Reactions of pyridyl donors with halogens and interhalogens: an X-ray diffraction and FT-Raman investigation

An Experimental and Theoretical Insight into I2 /Br2 Oxidation of Bis(pyridin-2-yl)Diselane and Ditellane

The reactivity between bis(pyridin-2-yl)diselane o Py2 Se2 and ditellane o Py2 Te2 (L1 and L2, respectively; o Py=pyridyn-2-yl) and I2 /Br2 is discussed. Single-crystal structure analysis revealed that the reaction of L1 with I2 yielded [(HL1+ )(I- )⋅5/2I2 ]∞ (1) in which monoprotonated cations HL1+ template a self-assembled infinite pseudo-cubic polyiodide 3D-network, while the reaction with Br2 yielded the dibromide Ho PySeII Br2 (2). The oxidation of L2 with I2 and Br2 yielded the compounds Ho PyTeII I2 (3) and Ho PyTeIV Br4 (6), respectively, whose structures were elucidated by X-ray diffraction analysis. FT-Raman spectroscopy measurements are consistent with a 3c-4e description of all the X-Ch-X three-body systems (Ch=Se, Te; X=Br, I) in compounds 2, 3, Ho PyTeII Br2 (5), and 6. The structural and spectroscopic observations are supported by extensive theoretical calculations carried out at the DFT level that were employed to study the electronic structure of the investigated compounds, the thermodynamic aspects of their formation, and the role of noncovalent σ-hole halogen and chalcogen bonds in the X⋅⋅⋅X, X⋅⋅⋅Ch and Ch⋅⋅⋅Ch interactions evidenced structurally.

Zinc-dual-halide complexes suppressing polyhalide formation for rechargeable aqueous zinc-halogen batteries

Aqueous zinc-halogen batteries suffer from poor coulombic efficiency and short cycle life owing to the formation and dissolution of polyhalides in electrolytes. Herein, we apply a zinc-dual-halide complex strategy to confine free halides and suppress polyhalide formation. The high stabilities of zinc-dual-halide complexes are identified to be essential for effective confinement. The resulting Zn-Br2 and Zn-I2 cells deliver excellent rate capability and cycling stability, as well as high coulombic efficiency and energy efficiency.

Self-Assembly of Supramolecular Architectures Driven by σ-Hole Interactions: A Halogen-Bonded 2D Network Based on a Diiminedibromido Gold(III) Complex and Tribromide Building Blocks

The reaction of the complex [Au(phen)Br₂](PF₆) (phen = 1,10-phenanthroline) with molecular dibromine afforded {[Au(phen)Br₂](Br₃)}_∞ (1). Single crystal diffraction analysis showed that the [Au(phen)Br₂]⁺ complex cations were bridged by asymmetric tribromide anions to form infinite zig-zag chains featuring the motif ···Au–Br···Br–Br–Br···Au–Br···Br–Br–Br···. The complex cation played an unprecedented halogen bonding (XB) donor role engaging type-I and type-II XB noncovalent interactions of comparable strength with symmetry related [Br₃]⁻ anions. A network of hydrogen bonds connects parallel chains in an infinite 2D network, contributing to the layered supramolecular architecture. DFT calculations allowed clarification of the nature of the XB interactions, showing the interplay between orbital mixing, analyzed at the NBO level, and electrostatic contribution, explored based on the molecular potential energy (MEP) maps of the interacting synthons.

Structural diversity in the products formed by the reactions of 2-arylselanyl pyridine derivatives and dihalogens

The presence of competing donor sites in L1–L4 influences their reactivity towards dihalogens and interhalogens.

The Halogen Bond

The halogen bond occurs when there is evidence of a net attractive interaction between an electrophilic region associated with a halogen atom in a molecular entity and a nucleophilic region in another, or the same, molecular entity. In this fairly extensive review, after a brief history of the interaction, we will provide the reader with a snapshot of where the research on the halogen bond is now, and, perhaps, where it is going. The specific advantages brought up by a design based on the use of the halogen bond will be demonstrated in quite different fields spanning from material sciences to biomolecular recognition and drug design.

Synthesis, crystal structure and magnetic properties of H2tppz[ReCl6] and [Cu(bpzm)2(μ-Cl)ReCl3(μ-ox)Cu(bpzm)2(μ-ox)ReCl3(μ-Cl)]n

Two new Re(iv) compounds of formulae H2tppz[ReCl6] (1) and [Cu(bpzm)2(μ-Cl)ReCl3(μ-ox)Cu(bpzm)2(μ-ox)ReCl3(μ-Cl)]n (2) [tppz = 2,3,5,6-tetrakis(2-pyridyl)pyrazine and bpzm = bis(pyrazolyl-1-yl)methane] have been prepared and their crystal structures determined by X-ray diffraction on single crystals. Compound 1 is a mononuclear species whose structure consists of octahedral hexachlororhenate(iv) anions and diprotonated H2tppz(2+) cations which are arranged in the unit cell as alternating anionic and cationic layers, held together by electrostatic forces. The structure of 2 is made up of alternating [Cu(1)(bpzm)2](2+) and [(ox)ReCl3(μ-Cl)Cu(2)(bpzm)2(μ-Cl)ReCl3(ox)](2-) entities interlinked by oxalate bridges to afford a neutral heterobimetallic chain. The oxalate group adopts the didentate (at Re)/monodentate (at Cu) bridging mode. The magnetic behavior of 1 and 2 has been investigated over the temperature range 1.9-295 K. 1 is a magnetically diluted Re(iv) complex, the relatively large value of the zero-field splitting of the ground level [D = -15.8(2) cm(-1)] accounting for the variation of χMT in the low temperature range. Weak intrachain ferromagnetic interactions between Re(iv) and Cu(ii) through oxalate (J1 = +0.15 cm(-1)) and single chloro (J2 = +4.9 cm(-1)) bridges occur in 2 which are obscured by the large zero-field splitting of the Re(iv) ion (DRe = 42 cm(-1)). In addition, interchain antiferromagnetic interactions are also involved in 2 which are responsible for the metamagnetic behavior observed, the value of the critical dc magnetic field (Hc) being 20 kOe.

Structures, vibrational frequencies, and stabilities of halogen cluster anions and cations, X(n)(+/-), n = 3, 4, and 5

The structures, vibrational frequencies, and thermodynamic stabilities of the homonuclear polyhalogen ions, X3(+), X3(-), X4(+), X4(-), X5(+), and X5(-) (X = Cl, Br, I), have been calculated at the CCSD(T) level. The energetics were calculated using the Feller-Peterson-Dixon approach for the prediction of reliable enthalpies of formation. The calculations allow the following predictions where stabilities are defined in terms of thermodynamic quantities. (1) The X3(+) cations are stable toward loss of X2; (2) the X3(-) anions are marginally stable toward loss of X2 with Cl3(-) being the least stable; (3) the X4(+) cations and X4(-) anions are only weakly bound dimers of X2(+1/2) and X2(-1/2) units, respectively, but the cations are marginally stable toward decomposition to X3(+) and X, with I4(+) having the lowest dissociation energy, whereas the X4(-) anions decompose spontaneously to X3(-) and X; (4) the X5(+) cations are only marginally stable at low temperatures toward loss of X2, with Cl5(+) being the least stable; and (5) the X5(-) anions are also only stable at low temperatures toward loss of X2, with Cl5(-) being the least stable.

2,5-Bis(pyridinium-2-yl)-3,6-bis-(2-pyrid-yl)pyrazine bis-[tetra-chlorido-aurate(III)]

In the title compound, (C(24)H(18)N(6))[AuCl(4)](2), the cation is located on an inversion center. Each of the two independent Au(III) ions lies on an inversion center and has a distorted square-planar geometry. In the crystal, inter-molecular C-H⋯Cl hydrogen bonds, π-π inter-actions [centroid-centroid distances = 3.5548 (16) and 3.7507 (16) Å] and Au⋯π inter-actions [Au⋯centroid distance = 3.6424 (10) Å] are effective in the stabilization of the structure, resulting in the formation of a supra-molecular structure. Intra-molecular N-H⋯N hydrogen bonds are present in the cation.

A unique case of oxidative addition of interhalogens IX (X=Cl, Br) to organodiselone ligands: nature of the chemical bonding in asymmetric I-Se-X polarised hypervalent systems

The reactivity of the imidazoline-2-selone derivatives 1,1'-methylenebis(3-methyl-4-imidazoline-2-selone) (D1) and 1,2-ethylenebis(3-methyl-4-imidazoline-2-selone) (D2) towards the interhalogens IBr and ICl has been investigated in the solid state with the aim of synthesising "T-shaped" hypervalent chalcogen compounds featuring the extremely rare linear asymmetric I-E-X moieties (E=S, Se; X=Br, Cl). X-ray diffraction analysis and FT-Raman measurements provided a clear indication of the presence in the compounds obtained of discrete molecular adducts containing I-Se-Br and I-Se-Cl hypervalent moieties following a unique oxidative addition of interhalogens IX (X=Cl, Br) to the organoselone ligands. In all asymmetric hypervalent systems isolated, a strong polarisation was observed, with longer bond lengths at the selenium atom involving the most electronegative halogen. A topological electron density analysis on model compounds based on the quantum theory of atoms-in-molecules (QTAIM) and electron localisation function (ELF) established the three-centre-four-electron (3c-4e) nature of the bonding in these very polarised selenium hypervalent systems and new criteria were suggested to define and ascertain the hypervalency of the selenium atoms in these and related halogen and interhalogen adducts.

Electrolytes for Dye-Sensitized Solar Cells Based on Interhalogen Ionic Salts and Liquids

In this paper, we report on the preparation of interhalogen ionic liquids of the general formula [K+]XY2-, where K+=1,3-dialkylimidazolium, 1,2,3-trialkylimidazolium, or N-alkylpyridinium; XY2-=IBr2- or I2Br-. These compounds were characterized in solution and the solid state by NMR, IR, Raman, and mass spectroscopy. The crystal structure of the compound [Me2BuIm]IBr2 (7) shows that the IBr2- anion has a linear Br-I-Br structure. Indications of an equilibrium between different forms of XY2- anions in solution are observed. Interhalogen ionic salts and liquids were used as electrolyte components for encapsulated monolithic dye-sensitized solar cells. Overall light-to-electricity conversion efficiencies up to 6.4%, 5.0%, and 2.4% at 1000 W/m2 were achieved by using electrolytes based on interhalogen ionic salts and gamma-butyrolactone, glutaronitrile, or native ionic liquids as solvents, respectively. Moreover, in terms of stability, the cell performance lost 9-14% of the initial performance after 1000 h illumination at 350 W/m2.

Investigation into the reactivity of the coordinatively unsaturated phosphonodithioato [Ni(MeOpdt)2] towards 2,4,6-tris(2-pyridyl)-1,3,5-triazine: goals and achievements

The reaction between the coordinatively unsaturated phosphonodithioato complex [Ni(MeOpdt)2] (1) [MeOpdt = (MeO)(4-MeOC(6)H(4))PS2-] and tptz [2,4,6-tris(2-pyridyl)-1,3,5-triazine] has been investigated. Spectrophotometric and conductometric titrations showed the formation of a neutral and an ionic species, i.e. [Ni(MeOdtp)2(tptz)] (2) and [Ni(tptz)2](MeOdtp)2 (3), in correspondence to 1 : 1 and 2 : 1 tptz : ratios, respectively. XRD studies confirmed the formation of both complexes isolated in the compounds 2.MeOH and 3.4H(2)O. In the neutral complex 2 the central Ni(II) ion features a distorted octahedral coordination, achieved through three N-atoms of tptz and three S-atoms belonging to two MeOpdt anions, one of which unexpectedly acts as a monodentate S-donor. In 3.4H(2)O, the two phosphonodithioato anions are non-coordinating and counterbalance the charge of the [Ni(tptz)2](2+) distorted octahedral complex. From the reaction 2 of with I2 and Br2, crystals of [Ni(tptz)2](I3)2 (5) and [Ni(tptz)Br(micro-Br)]2 (6) have been obtained. The dinuclear complex 6 features a structure showing tubular canals with openings of about 6 x 6 A.