Search

The development of highly efficient cyclometalated phosphorescent iridium(III) complexes is greatly promoted by their rational molecular design. Manipulating the excited states of iridophosphors could endow them with appealing photophysical properties, which play vital roles in triplet state-related photofunctional applications (

A new platinum(II) complex-based soft salt S1, ([Pt(tpp)(ed)]+[Pt(pba) (CN)2]-) (tpp = 2-(4-(trifluoromethyl)phenyl)pyridine, ed = ethane-1,2-diamine, pba = 4-(2-pyridyl)benzaldehyde), was designed and synthesized. UV-visible absorption and photoluminescence (PL) spectra were studied to elucidate the nature of ground and excited states. The soft salt complex was found to show self-assembly properties with the assistance of electrostatic, π-π stacking, and Pt···Pt interactions, resulting in the remarkable emergence of low-energy absorption and PL bands. Morphological transformation of S1 from undefined nanosized aggregates to nanofibers with different solvent compositions has been demonstrated. Interestingly, a luminescent polymer film was prepared by doping S1 into a polyethylene glycol matrix. The film displayed distinctive emission color change from yellow to red upon heating. Eventually, a high-level anti-counterfeiting application was accomplished using a time-resolved imaging technique based on the thermochromic luminescence property and long emission decay time displayed by S1. It is anticipated that this work can provide deep insights into the control of intermolecular interactions between cationic and anionic complexes of soft salt upon exposure to different external stimuli, resulting in the development of smart luminescent materials for various applications.

Luminescent copper(I) halide complexes with bi- and tridentate rigid ligands have gained wide research interests. In this paper, six tetracoordinate dinuclear copper(I) halide complexes, Cu2X2(ppda)2 [ppda = 2-[2-(dimethylamino)phenyl(phenyl)phosphino]-N,N-dimethylaniline, X = I (1), Br (2), Cl (3)] and Cu2X2(pfda)2 [pfda = 2-[2-(dimethylamino)-4-(trifluoromethyl)phenyl(phenyl)phosphino]-N,N-dimethyl-5-trifluoromethylaniline, X = I (4), Br (5), Cl (6)], were successfully prepared and systematically characterized on their structures and photophysical properties. Complexes 1-5 have a centrosymmetric form with a planar Cu2X2 unit, and complex 6 has a mirror symmetry form with a butterfly-shaped Cu2X2. Solid complexes 1, 4, and 5 emit delayed fluorescence at room temperature, intense blue to greenish yellow (λmax = 443-570 nm) light, and their peak wavelengths are located at 443-570 nm with microsecond lifetimes (τ = 0.4-19.2 μs, ΦPL = 0.05-0.48). Complexes 2, 3, and 6 show prompt fluorescence, very weak yellowish green to yellow (λmax = 534-595 nm) emission with peak wavelengths at 534-595 nm, and lifetimes in nanoseconds (τ = 4.4-9.3 ns, ΦPL < 0.0001). (Metal + halide) to ligand and intraligand charge transitions are the main origin of the emission of the complexes. Solution-processed, complex-4-based nondoped and doped devices emit yellow green light with CIE coordinated at (0.41, 0.51), a maximum EQE up to 0.17%, and luminance reaching 75.52 cd/m2.

A new sublimable dicopper(I) complex bearing 1,2-bis(diphenylphosphino)ethane and 5-trifluoromethyl-3-(2'-pyridyl)pyrazolate ligands has been designed and synthesized, and its crystalline solvated and nonsolvated compounds have also been obtained and investigated. It is shown that only the crystalline solvated compound exhibits reversible and selective luminescence vapochromism, arising from its unique "pyridyl/CH

Luminescent copper(I) halide complexes with bi- and tridentate rigid ligands have gained wide research interests. In this paper, six tetracoordinate dinuclear copper(I) halide complexes, Cu

Four platinum(II) complexes Pt-1, Pt-2, Pt-3, and Pt-4 with the isomeric donor-acceptor (D-A) conjugated ligand framework are designed and prepared, and their thermal, photophysical, and electrochemical characteristics investigated. Crystal structures for Pt-1 and Pt-4 are determined with single-crystal X-ray diffraction analysis, showing distorted and nonplanar geometry. Complex Pt-4 exhibits much greater distortion, attributed to the steric interactions between benzothiadiazole and naphthalene. Remarkably different photophysical, electrochemical, and electroluminescent properties are found for these platinum(II) complexes. Photoluminescence wavelengths of these complexes range from 590 to 800 nm with bandgaps of 1.7-2.0 eV. Coordination with [1,2,5]thiadiazolo[3,4- c]pyridine and triphenylamine can enhance D-A interactions, reducing the bandgap and producing near-infrared emission for Pt-3. Organic light-emitting devices (OLEDs) display electroluminescence with emission peaks at 626, 645, 826, and 571 nm, with maximum external quantum efficiencies of 0.13%, 0.04%, 0.49%, and 0.22% for Pt-1, Pt-2, Pt-3, and Pt-4 doped OLEDs, respectively. Thus, adjusting the coordination position with the isomeric conjugation framework ligand is an appropriate strategy to tune the light-emitting properties of platinum complexes in OLEDs.

Heteroaryl incorporated acetylide-functionalized pyridinyl ligands (L1-L6) with the general formula Py-C≡C-Ar (Py = pyridine and Ar = thiophene-2-yl, 2,2' -bithiophene]-5-yl, 2,2' :5',2″ -terthiophene]-5-yl, thieno[2,3- b]thiophen-2-yl, quinoline-5-yl, benzo[c][1,2,5]thiadiazole-5-yl) have been synthesized by Pd(0)/Cu(I)-catalyzed cross-coupling reaction of 4-ethynylpyridine and the respective heteroaryl halide. Ligands L1-L6 were isolated in respectable yields and characterized by microanalysis, IR spectroscopy, 1H NMR spectroscopy, and ESI-MS mass spectrometry. A series of dinuclear Cu(I) complexes 1-10 have been synthesized by reacting L1-L6 with CuI and triphenylphosphine (PPh3) (R1) or with an anchored phosphine derivative, 4-(diphenylphosphino) benzoic acid (R2)/2-(diphenylphosphino)benzenesulfonic acid (R3), in a stoichiometric ratio. The complexes are soluble in common organic solvents and have been characterized by analytical, spectroscopic, and computational methods. Single-crystal X-ray structure analysis confirmed rhomboid dimeric structures for complexes 1, 2, 4, and 5, and a polymeric structure for 6. Complexes 1-6 showed oxidation potential responses close to 0.9 V vs Fc0/+, which were chemically irreversible and are likely to be associated with multiple steps and core oxidation. Preliminary photovoltaic (PV) results of these new materials indicated moderate power conversion efficiency (PCE) in the range of 0.15-1.56% in dye-sensitized solar cells (DSSCs). The highest PCE was achieved with complex 10 bearing the sulfonic acid anchoring functionality.

A new series of bimetallic Cu(I) complexes 1–5 triply bridged by a monoanionic or charge-neutral functionalized 3-(2′-pyridyl)-1,2,4-triazole in a μ–η1(N),η2(N,N) tridentate binding mode and two bis(diphenylphosphino)methane (dppm) ligands have been synthesized. Complexes 1–5 are singly or doubly charged dinuclear Cu(I) species with an eight-membered Cu2C2P4 ring of {Cu(μ-dppm)2Cu} unit, in which 3 and 4 adopt the boat–boat conformation, while 1, 2, and 5 display the chair–boat form. In these dimeric copper(I) complex cations, one of the two Cu(I) ions is four-coordinated, in a highly distorted N2P2 tetrahedral environment and the other is three-coordinated, in a distorted NP2 trigonal planar arrangement. All these Cu(I) complexes exhibit a comparatively weak low-energy absorption in CH2Cl2 solution, ascribed to the charge-transfer transitions with appreciable 1MLCT contribution, as suggested by time-dependent density functional theory (TDDFT) analyses. Complexes 1–5 display good emission properties in bo...

Two new lanthanide complexes [Ln(hfaa)3(Py-Im)] [hfaa = hexafluoroacetylacetone, Py-Im = 2-(2-pyridyl)benzimidazole and Ln = Eu(III) (1) and Tb(III) (2)] were synthesized and characterized. An X-ra...

Phosphorescent dinuclear iridium(III) complexes that can show high luminescent efficiencies and good electroluminescent abilities are very rare. In this paper, highly phosphorescent 2-phenylpyrimidine-based dinuclear iridium(III) complexes have been synthesized and fully characterized. Significant differences of the photophysical and electrochemical properties between the mono- and dinuclear complexes are observed. The theoretical calculation results show that the dinuclear complexes adopt a unique molecular orbital spatial distribution pattern, which plays the key role of determining their photophysical and electrochemical properties. More importantly, the solution-processed organic light-emitting diode (OLED) based on the new dinuclear iridium(III) complex achieves a peak external quantum efficiency (η(ext)) of 14.4%, which is the highest η(ext) for OLEDs using dinuclear iridium(III) complexes as emitters. Besides, the efficiencies of the OLED based on the dinuclear iridium(III) complex are much higher that those of the OLED based on the corresponding mononuclear iridium(III) complex.

It is well-known that the variation of noncovalent interactions of luminophores, such as π–π interaction, metal-to-metal interaction, and hydrogen-bonding interaction, can regulate their emission colors. Electrostatic interaction is also an important noncovalent interaction. However, very few examples of luminescence color tuning induced by electrostatic interaction were reported. Herein, a series of Zn(II)-bis(terpyridine) complexes (Zn-AcO, Zn-BF4, Zn-ClO4, and Zn-PF6) containing different anionic counterions were reported, which exhibit counterion-dependent emission colors from green-yellow to orange-red (549 to 622 nm) in CH2Cl2 solution. More importantly, it was found that the excited states of these Zn(II) complexes can be regulated by changing the electrostatic interaction between Zn2+ and counterions. On the basis of this controllable excited state, white light emission has been achieved by a single molecule, and a white light-emitting device has been fabricated. Moreover, a novel type of data dec...

Two new dyads have been synthesized and studied as photosensitizers for the light-driven generation of H2 from aqueous protons. One of the dyads, Dy-1, consists of a strongly absorbing Bodipy (dipyrromethene-BF2) dye and a platinum diimine benzenedithiolate (bdt) charge transfer (CT) chromophore, denoted as PtN2S2. The two components are connected through an amide linkage on the bdt side of the PtN2S2 complex. The second dyad, Dy-2, contains a diketopyrrolopyrrole dye that is linked directly to the acetylide ligands of a Pt diimine bis(arylacetylide) CT chromophore. The two dyads, as well as the Pt diimine bis(arylacetylide) CT chromophore, were attached to platinized TiO2 via phosphonate groups on the diimine through sonication of the corresponding esters, and each system was examined for photosensitizer effectiveness in photochemical generation of H2 from aqueous protons and electrons supplied by ascorbic acid. Of the three photosensitizers, Dy-1 is the most active under 530 nm radiation with an initial turnover frequency of 260 h(-1) and a total of 6770 turnovers over 60 h of irradiation. When a "white" LED light source is used, samples with Dy-2 and the Pt diimine bis(arylacetylide) chromophore, while not as effective as Dy-1, perform relatively better. A key conclusion is that the presence of a strongly absorbing organic dye increases dyad photosensitizer effectiveness only if the energy of the CT excited state lies below that of the organic dye's lowest excited state; if not, the organic dye does not improve the effectiveness of the CT chromophore for promoting electron transfer and the light-driven generation of H2. The nature of the spacer between the organic dye and the charge transfer chromophore also plays a role in the effectiveness of using dyads to improve light-driven energy-storing reactions.

A series of single-stranded helical Re(I) complexes, of formula [Re(2)(L)Br(2)(CO)(6)], were prepared by reacting [Re(CO)(5)Br] with chiral quaterpyridines L1-4. By (1)H and (13)C NMR analysis, all the crude complexes consisted of a pair of stereoisomers. Sterically more demanding ligand L4 induced a higher ratio (80:20) than L1-3 (about 56:44). Stereochemically pure complexes could be obtained by recrystallization in CH(2)Cl(2). X-ray crystallographic analysis of single crystals from purified complexes showed a single-stranded helical structure with a bridging ligand wrapped around two distorted octahedral rhenium metals, both of which possessed one bromide ligand and three carbonyl ligands in a fac coordination. The helical core is established by extensive noncovalent electrostatic interactions and chiral information is transmitted from the ligand to the helix through these interactions. Solution behavior was studied by CD spectroscopy, and the strong Cotton effect confirms the integrity of the helical structure in solution. The diastereoselectivity of helicates is proposed to be induced by steric interaction between the bromine atom and the substituent of the bridging ligand.

We introduce the 1,2,3-tris(organylthiophenyl) group as a symmetrical, multidentate chelation link for building coordination networks. For this, zinc(II) 5,10,15,20-tetrakis[3',4',5'-tris(methylthio)phenyl]porphyrin was synthesized and integrated into a two-dimensional network via coordination with BiBr3. The coordination link exhibits an unusually complex bonding pattern, involving six S atoms from two neighboring ligands that form multiple Bi-S interactions (distances ranging from 3.08 to 3.63 A) with a dimerlike unit of Bi2Br6. The electronic interaction between the porphyrin center and the Bi2Br6 block was illustrated by the diffuse-reflectance spectrum of the network compound, in which a modest red-shifted feature at 1.8 eV was seen (while the Q-band absorption of the metalloporphyrin core continues to be dominant at 1.9 eV).

The synthesis and structural, photophysical, electrochemical, and electroluminescent properties of a novel class of trifunctional Pt(II) cyclometalated complexes are reported in which the hole-transporting triarylamine, electron-transporting oxadiazole, and electroluminescent metal components are integrated into a single molecule. These neutral metal chelates display good thermal stability (250 degrees C under N2) and morphological stability. All of them exhibit intense ligand-centered fluorescence and phosphorescence in fluid solutions at room temperature, but the emission spectra become largely dominated by triplet emission bands in CH2Cl2 glass at 77 K. Substituents with different electronic properties were introduced into the bipolar cyclometalating ligands to fine-tune the absorption and emissive characteristics of the compounds, and the results were correlated with theoretical calculations using density functional theory. A comparison of the photophysics and electrochemistry of our multifunctional systems to those only derived from each of the constituent components was also made and discussed. These Pt complexes can be vacuum-sublimed and applied as emissive dopants for the fabrication of vapor-deposited electrophosphorescent organic light-emitting devices (OLEDs), which generally exhibit good device performance with efficiencies up to 3.6%, 11.0 cd A-1, and 5.8 lm W-1. While the electroluminescence energy resembles that recorded in fluid solutions for these Pt emitters, these monochromatic OLEDs can emit tunable colors by varying the aryl ring substituents and the level of doping. Saliently, single dopant white-light electroluminescence, triggered by the simultaneous fluorescence/phosphorescence emission of the metal complexes and a variation of applied driving voltages, has also been realized based on some of these multifunctional complexes with peak electrophosphorescence efficiencies of 6.8 cd A-1 and 2.6%.

A trinuclear heterobimetallic Ru(II)-Cu(II) donor-acceptor complex, [Ru(II)((t)Bubpy)(CN)(4)-[Cu(II)(dien)](2)](ClO(4))(2) ((t)Bubpy = 4,4'-di-tert-butyl-2,2'-bipyridine; dien = diethylenetriamine) (1), has been synthesized and successfully used as an chemodosimetric ensemble for the specific detection of cyanide in aqueous DMF. X-ray crystallography, solid and solution IR spectroscopy, and conductivity measurements reveal that complex 1 is a one-dimensional polymer in the crystalline state and dissociates into its [Ru(II)((t)Bubpy)(CN)(2)[(CN)Cu(II)(dien)L](2)](2+) (L = solvent) monomeric units in polar solvents. The MLCT transition and luminescence properties of the solvatochromic [Ru(II)((t)Bubpy)(CN)(4)](2)(-) donor are perturbed by the coordination of two Cu(II) acceptors but restored in the presence of CN(-). Spectroscopic and mass spectrometric studies confirm the cleavage of the cyano bridge between Ru(II) and Cu(II) of the chemodosimetric ensemble after the binding of cyanide to the Cu(II) centers. The overall binding constant, K(B), between 1 and CN(-) is measured to be (7.39 +/- 0.23) x 10(6) M(-2). A detection limit of 1.2 microM (0.03 ppm) of CN(-) in aqueous DMF (pH 7.4) is achievable. Thermodynamic evaluation shows that the analyte specificity of chemodosimeter 1 is attributable to the relative stability of the donor-acceptor complex to that of adducts formed between the acceptor metal center and the analytes.

The coordination chemistry of the N-substituted arylamido ligands [N(R)(C6H3R'2-2,6)] [R = SiMe3, R' = Me (L1); R = CH2But, R' = Pri (L2)] toward FeII and CoII ions was studied. The monoamido complexes [M(L1)(Cl)(tmeda)] [M = Fe (1), Co (2)] react readily with MeLi, affording the mononuclear, paramagnetic iron(II) and cobalt(II) methyl-arylamido complexes [M(L1)(Me)(tmeda)] [M = Fe (3), Co (4)]. Treatment of 2:1 [Li(L2)(THF)2]/FeCl2 affords the unusual two-coordinate iron(II) bis(arylamide) [Fe(L2)2] (5).

Treatment of W2Cl6(THF)4 with alkylamine NH2R (R = Bus, Cy) affords a dinuclear species having the stoichiometry W2Cl4(NHR)2(NH2R)2 (R = Bus (1), Cy (2)). This has been confirmed by single-crystal X-ray diffraction studies for 2 with the following crystal data: tetragonal space group P421c, a = 12.774(2) A, c = 9.934(2) A, Z = 2. The molecule possesses an eclipsed structure with strong NH···Cl intramolecular hydrogen bonding, with disordering of the whole set of ligands containing the amide, amine, and chlorine ligands. Attempts have been made to treat and refine both ligand sets separately for this molecule, and the final refinement converges with reasonable bond distances and angles to R = 0.028 and wR2 = 0.066. In both orientations, the ligand arrangements are the same. Each W atom is surrounded by a trans set of two Cl and two N atoms with a W−W separation of 2.2884(9) A. Substitution of the amine ligands in 1 and 2 by the monodentate phosphine PMe3 proceeds smoothly to produce trans-W2Cl4(NHR)2(PMe...

The triply-bonded ditungsten(III) complexes of stoichiometry W2Cl4(NHR)2(PMe3)2 (R = Et, Prn, Bun) are formed by a two-step, one-pot, synthesis from the reaction of W2Cl6(THF)4 with the appropriate alkylamines NH2R (R = Et, Prn, Bun), followed by phosphine substitution. The dinuclear species W2Cl4(NHR)2(NH2R)2 are the probable intermediate complexes for such reactions. In each case, three isomeric forms have been detected in solution by 31P{1H}NMR spectroscopy, and they are formulated as the trans isomers and the two types of cis isomers possessing Ci and C2 symmetries. It has also been shown that the trans isomers are the initial (kinetic) products irrespective of the R group. The X-ray crystallographic characterization of the Ci isomer of cis-W2Cl4(NHEt)2(PMe3)2 (1), the C2 isomer of cis-W2Cl4(NHPrn)2(PMe3)2 (2), and the C2 isomer of cis-W2Cl4(NHBun)2(PMe3)2 (3a,b) has been accomplished. Crystallographic data are as follows: compound 1, triclinic space group P1, a = 7.4366(2) A, b = 8.8618(6) A, c = 9...

A new and convenient synthetic route to a series of W⋮W compounds with the general formula W2Cl4(NR2)2(PR‘3)2 has been developed. The method has been used in the preparation of W2Cl4(NR2)2(PMe3)2 (R = Et (2), Bu (3), Hex (4)) and W2Cl4(NR2)2(PEt2H)2 (R = Et (5), Bu (6), Hex (7)). Treatment of W2Cl6(THF)4 with the appropriate dialkylamine NHR2 (R = Et, Bu, Hex) affords an intermediate species having the stoichiometry W2Cl4(NR2)2(NHR2)2. This has been verified by single-crystal X-ray diffraction studies for W2Cl4(NEt2)2(NHEt2)2 (1) with the following crystallographic parameters: orthorhombic space group Iba2, a = 11.6704(9) A, b = 13.336(1) A, c = 17.321(2) A, Z = 4. The structure of 1 reveals that the molecule itself deviates from an eclipsed conformation with retention of a strong intramolecular N−H···Cl hydrogen bonding and the torsion angle involving the hydrogen bonded N and Cl atoms is 27.0°. Each W atom is coordinated by a cis set of two Cl and two N atoms with a W−W distance of 2.3084(5) A. There i...

Four new triply-bonded ditungsten complexes of the formula cis,cis-W2Cl4(NHCMe3)2(L-L) (L-L = dmpm (1), dmpe (2), dppm (3), dppe (4)) have been prepared by reaction of W2Cl4(NHCMe3)2(NH2CMe3)2 with the appropriate bidentate phosphines (L-L) in hydrocarbon solvents. These complexes are the first triply-bonded complexes of the form W2Cl4(NHR)2(L-L) where L-L groups are bidentate phosphines. The molecular structures have been investigated by X-ray crystallography. Crystal data are as follows: for 1, monoclinic space group P21/n, a = 13.807(1) A, b = 11.835(2) A, c = 15.348(1) A, β = 109.19(2)°, Z = 4; for 2, P21/n, a = 14.144(2) A, b = 11.991(1) A, c = 15.662(2) A, β = 109.50(1)°, Z = 4; for 3·CH2Cl2, P21/c, a = 18.777(6) A, b = 10.273(2) A, c = 21.082(3) A, β = 94.11(6)°, Z = 4; for 4, P21/n, a = 11.938(1) A, b = 18.583(3) A, c = 17.606(2) A, β = 106.54(6)°, Z = 4. The W−W bond lengths for 1, 2, 3·CH2Cl2, and 4 are 2.3247(4), 2.3274(5), 2.328(1), and 2.3452(5) A, respectively, which are consistent with a f...

Heterometallic cerium(IV) perrhenate, permanganate, and molybdate complexes containing the imidodiphosphinate ligand [N(i-Pr2PO)2](-) have been synthesized, and their reactivity was investigated. Treatment of Ce[N(i-Pr2PO)2]3Cl (1) with AgMO4 (M = Re, Mn) afforded Ce[N(i-Pr2PO)2]3(ReO4) (2) or Ce2[N(i-Pr2PO)2]6(MnO4)2 (3). In the solid state, 3 is composed of a [Ce2{N(i-Pr2PO)2}6(MnO4)](+) moiety featuring a weak Ce-OMn interaction [Ce-OMn distance = 2.528(8) Å] and a noncoordinating MnO4(-) counteranion. While 3 is stable in the solid state and acetonitrile solution, it decomposes readily in other organic solvents, such as CH2Cl2. 3 can oxidize ethylbenzene to acetophenone at room temperature. Treatment of 1 with AgBF4, followed by reaction with [n-Bu4N]2[MoO4], afforded [Ce{N(i-Pr2PO)2}3]2(μ-MoO4) (4). Reaction of trans-Ce[N(i-Pr2PO)2]2(NO3)2 (5), which was prepared from (NH4)2Ce(NO3)6 and K[N(i-Pr2PO)2], with 2 equiv of [n-Bu4N][Cp*MoO3] yielded trans-Ce[N(i-Pr2PO)2]2(Cp*MoO3)2 (6). 4 can catalyze the oxidation of methyl phenyl sulfide with tert-butyl hydroperoxide with high selectivity. The crystal structures of complexes 3-6 have been determined.

Two axially ligated rhodamine-Si(IV)-phthalocyanine (Rh-SiPc) conjugates, bearing one and two rhodamine B, were synthesized and their linear and two-photon photophysical, subcellular localization and photocytotoxic properties were studied. These Rh-SiPc conjugates exhibited an almost exclusive mitochondrial localizing property in human nasopharyngeal carcinoma (HK-1) cells and human cervical carcinoma (HeLa) cells. Strong photocytotoxic but low dark cytotoxic properties were also observed for the two Rh-SiPc conjugates toward the HK-1 cells. Using nuclei staining method and flow cytometric DNA content analysis, apoptotic cell death was induced by these conjugates upon photoactivation. This observation is consistent with their mitochondrial localization property. The observed properties of these conjugates qualify them as promising PDT agents.

Here we report the syntheses and crystal structures of a series of cobalt(II) and nickel(II) complexes derived from _RNP2 ligands (where R = OMe_(Bz), H_(Bz), Br_(Bz), Ph) bearing ethylene linkers between a single N and two P donors. The Co^(II) complexes generally adopt a tetrahedral configuration of general formula [(NP2)Co(I)_2], wherein the two phosphorus donors are bound to the metal center but the central N-donor remains unbound. We have found one case of structural isomerism within a single crystal structure. The Co^(II) complex derived from _(Bz)NP2 displays dual coordination modes: one in the tetrahedral complex [(_(Bz)NP2)Co(I)_2]; and the other in a square pyramidal variant, [(_(Bz)NP2)Co(I)_2]. In contrast, the Ni^(II) complexes adopt a square planar geometry in which the P(Et)N(Et)P donors in the ligand backbone are coordinated to the metal center, resulting in cationic species of formula [(_RNP2)Ni(I)]^+ with iodide as counterion. All Ni^(II) complexes exhibit sharp ^1H and ^(31)P spectra in the diamagnetic region. The Co^(II) complexes are high-spin (S = 3/2) in the solid state as determined by SQUID measurements from 4 to 300 K. Solution electron paramagnetic resonance (EPR) experiments reveal a high-spin/low-spin Co^(II) equilibrium that is dependent on solvent and ligand substituent.

A novel dicyanoosmium(III) complex, trans-Ph(4)P[Os(III)(salen)(CN)(2)].CH(2)Cl(2).H(2)O (1; Ph(4)P(+) = tetraphenylphosphonium cation, salen(2-) = N,N'-ethylenebis(salicylideneaminato) dianion), has been synthesized and structurally characterized. Reactions of 1 with [Cu(Me(3)tacn)(H(2)O)(2)](ClO(4))(2) (Me(3)tacn = 1,4,7-trimethyl-1,4,7-triazacyclononane) under different conditions produce the 1-D ferromagnetic zigzag chains [Os(salen)(CN)(2)](2)[Cu(Me(3)tacn)].CH(3)OH (2) and [Os(salen)(CN)(2)][Cu(Me(3)tacn)].ClO(4) (3).

A series of 3d-4f heterobimetallic phenylene-bridged Schiff base complexes of the general formula [Zn(mu-L1)Ln(NO3)3(S)n] [Ln = La (1), Nd (2), Gd (3), Er (4), Yb (5); S = H(2)O, EtOH; n = 1, 2; H2L1 = N,N'-bis(3-methoxysalicylidene)phenylene-1,2-diamine] and [Zn(mu-L2)Ln(NO3)3(H2O)n] [Ln = La (6), Nd (7), Gd (8), Er (9), Yb (10); n = 1, 2; H(2)L(2) = N,N'-bis(3-methoxy-5-p-tolylsalicylidene)phenylene-1,2-diamine] were synthesized and characterized. Complexes 1, 2, 4, and 7 were structurally characterized by X-ray crystallography. At room temperature in CH(3)CN, both neodymium(III) (2 and 7) and ytterbium(III) (5 and 10) complexes also exhibited, in addition to the ligand-centered emission in the UV-vis region, their lanthanide(III) ion emission in the near-infrared (NIR) region. The photophysical properties of the zinc(II) phenylene-bridged complexes (ZnL1 and ZnL2) were measured and compared with those of the corresponding zinc(II) ethylene-bridged complexes (ZnL3 and ZnL4). Our results revealed that, at 77 K, both ligand-centered triplet (3LC) and singlet (1LC) states existed for the ethylene-bridged complexes (ZnL3 and ZnL4), whereas only the (1)LC state was detected for the phenylene-bridged complexes (ZnL1 and ZnL2). NIR sensitization studies of [Zn(mu-L')Nd(NO3)3(H2O)n] (L' = L1-L4) complexes further showed that Nd3+ sensitization took place via the 3LC and 1LC states when the spacer between the imine groups of the Schiff base ligand was an ethylene and a phenylene unit, respectively. Ab initio calculations show that the observed differences can be attributed to the difference in the molecular vibrational properties and electron densities of the electronic states between the ethylene- and phenylene-bridged complexes.

Reactions of coordinatively unsaturated Ru[N(Ph2PQ)2]2(PPh3) (Q = S (1), Se (2)) with pyridine (py), SO2, and NH3 afford the corresponding 18e adducts Ru[N(Ph2PQ)2]2(PPh3)(L) (Q = S, L = NH3 (5); Q = Se, L = py (3), SO2 (4), NH3 (6)). The molecular structures of complexes 2 and 6 are determined. The geometry around Ru in 2 is pseudo square pyramidal with PPh3 occupying the apical position, while that in 6 is pseudooctahedral with PPh3 and NH3 mutually cis. The Ru-P distances in 2 and 6 are 2.2025(11) and 2.2778(11) A, respectively. The Ru-N bond length in 6 is 2.185(3) A. Treatment of 1 or 2 with substituted hydrazines L or NH2OH yields the respective adducts Ru[N(Ph2PQ)2]2(PPh3)(L) (Q = S, L = NH2NH2 (12), t-BuNHNH2 (14), l-aminopiperidine (C5H10NNH2) (15); Q = Se, L = PhCONHNH2 (7), PhNHNH2 (8), NH2OH (9), t-BuNHNH2 (10), C5H10NNH2 (11), NH2NH2 (13)), which are isolated as mixtures of their trans and cis isomers. The structures of cis-14 and cis-15 are characterized by X-ray crystallography. In both molecular structures, the ruthenium adopts a pseudooctahedral arrangement with PPh3 and hydrazine mutually cis. The Ru-N bond lengths in cis-14.CH2Cl2 and cis-15 are 2.152(3) and 2.101(3) A, respectively. The Ru-N-N bond angles in cis-14.CH2Cl2 and cis-15 are 120.5(4) and 129.0(2) degrees, respectively. Treatment of 1 with hydrazine monohydrate leads to the isolation of yellow 5 and red trans-Ru[N(Ph2PS)2]2(NH3)(H2O) (16), which are characterized by mass spectrometry, 1H NMR spectroscopy, and elemental analyses. The geometry around ruthenium in 16 is pseudooctahedral with the NH3 and H2O ligands mutually trans. The Ru-O and Ru-N bond distances are 2.118(4) and 2.142(6) A, respectively. Oxidation reactions of the above ruthenium hydrazine complexes are also studied.

Treatment of W(2)Cl(6)(THF)(4) with alkylamine NH(2)R (R = Bu(s), Cy) affords a dinuclear species having the stoichiometry W(2)Cl(4)(NHR)(2)(NH(2)R)(2) (R = Bu(s) (1), Cy (2)). This has been confirmed by single-crystal X-ray diffraction studies for 2 with the following crystal data: tetragonal space group Pfourmacr;2(1)c, a = 12.774(2) Å, c = 9.934(2) Å, Z = 2. The molecule possesses an eclipsed structure with strong N-H.Cl intramolecular hydrogen bonding, with disordering of the whole set of ligands containing the amide, amine, and chlorine ligands. Attempts have been made to treat and refine both ligand sets separately for this molecule, and the final refinement converges with reasonable bond distances and angles to R = 0.028 and wR2 = 0.066. In both orientations, the ligand arrangements are the same. Each W atom is surrounded by a trans set of two Cl and two N atoms with a W-W separation of 2.2884(9) Å. Substitution of the amine ligands in 1 and 2 by the monodentate phosphine PMe(3) proceeds smoothly to produce trans-W(2)Cl(4)(NHR)(2)(PMe(3))(2) (R = Bu(s) (3), Cy (4)) in high yields. In solution, both 3 and 4 readily undergo isomerization to the corresponding cis-W(2)Cl(4)(NHR)(2)(PMe(3))(2) (R = Bu(s) (5), Cy (6)). The characterization of 3-6 has been accomplished by IR, (1)H NMR, and (31)P{(1)H}NMR spectroscopy and mass spectrometry. The crystal data for 5 and 6 are as follows: for 5, monoclinic space group P2(1)/a, a = 13.339(3) Å, b = 13.446(3) Å, c = 15.179(3) Å, beta = 99.33(2) degrees, Z = 4; for 6, P2(1)/n, a = 8.455(1) Å, b = 25.714(3) Å, c = 13.454(1) Å, beta = 104.839(8) degrees, Z = 4. Each of these phosphine-containing complexes is characterized by a W(2)(6+) metal core unit and has an eclipsed W(2)Cl(4)N(2)P(2) conformation. The W-W bond distances for 5 and 6 are 2.321(1) and 2.3229(5) Å, respectively, and these compounds are shown to have PMe(3) ligands cis to the amides. On the other hand, kinetic studies by (31)P{(1)H}NMR spectroscopy show that the trans-to-cis transformation in solution is an irreversible process of the first order, which is different from the reversible process observed in the case of tert-butyl analog. The initial rate constant was 10(1) x 10(-)(3) min(-)(1), and the rate constants in the presence of excess PMe(3) were shown to be roughly constant (average 4.5 x 10(-)(3) min(-)(1)) over a range of [PMe(3)]. These observations could be understood if, in addition to a dissociative mechanism, internal flip steps operate as a second mechanism for the process, and the flip barrier is 25-29 kcal/mol.