Metal-halogen Bonds Research Articles

Automated design of hybrid halide perovskite monolayers for band gap engineering

The recent experimental confirmation of perovskite monolayers has sparked ongoing efforts in their prediction and synthesis, showcasing their flexible tunable band gap and potential in advanced functional devices. Although large-scale computational designs have been successfully performed for inorganic perovskite monolayers, the complexity introduced by organic cations hinders the same approaches applied to the hybrid halide perovskite monolayers. To address this challenge, we have proposed a high-throughput first-principles computational workflow that automates the design of hybrid halide perovskite monolayers. We strategically reduce the complexity of the configurations by analyzing the orientation of cations and the structural symmetry. Over 400 hybrid halide perovskite monolayers have been designed, and their structures and fundamental properties are stored in the database. Correlation analyses show a strong correlation between band gaps and metal-halogen-metal bond angles or metal-halogen bond lengths, consistent with prior studies for bulk and layered perovskites. The underlying physics that the band gap is modulated by the antibonding in the metal-halogen bond makes band gap engineering of hybrid halide perovskite monolayers feasible. Accordingly, initial research on lateral heterojunctions and solar cells has been conducted to explore the potential practical applications of the designed hybrid halide perovskite monolayers. Our study lays the foundation for further exploration of hybrid halide perovskite monolayers and highlights promising opportunities for their potential applications in electronic and optical devices.

Structures, Characterization and DFT Studies of Four Novel Nickel Phenanthroline Complexes

Four Ni–phen complexes were prepared and characterized by FTIR and thermal analysis. The X-ray structure determination shows that the geometry around NiII ions in complexes 1, [Ni(phen)2(H2O)(ONO2)](NO3); 2, [Ni(phen)2(H2O)Cl]Cl; 3, [Ni(phen)(CH3CN)(ONO2)(O2NO)] and 4, [Ni(phen)3](NO3)2.H2O.C2H5OH is considerably distorted octahedral. The coordination core geometries in 1, 2, 3 and 4 are NiN4O2, NiN4OCl, NiN3O3 and NiN6, respectively. The crystal packing and crystal supramolecularity analysis of the complexes reveal the importance of aryl∙∙∙aryl interactions, and both offset face-to-face (OFF) and edge-to-face (EF) motifs are dominant. Hydrogen bonding interactions in these structures reinforce aryl∙∙∙aryl interactions. FTIR proved the coordination of M-N and M-Cl as well as the presence of nitro groups in the complexes, while thermal analysis revealed that the loss of water, chloro and nitro groups occurred before the degradation of phenanthroline ligand in the complexes. DFT study indicates that a strong correlation exists among theoretical and experimentally determined geometric parameters with distorted octahedral geometry. The charge density in HOMO is localized on the metal halogen bond and nitrate group (NO3−), whereas the LUMO cloud density is mainly distributed on the phen ring, which indicates the electroactive nature of the ring.

Mononuclear half-sandwich nd7 metallo drug complexes based on bidentate N∩N dendritic scaffolds: DFT (B3LYP; BP86 and B3PW91) examination

Through an use of three functionals (B3PW91, B3LYP and BP86) associated to a generic basis set LanL2DZ for transition metals (as well as halogen atoms) and 6-311+G (d,p) for others atoms, an examination of the bonding properties of a series of mononuclear half-sandwich nd7 transition metal (anticancer) complexes based on N∩N dendritic scaffolds (L) has been done. Collectively, complexes studied have adopted the piano-stool environment. An examination of the performance of each functional has shown that for the most reliable geometrical analysis of Metal-Nitrogen and Metal-Halogen bonds, the B3LYP and B3PW91 functionalities are suitable respectively. Regardless of the halogen ligand adopted, the B3LYP metal-nitrogen bond lengths are the most widely overestimated. A correlation has been built between the retained charge on each divalent transition metal cation and its metal ion affinity (MIA). Topological examinations reveal the higher instability of metal-N bonds compared to metal-X ones (X = Cl and Br). By the mean of the energy decomposition analysis, a predominant electrostatic character of metal … halogen and [LCP]- … [MX]+ interaction has been demonstrated. The transition metal atom … (hydrophobic) surface (Cp*) interaction is most pronounced for the chloride rhodium complexes of rhodium (combined with (E)-N-(pyridin-2-ylmethylene) Propan-1-amine and 2,2′- dipyridylketone ligands and iridium combined with 2,2′- dipyridylketone ligand. The charge decomposition analysis displays the weakening of the [MLCP*]+−X− bonds in the studied complexes.

CO-CYCLIZATION OF ETNCO AND ME2CO AS THE RESULTS OF THEIR SELECTIVE INSERTION INTO THE NIOBIUM-CHLORINE BOND

Development of the new methods for drug production is impossible without reliance on the novel and unorthodox approaches to the synthesis of heterocyclic complexes and compounds.The method is based on the study of new aspects of the of two types of behavior of the coordinated molecules in reaction - their ability to insert into the same transition metal-halogen bond, and their ability to form the unusual heterocyclic ligands, or even molecules after leaving the complex’s coordination sphere. This will make it possible not only to synthesize the already-known compounds under milder conditions, but to also obtain new ones as products of such mixed condensation reactions. On the one hand, this opens up new possibilities for designing and performing the intraspherical "stitching" of ligands and their synthesis with high efficiency and selectivity. 
 On the other hand, these reactions can be considered a significant contribution to the fundamental coordination chemistry in terms of illustration of the new modalities of the mutual influence of ligands, namely their ability to stimulate each other for a mutual insertion, and sheds light on the mechanisms of the intraspheric condensation. Oxadiazine derivatives, just like the derivatives of triazine we synthesized and reported previously, could become a foundation for the generation of biologically-active compounds, often containing heterocyclic fragments and frequently used for the treatment of malignant tumors. It can be expected that the developed method will find use in the synthesis of the new classes of potential antitumor compounds.
 We have previously found that organic isocyanate not only themselves insert into M-Hal bond, but can also activate the insertion of acetonitrile, the resulting heteromolecular chain of inserted molecules being composed of two MeNCO and one MeCN fragments. Such a structure of this complexes was confirmed be synthesis of striazine derivatives on their base. In this work was to determine optimum condition for the insertion of ethyl isocyanate with acetone into niobium-chlorine bond, as well as their subsequent mixed co-cyclization with obtaining of oxadiazine derivative.

CO-CYCLIZATION OF ETNCO AND ME2CO AS THE RESULTS OF THEIR SELECTIVE INSERTION INTO THE NIOBIUM-CHLORINE BOND

Development of the new methods for drug production is impossible without reliance on the novel and unorthodox approaches to the synthesis of heterocyclic complexes and compounds.The method is based on the study of new aspects of the of two types of behavior of the coordinated molecules in reaction - their ability to insert into the same transition metal-halogen bond, and their ability to form the unusual heterocyclic ligands, or even molecules after leaving the complex’s coordination sphere. This will make it possible not only to synthesize the already-known compounds under milder conditions, but to also obtain new ones as products of such mixed condensation reactions. On the one hand, this opens up new possibilities for designing and performing the intraspherical "stitching" of ligands and their synthesis with high efficiency and selectivity. 
 On the other hand, these reactions can be considered a significant contribution to the fundamental coordination chemistry in terms of illustration of the new modalities of the mutual influence of ligands, namely their ability to stimulate each other for a mutual insertion, and sheds light on the mechanisms of the intraspheric condensation. Oxadiazine derivatives, just like the derivatives of triazine we synthesized and reported previously, could become a foundation for the generation of biologically-active compounds, often containing heterocyclic fragments and frequently used for the treatment of malignant tumors. It can be expected that the developed method will find use in the synthesis of the new classes of potential antitumor compounds.
 We have previously found that organic isocyanate not only themselves insert into M-Hal bond, but can also activate the insertion of acetonitrile, the resulting heteromolecular chain of inserted molecules being composed of two MeNCO and one MeCN fragments. Such a structure of this complexes was confirmed be synthesis of striazine derivatives on their base. In this work was to determine optimum condition for the insertion of ethyl isocyanate with acetone into niobium-chlorine bond, as well as their subsequent mixed co-cyclization with obtaining of oxadiazine derivative.

DFT-based study of the bulk tin mixed-halide CsSnI3-xBrx perovskite

Metal-halide perovskites compounds, such as CsSnX3 (X = halogen), have attracted a lot of attention as a photovoltaic material due to their astonishing optoelectronic properties, nevertheless, the improvement of its efficiency is still an issue. It has been observed that the mixing of halogens in the perovskite structure increases the compound stability. However, theoretical studies of the effects of this mixing are scarce; by understanding the most stable mixing positions it would be possible to enhance the stability of these structures, which in turn it would help to enhance the performance of a perovskite-based photovoltaic device. Thus, a Density Functional Theory study was performed on the CsSnI3-xBrx perovskite as a function of the bromine concentration (0 ≤ x ≤ 3). The distortions of the octahedral array and the energy gap of each system studied are highly dependent on the position of bromine atoms within the unit-cell. It was observed that stable compounds could be found at x = 0.5, 1.0, and 2.0 due to the strengthening of the metal-halogen bonds. These results could explain the literature-reported enhance of the performance, as a photovoltaic material, of CsSnI3-xBrx with respect to CsSnI3. Besides, non-covalent interactions between halogens and Cs atoms were found. Different energies attributed to such interactions were calculated and revealed that the off-centering of Cs atoms are driven by the countering effect of the I-(1−δ)-Sn-Br-(1+δ) polar bonds within CsSnI3-xBrx. These results give an insight of the properties of the CsSnI3-xBrx alloy and its stability which could be beneficial to the rising field of perovskite photovoltaics.

New reactivity at the silicon bridge in sila[1]ferrocenophanes.

We describe two new types of reactivity involving silicon-bridged [1]ferrocenophanes. In an attempt to form a [1]ferrocenophane with a bridging silyl cation, the reaction of sila[1]ferrocenophane [Fe(η-C5H4)2Si(H)TMP] (12) (TMP = 2,2,6,6-tetramethylpiperidyl) towards the hydride-abstraction reagent trityl tetrakis(pentafluorophenyl)borate ([CPh3][B(C6F5)4]) was explored. This yielded the unusual dinuclear species [Fe(η-C5H4)2Si(TMP·H)(η-C5H3)Fe(η-C5H4)Si(H)TMP][B(C6F5)4] [13][B(C6F5)4] in low yield. The formation of [13]+ is proposed to involve abstraction of hydride from the silicon bridge in 12 with subsequent C-H bond cleavage of a cyclopentadienyl group by the resulting electrophilic transient silyl cation intermediate. We also explored the reaction of dimethylsila[1]ferrocenophane [Fe(η-C5H4)2SiMe2] (1) with the Au(i) species AuCl(PMe3). This was found to result in addition of the Au-Cl bond across the Cpipso-Si bond to yield the ring-opened species [1'-(chlorodimethylsilyl)-ferrocenyl](trimethylphosphine)gold(i), [Fe(C5H4SiMe2Cl){C5H4Au(PMe3)}] (14). This represents the first example of ring-opening addition of a metallocenophane with a reagent possessing a transition metal-halogen bond.

Thermal and Flame Retardancy Behavior of Oil Palm Based Epoxy Nanocomposites

The aim of present study was to investigate the thermal properties and flame retardancy behavior of flame retardant (FR) epoxy nanocomposites from chemically treated (bromine water and tin chloride) oil palm empty fruit bunch (OPEFB) nano filler at different filler loading (1, 3, 5%). Thermal properties were evaluated through thermogravimetry analyzer, derivative thermogravimetry and differential scanning calorimetry. FR properties of nanocomposites are evaluated through UL-94 vertical burning test and limiting oxygen index (LOI). The functional group analysis of all composites was made by FTIR spectroscopy. Thermal analysis shows that degradation temperature of epoxy composites shifts from 370 to 410 °C and char yield also increases for 3% loading. Furthermore LOI value of 29% and UL-94 rating of V-0 with no flame dripping and cotton ignition, revealed that 3% oil palm nano filler filled epoxy nanocomposites display satisfactory flame retardancy. The superior flame retardancy of epoxy nanocomposites are attributed to the chemical reactions occurred in the gaseous phases and the profound synergistic flame retardation effect of tin with bromine in the treated nano OPEFB filler. All the epoxy nanocomposites displayed almost similar FTIR spectra with the characteristics metal-halogen bond supporting the synergism. Homogeneous dispersion of 3% oil palm nano filler act as highly effective combustion chain terminating agent compared with 1 and 5% nano OPEFB/epoxy nanocomposites.

The role of halogen interactions in the crystal structure of biscyclopentadienyl dihalides

The purpose of this survey is to examine the crystal packing of bent metallocenes, namely, group IV, V and VI biscyclopentadienyl dihalides and dihydrides, first synthesized in the late 1950s. This analysis is based on the present knowledge on new types of intermolecular contacts such as halogen and C–H⋯π interactions as well as dihydrogen bonds. Results are also supported by ab initio calculations that provide information on electrostatic charge distributions, in particular the effect of two V-shaped metal–halogen bonds on the molecular electron density distribution. Type I halogen interactions do not appear to be affected by this feature, specifically the geometric parameters and variation of atom polarizability, but the resultant electronic density distribution precludes the presence of Type II halogen bonds. Special attention is given to the competition among hydrogen and halogen interactions, in particular its influence on the nature and geometric orientations of the different supramolecular motifs and, ultimately, on the space groups observed for each crystal.

Adsorption Behavior of Nonplanar Phthalocyanines: Competition of Different Adsorption Conformations.

Using density functional theory augmented with state-of-the-art van der Waals corrections, we studied the geometric and electronic properties of nonplanar chlorogallium-phthalocyanine GaClPc molecules adsorbed on Cu(111). Comparing these results with published experimental data for adsorption heights, we found indications for breaking of the metal–halogen bond when the molecule is heated during or after the deposition process. Interestingly, the work-function change induced by this dissociated geometry is the same as that computed for an intact adsorbate layer in the “Cl-down” configuration, with both agreeing well with the experimental photoemission data. This is unexpected, as the chemical natures of the adsorbates and the adsorption distances are markedly different in the two cases. The observation is explained as a consequence of Fermi-level pinning due to fractional charge transfer at the interface. Our results show that rationalizing the adsorption configurations on the basis of electronic interface properties alone can be ambiguous and that additional insight from dispersion-corrected DFT simulations is desirable.

Interplay between the Supramolecular Motifs of Polypyridyl Metal Complexes and Halogen Bond Networks in Cocrystals

Combining [Ni(phen)3]I2 or [Ni(phen)3]Cl2 (phen = 1,10-phenanthroline) with the iodoperfluorobenzenes (IPFBs), 1,2-, 1,3-, 1,4-diiodotetrafluorobenzene (1,2-, 1,3-, and 1,4-DITFB, respectively), or 1,3,5-triiodotrifluorobenzene (1,3,5-TITFB) resulted in the formation of six different cocrystalline materials featuring halogen-bonded networks encapsulating [Ni(phen)3]2+ ions. The cocrystals have the general formula [Ni(phen)3][(IPFB)n(X2)(L)m]·solvate (n = 2 or 3; X = Cl– or I–; L = halogen-bonded H2O and/or MeOH; solvate = isolated H2O and/or MeOH). The halide ions balance the charge of the metal complexes and simultaneously act as halogen bond acceptors for the electronically polarized iodine atoms of the IPFB donors. The structures display a wide variety of supramolecular motifs in the context of both the aggregation of the metal complexes and the topology and connectivity of the halogen bond networks. The well-known supramolecular “aryl embrace” motifs of [Ni(phen)3] complexes are present but are structurally compromised to varying degrees in the crystals of [Ni(phen)3][(1,2-DITFB)2I2]·MeOH, [Ni(phen)3][(1,3-DITFB)2I2]·2MeOH, and [Ni(phen)3][(1,3-DITFB)2(H2O)2Cl2]·1.5MeOH. In [Ni(phen)3][(1,3-DITFB)3I2], the [Ni(phen3]2+ complexes are so thoroughly enclosed in halogen-bonded networks that the metal complexes have no significant supramolecular contact. In contrast, in [Ni(phen)3][(1,4-DITFB)3I2(MeOH)0.5] and [Ni(phen)3][(1,3,5-TITFB)2Cl2] the complexes are arranged in typical aryl embrace motifs (pairwise and 1D chains, respectively), but with adjacent complexes held in closer proximity to each other than they reside in crystals of the pure metal complex. The interplay between the supramolecular chemistry of the halogen-bonded networks and the metal complexes was examined in detail, and the results demonstrate that it is possible to significantly influence the aggregation of metal complexes by encapsulation in different halogen bond networks.

“Scorpionate-like” complexes that are held together by hydrogen bonds: Crystallographic and spectroscopic studies of (3-NH(t-butyl)-5-methyl-pyrazole)nMX2 (M = Zn, Ni, Co, Mn; n = 3, 4; X = Cl, Br)

The hydrogen bonding ligand, 3-NH(t-butyl)-5-methyl-pyrazole, forms “scorpionate-like” first row transition metal complexes that are held together by hydrogen bonds rather than covalent bonds. The formulae of these complexes are (LH)nMX2, where n=3, 4; X=Cl, Br; and LH=3-NH(t-butyl)-5-methyl-pyrazole. The amino-substituted pyrazole can hydrogen bond via both the amino group and the pyrazole NH to form intramolecular NH to halide hydrogen bonds. These complexes have been well characterized and show a 3:1 ratio of ligand to metal for zinc and cobalt (1 and 2), and a 4:1 ratio of ligand to metal for manganese and nickel (3 and 4). The hydrogen bonding interactions appear to be stronger for the 3:1 complexes. The crystallographic and spectroscopic studies (EPR and NMR) have shown that these hydrogen-bonding interactions are strong enough to perturb metal halogen bond distances and, with non-hydrogen bonding solvents, the hydrogen bonds appear to hold these complexes together in solution.

Large Mid-IR Second-Order Nonlinear-Optical Effects Designed by the Supramolecular Assembly of Different Bond Types without IR Absorption

Two new different-bond-type hybrid compounds, (Hg6P4Cl3)(PbCl3) (1) and (Hg23P12)(ZnCl4)6 (2), with supramolecular interactions between host and guest moieties, which based on metal-pnicogen, pnicogen-pnicogen, and metal-halogen bonds were obtained by solid-state reactions. Compounds 1 and 2 show large second-harmonic-generation (SHG) activity and are transparent in the wide mid-IR region, providing an effective route for searching new IR nonlinear-optical material systems by combining two or more different bond types with no IR absorption within a single compound through supramolecular assembly. Theory predications based on first-principles calculations are also performed on the SHG properties of 1 and 2.

Synthesis of carboxylate derivatives of molybdenum and tungsten based on joint insertion of CO2 and PhNCS or N, N′-dicyclohexylcarbodiimide into M-Cl bonds

Reactions of the higher molybdenum and tungsten chlorides with phenyl isothiocyanate or with N, N′-dicyclohexylcarbodiimide and carbon dioxide in dichloroethane are the first to demonstrate the possibility of insertion of carbon dioxide in combination with other heterocumulenes into transition metal-halogen bonds. IR spectroscopy and elemental analysis data show that the reactions result in the attachment of the ligands at the same metal-chlorine bond and the formation of heteromolecular insertion products with the compositions $$\left[ {MoOCl_3 \left\{ {N\left( {Ph} \right)C\left( S \right)} \right\}_2 Nc\left( {Me} \right)Cl} \right]$$ and $$MCl_x \left\{ {OC\left( O \right)\left[ {\left( {Hex} \right)NCN\left( {Hex} \right)} \right]_2 } \right\}Cl,$$ where x = 4 and 5 for the Mo and W derivatives, respectively.

Triggered formation of thixotropic hydrogels by balancing competitive supramolecular synthons

Two component hydrogels have been obtained by formation of 1 : 1 complexes of bis(pyridyl urea)s with a range of dicarboxylic acids. The gels are thixotropic and undergo an assembly process in which short segments can reversibly assemble into an interconnected fibrous network. NMR and IR spectroscopic data suggest that the gelators form neutral gelator–acid complexes rather than salts. The use of dicarboxylic acids to trigger gelation in bis(pyridyl urea)s parallels analogous triggered gelation of metal ions and halogen bond donors in related systems.

Reactions of ‘GaI’ with organometallic transition metal halides

Two approaches towards the synthesis of phosphine ligated half-sandwich complexes [(η x -C x H x )M(PR 3) 2GaI 2] n containing diiodogallyl ligands have been investigated. Insertion of ‘GaI’ into the Mo–I bond of (η 7-C 7H 7)Mo(CO) 2I has been shown to yield the crystallographically characterized dimeric complex [(η 7-C 7H 7)Mo(CO) 2GaI 2] 2 ( 2). Attempts to substitute the carbonyl ligands by the phosphine ligand dppe [dppe = bis(diphenylphosphino)ethane] have been shown instead to yield the sparingly soluble complex [(η 7-C 7H 7)Mo(CO) 2GaI 2] 2(μ-dppe) ( 3) in which the phosphine bridges two [(η 7-C 7H 7)Mo(CO) 2GaI 2] units via a pair of P → Ga donor/acceptor bonds. By contrast, attempts to insert ‘GaI’ directly into the metal-halogen bond of phosphine ligated complexes such as (η 5-C 5H 5)Ru(PPh 3) 2Cl or (η 5-C 5H 5)Ru(dppe)Cl have been shown to result in the formation of the tetraiodogallate species(η 5-C 5H 5)Ru(PPh 3) 2(μ-I)GaI 3 ( 5) and [(η 5-C 5H 5)Ru(dppe)] +[GaI 4] − ( 7).

A Systematic Study of the Structure and Bonding of Halogens on Low-Index Transition Metal Surfaces

The structure and bonding of halogens on various transition metal low-index surfaces has been studied by means of density functional theory (DFT) calculations using periodic slabs to model the surface. This approach is shown to be capable of reproducing available experimental data of naked and halogen-covered surfaces. Periodic trends are discerned and discussed for several properties, including metal-halogen bond distances and vibrational frequencies, adsorption energies, and bond ionicities, which have been evaluated by a Bader population analysis of the corresponding density. A simple correlation is discerned, relating the bond ionicity to the metal work function, so that higher work function surfaces are associated with more covalent bonding. Periodic trends in bond ionicities and metal-halogen vibrational frequencies are in harmony with corresponding data derived in an electrochemical environment, indicating that the metal-halogen bonding in vacuum share some features with the electrode metal surface-halogen bonding.

Electrochemical study of heteronuclear complex [Cp(CO)2MnCu(μ-C=CHPh)(μ-Cl)

The electrochemical behavior of the heteronuclear dimeric vinylidene complex [Cp(CO)2MnCu(μ-C=CHPh)(μ-Cl)]2 (I) is studied using polarography, cyclic voltammetry, and controlled-potential electrolysis on mercury and platinum electrodes in acetonitrile. The dimer is reduced in two two-electron stages: at the first stage, metal-halogen bonds are broken and binuclear monomers [Cp(CO)2MnCu(μ-C=CHPh)(Cl)]− are formed; at the second stage, mononuclear manganese complexes Cp(CO)2Mn=C=CHPh, metallic copper, and chloride ions are formed. The two-electron oxidation of dimer [Cp(CO)2MnCu(μ-C=CHPh)(μ-Cl)]2 also results in the formation of binuclear monomers, which decompose to complex Cp(CO)2Mn=C=CHPh, Cu2+ ions, and Cl− ions.

Insertion of the Ga(I) Bis-imidinate Ga(DDP) into the Metal Halogen Bonds of Rh(I) Complexes. How Electrophilic Are Coordinated Ga(DDP) Fragments?

The reactivity of Ga(DDP) (DDP = 2-((2,6-diisopropylphenyl)amino-4-((2,6-diisopropylphenyl)imino)-2-pentene) towards the rhodium-chloride bonds of [RhCl(PPh3)3] and [RhCl(COE)2]2 (COE = cyclooctene) is investigated. Reaction of the first complex leads to [(Ph3P)2Rh{Ga(DDP)}(mu-Cl)] (1), exhibiting a chloride bridging the gallium and the rhodium atoms, whereas the second complex leads to a full insertion of the Ga(DDP) ligand into the Rh-Cl bond giving [(COE)(benzene)Rh{(DDP)GaCl}] (2) on coordination of the solvent C6H6. Compounds 1 und 2 readily react with the halide abstracting reagent Tl[BArF] (BArF = B[3,5-(CF3)2C6H3]4), yet the products could not be isolated and characterized because of their lability. The Au(I) complex [{(DDP)Ga}Au{Ga(DDP)}Cl] reacts with Na[BArF] giving the linear, symmetric cationic complex [{(DDP)Ga.THF}2Au][BArF] (3.2THF), exhibiting two THF molecules coordinated to the Ga(DDP) moieties.

Non‐Covalent Interactions of Organic Halogen Compounds with Aromatic Systems – Analyses of Crystal Structure Data

AbstractThe Cambridge Structural Database showed in mid 2002 about 20.000 structures containing halogen atoms and aryl rests with distances d between the aryl center and the halogen atom, which would allow both hydrogen bonds with the aromatic hydrogens and/or van der Waalsinteractions with the π‐cloud. The latter are characterized by short distances d and by small angles α between the vector along the aryl centroid–halogen line and the perpendicular vector originating in the aryl center (the plane normal). The cases with d < 3.0 Å for F; and d < 3.5 Å for Cl, Br or I (outliers neglected), and α ≈ 10 ± 5°, indicating predominating van der Waals forces, amount to several hundreds. The majority of fragments exhibit larger d and α values, in line with avoidance of electrostatic repulsion between the negative partial charges of the halogens and the π‐cloud center, and with an increasing electrostatic attraction with the aromatic hydrogen atoms. The corresponding hydrogen bonds are characterized by longer distances d and by angle values of α > 60° (about 40 % of the fragments), with only very few cases close to linear hydrogen bonds (then with α = 90°). Compounds containing metal–halogen bonds were omitted in view of possible strong orientational interferences. The structures were screened with four different halogen binding modes, all of them containing the halogen attached to a carbon atom, but with different hybrizations at the connecting carbon centers. The results show only small differences in the distance distributions, with a slight preference for smaller α values for sp2 frameworks. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)