Eumelanins, the chief photoprotective pigments in man and mammals, owe their black color to an unusual broadband absorption spectrum whose origin is still a conundrum. Excitonic effects from the interplay of geometric order and disorder in 5,6-dihydroxyindole (DHI)-based oligomeric/polymeric structures play a central role, however the contributions of structural (scaffold-controlled) and redox (π-electron-controlled) disorder have remained uncharted. Herein, we report an integrated experimental-theoretical entry to eumelanin chromophore dynamics based on poly(vinyl alcohol)-controlled polymerization of a large set of 5,6-dihydroxyindoles and related dimers. The results a) uncover the impact of the structural scaffold on eumelanin optical properties, disproving the widespread assumption of a universal monotonic chromophore; b) delineate eumelanin chromophore buildup as a three-step dynamic process involving the rapid generation of oxidized oligomers, termed melanochromes (phase I), followed by a slow oxidant-independent band broadening (phase II) leading eventually to scattering (phase III); c) point to a slow reorganization-stabilization of melanochromes via intermolecular redox interactions as the main determinant of visible broadband absorption.

Eumelanin broadband absorption develops from aggregation-modulated chromophore interactions under structural and redox control / Micillo, Raffaella; Panzella, Lucia; Iacomino, Mariagrazia; Prampolini, Giacomo; Cacelli, Ivo; Ferretti, Alessandro; Crescenzi, Orlando; Koike, Kenzo; Napolitano, Alessandra; D'Ischia, Marco. - In: SCIENTIFIC REPORTS. - ISSN 2045-2322. - 7:(2017), p. 41532. [10.1038/srep41532]

Eumelanin broadband absorption develops from aggregation-modulated chromophore interactions under structural and redox control

Micillo, Raffaella;PANZELLA, LUCIA;IACOMINO, MARIAGRAZIA;CRESCENZI, ORLANDO;NAPOLITANO, ALESSANDRA;D'ISCHIA, MARCO
2017

Abstract

Eumelanins, the chief photoprotective pigments in man and mammals, owe their black color to an unusual broadband absorption spectrum whose origin is still a conundrum. Excitonic effects from the interplay of geometric order and disorder in 5,6-dihydroxyindole (DHI)-based oligomeric/polymeric structures play a central role, however the contributions of structural (scaffold-controlled) and redox (π-electron-controlled) disorder have remained uncharted. Herein, we report an integrated experimental-theoretical entry to eumelanin chromophore dynamics based on poly(vinyl alcohol)-controlled polymerization of a large set of 5,6-dihydroxyindoles and related dimers. The results a) uncover the impact of the structural scaffold on eumelanin optical properties, disproving the widespread assumption of a universal monotonic chromophore; b) delineate eumelanin chromophore buildup as a three-step dynamic process involving the rapid generation of oxidized oligomers, termed melanochromes (phase I), followed by a slow oxidant-independent band broadening (phase II) leading eventually to scattering (phase III); c) point to a slow reorganization-stabilization of melanochromes via intermolecular redox interactions as the main determinant of visible broadband absorption.
2017
Eumelanin broadband absorption develops from aggregation-modulated chromophore interactions under structural and redox control / Micillo, Raffaella; Panzella, Lucia; Iacomino, Mariagrazia; Prampolini, Giacomo; Cacelli, Ivo; Ferretti, Alessandro; Crescenzi, Orlando; Koike, Kenzo; Napolitano, Alessandra; D'Ischia, Marco. - In: SCIENTIFIC REPORTS. - ISSN 2045-2322. - 7:(2017), p. 41532. [10.1038/srep41532]
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11588/666805
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