Theoretical methodologies have been employed to study [Mg,C,N,O] isomers, which are possible species of interstellar interest. It has been found that, at all levels of theory used, the most stable isomer is the magnesium isocyanate radical. The corresponding cyanate counterpart lies 15.8 kcal/mol, at the CCSD­(T) level of theory, above MgNCO. Other isomers, such as the magnesium fulminate radical, MgCNO, the magnesium isofulminate radical, MgONC, and the two compounds that arise from the insertion of the magnesium atom between either O–N or O–C bonds, namely, OMgNC and OMgCN, are located clearly higher in energy than MgNCO. The barrier for the MgOCN → MgNCO process has been calculated to be 4.6 kcal/mol, suggesting a slow rate for the isomerization reaction. To examine the bonding interactions in the different [Mg,C,N,O] isomers, a natural bond orbital analysis, together with a topological analysis of the electron density in the framework of Bader’s quantum theory of atoms in molecules, has been carried out. For the two lowest lying isomers, predictions for the thermodynamic stabilities and spectroscopic parameters, which could aid in the detection of these species, have been made. The infrared (IR) spectra of both MgNCO and MgOCN are dominated by intense bands associated with the σ-NCO asymmetric stretching mode, especially in the case of MgNCO. Both MgNCO and MgOCN have large dipole moments (4.84 and 7.59 D, respectively, at the CCSD/aug-cc-pVTZ level). These two factors will likely make observation of both systems easier with either space-based IR or ground-based sum-mm telescopes. The global analysis of the relative stabilities and spectroscopic parameters suggests two linear isomers, namely, MgNCO (2Σ+) and MgOCN (2Σ+), as possible candidates for laboratory and space detection.

A theoretical study of monoboronyls of different metals has been carried out. We have chosen Mg as representative of s-block elements, Al for the p-block, and Group 11 metals (Cu, Ag, and Au) for the d-block. Different behaviors are observed: bonding through the oxygen atom is preferred in the case of Al, for all Group 11 monoboronyls bonding through the boron atom prevails and both interactions give rise to almost isoenergetic compounds in the case of Mg. Predictions for the spectroscopic parameters relevant for rotational and vibrational spectroscopy of the different competitive species are provided. Al and Group 11 boronyls have relatively high dissociation energies, whereas Mg boronyl has moderate dissociation energy. The molecular structure of metal boronyls has been rationalized through an analysis of the bonding. The similarities and differences between metal boronyls and their isoelectronic cyanide analogues have been discussed. © 2017 Wiley Periodicals, Inc.

The structure and spectroscopic parameters of the most relevant [C,H,N,Zn] isomers have been studied employing high-level quantum chemical methods. For each isomer, we provide predictions for their molecular structure, thermodynamic stabilities as well as vibrational and rotational spectroscopic parameters which could eventually help in their experimental detection. In addition, we have carried out a detailed study of the bonding situations by means of a topological analysis of the electron density in the framework of the Bader's quantum theory of atoms in molecules.