Synthesis, photophysical characterisation and photostability studies of NIR probes with aliphatic, aromatic and chlorinated terminals in 5- and 9-amino positions of benzo[a]phenoxazines

A new series of benzo[a]phenoxazinium chlorides possessing mono- or disubstituted amines with 3-chloropropyl groups at the 9-position, isopropyl, cyclohexyl and phenyl groups as terminals at 5-postion was synthesised. Photophysical studies were performed in dry ethanol and aqueous solutions. The terminals at the 5-amino position were found to influence the acid-base equilibrium. The presence of hydroxyl functionality at 2-position was found to introduce an additional basic form that is the one in equilibrium with the cationic acid form in dry ethanol solutions. The photostability of these compounds in different media was also investigated and a high resistance to photobleaching in model biological membranes was observed. In proteins a moderate of 20% photobleaching occurs in 1h 30min, while in water more than 60% of the compound molecules are photodegraded during the same time interval.Thanks are due to the Fundação para a Ciência e Tecnologia (FCT, Portugal) for financial support to the NMR portuguese network (PTNMR, Bruker Avance III 400-Univ. Minho), FCT and FEDER (European Fund for Regional Development)-COMPETE-QREN-EU for financial support to Research Centres CQ/UM [PEst-C/QUI/UI0686/2013 (FCOMP-01-0124-FEDER-037302)] and CFUM [PEst-C/FIS/UI0607/2013 (F-COMP-01-0124-FEDER-022711)]. Post-doctoral grant to B. R. Raju (SFRH/BPD/62881/2009) is also acknowledged to FCT, POPH-QREN, FSE

Higher dimensional dust collapse with a cosmological constant

The general solution of the Einstein equation for higher dimensional (HD) spherically symmetric collapse of inhomogeneous dust in presence of a cosmological term, i.e., exact interior solutions of the Einstein field equations is presented for the HD Tolman-Bondi metrics imbedded in a de Sitter background. The solution is then matched to exterior HD Scwarschild-de Sitter. A brief discussion on the causal structure singularities and horizons is provided. It turns out that the collapse proceed in the same way as in the Minkowski background, i.e., the strong curvature naked singularities form and that the higher dimensions seem to favor black holes rather than naked singularities.Comment: 7 Pages, no figure