Tunable Properties of Nature-Inspired N,N′-Alkylated Riboflavin Semiconductors

Abstract

A series of novel soluble nature-inspired flavin derivatives substituted with short butyl and bulky ethyl-adamantyl alkyl groups was prepared via simple and straightforward synthetic approach with moderate to good yields. The comprehensive characterization of the materials, to assess their application potential, has demonstrated that the modification of the conjugated flavin core enables delicate tuning of the absorption and emission properties, optical bandgap, frontier molecular orbital energies, melting points, and thermal stability. Moreover, the thin films prepared thereof exhibit smooth and homogeneous morphology with generally high stability over time.

Substrate and pH‐dependent homogeneous electrocatalysis using riboflavin for oxygen reduction

“…According to the SEM images, the riboflavin appeared to precipitate during the electrochemical treatment in a micro‐needle type structure. Such structures are reported in the literature for similar molecules like synthetic flavins, [ 15,27 ] anthraquinones, [ 48,49 ] or other organic pigments. [ 50,51 ] This deposited layer might be an explanation for the comparably low H 2 O 2 production with riboflavin at pH = 2.…”

“…[ 23,24 ] great scientific effort is made for synthesizing variations of flavin analogs with tailored properties for applications as organic semiconductors. [ 25–27 ]…”

“…Nevertheless, similar to the work of Kormányos et al [23,24] great scientific effort is made for synthesizing variations of flavin analogs with tailored properties for applications as organic semiconductors. [25][26][27] In the field of electrocatalytic ORR, the choice of electrode material is crucial, due to the high catalytic effects of many carbon-based electrode materials themselves. [28,29] Besides boron-doped diamond, all graphitic carbon electrode materials are reported to show significant ORR forming H 2 O 2 in a potential range similar to organic carbonyl-bearing electrocatalysts.…”

Organic π‐Conjugated Molecules: From Nature to Artificial Applications. Where are the Boundaries?

“…Recently, an effect of prolongation of the conjugated system on the optical, electrochemical and thermal properties of selected flavins was studied (see Scheme 7) [85] . It was also shown that N ‐alkylation can prevent hydrogen bonding, increase solubility and strongly enhance fluorescence while maintaining high thermal stability [87] . The flavin photocatalysis involves the triplet state as the active species in most cases and it can be, in principle, used for reductions as well as for oxidation reactions [88] .…”

“…[85] It was also shown that N-alkylation can prevent hydrogen bonding, increase solubility and strongly enhance fluorescence while maintaining high thermal stability. [87] The flavin photocatalysis involves the triplet state as the active species in most cases and it can be, in principle, used for reductions as well as for oxidation reactions. [88] Consequently, flavins have been employed in numerous organic photoredox-catalyzed reactions.…”