Search Results (67)

As part of a systematic study on the structures of the mixed halide isothiocyanates, Sn^IIHal(NCS), their single crystals were grown and structurally characterized. For Hal = F (1), the SnClF structure type was confirmed, while with Hal = Cl (2), Br (3), and I (4), there are three isostructural compounds of a new structure type, and for Hal = Cl (5), there is a second modification of a third structure type. These structure types have been described with respect to the composition and coordination geometry of the first, second, and van der Waals crust coordination spheres and their dependence on the halogen size and thiocyanate binding modes. With respect to the first coordination spheres, all three structure types constitute one-dimensional coordination polymers. In 1, “ladder”-type double chains result from μ₃-bridging fluorine atoms, and in 2–4, single-chains built up from μ₂-halogen atoms are pairwise “zipper”-like interconnected via κ²NS-bridging NCS ligands, which manage the halogen-linked chain assembly in the double chains of 5. Based on the octet rule, short atom distances are interpreted in terms of 2c-2e and various (symmetrical, quasi-symmetrical, and asymmetrical) kinds of 3c-4e bonds. Weak contacts, the topology of which suggests the extension of the latter bonding concept, are identified as electron-deficient, bifurcated tetrel bonds. Full article

The nucleophilic addition of 3-(4-cyanopyridin-2-yl)-1,1-dimethylurea (1) to cis-[Pt(CNXyl)₂Cl₂] (2) gave a new cyclometallated compound 3. It was characterized by NMR spectroscopy (¹H, ¹³C, ¹⁹⁵Pt) and high-resolution mass spectrometry, as well as crystallized to obtain two crystalline forms (3 and 3·2MeCN), whose structures were determined by X-ray diffraction. In the crystalline structure of 3, two conformers (3A and 3B) were identified, while the structure 3·2MeCN had only one conformer 3A. The conformers differed by orientation of the N,N-dimethylcarbamoyl moiety relative to the metallacycle plane. In both crystals 3 and 3·2MeCN, the molecules of the Pt(II) complex are associated into supramolecular dimers, either {3A}₂ or {3B}₂, via stacking interactions between the planes of two metal centers, which are additionally supported by hydrogen bonding. The theoretical consideration, utilizing a number of computational approaches, demonstrates that the C···d_z²(Pt) interaction makes a significant contribution in the total stacking forces in the geometrically optimized dimer [3A]₂ and reveals the d_z²(Pt)→π*(PyCN) charge transfer (CT). The presence of such CT process allowed for marking the C···Pt contact as a new example of a rare studied phenomenon, namely, tetrel bonding, in which the metal site acts as a Lewis base (an acceptor of noncovalent interaction). Full article

A series of lead(II) complexes incorporating benzoate derivative ligands was prepared: [Pb(2MeOBz)₂]_n (1), [Pb(2MeOBz)₂(H₂O)]_n (2), [Pb₂(1,4Bzdiox)₄(DMSO)]_n (3), [Pb(1,4Bzdiox)₂(H₂O)]_n (4), [Pb(Pip)₂(H₂O)]_n (5), and [Pb(Ac)(Pip)₂(MeOH)]_n (6) (2MeOBz: 2-methoxybenzoate; 1,4Bzdiox: 1,4-benzodioxan-5-carboxylate; DMSO: dimethylsulfoxide; Ac: acetate; Pip: piperonylate; MeOH: methanol). All compounds were characterized via elemental analysis, ATR-FTIR spectroscopy, and powder XRD. In addition, the crystal structures of some compounds were elucidated. Compounds 1 and 2, involving 2-methoxybenzoate, were closely related, only differing in the presence of one extra aqua ligand found for the latter. However, this implies key changes in the studied properties, e.g., 2 shows solid-state luminescence that displays a different color as a function of the crystal orientation, while 1 does not. The crystal structure of 2 revealed a 1D coordination polymer. A similar relationship was found between compounds 3 and 4, incorporating 1,4-benzodioxan-5-carboxylate. In this pair, only 4, with aqua ligands, displayed a greenish-yellow-color solid-state luminescence. Furthermore, two new lead(II) piperonylate complexes, 5 and 6, were obtained from the reaction between lead(II) acetate and piperonylic acid. In water, all acetate ligands in the metal precursor were displaced and [Pb(Pip)₂(H₂O)]_n (5) was isolated, while in methanol, a mixed acetate–piperonylate complex, [Pb(Ac)(Pip)₂(MeOH)]_n (6), was precipitated. Considering only conventional Pb-O bonds, the crystal structure of 6 was described as a 1D coordination polymer, although, additionally, the chains were associated via tetrel bonds, defining an extended 2D architecture. Full article

The tetrel bond between PhXF₂Y(TF₃) (T = C and Si; X = Cl, Br, and I; Y = F and Cl) and the electron donor MCN (M = Li and Na) was investigated at the M06-2X/aug-cc-pVDZ level of theory. As the electronegativity of the halogen atom X increases, the strength of the tetrel bond also increases, but as the electronegativity of the halogen atom Y increases, the strength of the tetrel bond decreases. The magnitude of the interaction energy in most –CF₃ complexes was found to be less than 10 kcal/mol, but to exceed 11 kcal/mol for PhClF₂Cl(CF₃)⋯NCNa. The tetrel bond is greatly enhanced when the –SiF₃ group interacts with LiCN or NaCN, with the largest interaction energy approaching 100 kcal/mol and displaying a covalent Si⋯N interaction. Along with this enhancement, the Si⋯N distance was found to be less than the X–Si bond length, the –SiF₃ group to be closer to the N atom, and in most –SiF₃ systems, the X–Si–F angle to be less than 90°; the –SiF₃ group therefore undergoes inversion and complete transfer in some systems. Full article

The tetrel bond (TB) between 1,2-benzisothiazol-3-one-2-TF₃-1,1-dioxide (T = C, Si) and the O atom of pyridine-1-oxide (PO) and its derivatives (PO-X, X = H, NO₂, CN, F, CH₃, OH, OCH₃, NH₂, and Li) is examined by quantum chemical means. The Si∙∙∙O TB is quite strong, with interaction energies approaching a maximum of nearly 70 kcal/mol, while the C∙∙∙O TB is an order of magnitude weaker, with interaction energies between 2.0 and 2.6 kcal/mol. An electron-withdrawing substituent on the Lewis base weakens this TB, while an electron-donating group has the opposite effect. The SiF₃ group transfers roughly halfway between the N of the acid and the O of the base without the aid of cooperative effects from a third entity. Full article

The structural stability of the extensively studied organic–inorganic hybrid methylammonium tetrel halide perovskite semiconductors, MATtX₃ (MA = CH₃NH₃⁺; Tt = Ge, Sn, Pb; X = Cl, Br, I), arises as a result of non-covalent interactions between an organic cation (CH₃NH₃⁺) and an inorganic anion (TtX₃⁻). However, the basic understanding of the underlying chemical bonding interactions in these systems that link the ionic moieties together in complex configurations is still limited. In this study, ion pair models constituting the organic and inorganic ions were regarded as the repeating units of periodic crystal systems and density functional theory simulations were performed to elucidate the nature of the non-covalent interactions between them. It is demonstrated that not only the charge-assisted N–H···X and C–H···X hydrogen bonds but also the C–N···X pnictogen bonds interact to stabilize the ion pairs and to define their geometries in the gas phase. Similar interactions are also responsible for the formation of crystalline MATtX₃ in the low-temperature phase, some of which have been delineated in previous studies. In contrast, the Tt···X tetrel bonding interactions, which are hidden as coordinate bonds in the crystals, play a vital role in holding the inorganic anionic moieties (TtX₃⁻) together. We have demonstrated that each Tt in each [CH₃NH₃⁺•TtX₃⁻] ion pair has the capacity to donate three tetrel (σ-hole) bonds to the halides of three nearest neighbor TtX₃⁻ units, thus causing the emergence of an infinite array of 3D TtX₆⁴⁻ octahedra in the crystalline phase. The TtX₄⁴⁻ octahedra are corner-shared to form cage-like inorganic frameworks that host the organic cation, leading to the formation of functional tetrel halide perovskite materials that have outstanding optoelectronic properties in the solid state. We harnessed the results using the quantum theory of atoms in molecules, natural bond orbital, molecular electrostatic surface potential and independent gradient models to validate these conclusions. Full article

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. Full article

The ion pairs [Cs⁺•TtX₃⁻] (Tt = Pb, Sn, Ge; X = I, Br, Cl) are the building blocks of all-inorganic cesium tetrel halide perovskites in 3D, CsTtX₃, that are widely regarded as blockbuster materials for optoelectronic applications such as in solar cells. The 3D structures consist of an anionic inorganic tetrel halide framework stabilized by the cesium cations (Cs⁺). We use computational methods to show that the geometrical connectivity between the inorganic monoanions, [TtX₃⁻]_∞, that leads to the formation of the TtX₆⁴⁻ octahedra and the 3D inorganic perovskite architecture is the result of the joint effect of polarization and coulombic forces driven by alkali and tetrel bonds. Depending on the nature and temperature phase of these perovskite systems, the Tt···X tetrel bonds are either indistinguishable or somehow distinguishable from Tt–X coordinate bonds. The calculation of the potential on the electrostatic surface of the Tt atom in molecular [Cs⁺•TtX₃⁻] provides physical insight into why the negative anions [TtX₃⁻] attract each other when in close proximity, leading to the formation of the CsTtX₃ tetrel halide perovskites in the solid state. The inter-molecular (and inter-ionic) geometries, binding energies, and charge density-based topological properties of sixteen [Cs⁺•TtX₃⁻] ion pairs, as well as some selected oligomers [Cs⁺•PbI₃⁻]_n (n = 2, 3, 4), are discussed. Full article

We report a broad theoretical study on [(PMe₃)₃MER]⁺ complexes, with M = Ni, Pd, Pt, E = C, Si, Ge, Sn, Pb, and R = Ar^Mes, Tbb, (Ar^Mes = 2,6-dimesitylphenyl; Tbb = C₆H₂-2,6-[CH(SiMe₃)₂]₂-4-^tBu). A few years ago, our group succeeded in obtaining heavier homologues of cationic group 10 carbyne complexes via halide abstraction of the tetrylidene complexes [(PMe₃)₃M=E(X)R] (X = Cl, Br) using a halide scavenger. The electronic structure and the M-E bonds of the [(PMe₃)₃MER]⁺ complexes were analyzed utilizing quantum-chemical tools, such as the Pipek–Mezey orbital localization method, the energy decomposition analysis (EDA), and the extended-transition state method with natural orbitals of chemical valence (ETS-NOCV). The carbyne, silylidyne complexes, and the germylidyne complex [(PMe₃)₃NiGeAr^Mes]⁺ are suggested to be tetrylidyne complexes featuring donor–acceptor metal tetrel triple bonds, which are composed of two strong π(M→E) and one weaker σ(E→M) interaction. In comparison, the complexes with M = Pd, Pt; E = Sn, Pb; and R = Ar^Mes are best described as metallotetrylenes and exhibit considerable M−E−C bending, a strong σ(M→E) bond, weakened M−E π-components, and lone pair density at the tetrel atoms. Furthermore, bond cleavage energy (BCE) and bond dissociation energy (BDE) reveal preferred splitting into [M(PMe₃)₃]⁺ and [ER] fragments for most complex cations in the range of 293.3–618.3 kJ·mol⁻¹ and 230.4–461.6 kJ·mol⁻¹, respectively. Finally, an extensive study of the potential energy hypersurface varying the M−E−C angle indicates the presence of isomers with M−E−C bond angles of around 95°. Interestingly, these isomers are energetically favored for M = Pd, Pt; E = Sn, Pb; and R = Ar^Mes over the less-bent structures by 13–29 kJ·mol⁻¹. Full article

The dual binding behavior of the metallylenes TH₂ (T = Si, Ge, Sn, Pb) with some selected Lewis acids (T’H₃F, T’ = Si, Ge, Sn, Pb) and bases (N₂, HCN, CO, and C₆H₆) has been investigated by using the high-level quantum chemical method. Two types (type-A and type-B) of tetrel-bonded complexes can be formed for TH₂ due to their ambiphilic character. TH₂ act as Lewis bases in type-A complexes, and they act as Lewis acids in type-B ones. CO exhibits two binding modes in the type-B complexes, one of which is TH₂···CO and the other is TH₂···OC. The TH₂···OC complexes possess a weaker binding strength than the other type-B complexes. The TH₂···OC complexes are referred to as the type-B2 complexes, and the other type-B complexes are referred to as the type-B1 complexes. The type-A complexes exhibit a relatively weak binding strength with E_int (interaction energy) values ranging from –7.11 to –15.55 kJ/mol, and the type-B complexes have a broad range of E_int values ranging from −9.45 to −98.44 kJ/mol. The E_int values of the type-A and type-B1 complexes go in the order SiH₂ > GeH₂ > SnH₂ > PbH₂. The AIM (atoms in molecules) analysis suggests that the tetrel bonds in type-A complexes are purely closed-shell interactions, and those in most type-B1 complexes have a partially covalent character. The EDA (Energy decomposition analysis) results indicate that the contribution values of the three energy terms go in the order electrostatic > dispersion > induction for the type-A and type-B2 complexes, and this order is electrostatic > induction > dispersion for the type-B1 complexes. Full article

In this manuscript substituent effects in several silicon tetrel bonding (TtB) complexes were investigated at the RI-MP2/def2-TZVP level of theory. Particularly, we have analysed how the interaction energy is influenced by the electronic nature of the substituent in both donor and acceptor moieties. To achieve that, several tetrafluorophenyl silane derivatives have been substituted at the meta and para positions by several electron donating and electron withdrawing groups (EDG and EWG, respectively), such as –NH₂, –OCH₃, –CH₃, –H, –CF₃ and –CN substituents. As electron donor molecules, we have used a series of hydrogen cyanide derivatives using the same EDGs and EWGs. We have obtained the Hammett’s plots for different combinations of donors and acceptors and in all cases we have obtained good regression plots (interaction energies vs. Hammet’s σ parameter). In addition, we have used the electrostatic potential (ESP) surface analysis as well as the Bader’s theory of atoms in molecules (AIM) and noncovalent interaction plot (NCI plot) techniques to further characterize the TtBs studied herein. Finally, a Cambridge Structural Database (CSD) inspection was carried out, retrieving several structures where halogenated aromatic silanes participate in tetrel bonding interactions, being an additional stabilization force of their supramolecular architectures. Full article

Twenty-five molecule–anion complex systems [I₄Tt···X⁻] (Tt = C, Si, Ge, Sn and Pb; X = F, Cl, Br, I and At) were examined using density functional theory (ωB97X-D) and ab initio (MP2 and CCSD) methods to demonstrate the ability of the tetrel atoms in molecular entities, I₄Tt, to recognize the halide anions when in close proximity. The tetrel bond strength for the [I₄C···X⁻] series and [I₄Tt···X⁻] (Tt = Si, Sn; X = I, At), was weak-to-moderate, whereas that in the remaining 16 complexes was dative tetrel bond type with very large interaction energies and short Tt···X close contact distances. The basis set superposition error corrected interaction energies calculated with the highest-level theory applied, [CCSD(T)/def2-TZVPPD], ranged from −3.0 to −112.2 kcal mol⁻¹. The significant variation in interaction energies was realized as a result of different levels of tetrel bonding environment between the interacting partners at the equilibrium geometries of the complex systems. Although the ωB97X-D computed intermolecular geometries and interaction energies of a majority of the [I₄Tt···X⁻] complexes were close to those predicted by the highest level of theory, the MP2 results were shown to be misleading for some of these systems. To provide insight into the nature of the intermolecular chemical bonding environment in the 25 molecule–anion complexes investigated, we discussed the charge-density-based topological and isosurface features that emanated from the application of the quantum theory of atoms in molecules and independent gradient model approaches, respectively. Full article

The effects of Lewis basicity and acidity on σ-hole interactions were investigated using two sets of carbon-containing complexes. In Set I, the effect of Lewis basicity was studied by substituting the X₃/X atom(s) of the NC-C₆H₂-X₃ and NCX Lewis bases (LB) with F, Cl, Br, or I. In Set II, the W-C-F₃ and F-C-X₃ (where X and W = F, Cl, Br, and I) molecules were utilized as Lewis acid (LA) centers. Concerning the Lewis basicity effect, higher negative interaction energies (E_int) were observed for the F-C-F₃∙∙∙NC-C₆H₂-X₃ complexes compared with the F-C-F₃∙∙∙NCX analogs. Moreover, significant E_int was recorded for Set I complexes, along with decreasing the electron-withdrawing power of the X₃/X atom(s). Among Set I complexes, the highest negative E_int was ascribed to the F-C-F₃∙∙∙NC-C₆H₂-I₃ complex with a value of −1.23 kcal/mol. For Set II complexes, E_int values of F-C-X₃ bearing complexes were noted within the −1.05 to −2.08 kcal/mol scope, while they ranged from −0.82 to −1.20 kcal/mol for the W-C-F₃ analogs. However, V_s,max quantities exhibited higher values in the case of W-C-F₃ molecules compared with F-C-X₃; preferable negative E_int were ascribed to the F-C-X₃ bearing complexes. These findings were delineated as a consequence of the promoted contributions of the X₃ substituents. Dispersion forces (E_disp) were identified as the dominant forces for these interactions. The obtained results provide a foundation for fields such as crystal engineering and supramolecular chemistry studies that focus on understanding the characteristics of carbon-bearing complexes. Full article

The co-crystallization of the lead(II) complex [Pb(S₂CNEt₂)₂] with tetraiodoethylene (C₂I₄) gave the co-crystal, [Pb(S₂CNEt₂)₂]∙½C₂I₄, whose X-ray structure exhibits only a small change of the crystal parameters than those in the parent [Pb(S₂CNEt₂)₂]. The supramolecular organization of the co-crystal is largely determined by an interplay between Pb⋯S tetrel bonding (TeB) and I⋯S halogen bonding (HaB) with comparable contributions from these non-covalent contacts; the TeBs observed in the parent complex, [Pb(S₂CNEt₂)₂], remain unchanged in the co-crystal. An analysis of the theoretical calculation data, performed for the crystal and cluster models of [Pb(S₂CNEt₂)₂]∙½C₂I₄, revealed the non-covalent nature of the Pb⋯S TeB (−5.41 and −7.78 kcal/mol) and I⋯S HaB (−7.26 and −11.37 kcal/mol) interactions and indicate that in the co-crystal these non-covalent forces are similar in energy. Full article