TY - JOUR A1 - Kogikoski Junior, Sergio A1 - Dutta, Anushree A1 - Bald, Ilko T1 - Spatial separation of plasmonic hot-electron generation and a hydrodehalogenation reaction center using a DNA wire JF - ACS nano N2 - Using hot charge carriers far from a plasmonic nanoparticle surface is very attractive for many applications in catalysis and nanomedicine and will lead to a better understanding of plasmon-induced processes, such as hot-charge-carrier- or heat-driven chemical reactions. Herein we show that DNA is able to transfer hot electrons generated by a silver nanoparticle over several nanometers to drive a chemical reaction in a molecule nonadsorbed on the surface. For this we use 8-bromo-adenosine introduced in different positions within a double-stranded DNA oligonucleotide. The DNA is also used to assemble the nanoparticles into nanoparticles ensembles enabling the use of surface-enhanced Raman scattering to track the decomposition reaction. To prove the DNA-mediated transfer, the probe molecule was insulated from the source of charge carriers, which hindered the reaction. The results indicate that DNA can be used to study the transfer of hot electrons and the mechanisms of advanced plasmonic catalysts. KW - plasmonics KW - DNA nanotechnology KW - hot electrons KW - charge transfer KW - SERS KW - superlattices Y1 - 2021 U6 - https://doi.org/10.1021/acsnano.1c09176 SN - 1936-0851 SN - 1936-086X VL - 15 IS - 12 SP - 20562 EP - 20573 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Titov, Evgenii T1 - On the low-lying electronically excited states of azobenzene dimers BT - Transition density matrix analysis JF - Molecules : a journal of synthetic chemistry and natural product chemistry / Molecular Diversity Preservation International N2 - Azobenzene-containing molecules may associate with each other in systems such as self-assembled monolayers or micelles. The interaction between azobenzene units leads to a formation of exciton states in these molecular assemblies. Apart from local excitations of monomers, the electronic transitions to the exciton states may involve charge transfer excitations. Here, we perform quantum chemical calculations and apply transition density matrix analysis to quantify local and charge transfer contributions to the lowest electronic transitions in azobenzene dimers of various arrangements. We find that the transitions to the lowest exciton states of the considered dimers are dominated by local excitations, but charge transfer contributions become sizable for some of the lowest pi pi* electronic transitions in stacked and slip-stacked dimers at short intermolecular distances. In addition, we assess different ways to partition the transition density matrix between fragments. In particular, we find that the inclusion of the atomic orbital overlap has a pronounced effect on quantifying charge transfer contributions if a large basis set is used. KW - azobenzene KW - dimer KW - transition density matrix KW - exciton KW - charge transfer KW - excited states KW - TD-DFT KW - ADC(2) Y1 - 2021 U6 - https://doi.org/10.3390/molecules26144245 SN - 1420-3049 VL - 26 IS - 14 PB - MDPI CY - Basel ER - TY - JOUR A1 - Schwarze, Thomas A1 - Kelling, Alexandra A1 - Sperlich, Eric A1 - Holdt, Hans-Jürgen T1 - Influence of regioisomerism in 9-anthracenyl-substituted dithiodicyanoethene derivatives on photoinduced electron transfer controlled by intramolecular charge transfer JF - ChemPhotoChem N2 - In this paper, we report on the fluorescence behaviour of three regioisomers which consist of two 9-anthracenyl fluorophores and of differently substituted dithiodicyanoethene moieties. These isomeric fluorescent probes show different quantum yields (phi(f)). In these probes, an oxidative photoinduced electron transfer (PET) from the excited 9-anthracenyl fluorophore to the dithiodicyanoethene unit quenches the fluorescence. This quenching process is accelerated by an intramolecular charge transfer (ICT) of the push-pull pi-electron system of the dithiodicyanoethene group. The acceleration of the PET depends on the strength of the ICT unit. The higher the dipole moment of the ICT unit, the stronger the observed fluorescence quenching. To the best of our knowledge, this is the first report of a regioisomeric influence on an oxidative PET by an ICT. KW - anthracene KW - charge transfer KW - electron transfer KW - fluorescence KW - isomerism Y1 - 2021 U6 - https://doi.org/10.1002/cptc.202100070 SN - 2367-0932 VL - 5 IS - 10 SP - 911 EP - 914 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Schwarze, Thomas A1 - Riemer, Janine A1 - Holdt, Hans-Jürgen T1 - A Ratiometric Fluorescent Probe for K+ in Water Based on a Phenylaza-18-Crown-6 Lariat Ether JF - Chemistry - a European journal N2 - This work presents two molecular fluorescent probes 1 and 2 for the selective determination of physiologically relevant K+ levels in water based on a highly K+/Na+ selective building block, the o-(2-methoxyethoxy)phenylaza-18-crown-6 lariat ether unit. Fluorescent probe 1 showed a high K+-induced fluorescence enhancement (FE) by a factor of 7.7 of the anthracenic emission and a dissociation constant (K-d) value of 38mm in water. Further, for 2+K+, we observed a dual emission behavior at 405 and 505nm. K+ increases the fluorescence intensity of 2 at 405nm by a factor of approximately 4.6 and K+ decreases the fluorescence intensity at 505nm by a factor of about 4.8. Fluorescent probe 2+K+ exhibited a K-d value of approximately 8mm in Na+-free solutions and in combined K+/Na+ solution a similar K-d value of about 9mm was found, reflecting the high K+/Na+ selectivity of 2 in water. Therefore, 2 is a promising fluorescent tool to measure ratiometrically and selectively physiologically relevant K+ levels. KW - charge transfer KW - crown compounds KW - fluorescence KW - potassium KW - ratiometric sensors Y1 - 2018 U6 - https://doi.org/10.1002/chem.201802306 SN - 0947-6539 SN - 1521-3765 VL - 24 IS - 40 SP - 10116 EP - 10121 PB - Wiley-VCH CY - Weinheim ER -