Selenium(IV) Polybromide Complexes: Structural Diversity Driven by Halogen and Chalcogen Bonding

Reactions between bromoselenate(IV)-containing solutions, dibromine and salts of pyridinium-family organic cations resulted in structurally diverse, bromine-rich polybromine-bromoselenates(IV): (4-MePyH)₅[Se₂Br₉][SeBr₆](Br₃)₂ (1), (2-MePyH)₂{[SeBr₆](Br₂)} (2), (PyH)₂{[SeBr₅]Br(Br₂)₂} (3), (1-MePy)₂{[SeBr₆](Br₂)} (4). The compounds feature halogen and (in the case of 3) chalcogen bonding in solid state, resulting in formation of supramolecular architectures of different dimensionality. DFT calculations allowed estimation of the energies of non-covalent interactions in 1–4; additionally, characterization by Raman spectroscopy was performed.

Translational dependence of the geometry of metallic mono- and bilayers optimized on semi-ionic supports: the cases of Pd on γ-Al2O3(110), monoclinic ZrO2(001), and rutile TiO2(001)

Geometries and cohesion energies while shifting (by 1 Å)/optimizing the Pd24 monolayer (2 × 2 unit cells) at γ-Al2O3(110) along the OX axis.

Oxochloroselenate(IV) with Incorporated {Cl2 }: The Case of Strong Cl⋅⋅⋅Cl Halogen Bonding

Reaction of SeO₂ , tetramethylammonium (TMA) chloride, aqueous HCl and Cl₂ yields oxochloroselenate with incorporated Cl₂ units, TMA₃ {[Se₂ O₂ Cl₇ ](Cl₂ )}. The main feature of this compound is the strong (up to 3.5 kcal mol^-1 , according to DFT calculations) Cl⋅⋅⋅Cl bonding, which is also detected by Raman spectroscopy.

Attractive fluorine···fluorine interactions between perfluorinated alkyl chains: a case of perfluorinated Cu(II) diiminate Cu[C2F5–C(NH)–CF=C(NH)–CF3]2

A synthesis of the perfluorinated copper diiminate complex Cu[C2F5–C(NH)–CF=C(NH)–CF3]2 (3) and its self-assembly into infinite 1D chains in the crystal via Type II C(sp3)–F···F–C(sp3) contacts between perfluoroethyl substituents is reported. Rare Type II F···F interactions were studied by DFT calculations and topological analysis of the electron density distribution within the formalism of Bader’s theory (QTAIM method). This is the first report which discusses Type II contacts between perfuoroalkyl chains.

Rule, Not Exclusion: Formation of Dichlorine-Containing Supramolecular Complexes with Chlorometalates(IV)

Supramolecular derivatives of chlorostannate(IV) and -plumbate(IV) with {Cl₂} units, Cat₂{[MCl₆](Cl₂)_x} (1-5; M = Sn, Pb, cat = 1-methylpyridinium (1-MePy), tetramethylammonium (TMA)) were prepared and characterized by X-ray diffractometry and Raman spectroscopy. In particular, the TMA-containing complexes demonstrate remarkable thermal stability, releasing Cl₂ only at elevated temperatures.

Opening the Third Century of Polyhalide Chemistry: Thermally Stable Complex with "Trapped" Dichlorine

Unlike polyhalides of heavier halogens, polychlorides still remain exotic curiosities. Herein, we report preparation and investigation of complexes Cat₂ {[TeCl₆ ](Cl₂ )} (cat=1-methylpyridinium (1) and tetramethylammonium (2)) where dichlorine units are "trapped" by chlorotellurate(IV) anions via a system of non-covalent Cl⋅⋅⋅Cl interactions. Complex 2 reveals a record thermal stability (>100 °C) for inclusion compounds with Cl₂ , indications that such compounds can be used as solid Cl₂ source.

Halogenated Diazabutadiene Dyes: Synthesis, Structures, Supramolecular Features, and Theoretical Studies

Novel halogenated aromatic dichlorodiazadienes were prepared via copper-mediated oxidative coupling between the corresponding hydrazones and CCl₄. These rare azo-dyes were characterized using ¹H and ¹³C NMR techniques and X-ray diffraction analysis for five halogenated dichlorodiazadienes. Multiple non-covalent halogen···halogen interactions were detected in the solid state and studied by DFT calculations and topological analysis of the electron density distribution within the framework of Bader’s theory (QTAIM method). Theoretical studies demonstrated that non-covalent halogen···halogen interactions play crucial role in self-assembly of highly polarizable dichlorodiazadienes. Thus, halogen bonding can dictate a packing preference in the solid state for this class of dichloro-substituted heterodienes, which could be a convenient tool for a fine tuning of the properties of this novel class of dyes.

Attractive halogen···halogen interactions in crystal structure of trans-dibromogold(III) complex

A synthesis of the trans-dibromogold(III) t-Bu-Xantphos complex and its self-assembly into infinite 1-dimensional chain in the solid state is reported. The new complex characterized using elemental analyses (C, H, N), ESI-MS, 1H and 13C NMR techniques and X-ray diffraction analysis. Results of DFT calculations followed by the topological analysis of the electron density distribution within the framework of QTAIM method at the ωB97XD/DZP-DKH level of theory reveal that strength of attractive intermolecular non-covalent interactions Br···Br in the crystal is 1.2–1.6 kcal/mol.

Anion–Cation Recognition Pattern, Thermal Stability and DFT-Calculations in the Crystal Structure of H2dap[Cd(HEDTA)(H2O)] Salt (H2dap = H2(N3,N7)-2,6-Diaminopurinium Cation)

The proton transfer between equimolar amounts of [Cd(H2EDTA)(H2O)] and 2,6-diaminopurine (Hdap) yielded crystals of the out-of-sphere metal complex H2(N3,N7)dap[Cd(HEDTA)(H2O)]·H2O (1) that was studied by single-crystal X-ray diffraction, thermogravimetry, FT-IR spectroscopy, density functional theory (DFT) and quantum theory of “atoms-in-molecules” (QTAIM) methods. The crystal was mainly dominated by H-bonds, favored by the observed tautomer of the 2,6-diaminopurinium(1+) cation. Each chelate anion was H-bonded to three neighboring cations; two of them were also connected by a symmetry-related anti-parallel π,π-staking interaction. Our results are in clear contrast with that previously reported for H2(N1,N9)ade [Cu(HEDTA)(H2O)]·2H2O (EGOWIG in Cambridge Structural Database (CSD), Hade = adenine), in which H-bonds and π,π-stacking played relevant roles in the anion–cation interaction and the recognition between two pairs of ions, respectively. Factors contributing in such remarkable differences are discussed on the basis of the additional presence of the exocyclic 2-amino group in 2,6-diaminopurinium(1+) ion.

Structural, Non-Covalent Interaction, and Natural Bond Orbital Studies on Bromido-Tricarbonyl Rhenium(I) Complexes Bearing Alkyl-Substituted 1,4-Diazabutadiene (DAB) Ligands

The synthesis, characterization, structural and computational studies of Re(I) tricarbonyl bromo complexes bearing alkyl-substituted 1,4-diazabutadiene ligands, [Re(CO)3(1,4-DAB)Br], where 1,4-DAB = N,N-bis(2,4-dimethylbenzene)-1,4-diazabutadiene, 2,4-Me2DAB (1); N,N-bis(2,4-dimethylbenzene)-2,3-dimethyl-1,4-diazabutadiene, 2,4-Me2DABMe (2); N,N-bis(2,4,6-trimethylbenzene)-1,4-diazabutadiene, 2,4,6-Me3DAB (3); and N,N-bis(2,6-diisopropylbenzene)-1,4-diazabutadiene, 2,6-ipr2DAB (4) are reported. The complexes were characterized by different spectroscopic methods such as FT-IR, 1H-NMR, 13C-NMR, and elemental analyses and their solid-state structures were confirmed by X-ray diffraction. In each complex, the Re(I) centre shows a distorted octahedral shape with a facial geometry of carbonyl groups. The gas phase geometry of the complexes was identified by density functional theory. Interesting intermolecular n…π* interactions of complexes 1 and 3 were investigated by non-covalent interaction index (NCI), and natural bond orbital (NBO) analyses. The intramolecular n…σ*, σ…π*, π…σ* interactions were also studied in complexes 3 and 4.

[{AgL}2Mo8O26]n– complexes: a combined experimental and theoretical study

Two sets of silver–molybdate complexes with L = XR₃ (X = P, As, Sb; R₃ = Ph₃, Ph₂Py) and functionalized pyridine-based ligands have been studied with different techniques.

Existence of untypical halogen-involving interactions in crystal packings: a statistical and first-principles study

There is a common perception by the scientific community that a halogen-involving interaction forms when the distance between the donor atom and the acceptor atom is less than the sum of their van der Waals (vdW) radii.

Chlorotellurate(iv) supramolecular associates with “trapped” Br2: features of non-covalent halogen⋯halogen interactions in crystalline phases

Reactions of chlorotellurates(iv) and Br₂ afford formation of supramolecular complexes Cat₂{[TeCl₆](Br₂)} (Cat = Me₃N⁺ (1), PyH⁺ (2), 4-MePyH⁺ (3) and 1-MePy⁺ (4)) where dibromine fragments are “trapped” by [TeCl₆]³⁻via Br⋯Cl halogen bonding.

Isomorphic substitution in molecular crystals and geometry of hypervalent tellurium: comments inspired by a case study of RMeTeI2 and [RMe2Te]+I− (R = Ph, Fc)

Unusual isomorphic substitution in the crystals of [FcMe₂Te]⁺I⁻ with an admixture of Te–I ionized [FcMeTeI⁺]I⁻ supports the 3c-4e as a general, seamless bonding model for the hypervalent tellurium in both the isolated molecules and crystals.

Halogen bonding in the structures of pentaiodobenzoic acid and its salts

Structural characterization of pentaiodobenzoic acid (PIBA) and its salts was performed for the first time.

Ligation-Enhanced π-Hole···π Interactions Involving Isocyanides: Effect of π-Hole···π Noncovalent Bonding on Conformational Stabilization of Acyclic Diaminocarbene Ligands

The reaction of cis-[PdCl₂(CNXyl)₂] (Xyl = 2,6-Me₂C₆H₃) with the aminoazoles [1 H-imidazol-2-amine (1), 4 H-1,2,4-triazol-3-amine (2), 1 H-tetrazol-5-amine (3), 1 H-benzimidazol-2-amine (4), 1-alkyl-1 H-benzimidazol-2-amines, where alkyl = Me (5), Et (6)] in a 2:1 ratio in the presence of a base in CHCl₃ at RT proceeds regioselectively and leads to the binuclear diaminocarbene complexes [(ClPdCNXyl)₂{μ-C(N-azolyl)N(Xyl)C═NXyl}] (7-12; 73-91%). Compounds 7-12 were characterized by C, H, N elemental analyses, high-resolution ESI⁺-MS, Fourier transform infrared spectroscopy, 1D (¹H, ¹³C) and 2D (¹H,¹H-COSY, ¹H,¹H-NOESY, ¹H,¹³C-HSQC, ¹H,¹³C-HMBC) NMR spectroscopies, and X-ray diffraction (XRDn). Inspection of the XRDn data and results of the Hirshfeld surface analysis suggest the presence in all six structures of intramolecular π-hole_isocyanide···π_arene interactions between the electrophilic C atom of the isocyanide moiety and the neighboring arene ring. These interactions also result in distortion of the Pd-C≡N-Xyl fragment from the linearity. Results of density functional theory calculations [M06/MWB28 (Pd) and 6-31G* (other atoms) level of theory] for model structures of 7-9 followed by the topological analysis of the electron density distribution within the framework of Bader's theory (QTAIM method) reveal the presence of these weak interactions also in a CHCl₃ solution, and their calculated strength is 1.9-2.2 kcal/mol. The natural bond orbital analysis of 7-9 revealed that π(C-C)Xyl → π*(C-N)isocyanide charge transfer (CT) takes place along with the intramolecular π-hole_isocyanide···π_arene interactions. The observed π(C-C)_Xyl → π*(C-N)_isocyanide CT is due to ligation of the isocyanide to the metal center, whereas in the cases of the uncomplexed p-CNC₆H₄NC and CNXyl species, the effects of CT are negligible. Available CCDC data were processed from the perspective of isocyanide-involving π-hole···π interactions, disclosed the role of metal coordination in the π-hole donor ability of isocyanides, and verified the π-hole_isocyanide···π_arene interaction effect on the stabilization of the in-conformation in metal-bound acyclic diaminocarbenes.

Redox reactive (RNC)CuII species stabilized in the solid state via halogen bond with I2

The crystal structure of [Cu2(μ-O)(μ-I)2(CNXyl)4]·I2 (2·I2) was determined from single-crystal X-ray diffraction data. The adduct 2·I2 represents the first example of structurally characterized isocyanide-copper(II) complexes. In the structure of 2·I2, 2 forms independent chains connected through molecular iodine via I···I–I···I halogen bonding. The DFT calculations and topological analysis of the electron density distribution within the formalism of Bader’s theory (QTAIM method) were performed for model complex 2·I2 and the obtained results allowed the attribution of these contacts to moderate strength (3.8–5.3 kcal/mol) non-covalent contacts exhibiting some covalent character.

Effect of geometry factors on the priority of σ-hole⋯π and π-hole⋯π bond in phosphorescent cocrystals formed by pyrene or phenanthrene and trihaloperfluorobenzenes

The effect of geometric factors on the assembly of luminescent cocrystals between pyrene or phenanthrene and trihaloperfluorobenzenes.