Seeing luminescence appear as crystals crumble. Isolation and subsequent self-association of individual [(C6H11NC)2Au]+ ions in crystals

Non-luminescent, isostructural crystals of [(C₆H₁₁NC)₂Au](EF₆)·C₆H₆ (E = As, Sb) lose benzene upon standing in air to produce green luminescent (E = As) or blue luminescent (E = Sb) powders. Previous studies have shown that the two-coordinate cation, [(C₆H₁₁NC)₂Au]⁺, self-associates to form luminescent crystals that contain linear or nearly linear chains of cations and display unusual polymorphic, vapochromic, and/or thermochromic properties. Here, we report the formation of non-luminescent crystalline salts in which individual [(C₆H₁₁NC)₂Au]⁺ ions are isolated from one another. In [(C₆H₁₁NC)₂Au](BArF₂₄) ((BArF₂₄)⁻ is tetrakis[3,5-bis(trifluoromethyl)phenyl]borate) each cation is surrounded by two anions that prohibit any close approach of the gold ions. Crystallization of [(C₆H₁₁NC)₂Au](EF₆) (E = As or Sb, but not P) from benzene solution produces colorless, non-emissive crystals of the solvates [(C₆H₁₁NC)₂Au](EF₆)·C₆H₆. These two solvates are isostructural and contain columns in which cations and benzene molecules alternate. With the benzene molecules separating the cations, the shortest distances between gold ions are 6.936(2) Å for E = As and 6.9717(19) Å for E = Sb. Upon removal from the mother liquor, these crystals crack due to the loss of benzene from the crystal and form luminescent powders. Crystals of [(C₆H₁₁NC)₂Au](SbF₆)·C₆H₆ that powder out form a pale yellow powder with a blue luminescence with emission spectra and powder X-ray diffraction data that show that the previously characterized [(C₆H₁₁NC)₂Au](SbF₆) is formed. In the process, the distances between the gold(i) ions decrease to ∼3 Å and half of the cyclohexyl groups move from an axial orientation to an equatorial one. Remarkably, when crystals of [(C₆H₁₁NC)₂Au](AsF₆)·C₆H₆ stand in air, they lose benzene and are converted into the yellow, green-luminescent polymorph of [(C₆H₁₁NC)₂Au](AsF₆) rather than the colorless, blue-luminescent polymorph. Paradoxically, the yellow, green-luminescent powder that forms as well as authentic crystals of the yellow, green-luminescent polymorph of [(C₆H₁₁NC)₂Au](AsF₆) are sensitive to benzene vapor and are converted by exposure to benzene vapor into the colorless, blue-luminescent polymorph.

Non-luminescent crystals of [(C₆H₁₁NC)₂Au](AsF₆)·C₆H₆ readily lose benzene to form the green-luminescent polymorph of [(C₆H₁₁NC)₂Au](AsF₆) rather than the blue-luminescent polymorph.     

Optical and ODMR Studies of Luminescent Halo(dimethylphenylphosphine)gold(I) Crystals

Crystals of {(Me(2)PhP)AuX}(n) (Me = methyl; Ph = phenyl; X = Cl, Br, I; n = 2, 3) show emission from two excited states. Both states are assigned a triplet multiplicity, on the basis of their lifetimes and zero-field splittings. The structured, higher energy emission originates at approximately 360 nm and has the greater relative intensity at low temperatures. It is assigned as intraligand phosphorescence from a phenyl-localized (3)pipi state. The unstructured, lower energy emission has a peak wavelength that varies in the range 630-730 nm. It is assigned as phosphorescence from the triplet state due to the gold-based sigma(p) <-- sigma(s,d) excitation. The corresponding singlet state is observed at 290-310 nm. The results of SCF-Xalpha-SW calculations on the model complexes H(3)PAuX and (H(3)PAuX)(2) are also presented.     

Redox characteristics of nickel and palladium complexes of the open-chain tetrapyrrole octaethylbilindione: a biliverdin model

Octaethylbiliverdin, C35H46N4O2, is a linear tetrapyrrole that can exist in coordinated form as the fully reduced trianion (OEB)3-, as the two electron oxidized monoanion, (OEBOx)-, or as the one electron oxidized radical, (OEB.)2-. The three-membered electron-transfer series involving [M(OEB)]n with n = +1, 0, and -1, and M = Ni or Pd has been characterized electrochemically. The most highly oxidized members of these series have been isolated in the form of their diamagnetic triiodide salts, [NiII(OEBOx)]I3 and [PdII(OEBOx)]I3, and characterized spectroscopically and by X-ray diffraction. [NiII(OEBOx)]I3 crystallizes in the orthorhombic space group Pbcn with a = 15.121(3) A, b = 16.777(3) A, and c = 14.628(3) A at 130(2) K with Z = 4. Refinement of 3311 reflections with 209 parameters and no restraints yielded wR2 = 0.136 and R = 0.054 for 2643 reflections with I > 2 sigma(I). The structure involves helical coordination of the linear tetrapyrrole ligand about the nickel with all four nitrogen atoms coordinated to the metal and Ni-N distances of 1.867(5) and 1.879(5) A. The triiodide ion is not coordinated to the nickel but sits over one of the meso carbon atoms of the tetrapyrrole. In the solid state, pairs of [NiII(OEBOx)]+ crystallize about a center of symmetry so that two identical tab/slot hydrogen-bonded arrangements involving the lactam oxygen of one complex and methine and two methylene protons of the adjacent cation. Similar hydrogen-bonded motifs are found in other complexes derived from octaethylbilindione. [PdII(OEBOx)]I3 is isomorphic with the nickel analogue and crystallizes in the orthorhombic space group Pbcn with a = 15.2236(6) A, b = 16.7638(7) A, and c = 14.6289(6) A at 90(2) K with Z = 4. Refinement of 6123 reflections with 209 parameters and no restraints yielded wR2 = 0.094 and R = 0.036 for 4042 reflections with I > 2 sigma(I). The odd electron compound PdII(OEB.) has also been isolated and characterized by single-crystal X-ray diffraction. Black PdII(OEB.) crystallizes in the monoclinic space group I2/a with a = 13.274(3) A, b = 18.655(4) A, c = 14.114(3) A, and beta = 116.00(3) degrees at 140(2) K with Z = 4. Refinement of 2030 reflections with 195 parameters and no restraints yielded wR2 = 0.090 and R = 0.042 for 1715 reflections with I > 2 sigma(I). The structure again involves helical coordination of the linear tetrapyrrole to the palladium through the four pyrrole nitrogen atoms. Reduction of the complex causes a slight elongation of the Pd-N bonds from 1.983(2) and 1.986(2) A in [PdII(OEBOx)]I3 to 2.011(4) and 2.012(4) A in PdII(OEB.).     

Insertion of acetylenes in the PdPd bond of Pd2 (Ph2 PCH2 PPh2)2 Cl2

Dimethylacetylene dicarboxylate and hexafluoro-2-butyne add to Pd₂(dpm)₂Cl₂ (dpm = Ph₂PCH₂PPh₂) to give crystalline adducts Pd₂(dp)₂(μ-acetylene)Cl₂. An X-ray crystal structure of Pd₂(dpm)₂(μ-C₄F₆)Cl₂ reveals that the acetylene has inserted into the metalmetal bond and has been transformed into a cis-dimetallated olefin. The central CC bond length of the bridging olefin is 1.338(16) Å. The coordination about each of the two similar palladium ions is planar and involves two trans-phosphines (one from each of the bridging dpm ligands), a terminal chloride, and one carbon of the bridging olefin. Both Pd₂(dpm)₂Cl₂ and Pd₂(dpm)₂(μ-C₂{CO₂H₃}₂)Cl₂ catalyze the cyclotrimerization of dimethyl-acetylene dicarboxylate.     

Kinetic and analytical study on precipitation reactions with110AgNO3 of some di (β-chloroethyl) amine derivates and hydrochlorides with esters of N-(p-aminobenzoyl)-L-aspartic acid as carriers from dimethylformamide-water solution

The kinetics of precipitation reactions with¹¹⁰AgNO₃ of some di (β-chlorethyl) amine derivates and hydrochlorides with esters of N-(p-aminobenzoyl)-L-aspartic acid as carriers in dimethylformamide-water mixture, were studied. The rate constants of these reactions were of the order of 10^?4 1 · mol^?1 · min^?1. The concentrations of the corresponding hydrochloride solutions were measured by radiometric titration with¹¹⁰AgNO₃ solution of given concentration.     

Cleavage of Carbon Disulfide by n-Propyldiphenylphosphine and Nickel(II) Bromide

Carbon disulfide is cleaved by n-propyldiphenylphosphine and nickel(II) bromide in a one-step process, to form two unprecedented complexes: orange, [Ni(S₂C₂(PⁿPrPh₂)₂)Br(PⁿPrPh₂)]Br⋅CS₂ ( 1 ) and purple [Ni{η²-SC(PⁿPrPh₂)₂}Br(PⁿPrPh₂)]Br⋅0.5CS₂ ( 2 ). Orange ( 1 ) contains a dithiolene-related ligand that results from carbon–carbon bond formation, while purple ( 2 ) contains a remarkable ligand in which two n-propyldiphenylphosphine molecules have added to a carbon atom of a CS unit that is coordinated to nickel.