Selected Rosindone Derivatives: Synthesis, Structural Characterization, and Photophysical Studies

\ua9 2024 Wiley-VCH GmbH. The reaction of 7-phenylbenzo[a]phenazine-5(7H)-one (rosindone) with one equivalent of a nitrating mixture (conc. H2SO4/HNO3) produced 6-nitro-7-phenylbenzo[a]phenazine-5(7H)-one (NROS), as confirmed by 1H NMR spectroscopy. The selectivity of the reaction is assigned to an electronic effect. The attempted sulphonation of rosindone with chlorosulfonic acid produced the chlorinated derivative 6-chloro-7-phenylbenzo[a]phenazine-5(7H)-one (CLROS), instead but in low yield. The nitro group of NROS was reduced with SnCl2 to produce a blue solid identified as 6-amino-7-phenylbenzo[a]phenazine-5(7H)-one (AMROS). The X-ray crystal structure confirmed the positioning of the amino group α to the carbonyl group. The reaction of rosindone with one equivalent of lithium trimethylsilylacetylide underwent a Michael addition to introduce the nucleophile β to the carbonyl group. The compound 6a-ethynyl-6a,7-dihydrobenzo[a]phenazine-5(6H)-one (rac-ACROS) was identified by an X-ray crystal structure determination. Coupling of rac-ACROS under standard Glazer conditions produced the dyad of the compound linked via the two ethynyl subunits. A different N-phenyl group was readily introduced into the rosindone basic structure by the reaction of methyl 2-((2-aminophenyl)amino)benzoate with 2-hydroxy-1,4-naphthoquinone to produce methyl 2-(5-oxobenzo[a]phenazine-7(5H)-yl)benzoate (MROS)

Coherent excitation transferring via dark state in light-harvesting process

We study the light absorption and energy transferring in a donor-acceptor system with a bionic structure. In the optimal case with uniform couplings, it is found that the quantum dynamics of this seemingly complicated system is reduced as a three-level system of $\Lambda$-type. With this observation, we show that the dark state based electromagnetically-induced transparency (EIT) effect could enhance the energy transfer efficiency, through a quantum interference effect suppressing the excited population of the donors. We estimate the optimal parameters of the system to achieve the maximum output power. The splitting behavior of maximum power may be used to explain the phenomenon that the photosynthesis systems mainly absorb two colors of light.Comment: 4 pages, 3 figure