H2S⋯Ag–I synthesized by a laser-ablation method and identified by its rotational spectrum

Equivalent and Complement of the ω-Bonding Model and Charge-Shift Bonding Model: A Natural Bond Orbital/Natural Resonance Theory/Atoms in Molecules Investigation via Cu/Ag/Au Bonding in BMX (B = H2O, H2S, NH3, and PH3; M = Cu, Ag, and Au; and X = F, Cl, Br, and I)

Chemical bonding is the language of logic for chemists. Two new resonance bonding models, ω-bonding and charge-shift (CS) bonding, are gaining popularity among chemists. This study investigated the Cu/Ag/Au bonding in BMX (B = H₂O, H₂S, NH₃, and PH₃; M = Cu, Ag, and Au; and X = F, Cl, Br, and I) complexes using natural bond orbital (NBO) analysis, natural resonance theory (NRT), and atoms in molecules (AIM) method. The main aim is to reveal the relation between ω-bonding model and CS bonding model via Cu/Ag/Au bonding. Our studies demonstrate that the Cu/Ag/Au bonds exhibit the characteristics of both ω-bonding and CS bonding. Further studies found that ω-bonding and CS bonding models are equivalent and complement each other in understanding the studied Cu/Ag/Au bonding. Another interesting finding is the implication of the omega symbol in the ω-bonding model. These findings could help to promote the communication and CS bonding understanding of many more similar ω-bonded complexes.

A theoretical investigation on Cu/Ag/Au bonding in XH2P⋯MY(X = H, CH3, F, CN, NO2; M = Cu, Ag, Au; Y = F, Cl, Br, I) complexes

Intermolecular interaction of XH₂P···MY (X = H, CH₃, F, CN, NO₂; M = Cu, Ag, Au; Y = F, Cl, Br, I) complexes was investigated by means of an ab initio method. The molecular interaction energies are in the order Ag < Cu < Au and increased with the decrease of R_P···M. Interaction energies are strengthened when electron-donating substituents X connected to XH₂P, while electron-withdrawing substituents produce the opposite effect. The strongest P···M bond was found in CH₃H₂P···AuF with -70.95 kcal/mol, while the weakest one was found in NO₂H₂P···AgI with -20.45 kcal/mol. The three-center/four-electron (3c/4e) resonance-type of P:-M-:Y hyperbond was recognized by the natural resonance theory and the natural bond orbital analysis. The competition of P:M-Y ↔ P-M:Y resonance structures mainly arises from hyperconjugation interactions; the bond order of b_P-M and b_M-Y is in line with the conservation of the idealized relationship b_P-M + b_M-Y ≈ 1. In all MF-containing complexes, P-M:F resonance accounted for a larger proportion which leads to the covalent characters for partial ionicity of MF. The interaction energies of these Cu/Ag/Au complexes are basically above the characteristic values of the halogen-bond complexes and close to the observed strong hydrogen bonds in ionic hydrogen-bonded species.

What's in a name? 'Coinage-metal' non-covalent bonds and their definition

Many complexes of the type BMX, (where B is a Lewis base such as H2, N2, ethyne, ethene, cyclopropane, H2O, H2S, PH3, or NH3, M is a coinage-metal atom Cu, Ag or Au, and X is a halogen atom) have now been characterised in the gas phase through their rotational spectra. It is pointed out that, for a given B, such complexes have angular geometries that are isomorphous with those of their hydrogen- and halogen-bonded counterparts BHX and BXY, respectively. Since the MX are, like the B, HX and XY referred to, closed-shell molecules, the complexes BMX also involve a non-covalent bond. Therefore, the name 'coinage-metal' bond is suggested for the non-covalent interaction in BMX, by analogy with hydrogen and halogen bonds. A generalised definition that covers all non-covalent bonds is also presented.

The covalent interaction between dihydrogen and gold: A rotational spectroscopic study of H2-AuCl

The pure rotational transitions of H2-AuCl have been measured using a pulsed-jet cavity Fourier transform microwave spectrometer equipped with a laser ablation source. The structure was found to be T-shaped, with the H-H bond interacting with the gold atom. Both 35Cl and 37Cl isotopologues have been measured for both ortho and para states of H2. Rotational constants, quartic centrifugal distortion constants, and nuclear quadrupole coupling constants for gold and chlorine have been determined. The use of the nuclear spin-nuclear spin interaction terms Daa, Dbb, and Dcc for H2 were required to fit the ortho state of hydrogen, as well as a nuclear-spin rotation constant Caa. The values of the nuclear quadrupole coupling constant of gold are χaa=-817.9929(35) MHz, χbb=504.0(27) MHz, and χcc=314.0(27). This is large compared to the eQq of AuCl, 9.63 312(13) MHz, which indicates a strong, covalent interaction between gold and dihydrogen.

Changes in the geometries of C₂H₂ and C₂H₄ on coordination to CuCl revealed by broadband rotational spectroscopy and ab-initio calculations

The molecular geometries of isolated complexes in which a single molecule of C2H4 or C2H2 is bound to CuCl have been determined through pure rotational spectroscopy and ab-initio calculations. The C2H2···CuCl and C2H4···CuCl complexes are generated through laser vaporization of a copper rod in the presence of a gas sample undergoing supersonic expansion and containing C2H2 (or C2H4), CCl4, and Ar. Results are presented for five isotopologues of C2H2···CuCl and six isotopologues of C2H4···CuCl. Both of these complexes adopt C(2v), T-shaped geometries in which the hydrocarbon binds to the copper atom through its π electrons such that the metal is equidistant from all H atoms. The linear and planar geometries of free C2H2 and C2H4, respectively, are observed to distort significantly on attachment to the CuCl unit, and the various changes are quantified. The ∠(*-C-H) parameter in C2H2 (where * indicates the midpoint of the C≡C bond) is measured to be 192.4(7)° in the r0 geometry of the complex representing a significant change from the linear geometry of the free molecule. This distortion of the linear geometry of C2H2 involves the hydrogen atoms moving away from the copper atom within the complex. Ab-initio calculations at the CCSD(T)(F12*)/AVTZ level predict a dihedral ∠(HCCCu) angle of 96.05° in C2H4···CuCl, and the experimental results are consistent with such a distortion from planarity. The bonds connecting the carbon atoms within each of C2H2 and C2H4, respectively, extend by 0.027 and 0.029 Å relative to the bond lengths in the isolated molecules. Force constants, k(σ), and nuclear quadrupole coupling constants, χ(aa)(Cu), [χ(bb)(Cu) - χ(cc)(Cu)], χ(aa)(Cl), and [χ(bb)(Cl) - χ(cc)(Cl)], are independently determined for all isotopologues of C2H2···CuCl studied and for four isotopologues of C2H4···CuCl.

A perspective on chemistry in transient plasma from broadband rotational spectroscopy

A review of recent experiments demonstrating the high value of broadband rotational spectroscopy applied to analyse molecular products of plasma chemistry.