Sterically Hindered Tellurium(IV) Catecholate as a Lewis Acid

Sterically hindered tellurium catecholate Te(Cat³⁶)₂ (Cat³⁶ = 3,6-di-tert-butyl-catecholate) was synthesized with the reaction of amorphous Te with 3,6-di-tert-butyl-o-benzoquinone. Adducts of Te(Cat³⁶)₂ with various O- and N-donors were isolated and characterized by means of single-crystal X-ray diffraction along with IR, UV-vis, and NMR (¹H, ¹³C, and ¹²⁵Te) spectroscopies. In the crystal structure of the adduct with 2,2'-bipyridine (bipy), the unprecedented μ-κ²N,N':κ²N,N'-bridging coordination mode of bipy was observed. Various intermolecular interactions Te...O, Te...N, and Te...C in adducts were analyzed using density functional theory calculations and quantum theory of atoms in molecules analysis. The estimated strength for appropriate short contacts varies from 0.9 to 5.3 kcal/mol, and they are attractive and purely non-covalent.

Bis-Heteroleptic Cationic Iridium(III) Complexes Featuring Cyclometalating 2-Phenylbenzimidazole Ligands: A Combined Experimental and Theoretical Study

In this report, we investigate a new family of cationic iridium(III) complexes featuring the cyclometalating ligand 2-phenylbenzimidazole and ancillary ligand 4,4'-dimethyl-2,2'-bipyridine. Our benchmark complex IrL¹₂ (L¹ = 2-phenylbenzimidazole) displays emission properties similar to those of the archetypical complex 2,2'-dipyridylbis(2',4'-phenylpyridine)iridium(III) in deaerated CH₃CN (Φ = 0.20, λ_em = 584 nm and Φ = 0.14, λ_em = 585 nm, respectively) but exhibits a higher photoluminescence quantum yield in deaerated CH₂Cl₂ (Φ = 0.32, λ_em = 566 nm and Φ = 0.20, λ_em = 595 nm, respectively) and especially a lower nonradiative constant (k_nr = 6.6 × 10⁵ s^-1 vs k_nr = 1.4 × 10⁶ s^-1, respectively). As a primary investigation, we explored the influence of the introduction of electron-donating and electron-withdrawing groups on the benzimidazole moiety and the synergetic effect of the substitution of the cyclometalating phenyl moiety at the para position with the same substituents. The emission energy displays very good correlation with the Hammett constants of the introduced substituents as well as with ΔE_redox values, which allow us to ascribe the phosphorescence of these series to emanate mainly from a mixed metal/ligand to ligand charge transfer triplet excited state (³M/LLCT*). Two complexes (IrL⁵₂ and IrL⁸₂) display a switch of the lowest triplet excited state from ³M/LLCT* to ligand centered (³LC*), from the less polar CH₂Cl₂ to the more polar CH₃CN. The observed results are supported by (TD)-DFT computations considering the vibrational contributions to the electronic transitions. Chromaticity diagrams based on the maximum emission wavelength of the recorded and simulated phosphorescence spectra demonstrate the strong promise of our complexes as emitting materials, together with the very good agreement between experimental and theoretical results.

Orientational isomerisation of guest molecules in equilibrium in a tubular host crystal formed via halogen and hydrogen bonding

Fine-tuning of the ratio of two different states is important in controlling the structures and functions of crystalline materials. Here we report that clathrated guest molecules inside a tubular host...

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.

Trinuclear molybdenum clusters with sulfide bridges as potential anionic receptors via chalcogen bonding

Trinuclear Mo₃S₇ cluster complexes with sulfide bridges as potential anionic receptors due to chalcogen bonding.

One-Dimensional Diiodine-Iodobismuthate(III) Hybrids Cat3{[Bi2I9](I2)3}: Syntheses, Stability, and Optical Properties

One-dimensional iodine-rich iodobismuthates(III), Cat₃{[Bi₂I₉](I₂)₃} [Cat = 1,4-MePy (1) and 1-EtBMAP (2)], feature the highest amount of "trapped" diiodine units in polyhalogen-halometalates of p-block elements. Both complexes have narrow optical band gaps (1.55 and 1.63 eV, respectively) and moderate thermal stability.

Halogen bonding-assisted assembly of bromoantimonate(v) and polybromide-bromoantimonate-based frameworks

Halogen bonding within bromo- and polybromoantimonates(v).

Chalcogen Bonding: An Overview

In the last few decades, "unusual" noncovalent interactions like anion-π and halogen bonding have emerged as interesting alternatives to the ubiquitous hydrogen bonding in many research areas. This is also true, to a somewhat lesser extent, for chalcogen bonding, the noncovalent interaction involving Lewis acidic chalcogen centers. Herein, we aim to provide an overview on the use of chalcogen bonding in crystal engineering and in solution, with a focus on the recent developments concerning intermolecular chalcogen bonding in solution-phase applications. In the solid phase, chalcogen bonding has been used for the construction of nano-sized structures and the self-assembly of sophisticated self-complementary arrays. In solution, until very recently applications mostly focused on intramolecular interactions which stabilized the conformation of intermediates or reagents. In the last few years, intermolecular chalcogen bonding has increasingly also been exploited in solution, most notably in anion recognition and transport as well as in organic synthesis and organocatalysis.

Non-covalent interactions observed in nevirapinium pentaiodide hydrate which include the rare I4–I−···O=C halogen bonding

In the course of screening for novel crystalline forms of antiviral drug nevirapine, co-crystallization of the latter with molecular iodine was attempted. This resulted in the formation of a hydrate salt form composed of the protonated nevirapinium cation and pentaiodide anion. In the X-ray structure of NVPH+I5 −·H2O, halogen and hydrogen bonding interactions were identified and studied by DFT calculations and topological analysis of the electron density distribution within the framework of QTAIM method at the B3LYP/DZP-DKH and M06/DZP-DKH levels of theory. Estimated energies of these contacts are 1.3–9.4 kcal/mol.

Tetrachloromethane as halogen bond donor toward metal-bound halides

Two annulated triazapentadiene systems, viz. 1,3,5,7,9-pentaazanona-1,3,6,8-tetraenate chloride complexes of PtII, form CCl4 solvates, containing the Cl3C–Cl···Cl–Pt halogen bonds. These halogen bonds are firstly reported type of Cl3C–Cl···Cl–M contacts. In the X-ray structures of two solvates different non-covalent interactions were detected and studied by DFT calculations and topological analysis of the electron density distribution within the framework of QTAIM method at the M06/DZP-DKH level of theory. Estimated energies of these supramolecular contacts vary from 0.6 to 2.4 kcal/mol.

Red photo- and electroluminescent half-lantern cyclometalated dinuclear platinum(II) complex

New cyclometalated dinuclear platinum(II) complex bearing bridged 4,6-dimethylpyrimidine-2(1H)-thiolate (μ-C6H7N2S-κN,S) ligands, [{Pt(ppy)(μ-C6H7N2S-κN,S)}2] (3) (ppy=(2-phenylpyridinato-C2,N)) was prepared via the reaction of chloro-bridged dimer [{Pt(ppy)Cl}2] with 4,6-dimethylpyrimidine-2(1H)-thione (C6H8N2S) in the presence of t-BuOK. The complex holds dinuclear frameworks with short Pt(II)···Pt(II) distance (2.8877(3) Å), and exhibit red intense luminescence from the triplet metal-metal-to-ligand charge-transfer at 697 nm in CH2Cl2 solution and at 649 nm in solid state at RT. Single crystal XRD analysis reveals the metallophilic interactions Pt···Pt with significant covalent contribution in the structure of 3 which were studied by quasi-relativistic and relativistic DFT calculations (viz., M06/MWB60(Pt) and 6-311+G* (other atoms); M06/DZP-DKH levels of theory) and topological analysis of the electron density distribution within the framework of Bader’s theory (QTAIM method). Estimated strength of the Pt···Pt contact is 8.1–12.2 kcal/mol and it is mostly determined by crystal packing effects and weak attractive interactions between the adjacent metal centers due to overlapping of their dz2 and pz orbitals. An organic light-emitting diode based on this complex showed red electroluminescence with maximal luminance of 115 cd/m2 and current efficiency of 2.45 cd/A at this luminance.

Iridium(iii)-catalysed cross-linking of polysiloxanes leading to the thermally resistant luminescent silicone rubbers

Iridium(iii) cross-linking catalysts for silicones show a unique temperature-curing profile and lead to thermally resistant and luminescent silicone rubbers.