are established. Using these data, the equilibrium structure of the (CH3)3SiNCSe molecule with symmetry C3v is described experimentally for the first time via gas electron diffraction. The following values of the main re parameters are determined (uncertainty 3σ is in parentheses): C=Se, 1.709(14) A; N=C, 1.190(10) A; N-Si, 1.767(15) A; Si-C, 1.847(13) A; N-Si-C, 106.4°; C-Si-C, 112.4°.

Electron diffraction is a complementary technique to single-crystal X-ray diffraction and powder X-ray diffraction for structure solution of unknown crystals. Crystals too small to be studied by single-crystal X-ray diffraction or too complex to be solved by powder X-ray diffraction can be studied by electron diffraction. The main drawbacks of electron diffraction have been the difficulties in collecting complete three-dimensional electron diffraction data by conventional electron diffraction methods and the very time-consuming data collection. In addition, the intensities of electron diffraction suffer from dynamical scattering. Recently, a new electron diffraction method, rotation electron diffraction (RED), was developed, which can overcome the drawbacks and reduce dynamical effects. A complete three-dimensional electron diffraction data set can be collected from a sub-micrometre-sized single crystal in less than 2 h. Here the RED method is applied forab initiostructure determination of an unknown complex intermetallic phase, the pseudo-decagonal (PD) quasicrystal approximant Al37.0(Co,Ni)15.5, denoted as PD2. RED shows that the crystal is F-centered, witha= 46.4,b= 64.6,c= 8.2 Å. However, as with other approximants in the PD series, the reflections with oddlindices are much weaker than those withleven, so it was decided to first solve the PD2 structure in the smaller, primitive unit cell. The basic structure of PD2 with unit-cell parametersa= 23.2,b= 32.3,c= 4.1 Å and space groupPnmmhas been solved in the present study. The structure withc= 8.2 Å will be taken up in the near future. The basic structure contains 55 unique atoms (17 Co/Ni and 38 Al) and is one of the most complex structures solved by electron diffraction. PD2 is built of characteristic 2 nm wheel clusters with fivefold rotational symmetry, which agrees with results from high-resolution electron microscopy images. Simulated electron diffraction patterns for the structure model are in good agreement with the experimental electron diffraction patterns obtained by RED.

The gas-phase structures of the disilanes 1,1,2,2-tetrakis(trimethylsilyl)disilane [(Me3Si)2HSiSiH(SiMe3)2] (1) and 1,1,2,2-tetrakis(trimethylsilyl)dimethyldisilane [(Me3Si)2MeSiSiMe(SiMe3)2] (2) have been determined by density functional theoretical calculations and by gas electron diffraction (GED) employing the SARACEN method. For each of 1 and 2 DFT calculations revealed four C2-symmetric conformers occupying minima on the respective potential-energy surfaces; three conformers were estimated to be present in sufficient quantities to be taken into account when fitting the GED data. For (Me3Si)2RSiSiR(SiMe3)2 [R = H (1), CH3 (2)] the lowest energy conformers were found by GED to have RSiSiR dihedral angles of 87.7(17)° for 1 and -47.0(6)° for 2. For each of 1 and 2 the presence of bulky and flexible trimethylsilyl groups dictates many aspects of the geometric structures in the gas phase, with the molecules often adopting structures that reduce steric strain.

β-naphthalene sulfonyl fluoride, β-NaphSF, and β-naphthalene sulfonyl chloride, β-NaphSCl, were studied by gas-phase electron diffraction (GED) and quantum chemical calculations (B3LYP and MP2 in combination with cc-pVDZ, aug-cc-pVDZ and cc-pVTZ basis sets). For each compound the calculations predicted the existence of two conformers which are enantiomers. On the basis of the experimental data it was found that the gas phase over β-NaphSF and NaphSCl at 357(5) K and 395(5) K, respectively, consists of molecular species of C1 symmetry in which the Cβ S Hal plane deviates from the perpendicular orientation relative to the naphthalene skeleton plane. The following geometrical parameters (A and degrees) were obtained from the experiment (uncertainties are in parentheses): rh1(C H)aver. = 1.097(7), rh1(C C)aver. = 1.410(3), rh1(C S) = 1.753(6), rh1(S O)aver. = 1.414(4), rh1(S F) = 1.559(5), ∠C Cβ C = 122.8(3), ∠Cβ S F = 103.3(30); Φ(Cα Cβ S F) = 104(6) for β-NaphSF, and rh1(C H)aver. = 1.089(4), rh1(C C)aver. = 1.411(3), rh1(C S) = 1.757(5), rh1(S O)aver. = 1.419(3), rh1(S Сl) = 2.053(4), ∠C Cβ C = 122.8(1), ∠Cβ S Cl = 102.2(7), Φ(Cα Cβ S Cl) = 108(3) for β-NaphSCl. The calculated barriers to internal rotation of the sulfonyl halide groups exceed considerably the thermal energy values corresponding to the temperatures of the GED experiments. Natural bond orbital (NBO) analyses of the electron density distribution were applied to explain the peculiarities of the molecular structure of the studied compounds and the deviation from the structures of their benzene analogs.

The lattice response of bismuth nanoparticles to femtosecond laser excitation is probed by ultrafast electron diffraction. The transient decay time after laser excitation is observed to be longer for diffraction from the (012) lattice planes compared to that from (110). From the position of the (012) diffraction peak, a transient lattice contraction due to hot electron blast force is observed over several picoseconds followed by expansion while the position of the (110) peak shows only expansion. The diffraction peak width indicates partial disorder of the nanoparticles consistent with formation of a liquid shell as the lattice is heated.

The molecular structure of tris-2,2,6,6-tetramethyl-heptane-3,5-dione indium, or In(thd)3, has been determined by gas-phase electron diffraction monitored by mass spectrometry (GED/MS) and quantum chemical (DFT) calculations. Both the DFT calculations and the GED data collected at 387(8) K indicate that the molecules have D 3 symmetry with a distorted anti-prismatic InO6 coordination geometry. According to GED refinements, the twist angle θ, i.e. the angle of rotation of the upper and lower O3 triangles in opposite directions relative to their positions in a regular prism is θ = ±24.9(1.2)° and the bond distances (r h1) in the chelate ring are In–O = 2.127(4) A, C–O = 1.268(3) A and C–C = 1.411(3) A, respectively. The DFT calculations yielded structure parameters in close agreement with those found experimentally.

The gas-phase molecular structure of the unsubstituted [30]trithia-2,3,5,10,12,13,15,20,22,23,25,30-dodecaazahexaphyrin (C30H15N15S3) has been studied by a synchronous gas electron diffraction and mass spectrometric experiment and density functional theory calculations using the B3LYP hybrid method and cc-pVTZ basis sets. The molecule has an equilibrium structure of D 3h symmetry with a planar macrocycle and the thiadiazole rings oriented in such a way that the sulfur atoms point outwards from the inner cavity. Tautomers of this compound have been studied by DFT computations.

International audience; Electron diffraction is a standard tool to investigate the atomic structure of surfaces, interfaces, and adsorbate systems. In particular, photoelectron diffraction is a promising candidate for real-time studies of structural dynamics combining the ultimate time resolution of optical pulses and the high scattering cross-sections for electrons. In view of future time-resolved experiments from molecular layers, we studied the sensitivity of photoelectron diffraction to conformational changes of only a small fraction of molecules in a monolayer adsorbed on a metallic substrate. 3,3′,5,5′-tetra-tert-butyl-azobenzene served as test case. This molecule can be switched between two isomers, trans and cis, by absorption of ultraviolet light. X-ray photoelectron diffraction patterns were recorded from tetra-tert-butyl-azobenzene/Au(111) in thermal equilibrium at room temperature and compared to patterns taken in the photostationary state obtained by exposing the surface to radiation from a high-intensity helium discharge lamp. Difference patterns were simulated by means of multiple-scattering calculations, which allowed us to determine the fraction of molecules that underwent isomerisation.

Using hydrosilylation and C-C coupling reactions, three compounds with phenyl and perfluoro¬phenyl rings bridged by (CH2)3 and (CH2)2SiMe2 units were synthesized. Their solid-state structures are domi¬nated by intermolecular π-stacking interactions, primarily leading to dimeric or chain-type aggregates. Structures of the free molecules de¬termined by gas-phase electron diffraction reveal the most abun¬dant conformer to be significantly stabilized by intra¬mole¬cular π-π-interactions. For the silicon compounds structures charac¬te¬ri¬-zed by σ-π inter¬actions between a methyl and (perfluoro)-phenyl groups are next higher in energy and cannot be excluded completely by the GED experiments. C6H6(CH2)3C6F5 in contrast is composed of a single conformer. The gas-phase structures serve as reference for the evaluation of a series of (dis¬persion-corrected) quantum-chemi¬cal methods.

Gas-phase electron diffraction is one of the principal techniques of molecular structure determination. A beam of fast electrons is scattered on a molecular beam in the experiment, and the resulting interference pattern is determined by the charge distribution of the molecule. The molecular component of the total electron scattering intensities is extracted from them and, aided by model building, the molecular parameters are determined from the molecular intensities. Fourier transformation of the molecular intensities leads to the so-called radial distribution, which is the probability density distribution of the internuclear distances in the molecule. The results of the structure determination appear as average internuclear distances or, in terms of internal coordinates, as bond lengths, bond angles, and angles of torsion. Gas-phase electron diffraction is an efficient tool of conformational analysis, yielding the geometries of the conformers and their relative abundances. In the best cases, the gas-phase electron diffraction technique yields precisions of a few tenths of a picometer for bond lengths, a few tenths of a degree for bond angles, and a few degrees for angles of torsion.

A semi-experimental equilibrium structure of free molecules of pyrazinamide has been determined for the first time using gas electron diffraction method. The refinement was carried using regularization of geometry by calculated quantum chemical parameters. It is discussed to which extent is the final structure experimental. A numerical approach for estimation of the amount of experimental information in the refined parameters is suggested. The following values of selected internuclear distances were determined (values are in angstrom with 1 sigma in the parentheses): r(e)(C-pyrazine-C-pyrazine)(av) = 1.397(2), r(e)(N-pyrazine-C-pyrazine)(av) = 1.332(3), r(e)(C-pyrazine-C-amide) = 1.493(1), r(e)(N-amide-C-amide) = 1.335(2), r(e)(O-amide-C-amide) = 1.219(1). The given standard deviations represent pure experimental uncertainties without the influence of regularization. (C) 2016 Elsevier B.V. All rights reserved.

The gas-phase molecular structures of a series of halogen-substituted disilanes [X3SiSiMe3 (X = H, F, Cl and Br)], 1,1,1-trimethyldisilane (H3SiSiMe3), 1,1,1-trifluoro-2,2,2-trimethyldisilane (F3SiSiMe3), 1,1,1-trichloro-2,2,2-trimethyldisilane (Cl3SiSiMe3) and 1,1,1-tribromo-2,2,2-trimethyldisilane (Br3SiSiMe3), have been determined in the gas phase by electron diffraction. Ab initio calculations at the HF and MP2 level were used to support the experimental investigation using the SARACEN method. All of the investigated structures were determined to adopt a staggered structure with C 3v symmetry. The effect of substitution on the Si–Si bond and the Si–Si–X bond angle was investigated and these results were compared to results obtained from a recent study of halogen-substituted disilanes [X3SiSiXMe2 (X = F, Cl, Br and I)] to consider the effect of the methyl groups on the substituted disilanes.

In this chapter, we outline the dynamical theory of high-energy transmission electron diffraction. There have been three major, and related, approaches to the subject; each was developed for specific applications.

Trichloromethyl thiocyanate, CCl3SCN, was structurally studied in both the gas and crystal phases by means of gas electron diffraction (GED) and single-crystal X-ray diffraction (XRD), respectively. Both experimental studies and quantum chemical calculations indicate a staggered orientation of the CCl3 group relative to the SCN group. This conclusion is supported by the similarity of the C-SCN bond length to that of the anti-structure of CH2ClSCN (Berrueta Martínez et al. Phys. Chem. Chem. Phys. 2015, 17, 15805-15812). Bond lengths and angles are similar for gas and crystal CCl3SCN structures; however, the crystal structure presents different intermolecular interactions. These include halogen and chalcogen type interactions, the geometry of which was studied. Characteristic C-Y⋯N angles (Y=Cl or S) close to 180° provide evidence for typical σ-hole interactions along the halogen/chalcogen-carbon bond in N⋯Cl and N⋯S, intermolecular units. Crystallize the difference: The crystal and gas-phase structures of CCl3SCN are studied by X-ray and gas electron diffraction techniques. In both phases, the CCl3 group presents a staggered orientation relative to the SCN group. Different intermolecular interactions are detected in the solid phase, including halogen- and chalcogen-type interactions. Fil: Berrueta Martinez, Yanina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Química Inorgánica "Dr. Pedro J. Aymonino". Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Centro de Química Inorgánica "Dr. Pedro J. Aymonino"; Argentina Fil: Rodriguez Pirani, Lucas Sebastian. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Química Inorgánica "Dr. Pedro J. Aymonino". Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Centro de Química Inorgánica "Dr. Pedro J. Aymonino"; Argentina Fil: Erben, Mauricio Federico. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Química Inorgánica "Dr. Pedro J. Aymonino". Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Centro de Química Inorgánica "Dr. Pedro J. Aymonino"; Argentina Fil: Boese, Roland. Universität Duisburg Essen; Alemania Fil: Reuter, Christian G.. Universität Bielefeld; Alemania Fil: Vishnevskiy, Yury V.. Universität Bielefeld; Alemania Fil: Mitzel, Norbert W.. Universität Bielefeld; Alemania Fil: Della Védova, Carlos Omar. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Química Inorgánica "Dr. Pedro J. Aymonino". Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Centro de Química Inorgánica "Dr. Pedro J. Aymonino"; Argentina