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Dímero cromofórico acoplado a excitón nulo muestra separación de carga de ruptura de simetría

Ebin Sebastian¹, Mahesh Hariharan¹

¹School of Chemistry, Indian Institute of Science Education and Research Thiruvananthapuram (IISER TVM), Maruthamala P.O., Vithura, Thiruvananthapuram 695551, Kerala, India.

Journal of the American Chemical Society

|August 9, 2021

Resumen

Los investigadores descubrieron un nuevo mecanismo para la separación eficiente de cargas en materiales moleculares. Este proceso, impulsado por el acoplamiento de excitones nulos, conduce a estados de carga separada altamente estables, avanzando las imitaciones fotosintéticas y la fotovoltaica molecular.

Área de la Ciencia:

Ciencias de los materiales
La fotoquímica
Química Física

Sus antecedentes:

Comprender las relaciones estructura-propiedad en los sistemas multicromóforos es crucial para el desarrollo de la fotosíntesis artificial y la fotovoltaica molecular.
La división del excitón nulo es un fenómeno clave en arquitecturas cromóforas específicas, que conduce a propiedades emergentes únicas.

Objetivo del estudio:

Investigar el nuevo fenómeno de la separación de cargas de ruptura de simetría fotoinducida asistida por acoplamiento de excitones nulos (SB-CS).
Para explorar las relaciones estructura-propiedad en un dímero de perilenodiimida espiro-conjugado orientado a la cruz griega (+) (Sp-PDI2).

Principales métodos:

Cálculos químicos cuánticos para racionalizar el comportamiento de acoplamiento de excitones nulos.
Espectroscopia de absorción transitoria de femtosegundo para caracterizar las firmas espectroscópicas catiónicas y aniónicas de los radicales.
Análisis de las tasas de separación y recombinación de cargas en disolventes polares.

Principales resultados:

Se observó una alta eficiencia de SB-CS en Sp-PDI2 facilitada por el acoplamiento selectivo de transferencia de orificios.
Los cálculos químicos cuánticos confirmaron que el acoplamiento Coulombic y la transferencia de carga son insignificantes, lo que resulta en firmas espectroscópicas similares a los monómeros.
Logró una proporción sin precedentes de tasas de recombinación de carga (CR) de SB-CS (2647 en acetonitrilo) debido a los efectos de la región invertida de Marcus.

Conclusiones:

El filtrado selectivo de carga en Sp-PDI2 rige la eficiencia de SB-CS.
Los hallazgos ofrecen nuevas perspectivas para el diseño de biomimética y materiales funcionales avanzados.
El acoplamiento de excitón nulo es una estrategia viable para mejorar la eficiencia de la separación de cargas.

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