Novel molecular electron donor-acceptor (DA) dyads, composed of a phytochlorin donor and a [60]fullerene acceptor, have been photochemically characterized. In these dyads, a pyrrolidine spacer group links the chlorin and the C 60 moieties covalently, forming a rigid dyad with a short and almost constant D-A distance. The photochemical behavior of the metal-free dyads and the corresponding Zn complexes was studied by means of fluorescence and absorption spectroscopies with femto-and picosecond time resolutions in polar benzonitrile and nonpolar toluene solutions. In consistence with the previous studies on porphyrin-fullerene dyads, the novel chlorin-fullerene dyads underwent a fast intramolecular photoinduced electron transfer in a benzonitrile solution. The recombination rates of the charge-transfer (CT) states were 4.8 × 10 10 s -1 for the Zn dyads and ca. 1.5 × 10 10 s -1 for the metal-free compounds. The CT state was preceded by at least three intermediate states in the time domain from 200 fs to 100 ps. Two of the states were identified as singlet excited states of either the phytochlorin or the fullerene moiety. The third state was attributed to an intramolecular exciplex, which was transformed to the CT state. In the frame of this model, the formation rate constant of the CT state was estimated to be 1.6 × 10 11 s -1 for the Zn dyads and 0.5 × 10 11 s -1 for the metal-free compounds. The formation of the exciplex was also observed in nonpolar solvents, e.g., toluene. In contrast to the behavior in polar solvents, the exciplex relaxed in toluene directly to the ground state, without the formation of the CT state. The lifetime of the exciplex was 140 ps for the Zn dyads and 1-2 ns for the metal-free compounds in toluene.
Tosylation and acylation of cellulose were performed under mild reaction conditions using imidazolium based ionic liquids (ILs) as solvents. The non-degradative nature, lower viscosity, as well as higher solubility of cellulose in [amim]Cl encouraged us to carry out the reactions in this media. The reactions described here were optimised for this particular solvent in order to obtain different cellulose derivatives with high yields, homogeneity and degree of substitution (DS). Two reagents employed for the in situ activation of carboxylic acids were N,N 0 -carbonyldiimidazole (CDI) and 1-ethyl-3-(3 0 -dimethylaminopropyl)carbodiimide hydrochloride (EDCI). Final products were characterised by solution and solid-state NMR techniques.
Elevated by the support: 2‐Alkynyl aniline cycloisomerization to indole is catalyzed by cationic Au NPs on a carbon support. Electroneutral and rich 2‐aryl indoles are further converted into 3,3′‐biindoles by oxidative homocoupling that is readily catalyzed by the Au NPs on carbon, and exclusively but also somewhat sluggishly by the carbon support.
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