Copper(I) Complexes Based on Five-Membered P∧N Heterocycles: Structural Diversity Linked to Exciting Luminescence Properties

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.

Design of luminescent complexes with different Cu4I4 cores based on pyridyl phenoxarsines

A series of luminescent Cu4I4 clusters with stair-step, cubane, and octahedral geometries supported by a novel type of cyclic As,N-ligand, pyridyl-containing 10-phenoxarsines, were synthesized and characterized by NMR spectroscopy, mass spectrometry, elemental analysis, and single-crystal X-ray diffraction analysis. An unusual arrangement of As,N-bidentate and μ2-iodo ligands was found in the octahedral cluster. The structural diversity of the Cu(I) complexes is reflected in their photophysical properties: the phosphorescence spectra of the compounds display emission in a broad spectral range of 495-597 nm. The complex with the Cu4I4L2 stoichiometry bearing a stair-step Cu4I4 core demonstrates temperature-dependent dual emission. The luminescence properties of all complexes were rationalized by DFT calculations.

From Mono- to Polynuclear 2-(Diphenylphosphino)pyridine-Based Cu(I) and Ag(I) Complexes: Synthesis, Structural Characterization, and DFT Calculations

A series of monometallic Ag(I) and Cu(I) halide complexes bearing 2-(diphenylphosphino)pyridine (PyrPhos, L) as a ligand were synthesized and spectroscopically characterized. The structure of most of the derivatives was unambiguously established by X-ray diffraction analysis, revealing the formation of mono-, di-, and tetranuclear complexes having general formulas MXL3 (M = Cu, X = Cl, Br; M = Ag, X = Cl, Br, I), Ag2X2L3 (X = Cl, Br), and Ag4X4L4 (X = Cl, Br, I). The Ag(I) species were compared to the corresponding Cu(I) analogues from a structural point of view. The formation of Cu(I)/Ag(I) heterobimetallic complexes MM'X2L3 (M/M' = Cu, Ag; X = Cl, Br, I) was also investigated. The X-ray structure of the bromo-derivatives revealed the formation of two possible MM'Br2L3 complexes with Cu/Ag ratios, respectively, of 7:1 and 1:7. The ratio between Cu and Ag was studied by scanning electron microscopy-energy-dispersive X-ray analysis (SEM-EDX) measurements. The structure of the binuclear homo- and heterometallic derivatives was investigated using density functional theory (DFT) calculations, revealing the tendency of the PyrPhos ligands not to maintain the bridging motif in the presence of Ag(I) as the metal center.

Copper(I) Complexes of Amide Functionalized Bisphosphine: Proximity Enhanced Metal-Ligand Cooperativity and Its Catalytic Advantage in C(sp3)-H Bond Activation of Unactivated Cycloalkanes in Dehydrogenative Carboxylation Reactions

The reactions of amide functionalized bisphosphine, o-Ph2PC6H4C-(O)N(H)C6H4PPh2-o (1) (BalaHariPhos), with copper salts is described. Treatment of 1 with CuX in a 1:1 molar ratio yielded chelate complexes of the type [CuX{(o-Ph2PC6H4C(O)N(H)C6H4PPh2-o)}-κ2-P,P] (X = Cl, 2; Br, 3; and I, 4), which on subsequent treatment with KOtBu resulted in a dimeric complex [Cu(o-Ph2PC6H4C(O)(N)C6H4PPh2-o)]2 (5). Interestingly, complexes 2-4 showed weak N-H···Cu interactions. These weak H-bonding interactions are studied in detail both experimentally and computationally. Also, CuI complexes 2-5 were employed in the oxidative dehydrogenative carboxylation (ODC) of unactivated cycloalkanes in the presence of carboxylic acids to form the corresponding allylic esters. Among complexes 2-5, halide-free dimeric CuI complex 5 showed excellent metal-ligand cooperativity in the oxidative dehydrogenative carboxylation (ODC) in the presence of carboxylic acids to form the corresponding allylic esters through C(sp3)-H bond activation of unactivated cycloalkanes. Mechanistic details of the catalytic process were established by isolating the precatalyst [Cu{(o-Ph2PC6H4C(O)(NH)C6H4PPh2-o)-κ2-P,P}(OOCPh)] (6) and fully characterized by mass spectrometry, NMR data, and single-crystal X-ray analysis. Density functional theory-based calculations further provided a quantitative understanding of the energetics of a series of H atom transfer steps occurring in the catalytic cycle.

Luminescent Water-Dispersible Nanoparticles Engineered from Copper(I) Halide Cluster Core and P,N-Ligand with an Optimal Balance between Stability and ROS Generation

The present work introduces the solvent exchange procedure as a route for conversion of the Cu4I4L2 complex, where the Cu4I4 cluster core is coordinated with two P,N-ligands (L), into an aqueous colloid. The analysis of both colloidal and supernatant phases revealed some losses in CuI going from the initial Cu4I4L2 complex to Cu2I2L3-based nanoparticles. The comparative analysis of IR, 31P NMR spectroscopy, ESI mass-spectrometry and luminescence data argued for a contribution of the “butterfly”-like structures of the Cu2I2 cluster core to Cu2I2L3-based nanoparticles, although the amorphous nature of the latter restricted structure evaluation from the PXRD data. The green luminescence of the colloids revealed their chemical stability under pH variations in the solutions of some amino acids and peptides, and to specify the temperature and concentration conditions triggering the oxidative degradation of the nanoparticles. The spin trap-facilitated ESR study indicated that the oxidative transformations were followed by the generation of reactive oxygen species (ROS). The physiological temperature level (310 K) enhanced the ROS generation by nanoparticles, but the ROS level was suppressed in the solution of GSH at pH = 7.0. The cytotoxicity of nanoparticles was evaluated in the M-HeLa cell line and is discussed in correlation with their cell internalization and intracellular oxidative transformations.

Deep-Blue Emissive Copper(I) Complexes Based on P-Thiophenylethyl-Substituted Cyclic Bisphosphines Displaying Photoinduced Structural Transformations of the Excited States

A synthetic method for a primary 2-(thiophen-2'-yl)ethylphosphine was developed. The reaction of thiophenylethylphosphine with paraformaldehyde and primary arylamines leads to the formation of cyclic bisphosphines, namely, 1,5-di(aryl)-3,7-bis(thiophenylethyl)-1,5-diaza-3,7-diphosphacyclooctane (aryl = phenyl, p-tolyl). The obtained bisphosphines form cationic bis-P,P-chelate complexes with copper(I) tetrafluoroborate, which were structurally characterized by NMR spectroscopy, mass spectrometry, and elemental and XRD analyses. Surprisingly, the copper(I) complexes display a multiband emission in the solid state with maxima at 355-360, 425-430, and 480-490 nm and nanosecond lifetimes (1.2-1.4 ns) upon a 335 nm excitation. The excitation of the complexes at 360 nm at room temperature results in a deep-blue emission at 425-430 nm and a tail at 460-490 nm. A temperature decrease leads to an increased intensity of the emission band at 480 nm, while the luminescence lifetimes insignificantly increased up to 14 ns. Quantum chemical calculations explain the observed unusual luminescent behavior by the existence of "undistorted" and "flattened" singlet excited states of copper(I) complexes at room temperature and at 77 K, respectively.

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.

Thermally Activated Delayed Fluorescence and Phosphorescence Quenching in Iminophosphonamide Copper and Zinc Complexes

The synthesis of copper and zinc complexes of four variably substituted iminophosphonamide ligands is presented. While the copper complexes form ligand-bridged dimers, the zinc compounds are monomeric. Due to different steric demand of the ligand the arrangement of the ligands within the dimeric complexes varies. Similar to the structurally related iminophosphonamide complexes of alkali metals and calcium, the steady-state and time-resolved photoluminescence (PL) of four of the seven compounds studied here as solids in a temperature range of 5-295 K can be described within the scheme of thermally activated delayed fluorescence (TADF). Accordingly, they exhibit bright blue-green phosphorescence at low temperatures (<100 K), which turns into delayed fluorescence by increasing the temperature. However, unusually, the fluorescence is practically absent in two copper complexes which otherwise still conform to the TADF scheme. In these cases, the excited singlet states decay essentially non-radiatively and their thermal population from the corresponding low-lying triplet states efficiently quenches PL (phosphorescence). Three other copper and zinc complexes only exhibit prompt fluorescence, evidencing a wide variation of photophysical properties in this class of compounds. The excited states of the copper complex with especially pronounced phosphorescence quenching were also investigated by low-temperature time-resolved infrared spectroscopy and quantum chemical calculations.

Bright bluish-green emitting Cu(I) complexes exhibiting efficient thermally activated delayed fluorescence

Three strongly emissive Cu(i) complexes [Cu(tBupzmpy)(POP)]BF4(1), [Cu(Phpzmpy)(POP)]BF4(2) and [Cu(Adpzmpy)(POP)]BF4(3) (tBupzmpy = 2-(5-(tert-butyl)-1H-pyrazol-3-yl)-6-methylpyridine, Phpzmpy = 2-methyl-6-(5-phenyl-1H-pyrazol-3-yl)pyridine, Adpzmpy = 2-(5-((3R,5R)-adamantan-1-yl)-1H-pyrazol-3-yl)-6-methylpyridine, and POP = bis[2-(diphenylphosphino)phenyl]ether) were synthesized and characterized. These complexes exhibit bright bluish-green photoluminescence in the solid state with quantum yields of 91% (1), 71% (2) and 77% (3) and lifetimes of 13.4 μs (1), 32.9 μs (2) and 34.1 μs (3) at room temperature. The results of theoretical calculations, coupled with the temperature dependence of the spectroscopic properties and emission decay behaviors, reveal that the title Cu(i) complexes emit efficient thermally activated delayed fluorescence (TADF) from excited states involving metal-to-ligand charge transfer (MLCT) transitions and ligand-to-ligand charge transfer (LLCT) transitions. The emissive-state characteristics and emission properties of the investigated Cu(i) complexes were tuned effectively by changing the steric and electronic structures of the diimine ligands.

Various Structural Design Modifications: para-Substituted Diphenylphosphinopyridine Bridged Cu(I) Complexes in Organic Light-Emitting Diodes

The well-known system of dinuclear Cu(I) complexes bridged by 2-(diphenylphosphino)pyridine (PyrPhos) derivatives Cu₂X₂L₃ and Cu₂X₂LP₂ (L = bridging ligand, P = ancillary ligand) goes along with endless variation options for tunability. In this work, the influence of substituents and modifications on the phosphine moiety of the NP-bridging ligand was investigated. In previous studies, the location of the lowest unoccupied molecular orbital (LUMO) of the copper complexes of the PyrPhos family was found to be located on the NP-bridging ligand and enabled color tuning in the whole visible spectrum. A multitude of dinuclear Cu(I) complexes based on the triple methylated 2-(bis(4-methylphenyl)phosphino)-4-methylpyridine (Cu-1b-H, Cu-1b-MeO, and Cu-1b-F) up to complexes bearing 2-(bis(4-fluorophenyl)phosphino)pyridine (Cu-6a-H) with electron-withdrawing fluorine atoms over many other variations on the NP-bridging ligands were synthesized. Almost all copper complexes were confirmed via single crystal X-ray diffraction analysis. Besides theoretical TDDFT-studies of the electronic properties and photophysical measurements, the majority of the phosphino-modified Cu(I) complexes was tested in solution-processed organic light-emitting diodes (OLEDs) with different heterostructure variations. The best results of the OLED devices were obtained with copper emitter Cu-1b-H in a stack architecture of ITO/PEDOT-PSS (50 nm)/poly-TPD (15 nm)/20 wt % Cu(I) emitter:CBP:TcTA(7:3) (45 nm)/TPBi (30 nm)/LiF(1 nm)/Al (>100 nm) with a high brightness of 5900 Cd/m² and a good current efficiency of 3.79 Cd/A.

Vapor-triggered Green-to-Yellow Luminescence Conversion due to the Variation of Ligand Orientations in Tetranuclear Copper(I) Complex

The reaction of 3,6-ditert-butyl-1,8-bis(diphenylphosphino)-9-methyl-9H-carbazole (L) with CuBr resulted in the isolation of tetranuclear copper(I) complex Cu₄Br₄L₂ as two colorless crystal morphs, i.e., green-emitting 1G and yellow-emitting 1Y. As demonstrated by X-ray crystallography, the Cu₄Br₄ moiety in both 1G and 1Y adopts the same chair conformations. When L is bonded perpendicularly to the Cu₄ plane, 1G with green emission is obtained, while it gives a yellow emission of 1Y once the L is parallelly bonded to Cu₄ plane. Theoretical computational studies suggest that the variation in ligand orientation results in a different degree of structural distortion in triplet state and thus different luminescent energy. Particularly, 1Y undergoes dramatic structural distortion from the ground (S₀) to triplet excied state (T₁). Interestingly, 1G can be converted into 1Y upon exposed to saturated hexane vapor, which would return to 1G upon exposure to acetonitrile vapor. As demonstrated experimentally and theoretically, the reversible luminescence transformation between 1G and 1Y is ascribed to the variation of ligand L orientations.

Copper(I) Phosphinooxazoline Complexes: Impact of the Ligand Substitution and Steric Demand on the Electrochemical and Photophysical Properties

A series of seven homoleptic Cu^I complexes based on hetero-bidentate P^N ligands was synthesized and comprehensively characterized. In order to study structure-property relationships, the type, size, number and configuration of substituents at the phosphinooxazoline (phox) ligands were systematically varied. To this end, a combination of X-ray diffraction, NMR spectroscopy, steady-state absorption and emission spectroscopy, time-resolved emission spectroscopy, quenching experiments and cyclic voltammetry was used to assess the photophysical and electrochemical properties. Furthermore, time-dependent density functional theory calculations were applied to also analyze the excited state structures and characteristics. Surprisingly, a strong dependency on the chirality of the respective P^N ligand was found, whereas the specific kind and size of the different substituents has only a minor impact on the properties in solution. Most importantly, all complexes except C3 are photostable in solution and show fully reversible redox processes. Sacrificial reductants were applied to demonstrate a successful electron transfer upon light irradiation. These properties render this class of photosensitizers as potential candidates for solar energy conversion issues.

Photoluminescent properties and molecular structures of dinuclear gold(i) complexes with bridged diphosphine ligands: near-unity phosphorescence from 3XMMCT/3MC

Dinuclear gold(i) complexes with bridged diphosphine ligands display near-unity phosphorescence in the crystalline state at room-temperature.

Copper(i) halide polymers derived from tris[2-(pyridin-2-yl)ethyl]phosphine: halogen-tunable colorful luminescence spanning from deep blue to green

A series of isostructural 1D coordination polymers bearing stair-step [Cu₄X₄] modules is reported. At ambient temperature, they feature bright halogen-modulated colorful luminescence spanning from deep blue to green.

New 1,2,3-triazole based bis- and trisphosphine ligands: synthesis, transition metal chemistry and catalytic studies

This paper describes a novel synthetic methodology for the preparation of 1,2,3-triazole based phosphines and their transition metal chemistry and preliminary catalytic studies.

Highly soluble fluorine containing Cu(i) AlkylPyrPhos TADF complexes

Luminescent Cu(i) AlkylPyrPhos complexes with a butterfly-shaped Cu₂I₂ core and halogen containing ancillary ligands, with a special focus on fluorine, have been investigated in this study. These complexes show extremely high solubilities and a remarkable (photo)chemical stability in a series of solvents. A tunable emission resulting from thermally activated delayed fluorescence with high quantum yields was determined by luminescence and lifetime investigations in solvents and solids. Structures of the electronic ground states were analyzed by single crystal X-ray analysis. The structure of the lowest excited triplet state was determined by transient FTIR spectroscopy, in combination with quantum chemical calculations. With the obtained range of compounds we address the key requirement for the production of organic light emitting diodes based on solution processing.

Bisimidazole-based phosphorescent thiocyanatocadmates

Simple room-temperature self-assemblies between Cd2+ salts, SCN- and bisimidazole molecules at pH = 2 created three new organically templated thiocyanatocadmates [H2(L1)][Cd(SCN)4]·H2O (L1 = 1,4-bis(1H-imidazol-1-yl)benzene) 1, [H2(L2)][Cd(SCN)4] (L2 = 1,3-bis(2-methylimidazol-1-yl)propane) 2, and [H2(L3)][Cd2(SCN)6] (L3 = 1,4-bis(2-methyl-1H-imidazol-1-yl)butane) 3. X-ray single-crystal diffraction analysis reveals that (i) in 1-3, the SCN- groups doubly bridge the Cd2+ centers to form different thiocyanatocadmates: a linear chain in 1; a zigzag chain in 2; and a 2-D layer network (63 net) in 3; and (ii) in 1, via Nbase-HNSCN interactions, the L1 molecules extend the thiocyanatocadmate chains into a 2-D supramolecular layer, whereas in 2, the zigzag thiocyanatocadmate chains self-assemble into a 3-D supramolecular network via weak SS interactions. Photoluminescence analysis indicates that the three title compounds all emit light: blue light for 1 and 2 and green light for 3. At low temperatures, the emission positions of the three compounds hardly change, but the emission intensities are largely enhanced. Interestingly, after turning off the UV lamp, 1 and 2 still briefly emit light (ca. 2 s), which means that 1 and 2 possess phosphorescence properties. Phosphorescence lifetimes at 77 K are 1619 ms for 1 and 247 ms for 2.

Copper(i)-polymers and their photoluminescence thermochromism properties

Under hydro(solvo)thermal conditions, four organic bidentate bridging N,N'-donor ligands 1,3-bis(2-methylimidazol-1-yl)propane (L1), 4,4'-di(1H-imidazol-1-yl)-1,1'-biphenyl (L2), 1,2-bis(2-methyl-1H-imidazol-1-ylmethyl)benzene (L3) and 5,6,7,8-tetrahydroquinoxaline (L4) were employed to react with CuBr/CuI, generating four 2-D layered copper(i)-polymer coordination polymer materials [Cu2Br2(L1)] 1, [CuI(L2)] 2, [CuI(L3)] 3 and [CuI(L4)0.5] 4. In 1-4, different Cu-X motifs are found: a cubic Cu4Br4 core in 1; a castellated Cu-I single chain in 2; a rhombic Cu2I2 core in 3; and a staircase-like Cu-I double chain in 4. The 2-D layer networks of 1-3 can all be simplified into a simple 44 topology (planar for 1 and 3; wave-like for 2), while the 2-D layer network of 4 has a 63 topology. The photoluminescence behaviors of 1-4 under a UV lamp suggest that 1 and 2 possess fluorescence thermochromism properties. Under the UV lamp, with the decrease in temperature, (i) 1 exhibits a yellow-to-red emission; (ii) 2 exhibits a yellow-to-green emission; (iii) 3 always emits green light; and (iv) 4 never emits light. These are further confirmed by their emission spectra. From 297 K to 77 K, the emission of 1 exhibits a large red shift from 561 nm to 623 nm; the emission of 2 exhibits a large blue shift from 571 nm to 515 nm; only a minor red shift is observed for the emission of 3; and no peaks appear in the emission spectra of 4. The crystal data of 1 and 2 at different temperatures have been collected for revealing the origination of their fluorescence thermochromism properties. Based on the above investigations, the effect of the rigidity/flexibility of the organic ligand on the fluorescence thermochromism properties of copper(i)-polymer coordination polymer materials is discussed. The quantum yields at 297 K and the photoluminescence lifetimes at 297 K and 77 K for 1-3 were also measured for better understanding their photoluminescence properties.

Luminescent complexes on a scaffold of P2N2-ligands: design of materials for analytical and biomedical applications

A variety of gold(I) and copper(I) complexes based on heterocyclic phosphine platform has been obtained. Due to the presence of exocyclic chromophoric pyridyl groups in the ligands complexes demonstrate noticeable phosphorescence. Cyclic nature of the phosphine ligands is responsible for supramolecular host-behavior of the complexes. Unique structure of complexes on a scaffold of the cyclic PNNP ligands favors the stimuli-induced structural reorganizations followed by stimuli-responsive luminescence. This, in turn, makes the complexes versatile building blocks for bottom-up design of smart nanomaterials for analytical and biomedical applications.

Diverse Architectures and Luminescence Properties of Group 11 Complexes Containing Pyrimidine-Based Phosphine, N-((Diphenylphosphine)methyl)pyrimidin-2-amine

In this article, the synthesis, structural studies, and luminescence properties of Cu^I, Ag^I, and Au^I complexes of pyrimidine-based phosphine [C₄H₃N₂-2-NH(CH₂PPh₂)] (1) are described. The reactions of 1 with CuX led to the isolation of one-dimensional (1D) chain, tetranuclear ladder, or cyclic derivatives. The structural features of these complexes are greatly influenced by the metal-to-ligand ratio, reaction conditions, and CuX (X = Cl, Br or I) employed. In the case of CuCl and CuBr, one-dimensional coordination polymers [{CuCl}{C₄H₃N₂-2-NH(CH₂PPh₂)}]_∞ (2) and [{CuBr}{C₄H₃N₂-2-NH(CH₂PPh₂)}]_∞ (3) were obtained, whereas CuI afforded tetracopper complex [{CuI}₄{C₄H₃N₂-2-NH(CH₂PPh₂)}₂(NCCH₃)₂] (4) having Cu₄ ladder structure supported by P∩N-bridging coordination of 1. The reaction of 1 with AgOTf yielded unprecedented one-dimensional chain structure [{AgOTf}{C₄H₃N₂-2-NH(CH₂PPh₂)}]_∞ (5), whereas the reaction with AgBF₄ produced a 12-membered dinuclear complex, [{Ag}{C₄H₃N₂-2-NH(CH₂PPh₂)}]₂[BF₄]₂ (6), with each silver atom having a linear geometry. Gold complex [{AuCl}{C₄H₃N₂-2-NH(CH₂PPh₂)}]₂ (7) was synthesized by reacting 1 with [AuCl(SMe₂)]. Compounds 2-4 were also prepared using a pestle and mortar by grinding method in almost quantitative yield. Complex 4 with a Cu···Cu distance of 2.828(5) Å shows high luminescence due to the nonbonded metal···metal interactions.

A P-H functionalized Al/P-based frustrated Lewis pair - hydrophosphination of nitriles, ring opening with cyclopropenones and evidence of P[double bond, length as m-dash]C double bond formation

Hydroalumination of R-P(H)-C[triple bond, length as m-dash]C-tBu with bulky H-Al[CH(SiMe3)2]2 afforded the new P-H functionalized Al/P-based frustrated Lewis pair R-P(H)-C[[double bond, length as m-dash]C(H)-tBu]-AlR2 [R = CH(SiMe3)2; FLP 7]. A weak adduct of 7 with benzonitrile (8) was detected by NMR spectroscopy, but could not be isolated. tert-Butyl isocyanide afforded a similar, but isolable adduct (9), in which the isocyanide C atom was coordinated to aluminium. The unique reactivity of 7 became evident from its reactions with the heteroatom substituted nitriles PhO-C[triple bond, length as m-dash]N, PhCH2S-C[triple bond, length as m-dash]N and H8C4N-C[triple bond, length as m-dash]N. Hydrophosphination of the C[triple bond, length as m-dash]N triple bonds afforded imines at room temperature which were coordinated to the FLP by Al-N and P-C bonds to yield AlCPCN heterocycles (10 to 12). These processes depend on substrate activation by the FLP. Diphenylcyclopropenone and its sulphur derivative reacted with 7 by addition of the P-H bond to a C-C bond of the strained C3 ring and ring opening to afford the fragment (Z)-Ph-C(H)[double bond, length as m-dash]C(Ph)-C-X-Al (X = O, S). The C-O or C-S groups were coordinated to the FLP to yield AlCPCX heterocycles (13 and 14). The thiocarbonyl derived compound 14 contains an internally stabilized phosphenium cation with a localized P[double bond, length as m-dash]C bond, a trigonal planar coordinated P atom and a short P[double bond, length as m-dash]C distance (168.9 pm). Insight into formation mechanisms, the structural and energetic properties of FLP 7 and compounds 13 and 14 was gained by quantum chemical DFT calculations.

Dinuclear Cu(I) Complex with Combined Bright TADF and Phosphorescence. Zero-Field Splitting and Spin-Lattice Relaxation Effects of the Triplet State

The three-fold bridged dinuclear Cu(I) complex Cu₂(μ-I)₂(1 N- n-butyl-5-diphenyl-phosphino-1,2,4-triazole)₃, Cu₂I₂(P^N)₃, shows bright thermally activated delayed fluorescence (TADF) as well as phosphorescence at ambient temperature with a total quantum yield of 85% at an emission decay time of 7 μs. The singlet (S₁)-triplet (T₁) energy gap is as small as only 430 cm^-1 (53 meV). Spin-orbit coupling induces a short-lived phosphorescence with a decay time of 52 μs ( T = 77 K) and a distinct zero-field splitting (ZFS) of T₁ into substates by ∼2.5 cm^-1 (0.3 meV). Below T ≈ 10 K, effects of spin-lattice relaxation (SLR) are observed and agree with the size of ZFS. According to the combined phosphorescence and TADF, the overall emission decay time is reduced by ∼13% as compared to the TADF-only process. The compound may potentially be applied in solution-processed OLEDs, exploiting both the singlet and triplet harvesting mechanisms.

New photoluminescent iodoargentates with bisimidazole derivatives as countercations

In this article, three bisimidazole derivatives (1,4-bis(2-ethylimidazol-1-yl)butane, L1; 4,4′-di(1H-imidazol-1-yl)-1,1′-biphenyl, L2′; and 1,3-bis(2-ethylimidazol-1-yl)propane, L3) were employed to solvothermally react with AgI in an acidic environment, creating three new 1-D chained iodoargentates [H(L1)][Ag₅I₆]·DMF (DMF = N,N′-dimethylformamide) 1, [L2][Ag₃I₅] (L2²⁺ = 4,4′-di(1H-imidazol-1-ium)-1,1′-biphenyl) 2, and [H₂(L3)][Ag₂I₄] 3. L2²⁺ in 2 originated from the in situ N-alkylation of L2′ with the CH₃OH solvent. X-ray single-crystal diffraction analysis reveals that (i) in 1, Ag⁺ and I⁻ aggregate to form a 1-D tube-like iodoargentate, which exhibits the same topology as the carbon tube; (ii) the chain structure of the iodoargentate in 2 is based on a kind of trinuclear Ag–I cluster, which can be viewed as a segment of the classical cubic M₄I₄ cluster; (iii) the chain structure of the iodoargentate in 3 is simple, which can be described as a linear arrangement of the AgI₄ tetrahedra by sharing edges. The photoluminescence analysis reveals that at 77 K, (i) 1 and 2 emit strong yellow light with ms-grade photoluminescence lifetimes (5.460 ms for 1, 6.931 ms for 2); (ii) 3 possesses photochromic luminescence properties. Upon excitation at 254 nm, it emits blue-green light, whereas upon excitation at 365 nm, it emits yellow light.

Three bisimidazole-based chained iodoargentates were solvothermally synthesized, and their photoluminescent behaviors at different temperatures were investigated. Of those, 3 has been found to possess photochromic luminescence properties.

Cooperative metal–ligand influence on the formation of coordination polymers, and conducting and photophysical properties of Tl(i) β-oxodithioester complexes

Eight novel luminescent and semiconducting Tl(i) β-oxodithioester complexes forming 1D/2D coordination polymeric structures were investigated using single crystal X-ray diffraction.

1,2,3-Triazole based bisphosphine, 5-(diphenylphosphanyl)-1-(2-(diphenylphosphanyl)-phenyl)-4-phenyl-1H-1,2,3-triazole: an ambidentate ligand with switchable coordination modes

The reaction of 1-(2-bromophenyl)-4-phenyl-1H-1,2,3-triazole (1) with Ph₂PCl yielded bisphosphine, 5-(diphenylphosphanyl)-1-(2-(diphenylphosphanyl)phenyl)-4-phenyl-1H-1,2,3-triazole (2). Bisphosphine 2 exhibits ambidentate character in either the κ²-P,N or κ²-P,P coordination mode. Treatment of 2 with [M(CO)₄(piperidine)₂] (M = Mo and W) yielded κ²-P,N and κ²-P,P coordinated Mo⁰ and W⁰ complexes [M(CO)₄(2)] [M = W-κ²-P,N (4); Mo-κ²-P,P (5); W-κ²-P,P (6)] depending on the reaction conditions. Formation and stability of κ²-P,P coordinated Mo⁰ and W⁰ complexes were assessed by time dependent ³¹P{¹H} NMR experiments and DFT studies. The complex 4 on treatment with [AuCl(SMe₂)] afforded the hetero-bimetallic complex [μ-PN,P-{o-Ph₂P(C₆H₄){1,2,3-N₃C(Ph)C(PPh₂AuCl)}-κ²-P,N}W(CO)₄] (7). The 1 : 1 reaction between 2 and [CpRu(PPh₃)₂Cl] yielded [(η⁵-C₅H₅)RuCl{o-Ph₂P(C₆H₄){1,2,3-N₃C(Ph)C(PPh₂)}}-κ²-P,P] (8), whereas the similar reaction with [Ru(η⁶-p-cymene)Cl₂]₂ in a 2 : 1 molar ratio produced a cationic complex [(η⁶-p-cymene)RuCl{o-Ph₂P(C₆H₄){1,2,3-N₃C(Ph)C(PPh₂)}}-κ²-P,N]Cl (9). Similarly, treatment of 2 with [M(COD)(Cl)₂] (M = Pd and Pt) in a 1 : 1 molar ratio yielded Pd^II and Pt^II complexes [{o-Ph₂P(C₆H₄){1,2,3-N₃C(Ph)C(PPh₂)}-κ²-P,P}PdCl₂] (10) and [{o-Ph₂P(C₆H₄){1,2,3-N₃C(Ph)C(PPh₂)}-κ²-P,P}PtCl₂] (11). The reaction of 2 with 2 equiv. of [AuCl(SMe₂)] afforded [Au₂Cl₂{o-Ph₂P(C₆H₄){1,2,3-N₃C(Ph)C(PPh₂)}}-μ-P,P] (12). Most of the complexes have been structurally characterized. Palladium complex 10 shows excellent catalytic activity towards Cu-free Sonogashira alkynylation/cyclization reactions.

This paper describes the synthesis of a triazole based bisphosphine and its transition metal chemistry and catalytic utility in Cu-free Sonogashira alkynylation/cyclization reaction.

The coordination- and photochemistry of copper(i) complexes: variation of N^N ligands from imidazole to tetrazole

Prediction rules for the coordination chemistry of copper(i) with neutral or deprotonated N^N ligands and different phosphines were derived and related to their photoluminescence.