We report here the synthesis of bis(DEDT –S,S)-μ-(naphthyl-1,8) digold(II) (1) (DEDT = diethyldithiocarbamate) with a formal Au-Au bond. Complex 1 is formed from the reaction of Au(DEDT)Cl2 with 1,8-dilithioaphthalene, a unique synthesis as gold(II) complexes are traditionally synthesized by oxidative addition of digold(I) complexes. Complex 1 was characterized by NMR, UV-Vis spectroscopy, X-ray and elemental analysis. Density Functional Theory calculations suggests the UV-Vis absorption of complex 1 at 379 nm is a transition from the σ(Au-Au) orbital into the σ*(Au-Au) orbital with some contribution from DEDT-to-metal charge transfer (LMCT). Complex 1 shows no emission at 298 K or 77 K, presumably because low-lying 3LMCT states foster rapid non-radiative decay.

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

We report here a series of emissive biphenyl cyclometalated gold(III) diethyl dithiocarbamate complexes having H, CF3, OMe, and tBu substitutions on the biphenyl moiety. Synthesis of these complexes was accomplished by a single-step reaction of the appropriate dilithio-biphenyl reagent with Au(dtc)Cl2 (dtc = diethyl dithiocarbamate). All four complexes exhibit weak room-temperature phosphorescence in solution and much more intense phosphorescence in the solid state and in low-temperature glasses with lifetimes in the microseconds. From experimental data and computational modeling, the emission originates mainly from a metal-perturbed 3(π–π*) state of the biphenyl moiety with a minor contribution from ligand-to-ligand charge transfer. Weak solution emission is attributed to deactivation via a distorted charge-transfer state that is less accessible in the solid state or in a low-temperature glass.

By introducing hydrogen-bonding groups into the coordination sphere Of Pt(IV) hydroxido complexes photogenerated hydroxyl radicals are tethered and directed to abstract a hydrogen atom from the ethyl group of a triethylphosphine ligand, even at 25 degrees C, to yield phosphaplatinacycle complexes.

Brominated polycyclic aromatic compounds are important synthons, but their synthesis can be difficult. Herein, we report that Pt(IV) centers σ-bonded to naphthalene and a dicarboximideperylene activate the ring systems to selective thermal and photochemical bromination. Thus, trans-Pt(PEt3)2(Br)3(4-bromo-1-naphthyl) and Br2 give trans-Pt(PEt3)2(Br)3(7,4-dibromo-1-naphthyl). Introduction of a second Pt(IV) center is achieved by double oxidative addition of 1,4-dibromonaphthalene to 2Pt(PEt3)4. Bromination of [trans-Pt(PEt3)2Br]2(1,4-naphthdiyl) yields [trans-Pt(PEt3)2(Br)3]2(1,4-naphthdiyl), which further brominates on the ring to give [trans-Pt(PEt3)2(Br)3]2(6,7-dibromo-1,4-naphthdiyl). Photoreduction of the Pt(IV) centers with 1-hexene gives first mixed-valent [trans-Pt(PEt3)2(Br)3][trans-Pt(PEt3)2(Br)](6,7-dibromo-1,4-naphthdiyl) and then [trans-Pt(PEt3)2Br]2(6,7-dibromo-1,4-naphthdiyl). Photoreduction of trans-Pt(PEt3)2(Br)3(PMI) (PMI = N-(2,5-di-tert-butylphenyl)perylen-3-yl-9,10-dicarboximide) withou...

Reinvestigation of trans-(P(OPh)3)2(CO)IrCl 1 and trans-(P(OPh)3)2(CO)IrBr 2 reveals unexpected coincidence in 31P NMR, IR carbonyl stretch, and UV–visible absorption properties. XRD structure studies show the complexes are isostructural, although the crystals are not isomorphous. The complexes were investigated via DFT and TD-DFT modeling which shows that the spectroscopic similarity can be attributed to low-level halogen orbital participation in key molecular orbitals, a balance between the halogen atom σ- and π-donation to the iridium center, and phenoxy group dominance of the phosphorus atom electronic structure.

With the goal of understanding and controlling photoreductive elimination reactions from d6 transition metal complexes as part of a solar energy storage cycle we have investigated the photochemistry of Pt(IV) bromo, chloro, hydroxo, and hydroperoxo complexes. Photoreductive elimination reactions occur for all of these complexes and appear to involve initial Pt-Br, Pt-Cl, or Pt-O bond fission. In the case of Pt-OH bond fission, the subsequent chemistry can be controlled through hydrogen bonding to the hydroxo group.

The Pt(IV) complexes trans-Pt(PEt3)2(Cl)3(R) 2 (R = Cl, Ph, 9-phenanthryl, 2-trifluoromethylphenyl, 4-trifluoromethylphenyl, 3-perylenyl) were prepared by chlorination of the Pt(II) complexes trans-Pt(PEt3)2(R)(Cl) 1 with Cl2(g) or PhICl2. Mixed bromo-chloro complexes trans,trans-Pt(PEt3)2(Cl)2(Br)(R) (R = 9-phenanthryl, 4-trifluoromethylphenyl), trans,cis-Pt(PEt3)2(Cl)2(Br)(4-trifluoromethylphenyl), trans,trans-Pt(PEt3)2(Br)2(Cl)(R) (R = 9-phenanthryl), and trans,cis-Pt(PEt3)2(Br)2(Cl)(4-trifluoromethylphenyl) were obtained by halide exchange or by oxidative addition of Br2 to 1 or Cl2 to trans-Pt(PEt3)2(R)(Br). Except for 2 (R = Ph, 4-trifluoromethylphenyl), all of the Pt(IV) complexes are photosensitive to UV light and undergo net halogen reductive elimination to give Pt(II) products, trans-Pt(PEt3)2(R)(X) (X = Cl, Br). Chlorine trapping experiments with alkenes indicate a reductive-elimination mechanism that does not involve molecular chlorine and is sensitive to steric effects at the Pt center. DFT calculations suggest a radical pathway involving (3)LMCT excited states. Emission from a triplet is observed in glassy 2-methyltetrahydrofuran at 77 K where photoreductive elimination is markedly slowed.

Photolysis (380 nm) of trans,cis-Pt(PEt3)2(Cl)2(OH)(4-tft) (4-tft = 4-trifluoromethylphenyl) at 77 K in 2-methyltetrahydrofuran gives triplet emission, platinum(III), and a hydroxo radical. Benzyl radical emission is observed in toluene from the reaction of a portion of the OH radicals with toluene. Warming the photolyzed solutions gives platinacycle trans-Pt(CH2CH2PEt2)(PEt3)(Cl)2(4-tft) by hydrogen-atom abstraction from a PEt3 ligand and trans-Pt(PEt3)2(Cl)(4-tft) from net HOCl photoelimination. The platinacycle undergoes thermal reductive elimination at 298 K or photolytic reductive elimination, even at 77 K.

Global energy consumption and the production of clean renewable energy have become greater challenges. Sunlight-induced splitting of water into H2 and O2 is one of the leading strategies to achieve clean and renewable energy. Transition metal photochemistry has considerable potential for making this task more viable. Along with water splitting, hydrohalic acid (HX) splitting is being thoroughly investigated. HX splitting is a more facile two electron process whereas water splitting is a relatively difficult four electron oxidation process. Light driven HX splitting and endergonic elimination of X2 (Br2 and Cl2) have received more attention as a potentially more economical and promising solar energy conversion process than water splitting. ...

Concentrated hydrogen peroxide addition to trans-Pt(PEt3)2Cl(R) [1 (R = 9-phenanthryl), 2 (R = 4-trifluoromethylphenyl)] yields hydroxo-hydroperoxo complexes trans-Pt(PEt3)2(Cl)(OOH)(OH)(R) [5 (R = 9-phenanthryl), 4 (R = 4-trifluoromethylphenyl)], where the hydroperoxo ligand is trans to R. Complex 5 is unstable and reacts with solvent CH2Cl2 to give trans,cis-Pt(PEt3)2(Cl)2(OH)(9-phenanthryl) (3). Treatment of 4 with HCl yields analogous trans,cis-Pt(PEt3)2(Cl)2(OH)(4-trifluoromethylphenyl) (6) and HBr gives trans-Pt(PEt3)2(Br)(Cl)(OH)(4-trifluoromethylphenyl) (7), where the Br and 4-trifluoromethylphenyl ligands are trans. Photolysis of 3 or 6 at 313 or 380 nm causes reduction to trans-Pt(PEt3)2Cl(R) (1 or 2, respectively). Expected coproduct HOCl is not detected, but authentic solutions of HOCl are shown to decompose under the reaction conditions. Chlorobenzene and other unidentified products that oxidize PPh3 to OPPh3 are detected in photolyzed benzene solutions. Photolysis of 3 or 6 in the presence of 2,3-dimethyl-2-butene (TME) yields the chlorohydrin (2-chloro-2,3-dimethyl-3-butanol), 3-chloro-2,3-dimethyl-1-butene, and acetone, all expected products from HOCl trapping, but additional oxidation products are also observed. Photolysis of mixed chloro-bromo complex 7 with TME yields the bromohydrin (2-bromo-2,3-dimethyl-3-butanol) and 2, consistent with cis-elimination of HOBr. Computational results (TDDFT and DFT) and photochemistry of related complexes suggest a dissociative triplet excited state reaction pathway and that HOCl elimination may occur by an incipient hydroxo radical abstraction of an adjacent halogen atom, but a pathway involving hydroxo radical reaction with solvent or TME to generate a carbon-based radical followed by halogen abstraction from Pt cannot be eliminated.

Photolysis (380 nm) of trans-Pt(PEt3)2(Cl)(OH)(OOH)(4-trifluoromethylphenyl) (1) at -78 °C in acetone-d6 or toluene-d8 yields HOOOH (16-20%) and trans-Pt(PEt3)2(Cl)(4-trifluoromethylphenyl) (2). Also observed in acetone-d6 are H2O2, (CD3)2C(OH)(OOH), and (CD3)2C(OOH)2. Thermal decomposition or room-temperature photolysis of 1 gives O2, water, and 2. Computational modeling (DFT) suggests two intramolecular hydrogen-bonding-dependent triplet pathways for the photolysis and two possible pathways for the thermolysis, one involving proton transfer from the OOH to the OH ligand and the other homolysis of the Pt-OOH bond, abstraction of the OH ligand, and decomposition of the resulting H2O3. Trapping studies suggest the latter pathway.

Pt(IV) complexes trans-Pt(PEt3)(2)(R)(Br)(3) (R = Br, aryl and polycyclic aromatic fragments) photoeliminate molecular bromine with quantum yields as high as 82%. Photoelimination occurs both in the solid state and in solution. Calorimetry measurements and DFT calculations (PMe3 analogs) indicate endothermic and endergonic photoeliminations with free energies from 2 to 22 kcal/mol of Br-2. Solution trapping experiments with high concentrations of 2,3-dimethyl-2-butene suggest a radical-like excited state precursor to bromine elimination.

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

Photolysis of Ir(triphos)X3 (triphos = 1,1,1-tris(diphenylphosphinomethyl)ethane; X = Cl, Br) yields an insoluble product believed to be oligomeric [Ir(triphos)X3]n with bridging triphos and halide ligands. Refluxing pyridine (py) dissolves the insoluble photoproducts ultimately yielding the dangling triphos complexes mer-Ir(κ(2)-triphos)(py)X3. Oxidation of the P center of the dangling arm of Ir(κ(2)-triphos)(py)Cl3 yields mer-Ir(κ(2)-P,P-triphosO)(py)Cl3 (triphosO = MeC(CH2P(O)Ph2)(CH2PPh2)2), which was characterized by single-crystal X-ray diffraction. mer-Ir(κ(2)-triphos)(py)Cl3 is also formed when Ir(triphos)Cl3 is photolyzed in the presence of py (ϕ = 26%). Both mer-Ir(κ(2)-triphos)(py)Cl3 and mer-Ir(κ(2)-P,P-triphosO)(py)Cl3 photoisomerize in pyridine to their thermally unstable fac-isomers. Density functional theory (DFT) and time-dependent DFT (TDDFT) calculations suggest triphos ligand arm dissociation occurs along a triplet pathway from an initial Franck-Condon ligand-field excited state that relaxes to a Jahn-Teller axially distorted octahedral triplet with a long Ir-P bond. Subsequent triphos arm dissociation yields a distorted trigonal-bipyramidal triplet that undergoes intersystem crossing to a square pyramidal singlet.