π-Hole bonding in a new co-crystal hydrate of gallic acid and pyrazine: static and dynamic charge density analysis

A new cocrystal hydrate of gallic acid with pyrazine (4GA, Py, 4H2O; GA4PyW4) was obtained and characterized by single crystal X-ray diffraction. In addition to structure determination, experimental charge density analysis was carried out in terms of Multipole Modelling (MP), X-ray wavefunction refinement (XWR) and maximum entropy method (MEM). As a part of XWR, the structural refinement via Hirshfeld atom refinement was carried out and resulted in O-H bond lengths close to values from neutron diffraction. A systematic comparison of molecular conformations and aromatic interactions in this new cocrystal hydrate was performed with other existing polymorphs of gallic acid. In GA4PyW4, the two symmetry-independent gallic acid molecules have a syn COOH orientation and form the common (COOH)2 dimeric synthon. The carboxyl C atom displays the characteristics of π-holes with electropositive regions above and below the molecular plane and engages in acceptor-donor interactions with oxygen atoms of acidic O-H groups and phenol groups of neighbouring gallic acid molecules. The signature of the π-hole was identified from experimental charge density analysis, both in static density maps in MP and XWR as well as dynamic density in MEM, but it cannot be pinned down to a specific atom-atom interaction. This study presents the first comparison between an XWR and a MEM experimental electron-density determination

Aurophilic Interactions Studied by Quantum Crystallography.

This is the first use of a wave-function-based crystallographic method to characterize aurophilic interactions from X-ray diffraction data. Theoretical calculations previously suggested the importance of electron correlation and dispersion forces, but no influence of relativistic corrections to the Au...Au interaction energy was found. In this study, we confirm the importance of relativistic corrections in the characterization of aurophilic interactions in addition to electron correlation and dispersion

Influence of modelling disorder on Hirshfeld atom refinement results of an organo-gold(I) compound.

Details of the validation of disorder modelling with Hirshfeld atom refinement (HAR) for a previously investigated organo-gold(I) compound are presented here. The impact of refining disorder on HAR results is discussed using an analysis of the differences of dynamic structure factors. These dynamic structure factor differences are calculated from thermally smeared quantum mechanical electron densities based on wavefunctions that include or exclude electron correlation and relativistic effects. When disorder is modelled, the electron densities stem from a weighted superposition of two (or more) different conformers. Here this is shown to impact the relative importance of electron correlation and relativistic effect estimates expressed by the structure factor magnitudes. The role of disorder modelling is also compared with the effect of the treatment of hydrogen anisotropic displacement parameter (ADP) values and atomic anharmonicity of the gold atom. The analysis of ADP values of gold and disordered carbon atoms showed that the effect of disorder significantly altered carbon ADP values and did not influence those of the gold atom

Synthesis, Structure and Bonding Analysis of the Zwitterionic PPP-Pincer Complex (6-Ph2P-Ace-5-)2P(O)AuCl2

The reaction of (6-Ph2P-Ace-5-)2P(O)H with (tht)AuCl3proceeds via elimination oftetrahydrothiophene (tht) and HCl, providing the zwitterionic PPP-pincer complex (6-Ph2P-Ace-5-)2P(O)AuCl2(1) as yellow crystals. The molecular structure of1was established and studied by X-raycrystallography. The electronic structure was computationally analyzed using a comprehensiveset of real-space bonding indicators derived from electron and electron-pair densities, providinginsight into the relative contributions of covalent and non-covalent forces to the polar-covalent Au–Cl,Au–P, and P–O−bonds; the latter being one of the textbook cases for strongly polarized covalentinteractions. Partial spatial complementarity between both bonding aspects is suggested by theelectronic properties of the distinctively different Au–Cl bonds

Lewis Superacidic Divalent Bis( m ‐terphenyl)element Cations [(2,6‐Mes 2 C 6 H 3 ) 2 E] + of Group 13 Revisited and Extended (E=B, Al, Ga, In, Tl)

In a combined experimental and computational study, the molecular and electronic structures of the divalent bis(m- terphenyl)element cations [(2,6-Mes2C6H3)2E]+ of group 13 (1, E=B; 2, E=Al; 3, E=Ga; 4, E=In; 5, E=Tl) were investigated. The preparation and characterization of 2, 3 and 5 were previously reported by Wehmschulte’s (Organometallics 2004, 23, 1965– 1967; J. Am. Chem. Soc. 2003, 125, 1470–1471) and our groups (Organometallics 2009, 28, 6893–6901). The indinium ion 4 was prepared and fully characterized for the first time. Attempts to prepare the borinium ion 1 by fluoride or hydride abstraction were unsuccessful. The electronic structures of 1–5 and the stabilization by the bulky m-terphenyl substituents were analyzed using quantum chemical calculations and compared to the divalent bis(m-terphenyl)pnictogenium ions [(2,6- Mes2C6H3)2E]+ of group 15 (6, E=P; 7, E=As; 8, E=Sb; 9, E=Bi) previously investigated by our group (Angew. Chem. Int. Ed. 2018, 57, 10080–10084). The calculated fluoride ion affinities (FIA) of 1–9 are higher than that of SbF5, which classifies them as Lewis superacids

Conformational trimorphism of bis(2,6-dimesitylphenyl)ditelluride

Besides the previously known α-form (monoclinic, P21/c, Z=4) of bis(2,6-dimesitylphenyl)ditelluride, two new polymorphic modifications, namely the β-form (monoclinic, P21/c, Z=8) and the γ-form (triclinic, P1̅, Z=2), were obtained serendipitously during chemical reactions. In all three modifications, the individual molecules possess significantly different conformations and bond parameters, such as Te–Te bond lengths, C–Te–Te bond angles, C–Te–Te–C torsion angles and intramolecular Menshutkin interactions, which is also reflected in their non-covalent interactions with adjacent molecules in the crystal lattice via London dispersion and electrostatic forces. The interplay between intermolecular and intramolecular forces in these conformational polymorphs was investigated using quantum chemical calculations, which reveal that the β-form should be thermodynamically stable at absolute zero. In contrast, crystallization experiments and thermoanalytical investigations indicate that the α-form is stable at high temperatures and therefore, both forms might be related by enantiotropis

Bis(6-diphenylphosphino-acenaphth-5-yl)sulfoxide. A New Ligand for Late Transition Metal Complexes

The synthesis of the new ligand bis(6-diphenylphosphinoacenaphth-5-yl)sulfoxide, [6-(Ph2P)-5-Ace-6](2)-SO (1), is presented along with six transition metal complexes thereof, namely,1 center dot MCl (M = Rh, Cu, Ag, Au) and1 center dot MCl2(M = Ni, Pd). Within these novel complexes, close metal-sulfur distances are observed and the nature of the M-S coordination, as well as the response of the(+)S-O(-)bond, are investigated in detail with a set of spectroscopic, crystallographic and real-space bonding indicators

Accurate H-atom parameters for the two polymorphs of L-histidine at 5, 105 and 295 K

The crystal structure of the monoclinic polymorph of the primary amino acid l-histidine has been determined for the first time by single-crystal neutron diffraction, while that of the orthorhombic polymorph has been reinvestigated with an untwinned crystal, improving the experimental precision and accuracy. For each polymorph, neutron diffraction data were collected at 5, 105 and 295 K. Single-crystal X-ray diffraction experiments were also performed at the same temperatures. The two polymorphs, whose crystal packing is interpreted by intermolecular interaction energies calculated using the Pixel method, show differences in the energy and geometry of the hydrogen bond formed along the c direction. Taking advantage of the X-ray diffraction data collected at 5 K, the precision and accuracy of the new Hirshfeld atom refinement method implemented in NoSpherA2 were probed choosing various settings of the functionals and basis sets, together with the use of explicit clusters of molecules and enhanced rigid-body restraints for H atoms. Equivalent atomic coordinates and anisotropic displacement parameters were compared and found to agree well with those obtained from the corresponding neutron structural models