@article{ZhangRadackiBraunschweigetal.2021,
  author    = {Zhang, Fangyuan and Radacki, Krzysztof and Braunschweig, Holger and Lambert, Christoph and Ravat, Prince},
  title     = {Zinc-[7]helicenocyanine and its discrete π-stacked homochiral Dimer},
  series = {Angewandte Chemie International Edition},
  volume    = {60},
  journal   = {Angewandte Chemie International Edition},
  doi       = {10.1002/anie.202109380},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-256534},
  pages     = {23656-23660},
  year      = {2021},
  abstract  = {In this communication, we demonstrate a novel approach to prepare a discrete dimer of chiral phthalocyanine (Pc) by exploiting the flexible molecular geometry of helicenes, which enables structural interlocking and strong aggregation tendency of Pcs. Synthesized [7]helicene-Pc hybrid molecular structure, zinc-[7]helicenocyanine (Zn-7HPc), exclusively forms a stable dimeric pair consisting of two homochiral molecules. The dimerization constants were estimated to be as high as 8.96×10\(^6\) M\(^{-1}\) and 3.42×107 M\(^{-1}\) in THF and DMSO, respectively, indicating remarkable stability of dimer. In addition, Zn\(^{-7}\)HPc exhibited chiral self-sorting behavior, which resulted in preferential formation of a homochiral dimer also in the racemic sample. Two phthalocyanine subunits in the dimeric form strongly communicate with each other as revealed by a large comproportionation constant and observation of an IV-CT band for the thermodynamically stable mixed-valence state.},
  language  = {en}
}
@article{WaechtlerKuebelBarthelmesetal.2016,
  author    = {W{\"a}chtler, Maria and K{\"u}bel, Joachim and Barthelmes, Kevin and Winter, Andreas and Schmiedel, Alexander and Pascher, Torbj{\"o}rn and Lambert, Christoph and Schubert, Ulrich S. and Dietzek, Benjamin},
  title     = {Energy transfer and formation of long-lived \(^3\)MLCT states in multimetallic complexes with extended highly conjugated bis-terpyridyl ligands},
  series = {Physical Chemistry Chemical Physics},
  volume    = {18},
  journal   = {Physical Chemistry Chemical Physics},
  number    = {4},
  doi       = {10.1039/c5cp04447b},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-191041},
  pages     = {2350-2360},
  year      = {2016},
  abstract  = {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.},
  language  = {en}
}
@article{TurkinHolzapfelAgarwaletal.2021,
  author    = {Turkin, Arthur and Holzapfel, Marco and Agarwal, Mohit and Fischermeier, David and Mitric, Roland and Schweins, Ralf and Gr{\"o}hns, Franziska and Lambert, Christoph},
  title     = {Solvent Induced Helix Folding of Defined Indolenine Squaraine Oligomers},
  series = {Chemistry—A European Journal},
  volume    = {27},
  journal   = {Chemistry—A European Journal},
  number    = {32},
  doi       = {10.1002/chem.202101063},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-256869},
  pages     = {8380-8389},
  year      = {2021},
  abstract  = {A protecting group strategy was employed to synthesise a series of indolenine squaraine dye oligomers up to the nonamer. The longer oligomers show a distinct solvent dependence of the absorption spectra, that is, either a strong blue shift or a strong red shift of the lowest energy bands in the near infrared spectral region. This behaviour is explained by exciton coupling theory as being due to H- or J-type coupling of transition moments. The H-type coupling is a consequence of a helix folding in solvents with a small Hansen dispersity index. DOSY NMR, small angle neutron scattering (SANS), quantum chemical and force field calculations agree upon a helix structure with an unusually large pitch and open voids that are filled with solvent molecules, thereby forming a kind of clathrate. The thermodynamic parameters of the folding process were determined by temperature dependent optical absorption spectra.},
  language  = {en}
}
@unpublished{SaalSwainSchmiedeletal.2023,
  author    = {Saal, Fridolin and Swain, Asim and Schmiedel, Alexander and Holzapfel, Marco and Lambert, Christoph and Ravat, Prince},
  title     = {Push-Pull [7]Helicene Diimide: Excited-State Charge Transfer and Solvatochromic Circularly Polarised Luminescence},
  edition   = {submitted version},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-345207},
  year      = {2023},
  abstract  = {In this communication we describe a helically chiral push-pull molecule named 9,10-dimethoxy-[7]helicene diimide, displaying fluorescence (FL) and circularly polarised luminescence (CPL) over nearly the entire visible spectrum dependent on solvent polarity. The synthesised molecule exhibits an unusual solvent polarity dependence of FL quantum yield and nonradiative rate constant, as well as remarkable gabs and glum values along with high configurational stability.},
  language  = {en}
}
@article{MuellerLuettigMalyetal.2019,
  author    = {Mueller, Stefan and L{\"u}ttig, Julian and Mal{\´y}, Pavel and Ji, Lei and Han, Jie and Moos, Michael and Marder, Todd B. and Bunz, Uwe H. F. and Dreuw, Andreas and Lambert, Christoph and Brixner, Tobias},
  title     = {Rapid multiple-quantum three-dimensional fluorescence spectroscopy disentangles quantum pathways},
  series = {Nature Communications},
  volume    = {10},
  journal   = {Nature Communications},
  doi       = {10.1038/s41467-019-12602-x},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-202529},
  pages     = {4735},
  year      = {2019},
  abstract  = {Coherent two-dimensional spectroscopy is a powerful tool for probing ultrafast quantum dynamics in complex systems. Several variants offer different types of information but typically require distinct beam geometries. Here we introduce population-based three-dimensional (3D) electronic spectroscopy and demonstrate the extraction of all fourth- and multiple sixth-order nonlinear signal contributions by employing 125-fold (1⨯5⨯5⨯5) phase cycling of a four-pulse sequence. Utilizing fluorescence detection and shot-to-shot pulse shaping in single-beam geometry, we obtain various 3D spectra of the dianion of TIPS-tetraazapentacene, a fluorophore with limited stability at ambient conditions. From this, we recover previously unknown characteristics of its electronic two-photon state. Rephasing and nonrephasing sixth-order contributions are measured without additional phasing that hampered previous attempts using noncollinear geometries. We systematically resolve all nonlinear signals from the same dataset that can be acquired in 8 min. The approach is generalizable to other incoherent observables such as external photoelectrons, photocurrents, or photoions.},
  language  = {en}
}
@article{MieczkowskiSteinmetzgerBessietal.2021,
  author    = {Mieczkowski, Mateusz and Steinmetzger, Christian and Bessi, Irene and Lenz, Ann-Kathrin and Schmiedel, Alexander and Holzapfel, Marco and Lambert, Christoph and Pena, Vladimir and H{\"o}bartner, Claudia},
  title     = {Large Stokes shift fluorescence activation in an RNA aptamer by intermolecular proton transfer to guanine},
  series = {Nature Communications},
  volume    = {12},
  journal   = {Nature Communications},
  doi       = {10.1038/s41467-021-23932-0},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-254527},
  pages     = {3549},
  year      = {2021},
  abstract  = {Fluorogenic RNA aptamers are synthetic functional RNAs that specifically bind and activate conditional fluorophores. The Chili RNA aptamer mimics large Stokes shift fluorescent proteins and exhibits high affinity for 3,5-dimethoxy-4-hydroxybenzylidene imidazolone (DMHBI) derivatives to elicit green or red fluorescence emission. Here, we elucidate the structural and mechanistic basis of fluorescence activation by crystallography and time-resolved optical spectroscopy. Two co-crystal structures of the Chili RNA with positively charged DMHBO+ and DMHBI+ ligands revealed a G-quadruplex and a trans-sugar-sugar edge G:G base pair that immobilize the ligand by π-π stacking. A Watson-Crick G:C base pair in the fluorophore binding site establishes a short hydrogen bond between the N7 of guanine and the phenolic OH of the ligand. Ultrafast excited state proton transfer (ESPT) from the neutral chromophore to the RNA was found with a time constant of 130 fs and revealed the mode of action of the large Stokes shift fluorogenic RNA aptamer.},
  language  = {en}
}
@article{MieczkowskiSteinmetzgerBessietal.2021,
  author    = {Mieczkowski, Mateusz and Steinmetzger, Christian and Bessi, Irene and Lenz, Ann-Kathrin and Schmiedel, Alexander and Holzapfel, Marco and Lambert, Christoph and Pena, Vladimir and H{\"o}bartner, Claudia},
  title     = {Large Stokes shift fluorescence activation in an RNA aptamer by intermolecular proton transfer to guanine},
  series = {Nature Communications},
  volume    = {12},
  journal   = {Nature Communications},
  doi       = {10.1038/s41467-021-23932-0},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-270274},
  year      = {2021},
  abstract  = {Fluorogenic RNA aptamers are synthetic functional RNAs that specifically bind and activate conditional fluorophores. The Chili RNA aptamer mimics large Stokes shift fluorescent proteins and exhibits high affinity for 3,5-dimethoxy-4-hydroxybenzylidene imidazolone (DMHBI) derivatives to elicit green or red fluorescence emission. Here, we elucidate the structural and mechanistic basis of fluorescence activation by crystallography and time-resolved optical spectroscopy. Two co-crystal structures of the Chili RNA with positively charged DMHBO+ and DMHBI+ ligands revealed a G-quadruplex and a trans-sugar-sugar edge G:G base pair that immobilize the ligand by π-π stacking. A Watson-Crick G:C base pair in the fluorophore binding site establishes a short hydrogen bond between the N7 of guanine and the phenolic OH of the ligand. Ultrafast excited state proton transfer (ESPT) from the neutral chromophore to the RNA was found with a time constant of 130 fs and revealed the mode of action of the large Stokes shift fluorogenic RNA aptamer.},
  language  = {en}
}
@article{MerzDietzVonhausenetal.2020,
  author    = {Merz, Julia and Dietz, Maximilian and Vonhausen, Yvonne and W{\"o}ber, Frederik and Friedrich, Alexandra and Sieh, Daniel and Krummenacher, Ivo and Braunschweig, Holger and Moos, Michael and Holzapfel, Marco and Lambert, Christoph and Marder, Todd B.},
  title     = {Synthesis, Photophysical and Electronic Properties of New Red-to-NIR Emitting Donor-Acceptor Pyrene Derivatives},
  series = {Chemistry - A European Journal},
  volume    = {26},
  journal   = {Chemistry - A European Journal},
  number    = {2},
  doi       = {10.1002/chem.201904219},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-207486},
  pages     = {438-453},
  year      = {2020},
  abstract  = {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.},
  language  = {en}
}
@article{MerzDietrichNitschetal.2020,
  author    = {Merz, Julia and Dietrich, Lena and Nitsch, J{\"o}rn and Krummenacher, Ivo and Braunschweig, Holger and Moos, Michael and Mims, David and Lambert, Christoph and Marder, Todd B.},
  title     = {Synthesis, Photophysical and Electronic Properties of Mono-, Di-, and Tri-Amino-Substituted Ortho-Perylenes, and Comparison to the Tetra-Substituted Derivative},
  series = {Chemistry - A European Journal},
  volume    = {26},
  journal   = {Chemistry - A European Journal},
  number    = {52},
  doi       = {10.1002/chem.202001475},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-217835},
  pages     = {12050 -- 12059},
  year      = {2020},
  abstract  = {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.},
  language  = {en}
}
@article{LuebtowMarciniakSchmiedeletal.2019,
  author    = {L{\"u}btow, Michael M. and Marciniak, Henning and Schmiedel, Alexander and Roos, Markus and Lambert, Christoph and Luxenhofer, Robert},
  title     = {Ultra-high to ultra-low drug loaded micelles: Probing host-guest interactions by fluorescence spectroscopy},
  series = {Chemistry - A European Journal},
  volume    = {25},
  journal   = {Chemistry - A European Journal},
  number    = {54},
  doi       = {10.1002/chem.201902619},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-206128},
  pages     = {12601-12610},
  year      = {2019},
  abstract  = {Polymer micelles are an attractive means to solubilize water insoluble compounds such as drugs. Drug loading, formulations stability and control over drug release are crucial factors for drug-loaded polymer micelles. The interactions between the polymeric host and the guest molecules are considered critical to control these factors but typically barely understood. Here, we compare two isomeric polymer micelles, one of which enables ultra-high curcumin loading exceeding 50 wt.\%, while the other allows a drug loading of only 25 wt.\%. In the low capacity micelles, steady-state fluorescence revealed a very unusual feature of curcumin fluorescence, a high energy emission at 510 nm. Time-resolved fluorescence upconversion showed that the fluorescence life time of the corresponding species is too short in the high-capacity micelles, preventing an observable emission in steady-state. Therefore, contrary to common perception, stronger interactions between host and guest can be detrimental to the drug loading in polymer micelles.},
  subject      = {Polymer-drug interaction},
  language  = {en}
}