Definition of the Pnictogen Bond: A Perspective

This article proposes a definition for the term “pnictogen bond” and lists its donors, acceptors, and characteristic features. These may be invoked to identify this specific subset of the inter- and intramolecular interactions formed by elements of Group 15 which possess an electrophilic site in a molecular entity.

Pyridylarsine-based Cu(I) complexes showing TADF mixed with fast phosphorescence: a speeding-up emission rate using arsine ligands

Can arsine ligands be preferred over similar phosphines to design Cu(I)-based TADF materials? The present study reveals that arsines can indeed be superior to reach shorter decay times of Cu(I) emitters. This has been exemplified on a series of bis(2-pyridyl)phenylarsine-based complexes [Cu₂(Py₂AsPh)₂X₂] (X = Cl, Br, and I), the emission decay times of which are significantly shorter (2-9 μs at 300 K) than those of their phosphine analogs [Cu₂(Py₂PPh)₂X₂] (5-33 μs). This effect is caused by two factors: (i) large ΔE(S₁-T₁) gaps of the arsine complexes (1100-1345 cm^-1), thereby phosphorescence is admixed with TADF at 300 K, thus reducing the total emission decay time compared to the TADF-only process by 5-28%; (ii) higher SOC strength of arsenic (ζ_l = 1202 cm^-1) against phosphorus (ζ_l = 230 cm^-1) makes the k_r(T₁ → S₀) rate of the Cu(I)-arsine complexes by 1.3 to 4.2 times faster than that of their phosphine analogs. It is also noteworthy that the TADF/phosphorescence ratio for [Cu₂(Py₂AsPh)₂X₂] at 300 K is halogen-regulated and varies in the order: Cl (1 : 1) < Br (3 : 1) ≈ I (3.5 : 1). These findings provide a new insight into the future design of dual-mode (TADF + phosphorescence) emissive materials with reduced lifetimes.

Luminescent Cu4I4-cubane clusters based on N-methyl-5,10-dihydrophenarsazines

Two luminescent Cu₄I₄-cubane tetramers with N-methyl-10-(p-halogenophenyl)-5,10-dihydrophenarsazine ligands were synthesized and characterized by NMR spectroscopy, mass spectrometry, elemental analysis, and single-crystal X-ray diffraction analysis. The UV-Vis absorption and emission properties were studied and rationalized by DFT and time-dependent DFT calculations. The luminescence behavior was found to be rather different from that of recently reported tetranuclear copper iodide cubane clusters based on As,O-analogues - 10-(aryl)phenoxarsines. The crystalline powders of both complexes exhibit the temperature-dependent dual-band emission: the low-energy emission originates from the cluster-centered (³CC) triplet state, whereas the high-energy emission was attributed to the intraligand (³IL) triplet state.

Platinum(II) Complexes with 10-(Aryl)phenoxarsines: Synthesis, Cis/Trans Isomerization, and Luminescence

Synthesis and structural and photophysical characterization of platinum dihalogenide complexes formulated as [PtHal₂L₂], where Hal = Cl and I, with different 10-(aryl)phenoxarsine ligands such as 10-(p-chlorophenyl)phenoxarsine, 10-(p-tolyl)phenoxarsine, and 10-(phenyl)phenoxarsine are reported. The structures of complexes were determined by NMR spectroscopy, mass spectrometry, and X-ray analysis. Cis/trans isomerism of the complexes in solution was studied by NMR spectroscopy. In the solid state, under UV irradiation, platinum diiodide trans complexes exhibit an intense orange-red emission, which was attributed to a metal halide-centered triplet state. The UV/vis absorption and emission properties were studied and rationalized by density functional theory (DFT) and time-dependent DFT calculations.

Structural diversity in copper(I) iodide complexes with 6-thioxopiperidin-2-one, piperidine-2,6-di-thione and isoindoline-1,3-di-thione ligands

Copper(I) iodide complexes are well known for displaying a diverse array of structural features even when only small changes in ligand design are made. This structural diversity is well displayed by five copper(I) iodide compounds reported here with closely related piperidine-2,6-di-thione (SNS), isoindoline-1,3-di-thione (SNS6), and 6-thioxopiperidin-2-one (SNO) ligands: di-μ-iodido-bis-[(aceto-nitrile-κN)(6-sulfanylidenepiperidin-2-one-κS)copper(I)], [Cu2I2(CH3CN)2(C5H7NOS)2] (I), bis-(aceto-nitrile-κN)tetra-μ3-iodido-bis-(6-sulfanylidenepiperidin-2-one-κS)-tetra-hedro-tetra-copper(I), [Cu4I4(CH3CN)4(C5H7NOS)4] (II), catena-poly[[(μ-6-sulfanylidenepiperidin-2-one-κ2 O:S)copper(I)]-μ3-iodido], [CuI(C5H7NOS)] n (III), poly[[(piperidine-2,6-di-thione-κS)copper(I)]-μ3-iodido], [CuI(C5H7NS2)] n (IV), and poly[[(μ-isoindoline-1,3-di-thione-κ2 S:S)copper(I)]-μ3-iodido], [CuI(C8H5NS2)] n (V). Compounds I and II crystallize as discrete dimeric and tetra-meric complexes, whereas III, IV, and V crystallize as polymeric two-dimensional sheets. To the best of our knowledge, compound III is the first instance of an extended hexa-gonal [Cu3I3] structure that is not supported by bridging ligands. Structures I, II, and IV display weak to moderately strong Cu⋯Cu cuprophilic inter-actions [Cu⋯Cu inter-nuclear distances range between 2.5803 (10) and 2.8485 (14) Å]. All structures except III display weak hydrogen-bonding inter-actions between the N-H of the ligand and the μ2 and μ3-I- atoms. Structure III contains classical N-H⋯O inter-actions between the SNO ligands that connect the mol-ecules in a three-dimensional framework. Complex V features π-π stacking inter-actions between the aryl rings of the SNS6 ligands within the same polymeric sheet. In structure IV, there were three partially occupied solvent mol-ecules of di-chloro-methane and one partially occupied mol-ecule of aceto-nitrile present in the asymmetric unit. The SQUEEZE routine [Spek (2015 ▸). Acta Cryst. C71, 9-18] was used to correct the diffraction data for diffuse scattering effects and to identify the solvent mol-ecules. The given chemical formula and other crystal data do not take into account the solvent mol-ecules.

Cu4I4-cubane clusters based on 10-(aryl)phenoxarsines and their luminescence

The synthesis, structural and photophysical characterization, and theoretical study of tetranuclear copper(i) cubane-type Cu₄I₄ clusters with different 10-(aryl)phenoxarsine ligands are presented.