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We present a unique new subclass of Cu(i) hybrid complexes, showing TADF with near-unity quantum yields as well as unprecedented solvatochromic emission and strong X-ray radioluminescence.

We report here a series of original ligand-supported trigonal planar Au@Ag

A series of complexes [Cu2X2(Pic3PO)2] (X = Cl, Br, I) based on tris(pyridin-2-ylmethyl)phosphine oxide (Pic3PO) has been synthesized. At 298 K, these compounds exhibit thermally activated delayed fluorescence (TADF) of 1(M+X)LCT type with λmax varying from 485 to 545 nm, and quantum efficiency up to 54%. In the TADF process, the halide effect appears as the emission intensification and bathochromic shift of λmax in the following order X = I < Br < Cl. Upon X-ray irradiation, the title compounds emit radioluminescence, the emission bands of which have the same shape as those at TADF, thereby meaning a similar radiative excited state. By contrast to TADF, the halide effect in the radioluminescence is reversed: its intensity grows in the order X = Cl < Br < I, since heavier atoms absorb X-rays more efficiently. These findings essentially contribute to our knowledge about the halide effect in the photo- and radioluminescent Cu(I) halide emitters.

A series of isostructural 1D coordination polymers (CPs), [Cu4X4(L)2]n where X = Cl (1), Br (2), I (3), have been synthesized via the reaction of Cu(I) halides with tris[2-(pyridin-2-yl)ethyl]phosphine (L). 1D chains of these CPs are built up by alternating stair-step [Cu4X4] modules bridged by “PyCH2CH2P” ligand arms. At ambient temperature, the titled polymers exhibit strong luminescence, the color of which is tuned by the halogen atoms spanning from deep-blue (λmax = 448 nm, for X = I) to green (λmax = 520 nm, for Cl) through cyan (λmax = 490 nm, for Br). The emission lifetimes fall close to the 13–24 μs region at 300 K, and PL quantum yields (45–62%) are the highest among yet known emitters bearing stair-step [Cu4X4] units. A combination of spectral studies and (TD)DFT computations suggests that the emission of the CPs represents phosphorescence stemmed from the 3(M + X)LCT excited states.

A set of alkynyl-tris(2-pyridyl)phosphine Au(i) complexes was synthesized and characterized. Free coordination functions on the ligand environment periphery, namely 'scorpionate' PPy3 and the C[triple bond, length as m-dash]C bond, allowed these ditopic metalloligands to be selectively linked to 1D coordination polymers by reaction with Cu(i), which used both Cu-(N-PPy3) and Cu-(η2-C[triple bond, length as m-dash]C) coordination modes. Single-crystal and powder XRD, NMR, and XPS techniques were used to characterize the coordination polymers obtained. Heterobimetallic Au(i)-Cu(i) coordination polymers demonstrate triplet photoluminescence which was studied by spectroscopic and computational methods to understand the pathway of energy transfer inside the chain of linked chromophore centres. The intriguing feature of the electronic structure of heterobimetallic supramolecular assemblies is the 'long-distance' electronic transition involving PhC2 and PPy3 ligands located at a distance of more than 1 nm from each other. Thus, the assembly of a heterobimetallic coordination polymer from relatively simple 'building blocks' retains the block-wise nature of the electronic structure, but the photophysical properties of the polymer are fundamentally different from the properties of discrete organometallic components.

A new organic–inorganic Cu(I) bromide complex based on triple protonated tris(2-pyridyl)phosphine (HPy)3P, [(HPy)3PCu2Br5] (1), has been synthesized by a straightforward reaction in solution or by modification of the [Cu2Br2(Py3P)2] complex using hydrobromic acid. At 77 K, the solid complex 1 exhibits near infra-red photoluminescence with λmax = 680 nm related to 3(M + X)LCT. The emission of 1 rapidly decreases with increasing temperature and is absent at 200 K due to thermal quenching with a small energy barrier ΔE ≈ 590 cm−1. The photophysical results are in good agreement with the TD-DFT calculations showing that in the ground state the cuprophilic interaction between copper ions is absent in spite of the short Cu⋯Cu distance. After annealing of complex 1 at 120 °C, photoluminescence occurred with λmax = 640 nm at 300 K. Complex 1 exhibits a luminescence response in ammonia gas consisting of the appearance of luminescence with λmax = 520 nm followed by the gradual enhancement of the luminescence intensity.

Coordination abilities of tris[2-(2-pyridyl)ethyl]phosphine (L) toward Ag(I) and Au(I) have been surveyed. Its reaction with AgClO4, AgNO3 and AgOTf results in self-assembly of 1D coordination polymers (CPs) of [Ag(L)X]n type (X = ClO4, NO3, OTf), built up by conjugated twelve-membered [Ag ( N C C C P P C C C N ) Ag] cycles. The reaction of this phosphine with AgCl affords CP [Ag4Cl4(L)2]n, where in stepped cubane [Ag4Cl4] modules are bridged by “PyCH2CH2P” arms. Interaction of L with Au(tht)Cl produces linear [Au(L)Cl] complex, in which P-coordination is observed. CPs [Ag(L)ClO4]n and [Ag4Cl4(L)2]n at ambient temperature show pronounced excitation wavelength dependent photoluminescence originated by intraligand transitions.

The first example of a triply bridging (μ3 -P) phosphine ligand has been discovered in the crown-shaped [Cu3 (μ2 -Hal)3 L] (Hal=Cl, Br, or I) complexes supported by tris[2-(2-pyridyl)ethyl]phosphine (L). Theoretical analysis completely confirms the observed μ3 -P-bridging pattern, revealing the interaction of the same lone pair of phosphorus with three valence 4s-orbitals of Cu atoms. The presented complexes exhibit outstanding blue phosphorescence (λem =442-465 nm) with the quantum efficiency reaching 100 %. The complex [Cu3 (μ2 -I)3 L] also exhibits remarkable thermo- and mechanochromic luminescence resulting in a sharp change in the emission colour upon external stimuli. These findings essentially contribute to coordination chemistry of the pnictine ligands.

Mononuclear zinc(ii) and cadmium(ii) complexes, ZnLCl2 (1), CdLCl2 (2), ZnL1Cl2·2H2O (3), and CdL1Cl2·2H2O (4), with chiral ligands containing a 2,2'-bipyridine moiety and natural terpene (+)-limonene (L) or (+)-3-carene (L1) moieties were synthesized. In these complexes the L and L1 ligands are shown to coordinate Zn2+ and Cd2+ ions through the 2,2'-bipyridine moiety. The acetamide group of the ligands interacts with M2+ ions by forming NM2+ and C[double bond, length as m-dash]OM2+ contacts and N-HCl hydrogen bonds with coordinated Cl- ions. In solutions the complexes have several conformers differing by the degree of the turn of the acetamide moiety relative to the ligand core and the type of its interaction with the coordination core. The ligands and complexes exhibit luminescence with the quantum yield increasing in the order: ligandcadmium(ii) complexzinc(ii) complex. The complexes 3 and 4 demostrate excitation wavelength independent single-channel fluorescence. As opposed to 3 and 4, the complexes 1 and 2 demonstrate excitation wavelength dependent emission with nanosecond and microsecond lifetimes of the excited states. According to our TD-DFT calculations, an interplay of ligand centered and halide to ligand transitions facilitates two deactivation channels in 1 and 2: S1-S0 and T1-S0.

Diphenyl(5-pyrimidyl)phosphine (L) has been synthesized and its coordination abilities toward Cu(I) and Au(I) have been surveyed. The reaction of L with Cu(MeCN)4BF4 or CuI produces 1D polymers [Cu(L)(MeCN)2]BF4 and [Cu2I2(L)2], or 2D grids [Cu2I2(L)2], wherein P,N-bridging pattern of the ligand always appears. Treatment of L with 1 or 3 equiv. of Au(tht)Cl affords linear [Au(L)Cl] or trigonal pyramidal [Au(L)3Cl] complexes, in which the ligand is P-coordinated to Au(I). At 300 K, 1D polymers [Cu(L)(MeCN)2]BF4 and [Cu2I2(L)2] exhibit weak yellow and moderate green emission, respectively, which strongly enhances upon colling to 77 K. Complex [Au(L)3Cl] at 300 K emits strong sky-blue phosphorescence (λem = 492 nm) with the quantum yield of 50%.

A series of Cu(I) halide complexes derived from tris(2-pyridyl)phosphine (Py3P), [Cu2(Py3P)2X2] (X = Cl, Br, I), have been synthesized by a straightforward reaction in solution or through a mechanochemical route. At room temperature, the solid complexes exhibit bright dual-mode photoluminescence (λmax = 520–550 nm, τ = 14.5–20.0 μs, and ΦPL ≈ 53%), expressed by thermally activated delayed fluorescence (TADF) combined with phosphorescence (PH), originating from 1(M + X)LCT and 3(M + X)LCT excited states, respectively. Remarkably, the balance of these radiative processes at 300 K is regulated by halogen atom nature, switching from TADF-assisted phosphorescence to PH-admixed TADF. The emission of [Cu2(Py3P)2Cl2] at 300 K is largely contributed by PH (73%) admixed with the TADF fraction (27%) and [Cu2(Py3P)2Br2] also emits mainly PH (65%) admixed with the larger TADF fraction (35%). Meanwhile, for [Cu2(Py3P)2I2], the TADF channel becomes dominating (61%) and PH contribution drops to 39%. The photophysical study corroborated by (TD)DFT computations has revealed that this effect arises mainly from the narrowing of the ΔE(S1 − T1) gap of the [Cu2(Py3P)2X2] complexes in the order Cl (1500 cm−1) > Br (1250 cm−1) > I (1000 cm−1) which facilitates the TADF pathway and suppresses PH in the same order.