TY  - INPR
A1  - Auerhammer, Nina
A1  - Schulz, Alexander
A1  - Schmiedel, Alexander
A1  - Holzapfel, Marco
A1  - Hoche, Joscha
A1  - Röhr, Merle I. S.
A1  - Mitric, Roland
A1  - Lambert, Christoph
T1  - Dynamic exciton localisation in a pyrene-BODIPY-pyrene dye conjugate
T2  - Physical Chemistry Chemical Physics
N2  - The photophysics of a molecular triad consisting of a BODIPY dye and two pyrene chromophores attached in 2-position are investigated by steady state and fs-time resolved transient absorption spectroscopy as well as by field induced surface hopping (FISH) simulations. While the steady state measurements indicate moderate chromophore interactions within the triad, the time resolved measurements show upon pyrene excitation a delocalised excited state which localises onto the BODIPY chromophore with a time constant of 0.12 ps. This could either be interpreted as an internal conversion process within the excitonically coupled chromophores or as an energy transfer from the pyrenes to the BODIPY dye. The analysis of FISH-trajectories reveals an oscillatory behaviour where the excitation hops between the pyrene units and the BODIPY dye several times until finally they become localised on the BODIPY chromophore within 100 fs. This is accompanied by an ultrafast nonradiative relaxation within the excitonic manifold mediated by the nonadiabatic coupling. Averaging over an ensemble of trajectories allowed us to simulate the electronic state population dynamics and determine the time constants for the nonradiative transitions that mediate the ultrafast energy transfer and exciton localisation on BODIPY.
KW  - Exciton localization dynamics
Y1  - 2019
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-198718
UR  - https://doi.org/10.1039/C9CP00908F
N1  - Accepted manuscript
ER  - 
TY  - INPR
A1  - Lambert, Christoph
A1  - Völker, Sebastian F.
A1  - Koch, Federico
A1  - Schmiedel, Alexander
A1  - Holzapfel, Marco
A1  - Humeniuk, Alexander
A1  - Röhr, Merle I. S.
A1  - Mitric, Roland
A1  - Brixner, Tobias
T1  - Energy Transfer Between Squaraine Polymer Sections: From helix to zig-zag and All the Way Back
T2  - Journal of the American Chemical Society
N2  - Joint experimental and theoretical study of the absorption spectra of squaraine polymers in solution provide evidence that two different conformations are present in solution: a helix and a zig-zag structure. This unique situation allows investigating ultrafast energy transfer processes between different structural segments within a single polymer chain in solution. The understanding of the underlying dynamics is of fundamental importance for the development of novel materials for light-harvesting and optoelectronic applications. We combine here femtosecond transient absorption spectroscopy with time-resolved 2D electronic spectroscopy showing that ultrafast energy transfer within the squaraine polymer chains proceeds from initially excited helix segments to zig-zag segments or vice versa, depending on the solvent as well as on the excitation wavenumber. These observations contrast other conjugated polymers such as MEH-PPV where much slower intrachain energy transfer was reported. The reason for the very fast energy transfer in squaraine polymers is most likely a close matching of the density of states between donor and acceptor polymer segments because of very small reorganization energy in these cyanine-like chromophores.
KW  - energy transfer dynamics
KW  - squaraine polymer
Y1  - 2015
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-159607
UR  - http://dx.doi.org/10.1021/jacs.5b03644
N1  - This document is the unedited Author's version of a Submitted Work that war subsequently accepted for publication in Journal of the American Chemical Society, copyright American Chemical Society after peer review. To access the final edited and published work see doi:10.1021/jacs.5b03644.
ER  - 
TY  - JOUR
A1  - Wächtler, Maria
A1  - Kübel, Joachim
A1  - Barthelmes, Kevin
A1  - Winter, Andreas
A1  - Schmiedel, Alexander
A1  - Pascher, Torbjörn
A1  - Lambert, Christoph
A1  - Schubert, Ulrich S.
A1  - Dietzek, Benjamin
T1  - Energy transfer and formation of long-lived \(^3\)MLCT states in multimetallic complexes with extended highly conjugated bis-terpyridyl ligands
JF  - Physical Chemistry Chemical Physics
N2  - Multimetallic complexes with extended and highly conjugated bis-2,2':6',2''-terpyridyl bridging ligands, which present building blocks for coordination polymers, are investigated with respect to their ability to act as light-harvesting antennae. The investigated species combine Ru(II)- with Os(II)- and Fe(II)-terpyridyl chromophores, the latter acting as energy sinks. Due to the extended conjugated system the ligands are able to prolong the lifetime of the \(^3\)MLCT states compared to unsubstituted terpyridyl species by delocalization and energetic stabilization of the \(^3\)MLCT states. This concept is applied for the first time to Fe(II) terpyridyl species and results in an exceptionally long lifetime of 23 ps for the Fe(II) \(^3\)MLCT state. While partial energy (>80%) transfer is observed between the Ru(II) and Fe(II) centers with a time-constant of 15 ps, excitation energy is transferred completely from the Ru(II) to the Os(II) center within the first 200 fs after excitation.
KW  - polypyridyl complexes
KW  - bis-terpyridyl ligands
KW  - multimetallic complexes
KW  - metal-to-ligand charge transfer (MLCT)
KW  - RU-(II) complexes
KW  - Ru(II)–Fe(II)–Ru(II) complex
Y1  - 2016
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-191041
VL  - 18
IS  - 4
ER  - 
TY  - JOUR
A1  - Ceyman, Harald
A1  - Rosspeintner, Arnulf
A1  - Schreck, Maximilian H.
A1  - Mützel, Carina
A1  - Stoy, Andreas
A1  - Vauthey, Eric
A1  - Lambert, Christoph
T1  - Cooperative enhancement versus additivity of two-photon-absorption cross sections in linear and branched squaraine superchromophores
JF  - Physical Chemistry Chemical Physics
N2  - The linear and nonlinear optical properties of a series of oligomeric squaraine dyes were investigated by one-photon absorption spectroscopy (1PA) and two-photon absorption (2PA) induced fluorescence spectroscopy. The superchromophores are based on two indolenine squaraine dyes with transoid (SQA) and cisoid configuration (SQB). Using these monomers, linear dimers and trimers as well as star-shaped trimers and hexamers with benzene or triphenylamine cores were synthesised and investigated. The red-shifted and intensified 1PA spectra of all superchromophores could well be explained by exciton coupling theory. In the linear chromophore arrangements we also found superradiance of fluorescence but not in the branched systems. Furthermore, the 2PA showed enhanced cross sections for the linear oligomers but only additivity for the branched systems. This emphasizes that the enhancement of the 2PA cross section in the linear arrangements is probably caused by orbital interactions of higher excited configurations.
KW  - 2-photon absorption
KW  - Vibronic contributions
KW  - One-photon
KW  - Molecules
KW  - Intensity
KW  - Multibranched structures
KW  - Optical properties
KW  - Dyes
KW  - Chromophores
KW  - Design
Y1  - 2016
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-188299
VL  - 18
IS  - 24
ER  - 
TY  - JOUR
A1  - Lambert, Christoph
A1  - Kaupp, Martin
A1  - Schleyer, Paul von Rague
T1  - “Inverted” Sodium-Lithium Electronegativity: Polarity and Metalation Energies of Organic and Inorganic Alkali-Metal Compounds
N2  - No abstract available
KW  - Anorganische Chemie
Y1  - 1993
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-60054
ER  - 
TY  - JOUR
A1  - Kole, Goutam Kumar
A1  - Košćak, Marta
A1  - Amar, Anissa
A1  - Majhen, Dragomira
A1  - Božinović, Ksenija
A1  - Brkljaca, Zlatko
A1  - Ferger, Matthias
A1  - Michail, Evripidis
A1  - Lorenzen, Sabine
A1  - Friedrich, Alexandra
A1  - Krummenacher, Ivo
A1  - Moos, Michael
A1  - Braunschweig, Holger
A1  - Boucekkine, Abdou
A1  - Lambert, Christoph
A1  - Halet, Jean‐François
A1  - Piantanida, Ivo
A1  - Müller‐Buschbaum, Klaus
A1  - Marder, Todd B.
T1  - Methyl Viologens of Bis‐(4’‐Pyridylethynyl)Arenes – Structures, Photophysical and Electrochemical Studies, and their Potential Application in Biology
JF  - Chemistry – A European Journal
N2  - A series of bis‐(4’‐pyridylethynyl)arenes (arene=benzene, tetrafluorobenzene, and anthracene) were synthesized and their bis‐N‐methylpyridinium compounds were investigated as a class of π‐extended methyl viologens. Their structures were determined by single crystal X‐ray diffraction, and their photophysical and electrochemical properties (cyclic voltammetry), as well as their interactions with DNA/RNA were investigated. The dications showed bathochromic shifts in emission compared to the neutral compounds. The neutral compounds showed very small Stokes shifts, which are a little larger for the dications. All of the compounds showed very short fluorescence lifetimes (<4 ns). The neutral compound with an anthracene core has a quantum yield of almost unity. With stronger acceptors, the analogous bis‐N‐methylpyridinium compound showed a larger two‐photon absorption cross‐section than its neutral precursor. All of the dicationic compounds interact with DNA/RNA; while the compounds with benzene and tetrafluorobenzene cores bind in the grooves, the one with an anthracene core intercalates as a consequence of its large, condensed aromatic linker moiety, and it aggregates within the polynucleotide when in excess over DNA/RNA. Moreover, all cationic compounds showed highly specific CD spectra upon binding to ds‐DNA/RNA, attributed to the rare case of forcing the planar, achiral molecule into a chiral rotamer, and negligible toxicity toward human cell lines at ≤10 μM concentrations. The anthracene‐analogue exhibited intracellular accumulation within lysosomes, preventing its interaction with cellular DNA/RNA. However, cytotoxicity was evident at 1 μM concentration upon exposure to light, due to singlet oxygen generation within cells. These multi‐faceted features, in combination with its two‐photon absorption properties, suggest it to be a promising lead compound for development of novel light‐activated theranostic agents.
KW  - cell imaging
KW  - DNA/RNA binding
KW  - methyl viologen
KW  - singlet oxygen
KW  - two-photon absorption
Y1  - 2022
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-287126
VL  - 28
IS  - 40
ER  - 
TY  - JOUR
A1  - Merz, Julia
A1  - Dietz, Maximilian
A1  - Vonhausen, Yvonne
A1  - Wöber, Frederik
A1  - Friedrich, Alexandra
A1  - Sieh, Daniel
A1  - Krummenacher, Ivo
A1  - Braunschweig, Holger
A1  - Moos, Michael
A1  - Holzapfel, Marco
A1  - Lambert, Christoph
A1  - Marder, Todd  B.
T1  - Synthesis, Photophysical and Electronic Properties of New Red-to-NIR Emitting Donor-Acceptor Pyrene Derivatives
JF  - Chemistry - A European Journal
N2  - We synthesized new pyrene derivatives with strong bis(para ‐methoxyphenyl)amine donors at the 2,7‐positions and n ‐azaacene acceptors at the K‐region of pyrene. The compounds possess a strong intramolecular charge transfer, leading to unusual properties such as emission in the red to NIR region (700 nm), which has not been reported before for monomeric pyrenes. Detailed photophysical studies reveal very long intrinsic lifetimes of >100 ns for the new compounds, which is typical for 2,7‐substituted pyrenes but not for K‐region substituted pyrenes. The incorporation of strong donors and acceptors leads to very low reduction and oxidation potentials, and spectroelectrochemical studies show that the compounds are on the borderline between localized Robin‐Day class‐II and delocalized Robin‐Day class‐III species.
KW  - orylation
KW  - K-region
KW  - luminescence
KW  - polycyclic aromatic hydrocarbons
KW  - redox
Y1  - 2020
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-207486
VL  - 26
IS  - 2
ER  - 
TY  - JOUR
A1  - Ferger, Matthias
A1  - Roger, Chantal
A1  - Köster, Eva
A1  - Rauch, Florian
A1  - Lorenzen, Sabine
A1  - Krummenacher, Ivo
A1  - Friedrich, Alexandra
A1  - Košćak, Marta
A1  - Nestić, Davor
A1  - Braunschweig, Holger
A1  - Lambert, Christoph
A1  - Piantanida, Ivo
A1  - Marder, Todd B.
T1  - Electron‐Rich EDOT Linkers in Tetracationic bis‐Triarylborane Chromophores: Influence on Water Stability, Biomacromolecule Sensing, and Photoinduced Cytotoxicity
JF  - Chemistry – A European Journal
N2  - Three novel tetracationic bis‐triarylboranes with 3,4‐ethylenedioxythiophene (EDOT) linkers, and their neutral precursors, showed significant red‐shifted absorption and emission compared to their thiophene‐containing analogues, with one of the EDOT‐derivatives emitting in the NIR region. Only the EDOT‐linked trixylylborane tetracation was stable in aqueous solution, indicating that direct attachment of a thiophene or even 3‐methylthiophene to the boron atom is insufficient to provide hydrolytic stability in aqueous solution. Further comparative analysis of the EDOT‐linked trixylylborane tetracation and its bis‐thiophene analogue revealed efficient photo‐induced singlet oxygen production, with the consequent biological implications. Thus, both analogues bind strongly to ds‐DNA and BSA, very efficiently enter living human cells, accumulate in several different cytoplasmic organelles with no toxic effect but, under intense visible light irradiation, they exhibit almost instantaneous and very strong cytotoxic effects, presumably attributed to singlet oxygen production. Thus, both compounds are intriguing theranostic agents, whose intracellular and probably intra‐tissue location can be monitored by strong fluorescence, allowing switching on of the strong bioactivity by well‐focused visible light.
KW  - boranes
KW  - DNA/RNA sensors
KW  - fluorescent probes
KW  - singlet oxygen
KW  - theranostics
Y1  - 2022
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-287241
VL  - 28
IS  - 48
ER  - 
TY  - JOUR
A1  - Griesbeck, Stefanie
A1  - Michail, Evripidis
A1  - Rauch, Florian
A1  - Ogasawara, Hiroaki
A1  - Wang, Chenguang
A1  - Sato, Yoshikatsu
A1  - Edkins, Robert M.
A1  - Zhang, Zuolun
A1  - Taki, Masayasu
A1  - Lambert, Christoph
A1  - Yamaguchi, Shigehiro
A1  - Marder, Todd B.
T1  - The Effect of Branching on the One‐ and Two‐Photon Absorption, Cell Viability, and Localization of Cationic Triarylborane Chromophores with Dipolar versus Octupolar Charge Distributions for Cellular Imaging
JF  - Chemistry – A European Journal
N2  - Two different chromophores, namely a dipolar and an octupolar system, were prepared and their linear and nonlinear optical properties as well as their bioimaging capabilities were compared. Both contain triphenylamine as the donor and a triarylborane as the acceptor, the latter modified with cationic trimethylammonio groups to provide solubility in aqueous media. The octupolar system exhibits a much higher two‐photon brightness, and also better cell viability and enhanced selectivity for lysosomes compared with the dipolar chromophore. Furthermore, both dyes were applied in two‐photon excited fluorescence (TPEF) live‐cell imaging.
KW  - boranes
KW  - cell imaging
KW  - fluorescence
KW  - lysosome
KW  - two-photon excited fluorescence
Y1  - 2019
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-212887
VL  - 25
IS  - 57
SP  - 13164
EP  - 13175
ER  - 
TY  - JOUR
A1  - Merz, Julia
A1  - Dietrich, Lena
A1  - Nitsch, Jörn
A1  - Krummenacher, Ivo
A1  - Braunschweig, Holger
A1  - Moos, Michael
A1  - Mims, David
A1  - Lambert, Christoph
A1  - Marder, Todd B.
T1  - Synthesis, Photophysical and Electronic Properties of Mono‐, Di‐, and Tri‐Amino‐Substituted Ortho‐Perylenes, and Comparison to the Tetra‐Substituted Derivative
JF  - Chemistry – A European Journal
N2  - We synthesized a series of new mono‐, di‐, tri‐ and tetra‐substituted perylene derivatives with strong bis(para‐methoxyphenyl)amine (DPA) donors at the uncommon 2,5,8,11‐positions. The properties of our new donor‐substituted perylenes were studied in detail to establish a structure‐property relationship. Interesting trends and unusual properties are observed for this series of new perylene derivatives, such as a decreasing charge transfer (CT) character with increasing number of DPA moieties and individual reversible oxidations for each DPA moiety. Thus, (DPA)‐Per possesses one reversible oxidation while (DPA)\(_{4}\)‐Per has four. The mono‐ and di‐substituted derivatives display unusually large Stokes shifts not previously reported for perylenes. Furthermore, transient absorption measurements of the new derivatives reveal an excited state with lifetimes of several hundred microseconds, which sensitizes singlet oxygen with quantum yields of up to 0.83.
KW  - borylation
KW  - intersystem crossing
KW  - luminescence
KW  - polycyclic aromatic hydrocarbon
KW  - triarylamine
Y1  - 2020
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-217835
VL  - 26
IS  - 52
SP  - 12050
EP  - 12059
ER  -