Using Room Temperature Phosphorescence of Gold(I) Complexes for PAHs Sensing

Unlocking Arene Phosphorescence in Bismuth-Organic Materials

Three novel bismuth-organic compounds, with the general formula [Bi2(HPDC)2(PDC)2]·(arene)·2H2O (H2PDC = 2,6-pyridinedicarboxylic acid; arene = pyrene, naphthalene, and azulene), that consist of neutral dinuclear Bi-pyridinedicarboxylate complexes and outer coordination sphere arene molecules were synthesized and structurally characterized. The structures of all three phases exhibit strong π-π stacking interactions between the Bi-bound PDC/HPDC and outer sphere organic molecules; these interactions effectively sandwich the arene molecules between bismuth complexes and thereby prevent molecular vibrations. Upon UV irradiation, the compounds containing pyrene and naphthalene displayed red and green emission, respectively, with quantum yields of 1.3(2) and 30.8(4)%. The emission was found to originate from the T1 → S0 transition of the corresponding arene and result in phosphorescence characteristic of the arene employed. By comparison, the azulene-containing compound displayed very weak blue-purple phosphorescence of unknown origin and is a rare example of T2 → S0 emission from azulene. The pyrene- and naphthalene-containing compounds both display radioluminescence, with intensities of 11 and 38% relative to bismuth germanate, respectively. Collectively, these results provide further insights into the structure-property relationships that underpin luminescence from Bi-based materials and highlight the utility of Bi-organic molecules in the realization of organic emission.

Heterometallic Au(I)-Cu(I) Clusters: Luminescence Studies and 1O2 Production

Two different organometallic gold(I) compounds containing naphthalene and phenanthrene as fluorophores and 2-pyridyldiphenylphosphane as the ancillary ligand were synthesized (compounds 1 with naphthalene and 2 with phenanthrene). They were reacted with three different copper(I) salts with different counterions (PF₆^-, OTf^-, and BF₄^-; OTf = triflate) to obtain six Au(I)/Cu(I) heterometallic clusters (compounds 1a-c for naphthalene derivatives and 2a-c for phenanthrene derivatives). The heterometallic compounds present red pure room-temperature phosphorescence in both solution, the solid state, and air-equilibrated samples, as a difference with the dual emission recorded for the gold(I) precursors 1 and 2. The presence of Au(I)-Cu(I) metallophilic contacts has been identified using single-crystal X-ray diffraction structure resolution of two of the compounds, which play a direct role in the resulting red-shifted emission with respect to the gold(I) homometallic precursors. Polystyrene (PS) and poly(methyl methacrylate) (PMMA) polymeric matrices were doped with our luminescent compounds, and the resulting changes in their emissive properties were analyzed and compared with those previously recorded in the solution and the solid state. All complexes were tested to analyze their ability to produce ¹O₂ and present very good values of Φ_Δ up to 50%.

Mono- and Dinuclear Gold(I) Coumarin Complexes: Luminescence Studies and Singlet Oxygen Production

The 4-(thiolmethyl)-7-(diethylamino)-2H-chromen-2-one ligand has been synthesized and used as chromophore in several mono- and dinuclear gold(I) compounds that contain a phosphane at the second coordination position. Four final products were able to obtain in pure form containing one coumarin and one phosphane ligand in the case of PTA (1,3,5-triaza-7-phosphatricyclo[3.3.1.13.7]decane) and PPh₃ (triphenylphosphine); one coumarin and two gold(I)-phosphane groups in the case of phosphane=DAPTA (3,7-diacetyl-1,3,7-triaza-5-phosphabicyclo[3.3.1]nonane) and two coumarin and two gold(I) atoms in the case of phosphane=DPEphos (bis[(2-diphenylphosphino)phenyl]ether), when it was used a diphosphane. Other diphosphane ligands used were not able to give the desired products in pure form. The luminescent properties of the compounds are governed by the fluorescence of the coumarin moiety in all compounds both for measurements carried out in solution and also immobilized in PMMA organic matrix. Phosphorescence emission can be detected in all cases at 77 K both for the uncoordinated coumarin ligand and the gold(I) derivatives, being more favoured in the presence of the gold(I) heavy atom. The compounds have been used as photosensitizers to generate ¹ O₂ with moderate quantum yields values.

Intra- vs Intermolecular Aurophilic Contacts in Dinuclear Gold(I) Compounds: Impact on the Population of the Triplet Excited State

Two series of dinuclear gold(I) complexes that contain two Au-chromophore units (chromophore = dibenzofurane or dimethylfluorene) connected through a diphosphane bridge that differs in the flexibility and length (diphosphane = dppb for 1,4-bis(diphenylphosphino)butane, DPEphos for bis[(2-diphenylphosphino)phenyl]ether, xanthphos for 4,5-bis(diphenylphosphino)-9,9-dimethylxanthene, and BiPheP for 2,2'-bis(diphenylphosphino)-1,1'-biphenyl) have been synthesized and structurally characterized. Their photophysical properties have been carefully investigated, paying attention to the role of the presence, or absence, of aurophilic contacts and their nature (intra- or intermolecular character). This analysis was permitted due to the X-ray crystallographic determination of all of the structures of the compounds discussed herein. The quantum yields of the triplet population, ϕ_T, have been calculated by nanosecond-laser flash photolysis measurements, and we could determine the main role of the character of the aurophilic contacts in the resulting ϕ_T, being especially favored in the presence of intermolecular contacts. Time-dependent density functional theory (TD-DFT) calculations support the absorption and emission assignments and the shorter distance between S₁ and the closest triplet excited state energy in the case of the compounds with a higher triplet-state population.

Aggregation of gold(I) complexes: phosphorescence vs. singlet oxygen production

Herein we report on the synthesis of six new phosphane-gold(I)-4-ethynylaniline complexes (neutral and cationic), with a tris-naphthalene substituted tertiary phosphane bearing a secondary amine as a linker and containing different halogen groups (Cl and Br) in the naphthyl group. We have demonstrated in this work how the careful control of the intermolecular aggregation process can modulate the competition between phosphorescence emission and energy transfer from the triplet state of the gold(I) complexes to produce singlet oxygen.