The macrocyclic phenanthrolinophane 2,9-[2,5,8-triaza-5-(N-anthracene-9-methylamino) ethyl]-[9]-1,10-henanthrolinophane(L) bearing a pendant arm containing a coordinating amine and an anthracene group forms stable complexes with Zn(II), Cd(II) and Hg(II) in solution. Stability constants of these complexes were determined in 0.10 mol dm(-3) NMe4Cl H2O-MeCN (1:1, v/v) solution at 298.1+/-0.1 K by means of potentiometric (pH metric) titration. The fluorescence emission properties of these complexes were studied in this solvent. For the Zn(II) complex, steady-state and time-resolved fluorescence studies were performed in ethanol solution and in the solid state. In solution, intramolecular pi-stacking interaction between phenanthroline and anthracene in the ground state and exciplex emission in the excited state were observed. From the temperature dependence of the photostationary ratio (I-Exc/I-M), the activation energy for the exciplex formation (E-a) and the binding energy of the exciplex (-DeltaH) were determined. The crystal structure of the [ZnLBr](ClO4).H2O compound was resolved, showing that in the solid state both intra- and inter-molecular pi-stacking interactions are present. Such interactions were also evidenced by UV-vis absorption and emission spectra in the solid state. The absorption spectrum of a thin film of the solid complex is red-shifted compared with the solution spectra, whereas its emission spectrum reveals the unique featureless exciplex band, blue shifted compared with the solution. In conjunction with X-ray data the solid-state data was interpreted as being due to a new exciplex where no pi-stacking (full overlap of the pi-electron cloud of the two chromophores-anthracene and phenanthroline) is observed. L is a fluorescent chemosensor able to signal Zn(II) in presence of Cd(II) and Hg(II), since the last two metal ions do not give rise either to the formation of pi-stacking complexes or to exciplex emission in solution.
ISI Document Delivery No.: 837GOTimes Cited: 30
Cited Reference Count: 59
Bencini, A Berni, E Bianchi, A Fornasari, P Giorgi, C Lima, JC Lodeiro, C Melo, MJ de Melo, JS Parola, AJ Pina, F Pina, J Valtancoli, B
Melo, Maria Joao/C-8594-2011; Pina, Fernando/C-8161-2011; Seixas de Melo, Sergio/A-5388-2008; Lodeiro, Carlos/B-4793-2013; Parola, A. Jorge/F-4048-2010; Pina, Joao /H-9948-2013; Lima, Joao/F-3658-2010
Seixas de Melo, Sergio/0000-0001-9708-5079; Lodeiro, Carlos/0000-0001-5582-5446; Parola, A. Jorge/0000-0002-1333-9076; Lima, Joao/0000-0003-0528-1967
Royal soc chemistry
Cambridge