856412-44-7Relevant academic research and scientific papers
Directional Self-Sorting with Cucurbit[8]uril Controlled by Allosteric π–π and Metal–Metal Interactions
Kotturi, Kondalarao,Masson, Eric
, p. 8670 - 8678 (2018)
To maximize Coulombic interactions, cucurbit[8]uril (CB[8]) typically forms ternary complexes that distribute the positive charges of the pair of guests (if any) over both carbonylated portals of the macrocycle. We present here the first exception to this recognition pattern. Platinum(II) acetylides flanked by 4′-substituted terpyridyl ligands (tpy) form 2:1 complexes with CB[8] in an exclusively stacked head-to-head orientation in a water/acetonitrile mixture. The host encapsulates the pair of tpy substituents, and both positive Pt centers sit on top of each other at the same CB[8] rim, leaving the other rim free of any interaction with the guests. This dramatic charge imbalance between the CB[8] rims would be electrostatically penalizing, were it not for allosteric π–π interactions between the stacked tpy ligands, and possible metal-metal interactions between both Pt centers. When both tpy and acetylides are substituted with aryl units, the metal-ligand complexes form 2:2 assemblies with CB[8] in aqueous medium, and the directionality of the assembly (head-to-head or head-to-tail) can be controlled, both kinetically and thermodynamically.
Photoinduced electron transfer in platinum(II) terpyridyl acetylide chromophores: Reductive and oxidative quenching and hydrogen production
Du, Pingwu,Schneider, Jacob,Jarosz, Paul,Zhang, Jie,Brennessel, William W.,Eisenberg, Richard
, p. 6887 - 6894 (2008/10/09)
A series of luminescent platinum(II) terpyridyl acetylide complexes, ([Pt(tpy)(C≡CPh)]ClO4 (1) and [Pt-(ttpy)(C≡C-p-C 6H4R)]ClO4, where tpy = terpyridine, ttpy = 4′-p-tolylterpyridine, R = H, Cl, Me) (2-4) were studied with regard to excited-state quenching by dialkylated bipyridinium cations as electron acceptors and triethanolamine (TEOA) as an electron donor and the photogeneration of hydrogen from systems containing the chromophore, the dialkylated bipyridinium cations, TEOA, and colloidal Pt as a catalyst. The dialkylated bipyridinium cations include methyl viologen (MV2+) and a series of diquats prepared from 2,2′-bipyridine or 4,4′-dimethyl-2, 2′-bipyridine. The quenching rates for the diquats for one of the chromophores (2) are close to the diffusion-controlled limit. The most effective electron acceptor and relay for hydrogen evolution has been found to be 4,4′-dimethyl-1,1′-trimethylene-2,2′-bipyridinium (DQ4) which on photoreduction by the chromohore provides the strongest reducing agent of the diquats studied. The rate of hydrogen evolution depends in a complex way on the concentration of the bipyridinium electron relay, increasing with concentration at low concentrations and then decreasing at high concentrations. The rate of H2 photogeneration also increases with TEOA concentration at low values and eventually reaches a plateau. The most effective system examined to date consists of the chromophore 2 (2.2 × 10-5 M), DQ4 (3.1 × 10-4 M), TEOA (2.7 × 10-2 M), and Pt colloid (6.0 × 10-5 M), and has produced 800 turnovers of H 2 (67% yield based on TEOA as sacrificial electron donor) after 20 h of photolysis with λ > 410 nm.
