Phosphine)-and (N-heterocyclic carbene)gold(I) derivatives of naphthalene and pyrene are reported, containing one or two gold atoms per hydrocarbon. The new complexes are prepared by arylation of gold(I) substrates by arylboronic acids or aryl pinacolboronate esters in the presence of cesium carbonate. Isolated yields range from 52% to 98%. The boron precursors themselves derive from the parent hydrocarbon, where boron is installed in an iridium-catalyzed reaction, or from the aromatic bromides, which are borylated with palladium catalysis. Most of the new gold(I) complexes are air-and moisture-stable colorless solids; they are characterized by multinuclear NMR and optical spectroscopy, combustion analysis, and high-resolution mass spectrometry. X-ray diffraction crystal structures are reported for seven. Gold binding red-shifts optical absorption profiles, which are characteristic of the aromatic skeleton. All compounds show triplet-state luminescence, and dual singlet and triplet emission occurs in some instances. Phosphorescence persists for milliseconds at 77 K and for hundreds of microseconds at room temperature. The compounds' photophysical characteristics, along with time-dependent density-functional theory calculations, suggest emission from ππ* states of the aromatic core. Triplet-state geometry optimization finds minimal geometric rearrangement upon one-electron promotion from the (singlet) ground state.

Transient absorption spectrum for isomer 2 showing vibrational progressions in the excited singlet state.Figure S2. Orbital plots of the HOMO -2 of 1′ and 2′. Full citation for ref. 32.

Cationic phosphine-terminated rhenium(III) chalcogenide clusters;[Re 6 Se 8 (Et 3 P) 5 I]I, [Re 6 S 8 -(Et 3 P) 5 Br]Br, [Re 6 Se 8 (Bu 3 P) 5 I]I, and [Re 6 S 8 (Bu 3 P) 5 Br]Br;were synthesized and encapsulated in silica nanospheres in a one-pot, base-catalyzed hydrolysis in acetonitrile. The cluster-doped silica nanoparticles have diameters of 10-20 nm, as observed by transmission electron microscopy (TEM). The diameter is dependent upon the volume of the solvent added to the system. Reactions conducted in >10 mL of acetonitrile led to the isolation of particles ∼200 nm in diameter. The absorption and emission properties of the clusters were maintained upon encapsulation. The 1 H resonance of the alkyl groups was not observed in the silica-cluster composites via nuclear magnetic resonance (NMR), and the emission blue-shifts, indicating that the clusters reside within the silica framework, rather than on the surface. Upon irradiation by light (λ > 420 nm), both the clusters and their silica composites can generate singlet oxygen, demonstrating the oxygen permeability of silica. The smaller silica-cluster composites are potential candidates for photodynamic therapy and for other applications of singlet oxygen. The encapsulation is ineffective for neutral and anionic clusters. Electrostatic interaction between cationic clusters and the anionic, deprotonated silanol groups is proposed to drive the encapsulation.

5,5′-Bis(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-2,2′-bithiophene was metalated with (triphenylphosphine)gold(I) at the 5,5′-positions to yield a di-gold(I)-substituted bithiophene. The resulting complex was characterized by X-ray diffraction crystallography, optical spectroscopy, and elemental analysis. The digold bithiophene complex emits green, structured luminescence in chloroform. Its absorption profile is red-shifted from those of 2,2′-bithiophene or the boronate ester starting material. Density-functional theory (DFT) calculations indicate that the frontier orbitals of the digold complex concentrate on the bithienyl bridge. Time-dependent DFT calculations find that the LUMO←HOMO promotion mostly accounts for the absorption onset in all three compounds and that configuration interaction with vacant orbitals on gold modulates this transition. This interaction contributes to red-shifted absorption profiles of σ-aurated gold(I) organometallics.