@article{ZakrevskyyTitovLomadzeetal.2014,
  author    = {Zakrevskyy, Yuriy and Titov, Evgenii and Lomadze, Nino and Santer, Svetlana},
  title     = {Phase diagrams of DNA-photosensitive surfactant complexes: Effect of ionic strength and surfactant structure},
  series = {The journal of chemical physics : bridges a gap between journals of physics and journals of chemistr},
  volume    = {141},
  journal   = {The journal of chemical physics : bridges a gap between journals of physics and journals of chemistr},
  number    = {16},
  publisher = {American Institute of Physics},
  address   = {Melville},
  issn      = {0021-9606},
  doi       = {10.1063/1.4899281},
  pages     = {8},
  year      = {2014},
  abstract  = {Realization of all-optically controlled and efficient DNA compaction is the major motivation in the study of interactions between DNA and photosensitive surfactants. In this article, using recently published approach of phase diagram construction [Y. Zakrevskyy, P. Cywinski, M. Cywinska, J. Paasche, N. Lomadze, O. Reich, H.-G. Lohmannsroben, and S. Santer, J. Chem. Phys. 140, 044907 (2014)], a strategy for substantial reduction of compaction agent concentration and simultaneous maintaining the light-induced decompaction efficiency is proposed. The role of ionic strength (NaCl concentration), as a very important environmental parameter, and surfactant structure (spacer length) on the changes of positions of phase transitions is investigated. Increase of ionic strength leads to increase of the surfactant concentration needed to compact DNA molecule. However, elongation of the spacer results to substantial reduction of this concentration. DNA compaction by surfactants with longer tails starts to take place in diluted solutions at charge ratios Z < 1 and is driven by azobenzene-aggregation compaction mechanism, which is responsible for efficient decompaction. Comparison of phase diagrams for different DNA-photosensitive surfactant systems allowed explanation and proposal of a strategy to overcome previously reported limitations of the light-induced decompaction for complexes with increasing surfactant hydrophobicity. (C) 2014 AIP Publishing LLC.},
  language  = {en}
}
@article{TitovLysyakovaLomadzeetal.2015,
  author    = {Titov, Evgenii and Lysyakova, Liudmila and Lomadze, Nino and Kabashin, Andrei V. and Saalfrank, Peter and Santer, Svetlana},
  title     = {Thermal Cis-to-Trans Isomerization of Azobenzene-Containing Molecules Enhanced by Gold Nanoparticles: An Experimental and Theoretical Study},
  series = {The journal of physical chemistry : C, Nanomaterials and interfaces},
  volume    = {119},
  journal   = {The journal of physical chemistry : C, Nanomaterials and interfaces},
  number    = {30},
  publisher = {American Chemical Society},
  address   = {Washington},
  issn      = {1932-7447},
  doi       = {10.1021/acs.jpcc.5b02473},
  pages     = {17369 -- 17377},
  year      = {2015},
  abstract  = {We report on the experimental and theoretical investigation of a considerable increase in the rate for thermal cis -> trans isomerization of azobenzene-containing molecules in the presence of gold nanopartides. Experimentally, by means of UV vis spectroscopy, we studied a series of azobenzene-containing surfactants and 4-nitroazobenzene. We found that in the presence of gold,nanoparticles the thermal lifetime of the cis isomer of the azobenzenecontaining molecules was decreased by up to 3 orders of magnitude in comparison to the lifetime in solution without nanoparticles. The electron transfer between azobenzene-containing molecules and a surface of gold nanopartides is a possible reason to promote the thermal cis trans switching. To investigate the effect of electron attachment to, and withdrawal from, the azobenzene-containing molecules on the isomerization rate, we performed density functional theory calculations of activation energy barriers of the reaction together with Eyring's transition state theory calculations of the rates for azobenzene derivatives with donor and acceptor groups in para position of one of the phenyl rings, as well as for one of the azobenzene-containing surfactants. We found that activation barriers are greatly lowered for azobenzene-containing molecules, both upon electron attachment and withdrawal, which leads, in turn, to a dramatic increase in the thermal isomerization rate.},
  language  = {en}
}
@article{KasyanenkoLysyakovaRamazanovetal.2015,
  author    = {Kasyanenko, Nina and Lysyakova, Liudmila and Ramazanov, Ruslan and Nesterenko, Alexey and Yaroshevich, Igor and Titov, Evgenii and Alexeev, G. and Lezov, Andrey and Unksov, I.},
  title     = {Conformational and Phase Transitions in DNA-Photosensitive Surfactant Solutions: Experiment and Modeling},
  series = {Biopolymers},
  volume    = {103},
  journal   = {Biopolymers},
  number    = {2},
  publisher = {Wiley-Blackwell},
  address   = {Hoboken},
  issn      = {0006-3525},
  doi       = {10.1002/bip.22575},
  pages     = {109 -- 122},
  year      = {2015},
  abstract  = {DNA binding to trans- and cis-isomers of azobenzene containing cationic surfactant in 5 mM NaCl solution was investigated by the methods of dynamic light scattering (DLS), low-gradient viscometry (LGV), atomic force microscopy (AFM), circular dichroism (CD), gel electrophoresis (GE), flow birefringence (FB), UV-Vis spectrophotometry. Light-responsive conformational transitions of DNA in complex with photosensitive surfactant, changes in DNA optical anisotropy and persistent length, phase transition of DNA into nanoparticles induced by high surfactant concentration, as well as transformation of surfactant conformation under its binding to macromolecule were studied. Computer simulations of micelles formation for cis- and trans-isomers of azobenzene containing surfactant, as well as DNA-surfactant interaction, were carried out. Phase diagram for DNA-surfactant solutions was designed. The possibility to reverse the DNA packaging induced by surfactant binding with the dilution and light irradiation was shown. (c) 2014 Wiley Periodicals, Inc. Biopolymers 103: 109-122, 2015.},
  language  = {en}
}
@article{KuleszaTitovDalyetal.2016,
  author    = {Kulesza, Alexander Jan and Titov, Evgenii and Daly, Steven and Wlodarczyk, Radoslaw and Megow, J{\"o}rg and Saalfrank, Peter and Choi, Chang Min and MacAleese, Luke and Antoine, Rodolphe and Dugourd, Philippe},
  title     = {Excited States of Xanthene Analogues: Photofragmentation and Calculations by CC2 and Time-Dependent Density Functional Theory},
  series = {ChemPhysChem : a European journal of chemical physics and physical chemistry},
  volume    = {17},
  journal   = {ChemPhysChem : a European journal of chemical physics and physical chemistry},
  publisher = {Wiley-VCH},
  address   = {Weinheim},
  issn      = {1439-4235},
  doi       = {10.1002/cphc.201600650},
  pages     = {3129 -- 3138},
  year      = {2016},
  abstract  = {Action spectroscopy has emerged as an analytical tool to probe excited states in the gas phase. Although comparison of gas-phase absorption properties with quantum-chemical calculations is, in principle, straightforward, popular methods often fail to describe many molecules of interest-such as xanthene analogues. We, therefore, face their nano-and picosecond laser-induced photofragmentation with excited-state computations by using the CC2 method and time-dependent density functional theory (TDDFT). Whereas the extracted absorption maxima agree with CC2 predictions, the TDDFT excitation energies are blueshifted. Lowering the amount of Hartree-Fock exchange in the DFT functional can reduce this shift but at the cost of changing the nature of the excited state. Additional bandwidth observed in the photofragmentation spectra is rationalized in terms of multiphoton processes. Observed fragmentation from higher-lying excited states conforms to intense excited-to-excited state transitions calculated with CC2. The CC2 method is thus suitable for the comparison with photofragmentation in xanthene analogues.},
  language  = {en}
}
@article{TitovGranucciGoetzeetal.2016,
  author    = {Titov, Evgenii and Granucci, Giovanni and Goetze, Jan Philipp and Persico, Maurizio and Saalfrank, Peter},
  title     = {Dynamics of Azobenzene Dimer Photoisomerization: Electronic and Steric Effects},
  series = {The journal of physical chemistry letters},
  volume    = {7},
  journal   = {The journal of physical chemistry letters},
  publisher = {American Chemical Society},
  address   = {Washington},
  issn      = {1948-7185},
  doi       = {10.1021/acs.jpciett.6b01401},
  pages     = {3591 -- 3596},
  year      = {2016},
  abstract  = {While azobenzenes readily photoswitch in solution, their photoisomerization in densely packed self-assembled monolayers (SAMs) can be suppressed. Reasons for this can be steric hindrance and/or electronic quenching, e.g., by exciton coupling. We address these possibilities by means of nonadiabatic molecular dynamics with trajectory surface hopping calculations, investigating the trans -> cis isomerization of azobenzene after excitation into the pi pi* absorption band. We consider a free monomer, an isolated dimer and a dimer embedded in a SAM-like environment of additional azobenzene molecules, imitating in this way the gradual transition from an unconstrained over an electronically coupled to an electronically coupled and sterically hindered, molecular switch. Our simulations reveal that in comparison to the single molecule the quantum yield of the trans -> cis photoisomerization is similar for the isolated dimer, but greatly reduced in the sterically constrained situation. Other implications of dimerization and steric constraints are also discussed.},
  language  = {en}
}
@article{TitovSaalfrank2016,
  author    = {Titov, Evgenii and Saalfrank, Peter},
  title     = {Exciton Splitting of Adsorbed and Free 4-Nitroazobenzene Dimers: A Quantum Chemical Study},
  series = {The journal of physical chemistry : A, Molecules, spectroscopy, kinetics, environment \& general theory},
  volume    = {120},
  journal   = {The journal of physical chemistry : A, Molecules, spectroscopy, kinetics, environment \& general theory},
  publisher = {American Chemical Society},
  address   = {Washington},
  issn      = {1089-5639},
  doi       = {10.1021/acs.jpca.5b10376},
  pages     = {3055 -- 3070},
  year      = {2016},
  abstract  = {Molecular photoswitches such as azobenzenes, which undergo photochemical trans <-> cis isomerizations, are often mounted for possible applications on a surface and/or surrounded by other switches, for example, in self-assembled monolayers. This may suppress the isomerization cross section due to possible steric reasons, or, as recently speculated, by exciton coupling to. neighboring switches, leading to ultrafast electronic quenching (Gahl et al., J. Am. Chem. Soc. 2010, 132, 1831). The presence of exciton coupling has been anticipated from a blue shift of the optical absorption band, compared to molecules in solution. From the theory side the need arises to properly analyze and quantify the change of absorption spectra of interacting and adsorbed switches. In particular, suitable methods should be identified, and effects of intermolecule and molecule surface interactions on spectra should be disentangled. In this paper by means of time-dependent Hartree-Fock. (TD-HF), various flavors of time-dependent density functional theory (TD-DFT), and the correlated wave function based, coupled cluster (CC2) method we investigated the 4-nitroazobenzene molecule as an:example: The low-lying singlet excited states in the isolated trans monomer and dieter as well as their composites with a silicon pentamantane nanocluster, which serves also as a crude model for a silicon surface, were determined. As most important results we found that (i) HF, CC2, range-separated density functionals, or global hybrids with large amount of exact exchange are able to describe exciton (Davydov) splitting properly, while hybrids with small amount of exact exchange fail producing spurious charge transfer. (ii) The exciton splitting in a free dimer would lead to a blue shift of the absorption signal; however, this effect is almost nullified or even overcompensated by the shift arising from van der Waals interactions between the two molecules. (iii) Adsorption on the Si "surface" leads to a further, strong red shift for the present system. (iv) At a next-nearest neighbor distance (of similar to 3.6 angstrom), the exciton splitting is similar to 0.3 eV, with or without "surface", suggesting a rapid quenching of the molecular pi ->pi* excitation. At larger distances, exciton splitting decreases rapidly.},
  language  = {en}
}
@phdthesis{Titov2017,
  author    = {Titov, Evgenii},
  title     = {Quantum chemistry and surface hopping dynamics of azobenzenes},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-394610},
  school      = {Universit{\"a}t Potsdam},
  pages     = {205},
  year      = {2017},
  abstract  = {This cumulative doctoral dissertation, based on three publications, is devoted to the investigation of several aspects of azobenzene molecular switches, with the aid of computational chemistry. In the first paper, the isomerization rates of a thermal cis → trans isomerization of azobenzenes for species formed upon an integer electron transfer, i.e., with added or removed electron, are calculated from Eyring's transition state theory and activation energy barriers, computed by means of density functional theory. The obtained results are discussed in connection with an experimental study of the thermal cis → trans isomerization of azobenzene derivatives in the presence of gold nanoparticles, which is demonstrated to be greatly accelerated in comparison to the same isomerization reaction in the absence of nanoparticles. The second paper is concerned with electronically excited states of (i) dimers, composed of two photoswitchable units placed closely side-by-side, as well as (ii) monomers and dimers adsorbed on a silicon cluster. A variety of quantum chemistry methods, capable of calculating molecular electronic absorption spectra, based on density functional and wave function theories, is employed to quantify changes in optical absorption upon dimerization and covalent grafting to a surface. Specifically, the exciton (Davydov) splitting between states of interest is determined from first-principles calculations with the help of natural transition orbital analysis, allowing for insight into the nature of excited states. In the third paper, nonadiabatic molecular dynamics with trajectory surface hopping is applied to model the photoisomerization of azobenzene dimers, (i) for the isolated case (exhibiting the exciton coupling between two molecules) as well as (ii) for the constrained case (providing the van der Waals interaction with environment in addition to the exciton coupling between two monomers). For the latter, the additional azobenzene molecules, surrounding the dimer, are introduced, mimicking a densely packed self-assembled monolayer. From obtained results it is concluded that the isolated dimer is capable of isomerization likewise the monomer, whereas the steric hindrance considerably suppresses trans → cis photoisomerization. Furthermore, the present dissertation comprises the general introduction describing the main features of the azobenzene photoswitch and objectives of this work, theoretical basis of the employed methods, and discussion of gained findings in the light of existing literature. Also, additional results on (i) activation parameters of the thermal cis → trans isomerization of azobenzenes, (ii) an approximate scheme to account for anharmonicity of molecular vibrations in calculation of the activation entropy, as well as (iii) absorption spectra of photoswitch-silicon composites obtained from time-demanding wave function-based methods are presented.},
  language  = {en}
}
@article{GouletHanssensUtechtMutrucetal.2017,
  author    = {Goulet-Hanssens, Alexis and Utecht, Manuel and Mutruc, Dragos and Titov, Evgenii and Schwarz, Jutta and Grubert, Lutz and Bleger, David and Saalfrank, Peter and Hecht, Stefan},
  title     = {Electrocatalytic Z -> E Isomerization of Azobenzenes},
  series = {Journal of the American Chemical Society},
  volume    = {139},
  journal   = {Journal of the American Chemical Society},
  number    = {1},
  publisher = {American Chemical Society},
  address   = {Washington},
  issn      = {0002-7863},
  doi       = {10.1021/jacs.6b10822},
  pages     = {335 -- 341},
  year      = {2017},
  abstract  = {A variety of azobenzenes were synthesized to study the behavior of their E and Z isomers upon electrochemical reduction. Our results show that the radical anion of the Z isomer is able to rapidly isomerize to the corresponding E configured counterpart with a dramatically enhanced rate as compared to the neutral species. Due to a subsequent electron transfer from the formed E radical anion to the neutral Z starting material the overall transformation is catalytic in electrons; i.e., a substoichiometric amount of reduced species can isomerize the entire mixture. This pathway greatly increases the efficiency of (photo)switching while also allowing one to reach photostationary state compositions that are not restricted to the spectral separation of the individual azobenzene isomers and their quantum yields. In addition, activating this radical isomerization pathway with photoelectron transfer agents allows us to override the intrinsic properties of an azobenzene species by triggering the reverse isomerization direction (Z -> E) by the same wavelength of light, which normally triggers E -> Z isomerization. The behavior we report appears to be general, implying that the metastable isomer of a photoswitch can be isomerized to the more stable one catalytically upon reduction, permitting the optimization of azobenzene switching in new as well as indirect ways.},
  language  = {en}
}
@article{RietzeTitovLindneretal.2017,
  author    = {Rietze, Clemens and Titov, Evgenii and Lindner, Steven and Saalfrank, Peter},
  title     = {Thermal isomerization of azobenzenes: on the performance of Eyring transition state theory},
  series = {Journal of physics : Condensed matter},
  volume    = {29},
  journal   = {Journal of physics : Condensed matter},
  publisher = {IOP Publ. Ltd.},
  address   = {Bristol},
  issn      = {0953-8984},
  doi       = {10.1088/1361-648X/aa75bd},
  pages     = {12},
  year      = {2017},
  abstract  = {The thermal Z -> E (back-) isomerization of azobenzenes is a prototypical reaction occurring in molecular switches. It has been studied for decades, yet its kinetics is not fully understood. In this paper, quantum chemical calculations are performed to model the kinetics of an experimental benchmark system, where a modified azobenzene (AzoBiPyB) is embedded in a metal-organic framework (MOF). The molecule can be switched thermally from cis to trans, under solvent-free conditions. We critically test the validity of Eyring transition state theory for this reaction. As previously found for other azobenzenes (albeit in solution), good agreement between theory and experiment emerges for activation energies and activation free energies, already at a comparatively simple level of theory, B3LYP/6-31G* including dispersion corrections. However, theoretical Arrhenius prefactors and activation entropies are in qualitiative disagreement with experiment. Several factors are discussed that may have an influence on activation entropies, among them dynamical and geometric constraints (imposed by the MOF). For a simpler model-Z -> E isomerization in azobenzene-a systematic test of quantum chemical methods from both density functional theory and wavefunction theory is carried out in the context of Eyring theory. Also, the effect of anharmonicities on activation entropies is discussed for this model system. Our work highlights capabilities and shortcomings of Eyring transition state theory and quantum chemical methods, when applied for the Z -> E (back-) isomerization of azobenzenes under solvent-free conditions.},
  language  = {en}
}
@article{MalyarTitovLomadzeetal.2017,
  author    = {Malyar, Ivan V. and Titov, Evgenii and Lomadze, Nino and Saalfrank, Peter and Santer, Svetlana},
  title     = {Photoswitching of azobenzene-containing self-assembled monolayers as a tool for control over silicon surface electronic properties},
  series = {The journal of chemical physics : bridges a gap between journals of physics and journals of chemistr},
  volume    = {146},
  journal   = {The journal of chemical physics : bridges a gap between journals of physics and journals of chemistr},
  publisher = {American Institute of Physics},
  address   = {Melville},
  issn      = {0021-9606},
  doi       = {10.1063/1.4978225},
  pages     = {8},
  year      = {2017},
  abstract  = {We report on photoinduced remote control of work function and surface potential of a silicon surface modified with a photosensitive self-assembled monolayer consisting of chemisorbed azobenzene molecules (4-nitroazobenzene). Itwas found that the attachment of the organic monolayer increases the work function by hundreds of meV due to the increase in the electron affinity of silicon substrates. The change in the work function on UV light illumination is more pronounced for the azobenzene jacketed silicon substrate (ca. 250 meV) in comparison to 50 meV for the unmodified surface. Moreover, the photoisomerization of azobenzene results in complex kinetics of thework function change: immediate decrease due to light-driven processes in the silicon surface followed by slower recovery to the initial state due to azobenzene isomerization. This behavior could be of interest for electronic devices where the reaction on irradiation should be more pronounced at small time scales but the overall surface potential should stay constant over time independent of the irradiation conditions. Published by AIP Publishing.},
  language  = {en}
}
@article{GouletHanssensRietzeTitovetal.2018,
  author    = {Goulet-Hanssens, Alexis and Rietze, Clemens and Titov, Evgenii and Abdullahu, Leonora and Grubert, Lutz and Saalfrank, Peter and Hecht, Stefan},
  title     = {Hole Catalysis as a General Mechanism for Efficient and Wavelength-Independent Z -> E Azobenzene Isomerization},
  series = {CHEM},
  volume    = {4},
  journal   = {CHEM},
  number    = {7},
  publisher = {Cell Press},
  address   = {Cambridge},
  issn      = {2451-9294},
  doi       = {10.1016/j.chempr.2018.06.002},
  pages     = {1740 -- 1755},
  year      = {2018},
  abstract  = {Whereas the reversible reduction of azobenzenes has been known for decades, their oxidation is destructive and as a result has been notoriously overlooked. Here, we show that a chain reaction leading to quantitative Z -> E isomerization can be initiated before reaching the destructive anodic peak potential. This hole-catalyzed pathway is accessible to all azobenzenes, without exception, and offers tremendous advantages over the recently reported reductive, radical-anionic pathway because it allows for convenient chemical initiation without the need for electrochemical setups and in the presence of air. In addition, catalytic amounts of metal-free sensitizers, such as methylene blue, can be used as excited-state electron acceptors, enabling a shift of the excitation wavelength to the far red of the azobenzene absorption (up to 660 nm) and providing quantum yields exceeding unity (up to 200\%). Our approach will boost the efficiency and sensitivity of optically dense liquid-crystalline and solid photo-switchable materials.},
  language  = {en}
}
@article{RietzeTitovGranuccietal.2020,
  author    = {Rietze, Clemens and Titov, Evgenii and Granucci, Giovanni and Saalfrank, Peter},
  title     = {Surface hopping dynamics for azobenzene photoisomerization},
  series = {The journal of physical chemistry : C, Nanomaterials and interfaces},
  volume    = {124},
  journal   = {The journal of physical chemistry : C, Nanomaterials and interfaces},
  number    = {48},
  publisher = {American Chemical Society},
  address   = {Washington},
  issn      = {1932-7447},
  doi       = {10.1021/acs.jpcc.0c08052},
  pages     = {26287 -- 26295},
  year      = {2020},
  abstract  = {Azobenzenes easily photoswitch in solution, while their photoisomerization at surfaces is often hindered. In recent work, it was demonstrated by nonadiabatic molecular dynamics with trajectory surface hopping [Titov et al., J. Phys. Chem. Lett. 2016, 7, 3591-3596] that the experimentally observed suppression of trans -> cis isomerization yields in azobenzenes in a densely packed SAM (self-assembled monolayer) [Gahl et al., J. Am. Chem. Soc. 2010, 132, 1831-1838] is dominated by steric hindrance. In the present work, we systematically study by ground-state Langevin and nonadiabatic surface hopping dynamics, the effects of decreasing packing density on (i) UV/vis absorption spectra, (ii) trans -> cis isomerization yields, and (iii) excited-state lifetimes of photoexcited azobenzene. Within the quantum mechanics/ molecular mechanics models adopted here, we find that above a packing density of similar to 3 molecules/nm(2), switching yields are strongly reduced, while at smaller packing densities, the "monomer limit" is quickly approached. The UV/vis absorption spectra, on the other hand, depend on packing density over a larger range (down to at least similar to 1 molecule/nm(2)). Trends for excited-state lifetimes are less obvious, but it is found that lifetimes of pi pi* excited states decay monotonically with decreasing coverage. Effects of fluorination of the switches are also discussed for single, free molecules. Fluorination leads to comparatively large trans -> cis yields, in combination with long pi pi* lifetimes. Furthermore, for selected systems, also the effects of n pi* excitation at longer excitation wavelengths have been studied, which is found to enhance trans -> cis yields for free molecules but can lead to an opposite behavior in densely packed SAMs.},
  language  = {en}
}
@article{Titov2021,
  author    = {Titov, Evgenii},
  title     = {On the low-lying electronically excited states of azobenzene dimers},
  series = {Molecules : a journal of synthetic chemistry and natural product chemistry / Molecular Diversity Preservation International},
  volume    = {26},
  journal   = {Molecules : a journal of synthetic chemistry and natural product chemistry / Molecular Diversity Preservation International},
  number    = {14},
  publisher = {MDPI},
  address   = {Basel},
  issn      = {1420-3049},
  doi       = {10.3390/molecules26144245},
  pages     = {24},
  year      = {2021},
  abstract  = {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.},
  language  = {en}
}
@article{TitovSharmaLomadzeetal.2021,
  author    = {Titov, Evgenii and Sharma, Anjali and Lomadze, Nino and Saalfrank, Peter and Santer, Svetlana and Bekir, Marek},
  title     = {Photoisomerization of an azobenzene-containing surfactant within a micelle},
  series = {ChemPhotoChem},
  volume    = {5},
  journal   = {ChemPhotoChem},
  number    = {10},
  publisher = {Wiley-VCH},
  address   = {Weinheim},
  issn      = {2367-0932},
  doi       = {10.1002/cptc.202100103},
  pages     = {926 -- 932},
  year      = {2021},
  abstract  = {Photosensitive azobenzene-containing surfactants have attracted great attention in past years because they offer a means to control soft-matter transformations with light. At concentrations higher than the critical micelle concentration (CMC), the surfactant molecules aggregate and form micelles, which leads to a slowdown of the photoinduced trans -> cis azobenzene isomerization. Here, we combine nonadiabatic dynamics simulations for the surfactant molecules embedded in the micelles with absorption spectroscopy measurements of micellar solutions to uncover the reasons responsible for the reaction slowdown. Our simulations reveal a decrease of isomerization quantum yields for molecules inside the micelles. We also observe a reduction of extinction coefficients upon micellization. These findings explain the deceleration of the trans -> cis switching in micelles of the azobenzene-containing surfactants.},
  language  = {en}
}
@article{TitovKoppHocheetal.2022,
  author    = {Titov, Evgenii and Kopp, Tristan and Hoche, Joscha and Humeniuk, Alexander and Mitrić, Roland},
  title     = {(De)localization dynamics of molecular excitons},
  series = {Physical chemistry, chemical physics : PCCP ; a journal of European chemical societies},
  volume    = {24},
  journal   = {Physical chemistry, chemical physics : PCCP ; a journal of European chemical societies},
  number    = {20},
  publisher = {Royal Society of Chemistry},
  address   = {Cambridge},
  issn      = {1463-9076},
  doi       = {10.1039/d2cp00586g},
  pages     = {12136 -- 12148},
  year      = {2022},
  abstract  = {Molecular excitons play a central role in processes of solar energy conversion, both natural and artificial. It is therefore no wonder that numerous experimental and theoretical investigations in the last decade, employing state-of-the-art spectroscopic techniques and computational methods, have been driven by the common aim to unravel exciton dynamics in multichromophoric systems. Theoretically, exciton (de)localization and transfer dynamics are most often modelled using either mixed quantum-classical approaches (e.g., trajectory surface hopping) or fully quantum mechanical treatments (either using model diabatic Hamiltonians or direct dynamics). Yet, the terms such as "exciton localization" or "exciton transfer" may bear different meanings in different works depending on the method in use (quantum-classical vs. fully quantum). Here, we relate different views on exciton (de)localization. For this purpose, we perform molecular surface hopping simulations on several tetracene dimers differing by a magnitude of exciton coupling and carry out quantum dynamical as well as surface hopping calculations on a relevant model system. The molecular surface hopping simulations are done using efficient long-range corrected time-dependent density functional tight binding electronic structure method, allowing us to gain insight into different regimes of exciton dynamics in the studied systems.},
  language  = {en}
}
@article{KuntzeViljakkaTitovetal.2022,
  author    = {Kuntze, Kim and Viljakka, Jani and Titov, Evgenii and Ahmed, Zafar and Kalenius, Elina and Saalfrank, Peter and Priimagi, Arri},
  title     = {Towards low-energy-light-driven bistable photoswitches},
  series = {Photochemical \& photobiological sciences / European Society for Photobiology},
  volume    = {21},
  journal   = {Photochemical \& photobiological sciences / European Society for Photobiology},
  number    = {2},
  publisher = {Springer},
  address   = {Heidelberg},
  issn      = {1474-905X},
  doi       = {10.1007/s43630-021-00145-4},
  pages     = {159 -- 173},
  year      = {2022},
  abstract  = {Thermally stable photoswitches that are driven with low-energy light are rare, yet crucial for extending the applicability of photoresponsive molecules and materials towards, e.g., living systems. Combined ortho-fluorination and -amination couples high visible light absorptivity of o-aminoazobenzenes with the extraordinary bistability of o-fluoroazobenzenes. Herein, we report a library of easily accessible o-aminofluoroazobenzenes and establish structure-property relationships regarding spectral qualities, visible light isomerization efficiency and thermal stability of the cis-isomer with respect to the degree of o-substitution and choice of amino substituent. We rationalize the experimental results with quantum chemical calculations, revealing the nature of low-lying excited states and providing insight into thermal isomerization. The synthesized azobenzenes absorb at up to 600 nm and their thermal cis-lifetimes range from milliseconds to months. The most unique example can be driven from trans to cis with any wavelength from UV up to 595 nm, while still exhibiting a thermal cis-lifetime of 81 days. <br /> [GRAPHICS] <br /> .},
  language  = {en}
}
@article{ReifarthBekirBapolisietal.2022,
  author    = {Reifarth, Martin and Bekir, Marek and Bapolisi, Alain M. and Titov, Evgenii and Nusshardt, Fabian and Nowaczyk, Julius and Grigoriev, Dmitry and Sharma, Anjali and Saalfrank, Peter and Santer, Svetlana and Hartlieb, Matthias and B{\"o}ker, Alexander},
  title     = {A dual pH- and light-responsive spiropyrane-based surfactant},
  series = {Angewandte Chemie : a journal of the Gesellschaft Deutscher Chemiker ; International edition},
  volume    = {61},
  journal   = {Angewandte Chemie : a journal of the Gesellschaft Deutscher Chemiker ; International edition},
  number    = {21},
  publisher = {Wiley-VCH},
  address   = {Weinheim},
  issn      = {1433-7851},
  doi       = {10.1002/anie.202114687},
  pages     = {10},
  year      = {2022},
  abstract  = {A cationic surfactant containing a spiropyrane unit is prepared exhibiting a dual-responsive adjustability of its surface-active characteristics. The switching mechanism of the system relies on the reversible conversion of the non-ionic spiropyrane (SP) to a zwitterionic merocyanine (MC) and can be controlled by adjusting the pH value and via light, resulting in a pH-dependent photoactivity: While the compound possesses a pronounced difference in surface activity between both forms under acidic conditions, this behavior is suppressed at a neutral pH level. The underlying switching processes are investigated in detail, and a thermodynamic explanation based on a combination of theoretical and experimental results is provided. This complex stimuli-responsive behavior enables remote-control of colloidal systems. To demonstrate its applicability, the surfactant is utilized for the pH-dependent manipulation of oil-in-water emulsions.},
  language  = {en}
}
@article{SchuermannTitovEbeletal.2022,
  author    = {Sch{\"u}rmann, Robin and Titov, Evgenii and Ebel, Kenny and Kogikoski Junior, Sergio and Mostafa, Amr and Saalfrank, Peter and Milosavljević, Aleksandar R. and Bald, Ilko},
  title     = {The electronic structure of the metal-organic interface of isolated ligand coated gold nanoparticles},
  series = {Nanoscale Advances},
  volume    = {4},
  journal   = {Nanoscale Advances},
  number    = {6},
  publisher = {Royal Society of Chemistry},
  address   = {Cambridge},
  issn      = {2516-0230},
  doi       = {10.1039/d1na00737h},
  pages     = {1599 -- 1607},
  year      = {2022},
  abstract  = {Light induced electron transfer reactions of molecules on the surface of noble metal nanoparticles (NPs) depend significantly on the electronic properties of the metal-organic interface. Hybridized metal-molecule states and dipoles at the interface alter the work function and facilitate or hinder electron transfer between the NPs and ligand. X-ray photoelectron spectroscopy (XPS) measurements of isolated AuNPs coated with thiolated ligands in a vacuum have been performed as a function of photon energy, and the depth dependent information of the metal-organic interface has been obtained. The role of surface dipoles in the XPS measurements of isolated ligand coated NPs is discussed and the binding energy of the Au 4f states is shifted by around 0.8 eV in the outer atomic layers of 4-nitrothiophenol coated AuNPs, facilitating electron transport towards the molecules. Moreover, the influence of the interface dipole depends significantly on the adsorbed ligand molecules. The present study paves the way towards the engineering of the electronic properties of the nanoparticle surface, which is of utmost importance for the application of plasmonic nanoparticles in the fields of heterogeneous catalysis and solar energy conversion.},
  language  = {en}
}