Synthesis of redox sensitive dyes based on a combination of long wavelength emitting fluorophores and nitroxides

New, nitroxide-fluorophore acceptor-donor compounds were synthesized based on long wavelength (570–790 nm) emitting 9-diethylamino-5H-benzo[a]phenoxazin-5-one, 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene and metal-ligand complex fluorophores. The fluorophores and nitroxides were linked via a robust CC bond. The steady-state spectral properties of the new donor-acceptor compounds and their diamagnetic (sterically hindered amine) derivatives were studied. Titration of nitroxides with ascorbic acid sodium salt to diamagnetic N-hydroxy compounds resulted in fluorescence enhancement. The Ru-complex modified with nitroxide exhibited fluorescence increase and electron paramagnetic resonance band broadening upon B-deoxyribonucleic acid addition providing evidence of binding with B-deoxyribonucleic acid.