Delayed fluorescence of porphyrins in different media

Lifetimes of TPPS₄ (meso-tetraphenylporphine tetrasulfonate) triplet states were measured for liquid solutions of different acidity and viscosity and as a function of acceptor concentration for different acceptors (bovine serum albumin, tryptophan and furfuryl alcohol). Triplet lifetimes were estimated by monitoring the decay of TPPS₄ delayed fluorescence of E-type. The lifetime of delayed fluorencence depends on the concentration of O₂, since the latter is an effective quencher of the triplet state. The lifetime is shown to be influenced mainly by degree of aggregation state of TPPS₄ and, therefore, by the pH of the solution, decreasing with pH and for each pH remaining constant over a wide range of acceptor concentrations. The monomeric species is found to have the longest triplet lifetime in aqueous phosphate-buffered saline solution at neutral pH, especially when bound to albumin, despite of the low viscosity and protonated nature of the medium.     

ansa-Metallocene Derivatives : IV. Synthesis and molecular structures of chiral ansa-titanocene derivatives with bridged tetrahydroindenyl ligands

A synthesis for racemic ethylene-bis(4,5,6,7-tetrahydro-1-indenyl)titanium dichloride is described. The molecular structures of this compound, of its meso- isomer and of a binaphtholate complex of the (S,S)-enantiomer have been determined. Cleavage of this binaphtholate complex gives the pure (S,tS)-enentiomer.     

Gezielte synthesen von zweifach μ3-verbrückten dreikernigen eisenclustern Fe3(CO)9(μ3-S)(μ3-X) (X = PR,AsR, SO) aus [Fe3(CO)9(μ3-S-t-C4H9)]−

The cluster anion [Fe₃(CO)₉(μ₃-S-t-C₄H₉)]^?, which is easily obtained by deprotonation from the cluster compound Fe₃(CO)₉(μ₂-H)(μ₃-S-t-C₄H₉), reacts with XCl₂ by elimination of t-C₄H₉Cl and Cl^? to give the clusters Fe₃(CO)₉(μ₃-S)(μ₃-X) (X = PR: I, X = AsR: II, X = SO: III), in which one edge of the iron triangle is opened. The μ₃-PR-bridged clusters I can also be obtained by reactions of SCl₂ with the anions [Fe₃(CO)₉(μ₃-PR)]^2?, prepared from Fe₃(CO)₉(μ₂-H)₂(μ₃-PR) by deprotonation. The geometry of I and II is exemplified by X-ray structure analyses. Experimental evidence for a reaction pathway, proposed for the high yield syntheses of I, is discussed.