meso- and β-Pyrrole-Linked Chlorin-Bacteriochlorin Dyads for Promoting Far-Red FRET and Singlet Oxygen Production.

Mykhaylo Dukh, Walter A Tabaczynski, Sairaman Seetharaman, Zhongping Ou, Karl M Kadish, Francis D'Souza, Ravindra K Pandey

Chemistry (Weinheim an der Bergstrasse, Germany) 2020 Nov 20

filter terms:

A series of chlorin-bacteriochlorin dyads (derived from naturally occurring chlorophyll-a and bacteriochlorophyll-a), covalently connected either through the meso-aryl or β-pyrrole position (position-3) via an ester linkage have been synthesized and characterized as a new class of far-red emitting fluorescence resonance energy transfer (FRET) imaging, and heavy atom-lacking singlet oxygen-producing agents. From systematic absorption, fluorescence, electrochemical, and computational studies, the role of chlorin as an energy donor and bacteriochlorin as an energy acceptor in these wide-band-capturing dyads was established. Efficiency of FRET evaluated from spectral overlap was found to be 95 and 98 % for the meso-linked and β-pyrrole-linked dyads, respectively. Furthermore, evidence for the occurrence of FRET from singlet-excited chlorin to bacteriochlorin was secured from studies involving femtosecond transient absorption studies in toluene. The measured FRET rate constants, kFRET , were in the order of 1011 s-1 , suggesting the occurrence of ultrafast energy transfer in these dyads. Nanosecond transient absorption studies confirmed relaxation of the energy transfer product, 1 BChl*, to its triplet state, 3 Bchl*. The 3 Bchl* thus generated was capable of producing singlet oxygen with quantum yields comparable to their monomeric entities. The occurrence of efficient FRET emitting in the far-red region and the ability to produce singlet oxygen make the present series of dyads useful for photonic, imaging and therapy applications. © 2020 Wiley-VCH GmbH.

Citation

Mykhaylo Dukh, Walter A Tabaczynski, Sairaman Seetharaman, Zhongping Ou, Karl M Kadish, Francis D'Souza, Ravindra K Pandey. meso- and β-Pyrrole-Linked Chlorin-Bacteriochlorin Dyads for Promoting Far-Red FRET and Singlet Oxygen Production. Chemistry (Weinheim an der Bergstrasse, Germany). 2020 Nov 20;26(65):14996-15006