Synthesis of covalently linked boron-dipyrromethene-chromophore conjugates using 3-bromo boron-dipyrromethene as a key precursor

3-Bromo boron dipyrromethene (3-bromo BODIPY) has been used as key synthon to prepare one ethynyl bridged and six ethynylphenyl bridged BODIPY-chromophore conjugates using mild Pd(0) coupling conditions. The chromophores possessing very distinct features, such as anthracene, BODIPY, terpyridine, porphyrin. Zn(II)porphyrin, 21,23-dithiaporphyrin and thiasapphyrin were connected at 3-position of boronboron-dipyrromethene dye by coupling of 3-bromo BODIPY with ethynyl or ethynylphenyl chromophore in toluene/triethylamine in the presence of catalytic amount of AsPh3/Pd-2(dba)(3) at 40 degrees C followed by column chromatographic purification. The spectral studies indicated that the interaction is stronger in ethynyl bridged BODIPY-chromophore conjugate compared to ethynylphenyl bridged BODIPY-chromophore conjugates. The steady-state fluorescence indicated that in ethynyl bridged BODIPY-anthracene conjugate, the BODIPY unit act as energy acceptor and showed a possibility of energy transfer from donor anthracene unit to acceptor BODIPY unit on selective excitation of anthracene unit. However, in ethynylphenyl bridged BODIPY-porphyrin conjugates, the BODIPY unit act as energy donor and exhibited a possibility of singlet-singlet energy transfer from BODIPY unit to porphyrin unit. (C) 2011 Elsevier Ltd. All rights reserved.