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.

Linkage of the Dinuclear Gold(I) Complex Luminescence and Origin of Endocyclic Amino Group of Cyclic P2N2-Bridging Ligands.

Gold(I) complexes of LAu2Cl2 composition based on P2N2 ligands, namely 1,5-diaza-3,7-diphosphacyclooctanes, containing ethylpyridyl substituents at the phosphorus atoms and sp2- or sp3-hybridized endocyclic nitrogen atoms were synthesized. The SCXRD analysis indicated the strong impact of the geometry of the nitrogen atom on the structure and conformational flexibility of the complexes. The N-aryl substituted ligand with the planar endocyclic nitrogen atom provides higher flexibility of the complex and an ability to bind the solvent molecules in the "host-guest" mode, whereas that kind of behavior is forbidden for the complex with an N-alkyl substituted ligand with a pyramidal nitrogen atom. The substituents at nitrogen atoms also control the origin of the emission, which is phosphorescence for the N-aryl substituted complex and fluorescence for the N-alkylaryl substituted complex. The phosphorescent gold(I) complex displays high cytotoxicity without selectivity toward the m-HeLa and normal cells, but the core-shell nanoparticles formed on the base of the complex demonstrate reduced cytotoxicity. The luminescence of the NPs allows tracking the complexes in the cell samples.

ROS-producing nanomaterial engineered from Cu(I) complexes with P2N2-ligands for cancer cells treating.

The work presents core-shell nanoparticles (NPs) built from the novel Cu(I) complexes with cyclic P2N2-ligands (1,5-diaza-3,7-diphosphacyclooctanes) that can visualize their entry into cancer and normal cells using a luminescent signal and treat cells by self-enhancing generation of reactive oxygen species (ROS). Variation of P- and N-substituents in the series of P2N2-ligands allows structure optimization of the Cu(I) complexes for the formation of the luminescent NPs with high chemical stability. The non-covalent modification of the NPs with triblock copolymer F-127 provides their high colloidal stability, followed by efficient cell internalization of the NPs visualized by their blue (⁓450 nm) luminescence. The cytotoxic effects of the NPs toward the normal and some of cancer cells are significantly lower than those of the corresponding molecular complexes, which correlates with the chemical stability of the NPs in the solutions. The ability of the NPs to self-enhanced and H2O2-induced ROS generation is demonstrated in solutions and intracellular space by means of the standard electron spin resonance (ESR) and fluorescence techniques correspondingly. The anticancer specificity of the NPs toward HuTu 80 cancer cells and the apoptotic cell death pathway correlate with the intracellular level of ROS, which agrees well with the self-enhancing ROS generation of the NPs. The enhanced level of ROS revealed in HuTu 80 cells incubated with the NPs can be associated with the significant level of their mitochondrial localization.

First Example of Cage P4N4-Macrocycle Copper Complexes with Intracavity Location of Unusual Cu2I Fragments.

In this study, 28-membered macrocyclic 1,5(1,5)-di(1,5-diaza-3,7-diphosphacyclooctana)-2,4,6,8(1,4)-tetrabenzenacyclooctaphane were synthesized by condensation of pyridinephosphine, paraformaldehyde, and primary diamines (bis(4-aminophenyl)methane or -sulfide. The first representatives of binuclear copper(I) complexes of P,N-containing cyclophanes with two 1,5-diaza-3,7-diphosphacyclooctane rings incorporated into a macrocyclic core and intracavity location of unusual, developed angle Cu2I moiety were obtained. The structure of one complex was established by X-ray diffraction analysis. The complexation led to a slight distortion of the cyclophane conformations.

Green Emissive Copper(I) Coordination Polymer Supported by the Diethylpyridylphosphine Ligand as a Luminescent Sensor for Overheating Processes.

Tertiary diethylpyridylphosphine was synthesized by the reaction of pyridylphosphine with bromoethane in a suberbasic medium. The reaction of phosphine with the copper(I) iodide led to the formation of a copper(I) coordination polymer, which, according to the X-ray diffraction data, has an intermediate structure with a copper-halide core between the octahedral and stairstep geometries of the Cu4I4 clusters. The obtained coordination polymer exhibits a green emission in the solid state, which is caused by the 3(M+X)LCT transitions. The heating up of the copper(I) coordination polymer to 138.5 °C results in its monomerization and the formation of a new solid-state phase. The new phase exhibits a red emission, with the emission band maximum at 725 nm. According to the experimental data and quantum chemical computations, it was concluded that depolymerization probably leads to a complex that is formed with the octahedral structure of the copper-halide core. The resulting solid-state phase can be backward-converted to the polymer phase via recrystallization from the acetone or DMF. Therefore, the obtained coordination polymer can be considered a sensor or detector for the overheating of processes that should be maintained at temperatures below 138 °C (e.g., engines, boiling liquids, solar heat systems, etc.).

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.

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.

Assembly of Heterometallic AuICu2I2 Cores on the Scaffold of NPPN-Bridging Cyclic Bisphosphine.

The row of metallocyclic dinuclear gold(I) complexes with cyclic diphosphines, namely, P-pyridylethyl-substituted 1,5-diaza-3,7-diphosphacyclooctanes, has been obtained. Further interaction of the dinuclear gold(I) complexes with copper(I) iodide gave the first examples of hexanuclear AuI/CuI complexes containing two unusual trinuclear AuICu2I2 fragments. The structures of di- and hexanuclear complexes were confirmed by NMR spectroscopy, ESI mass spectrometry, elemental analysis, and single-crystal X-ray diffraction. All of the obtained complexes are moderate emitters in the solid state. Dinuclear gold(I) complexes displayed a greenish emission with the maxima in the emission spectra at ca. 550 nm. The obtained hexanuclear heterobimetallic AuI/CuI complexes are triplet solid-state blue emitters with the maximum in the emission spectra at 463 and 484 nm. According to the TD-DFT calculations, the observed emission of all studied complexes had a triplet origin and was caused by the 3CC or 3(MLCT) T1 → S0 transitions for dinuclear and hexanuclear complexes, respectively.

Dynamic Covalent Chemistry Approach toward 18-Membered P4N2 Macrocycles and Their Nickel(II) Complexes.

A dynamic covalent chemistry approach was used for the stereoselective synthesis of 1,10-diaza-3,8,12,17-tetraphosphacyclooctadecanes via condensation reaction of 1,4-bis(organylphosphino)butane, formaldehyde, and primary amines. The obtained 18-membered P4N2 macrocycles were isolated in pure form as meso- (RPSPSPRP) or rac- (RPRPRPRP/SPSPSPSP) isomers. The structural features of the individual stereoisomers were revealed by NMR spectroscopy and X-ray structure analysis. All P4N2 macrocycles form square-planar nickel(II) complexes with the RPSPSPRP isomer only, in which the orientation of the lone pairs of electrons at phosphorus favors this coordination mode, independent of the initial configuration of the ligand, indicating the ability of the 18-membered P4N2 macrocycles to stereoisomerize in the course of the complexation.

Synthesis and Structure of Iron (II) Complexes of Functionalized 1,5-Diaza-3,7-Diphosphacyclooctanes.

In order to synthesize new iron (II) complexes of 1,5-diaza-3,7-diphosphacyclooctanes with a wider variety of the substituents on ligands heteroatoms (including functionalized ones, namely, pyridyl groups) and co-ligands, it was found that these ligands with relatively small phenyl, benzyl, and pyridin-2-yl substituents on phosphorus atoms in acetonitrile formed bis-P,P-chelate cis-complexes [L2Fe(CH3CN)2]2+ (BF4)2-, whereas P-mesityl-substituted ligand formed only monoligand P,P-complex [LFe(CH3CN)4]2+ (BF4)2-. 3,7-dibenzyl-1,5-di(1'-(R)-phenylethyl)-1,5-diaza-3,7-diphosphacyclooctane reacted with hexahydrate of iron (II) tetrafluoroborate in acetone to give an unusual bis-ligand cationic complex of the composition [L2Fe(BF4)]+ BF4-, where two fluorine atoms of the tetrafluoroborate unit occupied two pseudo-equatorial positions at roughly octahedral iron ion, according to X-ray diffraction data. 1,5-diaza-3,7-diphosphacyclooctanes replaced tetrahydrofurane and one of the carbonyl ligands of cyclopentadienyldicarbonyl(tetrahydrofuran)iron (II) tetrafluoroborate to form heteroligand complexes [CpFeL(CO)]+BF4-. The structural studies in the solid phase and in solutions showed that diazadiphosphacyclooctane ligands of all complexes adopted chair-boat conformations so that their nitrogen atoms were in close proximity to the central iron ion. The redox properties of the obtained complexes were performed by the cyclic voltammetry method.

Triple-bridged helical binuclear copper(i) complexes: Head-to-head and head-to-tail isomerism and the solid-state luminescence.

A family of helical dinuclear copper(i) pyridylphospholane complexes [Cu2L3X]X (X = BF4-, Cl- and Br-) was prepared. The family includes the first examples of this type of complex based on copper(i) chloride and copper(i) bromide. The two isomers typical of this class of compounds, namely head-to-head and head-to-tail complexes, were studied in solution by spectroscopic and optical methods, and in the solid state by X-ray diffraction. Furthermore, the solid-state luminescence of the complexes at different temperatures was studied, and the results were interpreted using quantum-chemical calculations. It was shown that the luminescence of the complexes is attributed to the 3(M + X)LCT transitions.

Binuclear Gold(I) Phosphine Alkynyl Complexes Templated on a Flexible Cyclic Phosphine Ligand: Synthesis and Some Features of Solid-State Luminescence.

A flexible bidentate cyclic phosphine, namely, 1,5-bis(p-tolyl)-3,7-bis(pyridin-2-yl)-1,5-diaza-3,7-diphosphacyclooctane (PNNP), was used as a template to construct a family of binuclear heteroleptic phosphine alkynyl complexes [PNNP(AuC2R)2], with R = Ph, C6H10OH, C5H8OH, (CH3)2COH, Ph2COH. All complexes obtained were characterized by CHN elemental analysis, NMR spectroscopy, and single-crystal X-ray analysis. It was found that the gold(I) complexes demonstrate a different organization of the crystal structure depending on the nature of the cocrystallized solvent (dichloromethane, acetone, and acetonitrile) because of formation of the supramolecular complexes through hydrogen bonding. These weak interactions appear to determine the conformation, packing, and spatial cooperation of flexible complex molecules that are reflected in the photophysical properties, which were carefully investigated in solution and in the solid state. The complexes demonstrate weak emission in solution at room temperature, and freezing results in blue shifting of the emission, which is accompanied by a significant increase in the luminescence intensity. Being isolated from dichloromethane, all gold(I) complexes exhibit green phosphorescence in the solid state, and the complexes with R = Ph and Ph2COH display substantial variation of their emission color after recrystallization from acetone and acetonitrile, respectively, which manifests itself as a significant bathochromic shift of up to 120 nm. The structural nonrigidity of the gold(I) complexes obtained and its impact on the properties of low-energy excited states were investigated in detail by density functional theory calculations, which indicate the significant role of the structural flexibility of the PNNP ligand in the formation of the low-energy excited states and confirm the impact of rotation of the functional groups in the coordination sphere on the emission properties of complexes.

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

In this work, we present the synthesis, structural and photophysical characterization, and theoretical study of tetranuclear copper(i) cubane-type Cu4I4 clusters 6-10 with different 10-(aryl)phenoxarsine ligands - 10-(p-fluorophenyl)phenoxarsine (1), 10-(p-ethoxyphenyl)phenoxarsine (2), 10-(phenyl)phenoxarsine (3), 10-(m-fluorophenyl)phenoxarsine (4), and 10-(o-methoxyphenyl)phenoxarsine (5), respectively. The structures of 1-5 were confirmed by NMR spectroscopy, mass spectrometry, elemental analysis and for complexes 6, 7, and 10 by single-crystal X-ray diffraction analysis. The UV/Vis absorption and emission properties were studied and rationalized by DFT and time-dependent DFT calculations. In the solid state, under UV irradiation, all complexes exhibit an intense green emission, which was attributed to a cluster-centered triplet state.

Intriguing Near-Infrared Solid-State Luminescence of Binuclear Silver(I) Complexes Based on Pyridylphospholane Scaffolds.

A series of novel charged disilver(I) complexes with pyridyl-containing phospholanes was synthesized. These complexes were characterized using a range of spectroscopic techniques and single-crystal and powder X-ray diffraction. The complexes demonstrate solid-state near-infrared (NIR) luminescence (765-902 nm) that is unique for dinuclear AgI complexes. Combined spectroscopic/quantum chemical analysis suggests that the NIR luminescence of complexes 4-6 in the solid state is mainly due to crystal packing effects.

The Assembly of Unique Hexanuclear Copper(I) Complexes with Effective White Luminescence.

The unique L2Cu6I6 complexes containing two Cu3I3 units have been obtained via reaction of 1,5-diaza-3,7-diphosphacyclooctanes bearing ethylpyridyl substituents at phosphorus atoms with an excess of copper iodide. The structure of one of the complexes was confirmed by X-ray diffraction. It was shown that the complexes can exist in two crystalline phases with different parameters of the unit cell, which were detected by the PXRD data analyses. The solvent-free crystalline phases of the complexes display rare solid-state white emission at room temperature, which is observed due to the presence of two broad bands in the emission spectra with maxima at 464 and 610 nm. Quantum chemical computations show that the high-energy band has 3(M+X)LCT origin, whereas the low-energy band is interpreted as 3CC. The quantum yields of white luminescence of complexes reach 15-20%.

Amido Ca and Yb(II) Complexes Coordinated by Amidine-Amidopyridinate Ligands for Catalytic Intermolecular Olefin Hydrophosphination.

A series of amido Ca and Yb(II) complexes LM[N(SiMe3)2](THF) (1Yb, 1-4Ca) coordinated by amidine-amidopyridinate ligands L1-4 were synthesized via a transamination reaction between proligands L1-4H and bisamido complexes M[N(SiMe3)2]2(THF)2 (M = Yb, Ca). The reactions of Yb[N(SiMe3)2]2(THF)2 with proligands L2H-L4H containing CF3 and C6H4F fragments do not allow for preparing the target Yb(II) complexes, while the Ca analogues were synthesized in good yields. Complexes 1Yb and 1-4Ca were evaluated as precatalysts for hydrophosphination of styrene, p-substituted styrenes, α-Me-styrene, and 2,3-dimethylbutadiene with various primary and secondary phosphines (PhPH2, 2,4,6-Me3C6H2PH2, 2-C5NH4PH2, Ph2PH, Cy2PH). Complexes 1Yb, 1-4Ca performed high catalytic activities in styrene hydrophosphination with PhPH2 and Ph2PH and demonstrated high regioselectivity affording exclusively the anti-Markovnikov addition products. For primary PhPH2 the reactions (1:1 molar ratio of substrates) catalyzed by 1Yb, 1Ca, and 2Ca proved to be highly chemoselective affording the secondary phosphine Ph(PhCH2CH2)PH; however, complexes 3Ca and 4Ca led to the formation of both secondary and tertiary phosphines in 80:20 and 86:14 ratios. Styrene hydrophosphinations with 2,4,6-Me3C6H2PH2 and 2-pyridylphosphine for all complexes 1Yb and 1-4Ca proceeded much more slowly compared to PhPH2. Addition of 2-C5NH4PH2 to styrene catalyzed by complex 1Yb turned out to be non-regioselective and led to the formation of a mixture of Markovnikov and anti-Markovnikov addition products, while all Ca complexes enabled regioselective anti-Markovnikov addition. Complexes 1Ca and 1Yb containing catalytic centers featuring similar ionic radii performed different catalytic activity: the ytterbium analogue proved to be a more active catalyst for intermolecular hydrophosphination of styrene with Cy2PH, 2-C5NH4PH2, and PhPH2, but less active with sterically demanding 2,4,6-Me3C6H2PH2. Styrenes containing in p-position electron-donating groups (Me, tBu, OMe) performed with noticeably lower rates in the reactions with PhPH2 compared to styrene. Complexes 1Yb, 1Ca, 2Ca, 3Ca, and 4Ca enabled addition of PhPH2 toward the double C═C bond of α-Me-styrene, and the reaction rate for this substrate is noticeably lower; however quantitative conversions were reached in ∼40 h. Complexes 1Ca and 2Ca promoted 1,2-addition of PhPH2 to 2,3-dimethyl butadiene with excellent regio- and chemoselectivity to afford linear secondary phosphines. Hydrophosphination of inert 1-nonene with Ph2PH with 40% conversion becomes possible due to the application of complex 2Ca (40 h, 70 °C). The rate law for the hydrophosphination of styrene with Ph2PH catalyzed by 1Ca was found to agree with the idealized equation: v = k[styrene]1[1Ca]1.

Synthesis and unique reversible splitting of 14-membered cyclic aminomethylphosphines on to 7-membered heterocycles.

A novel type of 14-membered cyclic polyphosphine, namely 1,8-diaza-3,6,10,13-tetraphosphacyclotetradecanes 2a­4ahas been synthesized by the condensation of 1,2-bis(phenylphosphino)ethane, formaldehyde and alkylamines (isopropylamine, ethylamine and cyclohexylamine) as a RRRR/SSSS-stereoisomer. The structure of macrocycle 2a was investigated by NMR-spectroscopy and X-ray crystal structure analysis. The unique reversible processes of macrocycles 2a­4a splitting onto the corresponding rac- (2b­4b) and meso- (2c­4c) stereoisomers of 1-aza-3,6-diphosphacycloheptanes were discovered.

Alternating stereoselective self-assembly of SSSS/RRRR or RSSR isomers of tetrakisphosphines in the row of 14-, 16-, 18- and 20-membered macrocycles.

Novel 18- and 20-membered P,N-macrocycles have been obtained stereoselectively by covalent self-assembly of α,ω-bisphosphines, formaldehyde and benzylamine. Alternating SSSS/RRRR or RSSR diastereomers were formed in the row of the 14-, 16-, 18- and 20-membered macrocyclic aminomethylphosphines. For the first time it was demonstrated that the stereochemical result of the reaction depends on the even or odd number of the methylene groups between the two chiral phosphorus atoms in the initial α,ω-bisphosphines.

New functional cyclic aminomethylphosphine ligands for the construction of catalysts for electrochemical hydrogen transformations.

Eight-membered cyclic functional bisphosphines, namely 1,5-di-aryl-3,7-di(2-pyridyl)-1,5-diaza-3,7-diphosphacyclooctanes (aryl=2-pyridyl, m-tolyl, p-tolyl, diphenylmethyl, benzyl, (R)-(+)-(α-methyl)benzyl), with 2-pyridyl substituents on the phosphorus atoms have been synthesized by condensation of 2-pyridylphosphine, formaldehyde, and the corresponding primary amine. The structures of some of these bisphosphines have been investigated by X-ray crystallography. The bisphosphines readily form neutral P,P-chelate complexes [(κ(2)-P,P-L)MCl2], cationic bis-P,P-chelate complexes [(κ(2)-P,P-L)2 M](2+), or a five-coordinate complex [(κ(2)-P,P-L)2 NiBr]Br. The electrochemical behavior of two of the nickel complexes, and their catalytic activities in electrochemical hydrogen evolution and hydrogen oxidation, including the fuel-cell test, have been studied.