An iron(II) complex of trans, trans, trans-bis(azido)bis(4-amino-3,5-bis(2-pyridyl)-1,2,4-triazole): Insight into molecular and supramolecular structures using Hirshfeld surface analysis and DFT studies

Bis(azido-κN)bis-(quinolin-8-amine-κ2 N,N')iron(II) monohydrate

In the hydrated title complex, [Fe(N3)2(AQ)2]·H2O (AQ is 8-amino-quinoline, C9H9N2), the FeII ion is coordinated in a distorted octa-hedral manner by two neutral, chelating AQ ligands and two anionic, monodentate azide (N3 -) ions in a syn,cis-configuration. From the two AQ ligands, the pyridyl N atoms are opposite to each other and the amino groups trans to the azide ligands. Distortion results from different Fe-N bond lengths [2.112 (2)-2.231 (2) Å] and 〈(N-Fe-N) cis [75.25 (6)-99.91 (7)°] and 〈(N-Fe-N) trans [159.98 (7)-170.62 (7)°] bond angles. The water mol-ecule acts as the acceptor of hydrogen bonds with the NH2 groups of both AQ-ligands in one and the same mol-ecule, and as donor to the γ-N and α-N atoms of the azido ligands of two adjacent iron complexes. In addition, both terminal N atoms of the azido ligands are involved in hydrogen bonds with NH2 groups in neighboring iron complexes, so that the hydrogen-bonding pattern leads to a rod-like arrangement of the mol-ecules in the b-axis direction.

Bis(azido-κN 1)bis-(2,2'-di-pyridyl-amine-κ2 N 1,N 1')iron(II) monohydrate

In the hydrated title complex, [Fe(dpa)2(N3)2]·H2O (dpa is 2,2'-di-pyridyl-amine, C10H9N3), the FeII ion is coordinated in a distorted octa-hedral manner by two neutral, chelating dpa ligands and two anionic, monodentate azide (N3 -) ions in a cis-configuration. Distortion results from different Fe-N bond lengths [2.1397 (13)-2.2254 (12) Å] and (N-Fe-N) cis [80.12 (4)-96.72 (5)°] and (N-Fe-N) trans [166.73 (4)-176.62 (5)°] bond angles. Hydrogen bonds exist between two symmetry-related water mol-ecules as hydrogen donors to the γ-N atoms of azido ligands of two adjacent iron complexes and as acceptors from the amide group of the dpa ligands of two additional iron complexes. The hydrogen-bonding pattern results in eight-membered ⋯H-O-H⋯N⋯ rings and a band-like arrangement of the mol-ecules involved. Additional, weaker hydrogen bonds between the α-N atom of the second azido ligand as acceptors and the amide groups of the second dpa ligands as donors cross-link neighboring bands to layers extending parallel to (001).

Azido-mediated intermolecular interactions of transition metal complexes

The coordinated azido ligand has a variety of ways to establish intermolecular contacts whose nature is computationally analysed in this work on dimers of the [N3-Hg(CF3)] complex with different interactions involving only N⋯N contacts, or with an additional Hg⋯N contact. The applied tools include the molecular electrostatic map of the monomer, an energy decomposition analysis (EDA), a topological AIM analysis of the electron density and the study of NCI (non-covalent interactions) isosurfaces. The interactions between two azido ligands are found to be weakly stabilizing (by 0.2 to 2.7 kcal mol-1), topology-dependent and require dispersion forces to complement orbital and electrostatic stabilization. Those interactions are supplemented by the formation of simultaneous Hg⋯N secondary interactions by about -1 kcal mol-1, and by the ability of the monomer to simultaneously interact with several neighbours in the crystal structure.

Static and Dynamical Quantum Studies of CX3-AlX2 and CSiX3-BX2 (X = F, Cl, Br) Complexes with Hydrocyanic Acid: Unusual Behavior of Strong π-Hole at Triel Center

The set of TX₃-TrX₂ (T = C, Si, Ge; Tr = B, Al, Ga; X = F, Cl, Br) molecules offers a rather unique opportunity to study both σ-hole and π-hole dimerization on the tetrel and triel ends, respectively. According to the molecular electrostatic potential (MEP) distribution, the π-hole extrema (acidic sites) were more intense than their σ-hole counterparts. The molecules owning the most (CX₃-AlX₂) and least (SiX₃-BX₂) intense π-holes were chosen to evaluate their capacities to attract one and two HCN molecules (Lewis bases). We discovered that the energetic characteristics of π-hole dimers severely conflict with the monomers MEP pattern since the weakest π-hole monomer forms a dimer characterized by interaction energy compared to those created by the monomers with noticeably greater power in the π-hole region. This outcome is due to the deformation of the weakest π-hole donor. Furthermore, the MEP analysis for monomers in the geometry of respective dimers revealed a "residual π-hole" site that was able to drive second ligand attachment, giving rise to the two "unusual trimers" examined further by the NCI and QTAIM analyses. Apart from them, the π-hole/π-hole and σ-hole/π-hole trimers have also been obtained throughout this study and described using energetic and geometric parameters. The SAPT approach revealed details of the bonding in one of the "unusual trimers". Finally, Born-Oppenheimer Molecular Dynamics (BOMD) simulations were carried out to investigate the time evolution of the interatomic distances of the studied complexes as well as their stability.