Unexpected formation of a fused double cycle trinuclear gold(i) complex supported by ortho-phenyl metallated aryl-diphosphine ligands and strong aurophilic interactions.

The first homoleptic trinuclear arylgold(i) complex, [Au3(L')2](NO3) (3), based on an ortho-phenyl metallated aryl-diphosphine ligand (L' = o-C6H4PPh(C15H10O)PPh2), has been obtained through a new thermolytic reaction of the corresponding diauracycle, [Au2(L)2](NO3)2 (L = xantphos). The formation of 3 involves activation of the ortho-phenyl C-H bond of the xantphos ligands. The presence of Au-C bonds in this new gold-diphosphine cluster is not its only remarkable feature, since it also displays two 12-membered rings fused together and a linear {Au3} chain with aurophilic interactions. Complex 3 exhibits strong sky-blue luminescence that can be assigned to a triplet metal-metal ((3)MM) transition partially mixed with a ligand-to-metal-metal charge transfer ((3)LMMCT) transition related to the aurophilic bonding. This [Au3(L')2](+) triauracycle also shows AIEE-activity, and is a selective luminescent chemosensor for metal ions.

Synthesis and Enantiomeric Recognition Studies of Optically Active Pyridino-Crown Ethers Containing an Anthracene Fluorophore Unit.

Novel enantiopure pyridino-18-crown-6 ether-based sensor molecules containing an anthracene fluorophore unit were synthesized. Their enantiomeric recognition abilities toward the enantiomers of 1-phenylethylamine hydrogen perchlorate (PhEt), 1-(1-naphthyl)ethylamine hydrogen perchlorate (NapEt), phenylglycine methyl ester hydrogen perchlorate (PhgOMe), and phenylalanine methyl ester hydrogen perchlorate (PheOMe) were examined in acetonitrile using fluorescence spectroscopy. The sensor molecules showed appreciable enantiomeric recognition toward the enantiomers of NapEt, PhEt, and PhgOMe. The highest enantioselectivity was found in the case of crown ether containing isobutyl groups in the macroring and the enantiomers of NapEt. Chirality 28:562-568, 2016. © 2016 Wiley Periodicals, Inc.

Mechano-induced reversible colour and luminescence switching of a gold(i)-diphosphine complex.

A gold(i)-diphosphine simultaneously exhibits reversible mechanochromism and mechanochromic luminescence. The mechanical grinding can trigger a transformation from a neutral mononuclear structure exhibiting white colour and blue photoluminescence to an ionic dinuclear structure with intramolecular aurophilic interactions exhibiting yellow colour and red emission.

Anion-, Solvent-, Temperature-, and Mechano-Responsive Photoluminescence in Gold(I) Diphosphine-Based Dimers.

A series of [Au2 (nixantphos)2](X)2 (nixantphos=4,6-bis(diphenylphosphino)-phenoxazine; X=NO3, 1; CF3 COO, 2; CF3 SO3, 3; [Au(CN)2], 4; and BF4, 5) complexes that exhibit intriguing anion-switchable and stimuli-responsive luminescent photophysical properties have been synthesized and characterized. Depending on their anions, these complexes display yellow (3), orange (4 and 5), and red (1 and 2) emission colors. They exhibit reversible thermo-, mechano-, and vapochromic luminescence changes readily perceivable by the naked eye. Single-crystal X-ray studies show that the [Au2 (nixantphos)2](2+) cations with short intramolecular Au⋅⋅⋅Au interactions are involved as donors in an infinite N-H⋅⋅⋅X (X=O and N) hydrogen-bonded chain formation with CF3 COO(-) (2 C) and aurophilically linked [Au(CN)2](-) counterions (4 C). Both crystals show thermochromic luminescence; their room temperature red (2 C) and orange (4 C) emission turns into yellow upon cooling to 77 K. They also exhibit reversible mechanochromic luminescence by changing their emission color from red to dark (2 C), and orange to red (4 C). Compounds 1-5 also display reversible mechanochromic luminescence, altering their emission colors between orange (1) or red (2) to dark, as well as between yellow (3) or orange (4 and 5) to red. Detailed photophysical investigations and correlation with solid-state structural data established the significant role of NH⋅⋅⋅X interactions in the stimuli-responsive luminescent behavior.

Mechanochemical synthesis of crystalline and amorphous digold(I) helicates exhibiting anion- and phase-switchable luminescence properties.

For the first time, mechanochemical synthesis has been used for the preparation of crystalline and amorphous dinuclear gold(i) helicates, [Au2L2](X)2 (L = xantphos; X = CF3SO3, SCN, BF4 and PF6), that show anion- and phase-switchable luminescence properties. This solid-state approach provides strategies for developing switchable luminescent materials.

Photodynamic effects of novel 5,15-diaryl-tetrapyrrole derivatives on human colon carcinoma cells.

Preliminary in vitro cytotoxicity studies on a panel of meso diaryl-substituted tetrapyrrole derivatives newly synthesized in our laboratory have shown that these compounds are photodynamically active on the human colon carcinoma cell line HCT116. In the present study, we investigate some mechanistic aspects of the photodynamic action of the most active compounds in the series, namely the 5-phenyl-15-(3-methoxyphenyl)porphyrin (1), the 5-phenyl-15-(3-hydroxyphenyl)porphyrin (2) and the 5,15-diphenylporphyrin (3). The results of the cytotoxicity studies indicate that the novel photosensitisers (PSs) are more potent in vitro than m-THPC (Foscan), a powerful PS already approved for clinical use in photodynamic therapy (PDT). A series of experiments were performed to elucidate a number of aspects in the mechanism of PS-induced phototoxicity, including, intracellular accumulation and subcellular localization of the PSs, induction of apoptosis, and generation of reactive oxygen species (ROS) and NO*. All the compounds tested exhibit similar singlet oxygen quantum yields; differential intracellular accumulation can contribute to the observed differences in phototoxicity. Flow cytometric studies indicate that all the tested compounds induce apoptosis; however, their cytotoxic effect does not seem to rely solely on this process. Generation of significant amounts of reactive oxygen species (ROS) and NO* were also observed; however, the contribution of this latter effect to the overall phototoxicity is unclear. Taken together, our observations suggest that the diaryl derivatives included in the present study could represent promising leads for the development of novel photosensitizing agents.

Absorption, fluorescence, and cd spectroscopic study of chiral recognition by a binaphthyl-derived chromogenic calixcrown host.

The (R)- and (S)-enantiomers of a binaphthyl-appended calix[4]crown-6 ether with two 2,4-dinitrophenylazo chromophore units ((R)-1 and (S)-1) as chiral hosts were tested in their reactions with the enantiomers of alpha-methylbenzylamine ((R)-MBA, (S)-MBA)) and phenylglycinol ((R)-PGL, (S)-PGL) as chiral guests. The visible absorption spectra indicate a two-step process: the first is a nonenantioselective proton transfer from the host to the guest, which is followed by the enantioselective real complexation. In the visible range of the CD spectra a positive/negative band belongs to the absorption of pure (R)-1/(S)-1, and a negative/positive exciton couplet to the absorption of (R)-1-(S)-MBA/(S)-1-(R)-MBA complexes. The latter phenomenon suggests that the complexation of amines is accompanied by a chiral arrangement of the two chromophore units in the hosts. The UV fluorescence of (R)-1/(S)-1 arising from the binaphthyl moiety is quenched by K+ ions, but not by the amine guests, showing that the interaction between the binaphthyl group and the complexed amines is weak.