Structural Diversity and Rare η1 Cu-C Interactions in CuI Complexes of 1,2,3-Triazole-Functionalized Bisphosphines

This manuscript describes the synthesis of copper complexes of 1,2,3-triazolyl-phosphines: o-Ph2P(C6H4){1,2,3-N3CC6H5)C(PPh2)} (L1), (C6H5){1,2,3-N3C(C6H4(o-PPh2))-C(PPh2)} (L2), 3-Ph2P(C5H3N){1,2,3-N3C(C6H5)C(PPh2)} (L3), o-Ph2P(C6H4){1,2,3-N3C(C5H5N)C(PPh2)} (L4), and {(3,5-Ph2PC6H4-o)21,2,3-N3CCH} (L5). The reactions of L1-L3 with CuI salts afforded dimeric complexes having the general formula [Cu2(μ -X)2L2] (L = L1, X = Cl, Br and I: 1 - 3; L= L2, X = Cl, Br and I: 4- 6; L = L3; X = Cl, Br, and I: 7-9). The reaction of L4 with CuI in a 1:2 molar ratio afforded 1D-coordination polymer [{(CuI)2{o-Ph2P(C6H4){1,2,3-N3C(C5H5N)C(PPh2)}-μ-((k1-N)(k2-P,P))}}]n (10). The reaction of L5 with cuprous halides (CuX) (X = Br, I) yielded mononuclear complexes [CuX{(3,5-Ph2PC6H4-o)21,2,3-N3CCH}-κ2P,P] (X = Br, 12; I, 13). Crystal structures of complexes 12 and 13 showed close interactions between CuI and the triazole C7 carbon. These relatively short Cu···C7 separations may be due to the η1-C interaction (dπ-pπ bond) between the triazolic carbon atom (via pz orbital) and CuI or three-centered two-electron interaction between CuI and the triazolic C-H bond. The existence of the Cu···C interaction was further evinced by the QTAIM analysis in compounds 12 and 13.

Emission and Luminescent Vapochromism Control of Octahedral Cu4 I4 Complexes by Conformationally Restricted P,N Ligands

A conformationally restricted P,N-ligand capable of the design of polynuclear copper(I) complexes was synthesized via the reaction of primary pyridylphosphine, paraformaldehyde, and benzhydrylamine. The reaction of the ligand with copper(I) iodide leads to the tetranuclear copper(I) complex with the octahedral type of copper-iodide core. Different orientation of coordination bonds of the ligands relative to the P,N₂ -heterocyclic fragments and to the Cu₄ I₄ cores leads to the existence of two types of conformers of the complex with "compact" or "stretched" geometry of the Cu₄ I₄ cluster. This lability of the complex allowed for obtaining two crystalline phases displaying green or red luminescence. The TDDFT computations along with XRD structural analysis gave a strong interpretation of the green emission belonging to the "compact" form of the complex and belonging of the red emission to the "stretched" form. Moreover, both crystalline phases demonstrate the strong vapochromic responses of luminescence on the vapors of wide range of solvents.

Tris(2-Pyridyl)Arsine as a New Platform for Design of Luminescent Cu(I) and Ag(I) Complexes

The coordination behavior of tris(2-pyridyl)arsine (Py₃As) has been studied for the first time on the example of the reactions with CuI, CuBr and AgClO₄. When treated with CuI in CH₂Cl₂ medium, Py₃As unexpectedly affords the scorpionate complex [Cu(Py₃As)I]∙CH₂Cl₂ only, while this reaction in MeCN selectively leads to the dimer [Cu₂(Py₃As)₂I₂]. At the same time, the interaction of CuBr with Py₃As exclusively gives the dimer [Cu₂(Py₃As)₂Br₂]. It is interesting to note that the scorpionate [Cu(Py₃As)I]∙CH₂Cl₂, upon fuming with a MeCN vapor (r.t., 1 h), undergoes quantitative dimerization into the dimer [Cu₂(Py₃As)₂I₂]. The reaction of Py₃As with AgClO₄ produces complex [Ag@Ag₄(Py₃As)₄](CIO₄)₅ featuring a Ag-centered Ag₄ tetrahedral kernel. At ambient temperature, the obtained Cu(I) complexes exhibit an unusually short-lived photoluminescence, which can be tentatively assigned to the thermally activated delayed fluorescence of (M + X) LCT type (M = Cu, L = Py₃As; X = halogen). For the title Ag(I) complexes, QTAIM calculations reveal the pronounced argentophilic interactions for all short Ag∙∙∙Ag contacts (3.209–3.313 Å).

Simultaneous Occurrence of Vapochromism and Vapoluminescence in Formaldehyde-Responsive Amino-Functionalized Copper(I) Polymorphic Coordination Polymers

The use of vapor-responsive chromic materials in sensing applications for the detection of harmful volatile organic chemicals is rapidly expanding. Herein, four new amino-functionalized Cu(I) coordination polymers of [CuI(pyt-NH₂)]_n (1) and (2) and [CuSCN(pyt-NH₂)]_n (3) and (4) (where pyt-NH₂ = 2-amino-5-(4-pyridinyl)-1,3,4-thiadiazole) were successfully synthesized. Single-crystal X-ray diffraction analysis reveals that 1 and 2 are iodo-based polymorphs, while 3 and 4 are thiocyanato-based polymorphs. They possess densely diverse crystalline architectures decorated by uncoordinated amino groups as a binding site. Also, 1-4 show a variety of color and luminescence based on the structural diversity. Remarkably, 1 and 2 undergo the change of color and naked-eye solid-state luminescence in response to formaldehyde (FA) vapor, demonstrating simultaneous vapochromism and vapoluminescence. The chromic Cu(I) coordination polymers in this work present for the first time dual-mode vapochromism and vapoluminescence in a highly selective response to FA vapor. The responsive mechanism has been clarified by Fourier transform infrared spectroscopy (FT-IR), electrospray ionization mass spectrometry (ESI-MS), ¹H nuclear magnetic resonance (NMR), powder X-ray diffraction (PXRD), and luminescence lifetime measurements, which reveal carbinolamine formation via the specific reaction between FA and the active amino groups of coordinated pyt-NH₂. The carbinolamine formation can trigger the structural transformation of 1 and 2, leading to the concurrently selective vapochromism and vapoluminescence induced by FA vapor.

The Tail Wags the Dog: The Far Periphery of the Coordination Environment Manipulates the Photophysical Properties of Heteroleptic Cu(I) Complexes

In this work we show, using the example of a series of [Cu(Xantphos)(N^N)]+ complexes (N^N being substituted 5-phenyl-bipyridine) with different peripheral N^N ligands, that substituents distant from the main action zone can have a significant effect on the physicochemical properties of the system. By using the C≡C bond on the periphery of the coordination environment, three hybrid molecular systems with -Si(CH3)3, -Au(PR3), and -C2HN3(CH2)C10H7 fragments were produced. The Cu(I) complexes thus obtained demonstrate complicated emission behaviour, which was investigated by spectroscopic, electrochemical, and computational methods in order to understand the mechanism of energy transfer. It was found that the -Si(CH3)3 fragment connected to the peripheral C≡C bond changes luminescence to long-lived intra-ligand phosphorescence, in contrast to MLCT phosphorescence or TADF. The obtained results can be used for the design of new materials based on Cu(I) complexes with controlled optoelectronic properties on the molecular level, as well as for the production of hybrid systems.

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.

Self-assembled luminescent Cu(i) tetranuclear metallacycles based on 3,3′-bipyridine ligands

Three luminescent tetranuclear macrocycles are obtained selectively, applying coordination-driven supramolecular processes to the reaction of 3,3′-bipyridine ligand with in situ formed Cu(i) bimetallic units bearing a coordination angle of ca. 120°.

Coordination-driven supramolecular syntheses of new homo- and hetero-polymetallic Cu(i) assemblies: solid-state and solution characterization

New luminescent Cu(i) discrete assemblies D and FM and 1D coordination polymer E are reported. Deep insights of self-assembly processes based on flexible Cu(i) precursors are highlighted together with the preservation in solution of Cu(i) assemblies.

Vapochromic luminescence of a spin-coated copper(I) complex thin film by the direct coordination of vapour molecules

A homogeneous thin film of a simple and highly luminescent Cu(i) complex, [CuI(PPh3)2(py)] (PPh3 = triphenylphosphine, py = pyridine) (Cu-py), was fabricated via spin coating using polyvinylpyrrolidone (PVP) and pyridine without destroying the complex. The thin film (Cu-py@PVP), with a thickness of 1 μm, exhibited efficient response to vapour, exhibiting reversible luminescence changes between blue-green and yellow upon exposure to vapours of N-heteroaromatic compounds such as py and 2-methylpyrazine (Mepyz). Vapochromic luminescence colour change resulting from ligand substitution was also observed in the crystal state, but the response of the thin film was remarkably faster than that of the crystalline samples. The vapour-induced ligand exchange on the thin film was fully characterised by comparing the luminescence properties of the Cu-py crystal with the newly prepared Cu(i) complex, [CuI(Mepyz)(PPh3)2] (Cu-Mepyz).