Search

In molecular biology research, a vitamin E (VE) vehicle (VE dissolved in organic solvent) is often added to water media without a stabilizer. However, the detailed behavior of VE colloids in water media is unclear. In this study, we reveal that VE nanoemulsion readily forms in water-based media through the existing protocol. The colloid size was changed from 39 nm to the submicron scale by adjusting the initial concentration of the VE solution and adding a buffer. The radical scavenging effect of the dispersed nanosized VEs is comparable to that of the water-soluble antioxidant Trolox, providing excellent antioxidant performance in colloid form. The cytoprotection effect of the VE colloids under a lipid oxidation condition largely depends on the size of the nanodispersion. Smaller dispersed particles are more efficient radical scavengers than larger particles for a constant VE amount owing to sophisticated uptake behavior of cell. This unveiled fundamental knowledge pave the way for a preparative protocol of stabilizer-free VE vehicles, which are expected to become widely used in molecular biology research.

A series of platinum(II) complexes bearing a chiral β-diketonato ligand and a cyclometalated ligand have been prepared. The platinum(II) complexes, (SP-4-3)-[Pt(ppy)(D-tac)] (ppy = 2-phenylpyridine, D-tac = 3-trifluoroacetyl-(D)-camphor), (SP-4-4)-[Pt(ppy)(D-tac)], (SP-4-3)-[Pt(ppy)(D-pbc)] (D-pbc = 3-perfluorobutyryl-(D)-camphor), and (SP-4-4)-[Pt(ppy)(D-pbc)], and their enantiomers were isolated and characterized by elemental analysis, NMR, and X-ray structural analysis. Photoisomerization between SP-4-3 (

A simple N-heterocyclic carbene (NHC) ligand linked to a flexible propylene linker allows the formation of "Cu-Cu"- and "2 Cu"-type geometries inside a molecular framework. The incorporation of two Cu(i) ions in close proximity was observed in the Cu-Cu-type geometry but not in the 2 Cu-type geometry. In this study, the ground-state geometries of solid-state di-copper(i) complexes containing NHC ligands with ethyl substituents were modulated by external stimuli. A crystal with the 2 Cu-type geometry was obtained by the mechanical grinding and heating of a crystal with the Cu-Cu-type geometry, as confirmed by the disappearance of the absorption peak attributed to cuprophilic interaction in the diffuse reflection spectrum. The mechanical grinding of both crystals afforded composite states comprising small crystallites of the corresponding crystalline phases and an amorphous domain. This structural transition was accompanied by tribochromism and chronochromism. The results suggest that these di-copper(i) complexes show promise for the development of stimuli-responsive photoluminescent Cu(i) complexes.

Mixed-ligand Cu(I) complexes have attracted attention as alternatives to the noble- and/or rare-metal complexes, because of their remarkable photofunctions. To develop mixed-ligand Cu(I) complexes with rich photofunctions, an investigation of a suitable combination of ligands has captured more and more research interests. Herein, we report the first examples of emissive heteroleptic diphosphine-disulfide Cu(I) complexes combined with diphosphine ligands. The systematic study using a series of diphosphine ligands revealed that large π-conjugated bridging moieties between the two P atoms in the diphosphine ligands result in higher light-emission performance. When the diphosphine ligand was (

Aiming to diversify photocatalytic systems for CO2 reduction using metal complexes, this study investigated the use of various ionic liquids as reaction solvents. The photophysical properties of an Ir(III) complex, functioning as a photosensitiser, and the photocatalytic ability of mixed systems consisting of the Ir(III) photosensitiser and a Re(I) catalyst in twelve kinds of ionic liquids were systematically investigated by comparison with those in N,N-dimethylacetamide (DMA), which is a standard solvent for photocatalytic CO2 reduction. Even though the photophysical properties of the Ir(III) complex in ionic-liquid solutions were quite similar to those in DMA, both the photosensitising ability of the Ir complex and the photocatalytic abilities of the systems strongly depended on the structures of the ionic liquids. Several ionic liquids were successfully used as new solvents for the photocatalytic systems showing durability similar to or higher than DMA solutions. The results demonstrated that even a small modification of the molecular structures of ionic liquids can control the efficiencies of both the photosensitising cycles and the catalytic cycles for CO2 reduction.

Pd(0) complexes with monodentate phosphine ligands, [Pd(P)n] (n = 3, 4), are well-known catalysts. However, the nature of the Pd(0) complex, especially the basic photophysical properties of the Pd(0) complexes, has not been extensively explored. In this work, we measured the general photophysical properties and crystal structures of Pd(0)-bearing PPh3 derivatives in the solid state and in solution. In the solid state, four-coordinated Pd(0) complexes exhibited blue-yellow emission. On the other hand, three-coordinated Pd(0) complexes displayed yellow-orange emission. In solution, orange emission of three-coordinated complexes was observed, and prompt fluorescence was detected using time-resolved emission spectroscopy, which suggests a thermally activated delayed fluorescence mechanism. Density functional theory (DFT) and time-dependent DFT calculations show that the difference in the transition mechanism between the [Pd(PPh3)4] and [Pd(PPh3)3] complexes explains the different emission colors. The emitting states of both complexes have metal-to-ligand charge-transfer character, but the metal-centered d → p transition is considerably incorporated for emission of the tris complex.

Development of a novel antioxidant-delivery vehicle exerting biosafety has been attracting a great deal of interest. In this study, a vehicle comprising a natural composite consisting of vitamin E (α-tocopherol, Toc) and cyclodextrin (CD) additives was developed, directed toward aqua-related biological applications. Not only β-CD, but also γ-CD, tended to form a water-insoluble aggregate with Toc in aqueous media. The aggregated vehicle, in particular the γ-CD-added system, showed a remarkable sustained effect because of slow dynamics. Furthermore, a prominent cytoprotective effect by the γ-CD–Toc vehicle under the oxidative stress condition was confirmed. Thus, the novel vitamin E vehicle motif using γ-CD as a stabilizer was proposed, widening the usability of Toc for biological applications.

We newly synthesized a copper(I) complex bearing a 2,2′-bicinchoninic acid dipotassium salt (biq(COOK)2) ligand and characterized the complex by elemental analysis, NMR and UV-vis spectroscopy, and electrochemistry with the help of comparative compounds. The complex in water shows intense absorption in the red light region due to metal to ligand charge transfer. The wavelength value at the absorption maximum of the charge transfer, λabs_max, is 556 nm, and the value of the molar extinction coefficient, e, at the shoulder of the absorption at 670 nm is 1 × 103 M−1 cm−1. The water solution is purple, and the frozen one is green. The colour change is repeatable. The colour change is not observed when DMSO and ethanol are used. The UV-vis spectra related to absorption using an integrated sphere of the water solution and a frozen one show the repeatable colour change.

Aiming to diversify photocatalytic systems for CO2 reduction using metal complexes, this study investigated the use of various ionic liquids as reaction solvents. The photophysical properties of an Ir(iii) complex, functioning as a photosensitiser, and the photocatalytic ability of mixed systems consisting of the Ir(iii) photosensitiser and a Re(i) catalyst in twelve kinds of ionic liquids were systematically investigated by comparison with those in N,N-dimethylacetamide (DMA), which is a standard solvent for photocatalytic CO2 reduction. Even though the photophysical properties of the Ir(iii) complex in ionic-liquid solutions were quite similar to those in DMA, both the photosensitising ability of the Ir complex and the photocatalytic abilities of the systems strongly depended on the structures of the ionic liquids. Several ionic liquids were successfully used as new solvents for the photocatalytic systems showing durability similar to or higher than DMA solutions. The results demonstrated that even a small modification of the molecular structures of ionic liquids can control the efficiencies of both the photosensitising cycles and the catalytic cycles for CO2 reduction.

A series of copper(I) complexes bearing a bis(diphenylphosphoryl)amide (dppaO2–) ligand and a diphosphine ligand were synthesized, and their photophysical properties were investigated. Two complexes, [Cu(dppaO2)(DPEphos)] {DPEphos = bis[2-(diphenylphosphanyl)phenyl] ether} and [Cu(dppaO2)(XANTPHOS)] [XANTPHOS = 9,9-dimethyl-4,5-bis(diphenylphosphanyl)xanthene], show bright white-blue and deep blue luminescence, respectively, in the solid state. The quantum yield of [Cu(dppaO2)(XANTPHOS)] is 0.76 under argon and 0.38 under air. The emission decay curves under argon [τ = 7.9 (17 %), 30.0 µs (83 %)] in the solid state are longer than those under air [τ = 2.5 (19 %), 13.9 µs (81 %)]. The photophysical properties of the complexes are discussed together with the results of DFT and time-dependent DFT (TD-DFT) calculations.

We report the synthesis and photophysical properties of Cu(I) complexes with 1,10-phenanthroline (phen) and monodentate phosphine ligands. Single crystal X-ray structural analysis revealed that these have three-coordinated trigonal planar geometries. We also found that one of them, [Cu(phen)(Johnphos)]BF4 (Johnphos = 2-(di-tert-butylphosphino)biphenyl), is considerably emissive both in solution and solid states. The emission maximum wavelength of the emission of the complex is 580 nm, and the lifetime of the emission is 2 μs in solution. Moreover, we have systematically investigated the photophysical and redox properties of four-coordinate complexes [Cu(NN)(P)2]+ in addition to three-coordinate complexes [Cu(NN)(P)]+. Charge transfer transitions play a key role in the photophysics of these complexes.

The synthesis, characterization, and emission properties of 2-coordinate dicopper(I) complexes bearing two trimethylene-bridged bis-NHC ligands, [Cu2(L3Me)2](PF6)2 (1), [Cu2(L3Et)2](PF6)2 (2), [Cu2(L3Bu)2](PF6)2 (3), [Cu2(L3MeOPh)2](PF6)2 (4) and [Cu2(L3Mes)2](PF6)2 (5), where L3R denotes trimethylene-bridged bis(N-heterocyclic)carbene (NHC) ligand substituted by two R groups at the nitrogen atoms of NHC, have been investigated. The quantum yield, Φ, and the lifetime, τ, of the emission of 2, are 0.21 and 25 μs, respectively in methanol, which is a well-known solvent for quenching the luminescence of many copper(I) complexes. The 8-shaped geometry of the dicopper(I) complexes brings a considerable copper(I)–copper(I) interaction which affects the luminescent properties. Additionally, we find that methoxyphenyl and mesityl groups substituted at the nitrogen atom of the NHC moiety drastically stabilize the bis(NHC) copper(I) complexes even in air-saturated acetone-d6.

Copper(I) complexes bearing (R)-(+)-2,2′-bis(di-p-tolylphosphino)-1,1′-binaphthyl and 2,2′-bipyridine derivative ligands were newly synthesized and characterized. Despite many known copper(I) complexes bearing diimine and diphosphine ligands, which are well-investigated for their photofuntions, exhibit irreversible oxidation, the present complex shows clear spectral changes on oxidation and reduction reactions.

The title compound, [Cu(dppaS2)(PPh3)2], is a neutral mononuclear copper(I) complex bearing an N,N-bis­(di­phenyl­phospho­rothio­yl)amidate (dppaS2 −) ligand and two tri­phenyl­phosphane ligands. The structure of this complex was obtained by X-ray diffraction and supported by DFT calculations., The title compound, [Cu(C24H20NP2S2)(C18H15P)2]·CH2Cl2 or [Cu(dppaS2)(PPh3)2]·CH2Cl2, is a neutral mononuclear copper(I) complex bearing an N,N-bis­(di­phenyl­phospho­rothio­yl)amidate (dppaS2 −) ligand and two tri­phenyl­phosphane ligands. The molecular structure shows that the two S atoms of the dppaS2 − ligand [Cu—S = 2.3462 (9) and 2.3484 (9) Å] and the two P atoms of the two tri­phenyl­phosphane ligands [Cu—P = 2.3167 (9) and 2.2969 (9) Å] coordinate to the copper(I) atom, resulting in a tetra­hedral coordination geometry. The crystallographically observed mol­ecular structure is compared to the results of DFT calculations.

The development of efficient redox-photosensitizers based on the earth-abundant metal ions as an alternative toward noble- and/or rare-metal based photosensitizers is very desirable. In recent years, heteroleptic diimine-diphosphine Cu(I) complexes have been well investigated as one of the most remarkable candidates because of their great potentials as efficient photosensitizers. Here, we investigated the effects of the structure of the diphosphine ligands on the photosensitizing abilities using a series of Cu(I) complexes bearing 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (dmpp) and various diphosphine ligands in order to explore the suitable structure for the photosensitizing reactions. The number of methylene chains between the two phosphorous atoms in the diphosphine ligands was systematically changed from two to four, and the relationship between the length of the carbon chains and the photosensitizing abilities were investigated by conducting photocatalytic CO2 reduction with the Cu(I) complexes as photosensitizers. Turnover frequencies of the CO2 reduction drastically increased with increasing the length of the carbon chains. The systematic study herein reported suggests that the large P-Cu-P angles should be one of the most important factors for enhancing the photosensitizing abilities.

The understanding of the basic physicochemical properties of trehalose lipid is indispensable to extending their availability. In this study, the hydrate crystal (Cr), the liquid crystalline (LC) phase and the glassy state formations of 6-O-acyl trehalose fatty acid monoester (TREn) were examined under in a desiccated system. TREn (n = 10, 12, 14, 16) formed monohydrate Cr and showed the hydrate Cr-glassy fluid lamellar LC (Lα) phase transition via dehydration in the heating process. Here, Lα phase for TRE10 and TRE12 was kinetically formed by the dehydration below the glass transition temperature (Tg). On the dehydration temperature (Tdeh), Tgs, and heat capacity changes (ΔCps) at these Tgs, no distinct effects by the difference of the acyl chain length were recognized, possibly because the core structure of containing sugar hydrate Cr or sugar moieties should be similar regardless of the acyl chain length. Besides, TRE10 having a relatively high hydrophilic/hydrophobic balance (HLB) afforded to form the cubic LC (Q) phase and the corresponding glassy phase, while TRE14 and TRE16 having low HLB afforded the Lα phase as well as the corresponding glassy phases above Tg. TRE12 having middle HLB afforded both LCs and the corresponding glassy phase by controlling the kinetics of LC-LC phase transition between Lα and Q phases. Furthermore, the anomalous reversible phase transition during both the heating and cooling processes was also ascertained in the glassy phase for TRE16, which was considered the phase transition between glassy Lα and glassy lamellar gel (Lβ) phase. It greatly empathizes the two-dimensional trehalose glass layer and fluid hydrocarbon chains in the TREn glassy phase. Thus, in this study, it was demonstrated that TREn as the simplest trehalose lipid exhibited the glassy formation performance as well as the hydrate Cr formation, which showed less chain length dependence, together with the LC formation and the phase transition between glassy Lα and glassy Lβ phase, which depended on chain length greatly.

The first dendrimers consisting of self-assembled zinc chlorophyll derivatives are reported. Coordination-directed self-assembly of pyridine-appended zinc chlorophyll derivatives tethering a dendron moiety results in cyclic tetramers peripherally functionalized by dendrons via intermolecular axial coordination interaction between the nitrogen atom in the pyridine ring and the zinc atom in the chlorin ring. We characterized the formation of the cyclic tetramers by use of 1 H NMR measurements including diffusion-ordered spectroscopy (DOSY). Four different types of dendrons were introduced in the zinc chlorophyll component to investigate the tolerance of the self-assembly to the dendron structure. All dendrimers exhibited similar stabilities, which demonstrates that the dendron moiety does not interfere with the self-assembly, such that more than 90% of the molecules are in the assembly at concentrations >0.2 mM in benzene.

Silver(I) complexes bearing N-heterocyclic carbene and diphenylphosphinobenzene ligands, [Ag(IPr)(dppbz)]BPh4 (1, IPr = bis(2,6-diisopropylphenyl)imidazole-2-ylidene, dppbz = 1,2-bis(diphenylphosphino)benzene), [Ag(IPr)(dfpbz)]BPh4 (2, dfpbz = 1,2-bis[di(4-fluorophenyl)phosphino]benzene), and [Ag(IPr)(dtbpbz)]BPh4 (3, dtbpbz = 1,2-bis[bis[3,5-di(tert-butyl)phenyl]phosphino]benzene), were newly synthesized and characterized. These complexes, especially 3, exhibit intense blue emission in the solid state. The maximum wavelength and lifetime of the photoluminescence of 3 are 440 nm and 14 μs, respectively. The quantum yield of the photoluminescence of 3 in the solid state is 0.5, which is one of the highest values among blue-emissive silver(I) complexes ever reported. Introduction of bulky tert-butyl groups at 3- and 5-positions of the phenyl groups in the diphosphine ligand plays a key role in both the blue-shift and the enhancement of the photoluminescence. Additionally, the reversible hypsochromic shift of the long-lived emission caused by the grinding process is observed for one of the complexes.

We prepared enantiomers of chiral Pt(II) complexes, Pt(pppb)Cl and Pt(pppb)CN (pppbH=1-pyridyl-3-(4,5-pinenopyridyl)benzene), and measured their CPL (circularly polarized luminescence) spectra for excimer and trimer emission. The contribution of the pinene moiety to CPL was considerably low for the π-π* emission of the monomer but large for MMLCT (metal-metal-to-ligand charge-transfer) of the excimer and trimer which had a helical structure induced in a face-to-face stacking fashion. The trimer CPL for (+)-Pt(pppb)Cl was larger in intensity than that of excimer CPL; on the other hand, that for (+)-Pt(pppb)CN was opposite in sign compared with that of excimer CPL. We conclude that differences in the excited-state structure of the aggregate between Pt(pppb)Cl and Pt(pppb)CN account for the variation in the CPL spectra. By the aid of TD-DFT calculations it was predicted that the dihedral angle θ(Cl-Pt-Pt-Cl) was 50-60° or 110-140° for Pt(pppb)Cl aggregates and 160° for Pt(pppb)CN aggregates.

We have examined emission and redox properties of a copper(I) complex bearing a phenanthroline type ligand and the 1,4-bis(diphenylphosphino)butane ligand. Changes in the absorption spectra upon electrolysis and light irradiation in the presence of chloroform indicate the formation of bis(diimine)copper(I) complexes.

The dication of the title compound, [Cu2(C28H28P2)2(C16H16N2)2](PF6)2·2CH2Cl2, has crystallographically imposed inversion symmetry. The copper(I) cation is coordinated in a distorted tetrahedral geometry by two N atoms of a chelating 3,4,7,8-tetramethyl-1,10-phenanthroline ligand and two P atoms of two bridging 1,4-bis(diphenylphosphanyl)butane ligands, forming a 14-membered ring. An intramolecular π–π interaction stabilizes the conformation of the dication. In the crystal, dications are linked by π–π interactions involving adjacent phenanthroline rings, forming chains running parallel to [111]. Weak C—H...F hydrogen interactions are also observed.

A highly emissive copper(I) complex bearing (4R,5R)-(-)-4,5-bis(diphenylphosphinomethyl)-2,2-dimethyl-1,3-dioxolane (diop) and 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (dmpp), [Cu(dmpp)(diop)]PF6 (1·PF6), was newly synthesized. The quantum yield of the luminescence of 1·PF6 in degassed dichloromethane is 0.38, which is one of the highest values among all copper(I) complexes bearing two bidentate ligands, diimine and diphosphine, under the same conditions. The long lifetime (26 μs) and high intensity of the emission come from the small non-radiative decay rate of the excited states. The TD-DFT study indicates that the charge transfer transition from both copper and diphosphine to diimine orbitals plays an important role in the photophysical properties. Photophysics of [Cu(dmp)(diop)]PF6 (2·PF6, dmp = 2,9-dimethyl-1,10-phenanthroline) was also studied in order to reveal the effects of the introduction of the phenyl group at 4- and 7-positions of phenanthroline.

Redox behavior of [UO2(gha)DMSO]−/0 couple (gha = glyoxal bis(2-hydroxanil)ate, DMSO = dimethyl sulfoxide) in DMSO solution was investigated by cyclic voltammetry and UV-vis-NIR spectroelectrochemical technique, as well as density functional theory (DFT) calculations. [UO2(gha)DMSO]− was found to be formed via one-electron reduction of UO2(gha)DMSO without any successive reactions. The observed absorption spectrum of [UO2(gha)DMSO]−, however, has clearly different characteristics from those of uranyl(V) complexes reported so far. Detailed analysis of molecular orbitals and spin density of the redox couple showed that the gha2− ligand in UO2(gha)DMSO is reduced to gha●3− to give [UO2(gha)DMSO]− and the formal oxidation state of U remains unchanged from +6. In contrast, the additional DFT calculations confirmed that the redox reaction certainly occurs at the U center in other uranyl(V/VI) redox couples we found previously. The non-innocence of the Schiff base ligand in the [UO2(gha)DMSO]−/0 is due to the lower energy level of LUMO in this ligand relative to those of U 5f orbitals. This is the first example of the non-innocent ligand system in the coordination chemistry of uranyl(VI).

A series of tetragold(I) complexes supported by tetraphosphine ligands, meso- and rac-bis[(diphenylphosphinomethyl)phenylphosphino]methane (meso- and rac-dpmppm) were synthesized and characterized to show that the tetranuclear Au(I) alignment varies depending on syn- and anti-arrangements of the two dpmppm ligands with respect to the metal chain. The structures of syn-[Au4 (meso-dpmppm)2X]X'3 (X = Cl; X' = Cl (4 a), PF6 (4 b), BF4 (4 c)) and syn-[Au4 (meso-dpmppm)2]X4 (X = PF6 (4 d), BF4 (4 e), TfO (4 f); TfO = triflate) involved a bent tetragold(I) core with a counter anion X incorporated into the bent pocket. Complexes anti-[Au4 (meso-dpmppm)2]X4 (X = PF6 (5 d), BF4 (5 e), TfO (5 f)) contain a linearly ordered Au4 string and complexes syn-[Au4 (rac-dpmppm)2X2]X'2 (X = Cl, X' = Cl (6 a), PF6 (6 b), BF4 (6 c)) and syn-[Au4 (rac-dpmppm)2]X4 (X = PF6 (6 d), BF4 (6 e), TfO (6 f)) consist of a zigzag tetragold(I) chain supported by the two syn-arranged rac-dpmppm ligands. Complexes 4 d-f, 5 d-f, and 6 d-f with non-coordinative large anions are strongly luminescent in the solid state (λmax = 475-515 nm, Φ = 0.67-0.85) and in acetonitrile (λmax = 491-520 nm, Φ = 0.33-0.97); the emission was assigned to phosphorescence from (3) [dσ*σ*σ* pσσσ] excited state of the Au4 centers on the basis of DFT calculations as well as the long lifetime (a few μs). The emission energy is predominantly determined by the HOMO and LUMO characters of the Au4 centers, which depend on the bent (4), linear (5), and zigzag (6) alignments. The strong emissions in acetonitrile were quenched by chloride anions through simultaneous dynamic and static quenching processes, in which static binding of chloride ions to the Au4 excited species should be the most effective. The present study demonstrates that the structures of linear tetranuclear gold(I) chains can be modified by utilizing the stereoisomeric tetraphosphines, meso- and rac-dpmppm, which may lead to fine tuning of the strongly luminescent properties intrinsic to the Au(I) 4 cluster centers.

The crystal structure of a dinuclear copper(I) complex bearing bridging 1,4-bis­(di­phenyl­phosphan­yl)butane and 3,4,7,8-tetra­methyl-1,10-phenanthroline ligands is described., The dication of the title compound, [Cu2(C28H28P2)2(C16H16N2)2](PF6)2·2CH2Cl2, has crystallographically imposed inversion symmetry. The copper(I) cation is coordinated in a distorted tetra­hedral geometry by two N atoms of a chelating 3,4,7,8-tetra­methyl-1,10-phenanthroline ligand and two P atoms of two bridging 1,4-bis­(di­phenyl­phosphan­yl)butane ligands, forming a 14-membered ring. An intra­molecular π–π inter­action stabilizes the conformation of the dication. In the crystal, dications are linked by π–π inter­actions involving adjacent phenanthroline rings, forming chains running parallel to [111]. Weak C—H⋯F hydrogen inter­actions are also observed.

The sulfur transfer reaction from phosphine sulfides to various phosphines in the presence of metal ion was studied; in the presence of Cu(I), a sulfur transfer reaction from dppmS2 (bis(diphenylphosphino)methane disulfide) to dppm (bis(diphenylphosphino)methane) or to dppa (bis(diphenylphosphino)amine) occurs and the product [Cu(dppmS)2]+ (1) and [Cu(dppmS)(dppaS)]+ (2) was obtained quantitatively. In the presence of Zn(II), sulfur transfer to various phosphines can be carried out catalytically. The reaction mechanism has been proposed from the difference in the reactivity of diphosphines and metal ions.

An improved synthetic method of palladium(II) dinuclear macrocyclic complexes have been described. Each of the two isomers of the complexes [Pd2LBr2] has a macrocyclic ligand L in which two 2,6-bis(diaminomethyl)phenyl units coordinate to the Pd(II) centers with N, C, N donor atoms. Substitution of the bromo ligands of one of the isomer of the complexes with acetonitrile ligands affords a new dinuclear complex. Catalytic activities of these complexes were studied for the Mizoroki–Heck type reactions of iodobenzene and styrene. High turnover number up to 30,000 was achieved using one of the isomer of the complexes.

A luminescent copper(I) complex bearing two bidentate ligands, a 1,3-bis(diphenylphosphino)propane and a 4,4′-dimethoxy-2,2′-bipyridine, was newly synthesized and characterized. The methoxy group s...

Correlation between the photophysics and the structures of three Ag(I)-bis(diphosphine) complexes ([Ag(dppbz)(2)]NO(3) (1.NO(3)), [Ag(dppe)(2)]NO(3) (2.NO(3)), and [Ag(dppp)(2)]NO(3) (3.NO(3)) (dppbz = 1,2-bis(diphenylphosphino)benzene, dppe = 1,2-bis(diphenylphosphino)ethane, dppp = 1,3-bis(diphenylphosphino)propane) has been investigated using temperature-dependent emission measurements and electrochemical and theoretical methods. All three Ag(I)-bis(diphosphine) complexes have relatively low oxidation potential, which allows metal-to-ligand charge transfer (MLCT) contribution in the lowest excited state of the tetrahedral geometry, which is difficult in other Ag(I) complexes. Both 1.NO(3) and 2.NO(3) show orange phosphorescence with moderate quantum yield in air-free methanol at room temperature, while 3.NO(3) is less emissive in solution at room temperature. In all three complexes the temperature-dependent luminescence measurements in EtOH/MeOH 4:1 (v/v) solution indicate the blue-shift of the emission maximum and the increase of the emission intensity on lowering the temperature. In particular, the sequential emission spectral change with decreasing temperature is observed in 1.NO(3) and 2.NO(3). In the glass state at 90 K, all three complexes show intense blue phosphorescence. The theoretical calculation using density functional theory (DFT) suggests that the orange and blue emissions mainly originate from the (3)MC excited state based on a square-planar geometry and the (3)IL+(3)MLCT excited state based on a tetrahedral geometry, respectively.

Mixed-ligand Cu(I) complexes containing phosphinesulfide ligands were synthesized, and the structure and emission properties were studied for the Cu(I) complexes. X-ray crystallographic study showed that a chelating phosphinesulfide and diimine are coordinated to Cu(I) center. Coordination geometry around Cu(I) center of each complex is described as a distorted tetrahedron. Some of the complexes show photoluminescence in the solid state.

The study in the area of luminescent d10 complexes has been developing rapidly. The metals with d10 electronic configuration have a closed d-shell, therefore the nature of the complexes are quite different from regular transition metal complexes. The complexes show a diversity of the electronic excited states. This paper reviews the characteristic nature of the d10 metal complexes with interesting examples. Copper(I), silver(I), gold(I), nickel(0),palladium(0) and platinum(0) complexes are discussed. Luminescent copper(I) complexes are classified into two groups; the first includes the complexes bearing halogen ligands, and the second have no halogen ligands. In the second group, the complexes with phosphine and diimine type ligands are mainly discussed. As for the silver(I) and gold(I) complexes, multinuclear complexes are mostly described. For the palladium(0) and platinum(0) complexes, although a small number of works have been published so far, some interesting studies including our works have been described. In addition to the recent studies on the photophysical properties of the complexes, some applications are described in this review.

The synthesis, structure, and photoluminescence of palladium(0) and platinum(0) complexes containing biarydiphosphines, biphep (biphep = 2,2'-bis(diphenylphosphino)-1,1'-biphenyl) and binap (binap = 2,2'-bis(diphenylphosphino)-1,1'-binaphthyl) have been studied. X-ray structure analysis of [Pt(biphep)(2)] revealed the distorted-tetrahedral geometry of the complex. The photophysical properties of the three complexes [Pd(biphep)(2)], [Pt(biphep)(2)], and [Pd(binap)(2)] were investigated and compared with that of the previously reported [Pt(binap)(2)] complex. The [Pd(biphep)(2)] complex shows the strongest luminescence with a high quantum yield (38%) and a long lifetime (3.2 micros) in a toluene solution at room temperature. The luminescence should be due to metal-to-ligand charge transfer excited states. At room temperature, radiative rate constants of the four complexes show similar values. The difference in the luminescent properties should reflect the different nonradiative rate constants of the complexes. The temperature-dependence of the luminescence spectra and lifetime of the complexes were also discussed.

Luminescence properties of a family of newly synthesized copper(I) complexes bearing 2,2′-bipyridine derivatives and 1,2-bis[bis(pentafluorophenyl)phosphino]ethane (dfppe), [Cu(diimine)(dfppe)]PF6, were investigated. The quantum yield and the lifetime of the emission of [Cu(6dmbpy)(dfppe)]PF6 (6dmbpy = 6,6′-dimethyl-2,2′-bipyridine) in the solid state under argon (Φ = 9%, τ = 16, 180 μs), which is one of the longest lifetimes among all copper(I) complexes bearing diimine and diphosphine, are much larger than those under air (Φ < 0.5%, τ = 1.5, 8.0 μs). Crystal packing, structural rearrangement in the excited state, and nature of the transitions are important for the photophysics of dfppe complexes. The voids in the crystals as well as the very long lifetimes of the excited states play a key role for oxygen responsive photoluminescence in the solid state.

A series of novel Cu(I) complexes with an s-binap ligand and a diimine ligand, [Cu(s-binap)(bpy)]PF6, [Cu(s-binap)(phen)]PF6, and [Cu(s-binap)(dmp)]PF6, were synthesized, where bpy = 2,2′-bipyridin...

A tris(2,2'-bipyridine)ruthenium(II) derivative having two N-(3-ammoniopropyl)carbamoyl pendant units has been prepared and reacted with cis-PtCl2(DMSO)2 (DMSO = dimethyl sulfoxide) to give a heteronuclear Ru(II)Pt(II) dimer having a cis-Pt(II)Cl2(aliphatic amine)2 unit, [Ru(bpy)2(mu-bridge)PtCl2](PF6)2 (bpy = 2,2'-bipyridine, bridge = 4,4'-bis(N-(3-aminopropyl)carbamoyl)-2,2'-bipyridine). The ESI-TOF mass spectrum of the Ru(II)Pt(II) dimer shows a set of signals corresponding to {[Ru(bpy)2(mu-bridge)PtCl2](PF6)}(+) (m/z 1181.1). The MLCT (metal-to-ligand charge transfer) luminescence intensity is enhanced upon the platination of two amine units, presumably due to the formation of a relatively rigid metallocycle. More interestingly, the luminescence intensity is further enhanced by the complexation of the Ru(II)Pt(II) dimer with either 5'-GMP (guanosine 5'-monophosphate disodium salt) or calf thymus DNA. Visible-light-induced scission of supercoiled pBR322 DNA is found to be efficiently enhanced in the presence of the title Ru(II)Pt(II) dimer.

In the title compound, [Pt2(μ-C14H16N3O)2(NH3)4](ClO4)6·2H2O, the diplatinum(II) cation is found to be a head-to-tail isomer. The intradimer Pt—Pt distance [3.0304 (7) A] is much shorter than the value of 3.0852 (13) A reported for the analogous cis-diammineplatin­um(II) dimer bridged by 2-(N′-methyl-4,4′-bipyridinium-1-yl)­acetamidates [Sakai, Ikuta, Tsu­bomura, Kato, Yokoyama, Kajiwara & Ito (2003). Acta Cryst. E59, m780–m783], showing that the electron density at the metal centers is higher in the title system than in the previously reported system. The shortest interdimer Pt⋯Pt distance is 8.4585 (8) A.

[Pt(0)(binap)(2)] (binap = 2,2'-bis(diphenylphosphino)-1,1'-binaphthyl) is found to exhibit a luminescence from metal-to-ligand charge transfer state (MLCT) with a quantum yield of 0.12 and a lifetime of 1.2 micros in toluene at an ambient temperature. Prompt fluorescence with a quantum yield of 1.6 x 10(-)(4) is observed by means of a picosecond time-correlated single photon counting technique. The spectrum of the steady-state luminescence is almost identical to that of the prompt fluorescence, indicating that the intense luminescence is mainly delayed fluorescence from thermally activated (1)MLCT. The analysis of the temperature-dependent emission indicates that the energy difference between the (1)MLCT and (3)MLCT is 1.15 x 10(3) cm(-)(1). The lifetime of the prompt fluorescence is determined to be 3.2 ps from the decay of stimulated emission overlapped on subpicosecond transient absorption spectra. The lifetime of the (1)MLCT is much longer than expected from the large spin-orbit coupling constant of 5d (Pt) electrons (4000 cm(-)(1)). Theoretical analysis based on density functional theory reveals that structural distortion in the MLCT states causes large energy splitting between HOMO and HOMO - 1, which prevents a very fast ISC induced by strong spin-orbit interactions between these orbitals. The relatively slow ISC is therefore induced by weak spin-orbit interactions (ca. 50 cm(-)(1)) between ligand-centered molecular orbitals. Theoretical calculations indicate that the phosphorescence observed at lower temperatures is due to intensity borrowing from 4(1)B(2) --GS transition. However, the large energy difference between HOMO and HOMO - 2 reduces the extent of mixing between the lowest (3)MLCT and 4(1)B(2) due to spin-orbit interaction, thereby decreasing the radiative rate of the phosphorescence.

In the title compound, [Pt2(μ-C13H14N3O)2(NH3)4](ClO4)6·2H2O, the dinuclear PtII cation is found to be a head-to-tail isomer having pseudo-C2 symmetry. Two positively charged viologen moieties tethered to the diplatinum unit are located at the farthest position to minimize the electrostatic repulsion between the moieties, and also serve as relatively strong electron-withdrawing groups, giving rise to a very long intradimer Pt⋯Pt distance [3.0852 (13) A] which is the longest distance among those reported for amidate-bridged cis-diammineplatinum(II) dimers to date.