@article{WirthHatterDrostetal.2015, author = {Wirth, Jonas and Hatter, Nino and Drost, Robert and Umbach, Tobias R. and Barja, Sara and Zastrow, Matthias and R{\"u}ck-Braun, Karola and Pascual, Jose Ignacio and Saalfrank, Peter and Franke, Katharina J.}, title = {Diarylethene Molecules on a Ag(111) Surface: Stability and Electron-Induced Switching}, series = {The journal of physical chemistry : C, Nanomaterials and interfaces}, volume = {119}, journal = {The journal of physical chemistry : C, Nanomaterials and interfaces}, number = {9}, publisher = {American Chemical Society}, address = {Washington}, issn = {1932-7447}, doi = {10.1021/jp5122036}, pages = {4874 -- 4883}, year = {2015}, abstract = {Diarylethene derivatives are photochromic molecular switches, undergoing a ring-opening/-closing reaction by illumination with light. The symmetry of the closed form is determined by the WoodWard Hoffinann rules according to which the reaction proceeds by corirotatory rotation -in that case. Here, we show by a cOrnbined approach of scanning tunneling microscopy (STM) and density functional theory (DFT) calculations that the Open isomer of 4,4'-(4,4'-(perfluorocydopent-1-ene-1,2-diyl)bis(5-methyl-thiophent-4,2,4-dipyridine) (PDTE) retains its open form upon adsorption on a Ag(111) surface. It caribe switched into a closed form, which we identify as the digrotatOly cydization product, by controlled manipulation 'With the STM tip, Evidence of an electric-field dependent switching-process 'is interpreted on the basis of a Simple electroStatic Model, which suggests that the reaction proceedS via an "upright" intermediate state. This pathway thus strongly differs from the switching reaction in solution.}, language = {en} } @article{TongWirthKirschetal.2015, author = {Tong, Yujin and Wirth, Jonas and Kirsch, Harald and Wolf, Martin and Saalfrank, Peter and Campen, Richard Kramer}, title = {Optically probing Al-O and O-H vibrations to characterize water adsorption and surface reconstruction on alpha-alumina: An experimental and theoretical study}, series = {The journal of chemical physics : bridges a gap between journals of physics and journals of chemistr}, volume = {142}, journal = {The journal of chemical physics : bridges a gap between journals of physics and journals of chemistr}, number = {5}, publisher = {American Institute of Physics}, address = {Melville}, issn = {0021-9606}, doi = {10.1063/1.4906346}, pages = {12}, year = {2015}, abstract = {Oxide/water interfaces are ubiquitous in a wide variety of applications and the environment. Despite this ubiquity, and attendant decades of study, gaining molecular level insight into water/oxide interaction has proven challenging. In part, this challenge springs from a lack of tools to concurrently characterize changes in surface structure (i.e., water/oxide interaction from the perspective of the solid) and O-H population and local environment (i.e., water/oxide interaction from the water perspective). Here, we demonstrate the application of surface specific vibrational spectroscopy to the characterization of the interaction of the paradigmatic alpha-Al2O3(0001) surface and water. By probing both the interfacial Al-O (surface phonon) and O-H spectral response, we characterize this interaction from both perspectives. Through electronic structure calculation, we assign the interfacial Al-O response and rationalize its changes on surface dehydroxylation and reconstruction. Because our technique is all-optical and interface specific, it is equally applicable to oxide surfaces in vacuum, ambient atmospheres and at the solid/liquid interface. Application of this approach to additional alumina surfaces and other oxides thus seems likely to significantly expand our understanding of how water meets oxide surfaces and thus the wide variety of phenomena this interaction controls. (C) 2015 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} } @misc{SchulzeUtechtMoldtetal.2015, author = {Schulze, Michael and Utecht, Manuel Martin and Moldt, Thomas and Przyrembel, Daniel and Gahl, Cornelius and Weinelt, Martin and Saalfrank, Peter and Tegeder, Petra}, title = {Nonlinear optical response of photochromic azobenzene-functionalized self-assembled monolayers}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-81198}, year = {2015}, abstract = {The combination of photochromic and nonlinear optical (NLO) properties of azobenzene-functionalized self-assembled monolayers (SAMs) constitutes an intriguing step towards novel photonic and optoelectronic devices. By utilizing the second-order NLO process of second harmonic generation (SHG), supported by density-functional theory and correlated wave function method calculations, we demonstrate that the photochromic interface provides the necessary prerequisites en route towards possible future technical applications: we find a high NLO contrast on the order of 16\% between the switching states. These are furthermore accessible reversibly and with high efficiencies in terms of cross sections on the order of 10-18 cm2 for both photoisomerization reactions, i.e., drivable by means of low-power LED light sources. Finally, both photostationary states (PSSs) are thermally stable at ambient conditions.}, language = {en} } @article{SchulzeUtechtMoldtetal.2015, author = {Schulze, Michael and Utecht, Manuel Martin and Moldt, Thomas and Przyrembel, Daniel and Gahl, Cornelius and Weinelt, Martin and Saalfrank, Peter and Tegeder, Petra}, title = {Nonlinear optical response of photochromic azobenzene-functionalized self-assembled monolayers}, series = {Physical chemistry, chemical physics : a journal of European Chemical Societies}, volume = {17}, journal = {Physical chemistry, chemical physics : a journal of European Chemical Societies}, number = {27}, publisher = {Royal Society of Chemistry}, address = {Cambridge}, issn = {1463-9076}, doi = {10.1039/c5cp03093e}, pages = {18079 -- 18086}, year = {2015}, abstract = {The combination of photochromic and nonlinear optical (NLO) properties of azobenzene-functionalized self-assembled monolayers (SAMs) constitutes an intriguing step towards novel photonic and optoelectronic devices. By utilizing the second-order NLO process of second harmonic generation (SHG), supported by density-functional theory and correlated wave function method calculations, we demonstrate that the photochromic interface provides the necessary prerequisites en route towards possible future technical applications: we find a high NLO contrast on the order of 16\% between the switching states. These are furthermore accessible reversibly and with high efficiencies in terms of cross sections on the order of 10(-18) cm(2) for both photoisomerization reactions, i.e., drivable by means of low-power LED light sources. Finally, both photostationary states (PSSs) are thermally stable at ambient conditions.}, language = {en} } @article{SchulzeUtechtMoldtetal.2015, author = {Schulze, Michael and Utecht, Manuel Martin and Moldt, Thomas and Przyrembel, Daniel and Gahl, Cornelius and Weinelt, Martin and Saalfrank, Peter and Tegeder, Petra}, title = {Nonlinear optical response of photochromic azobenzene-functionalized self-assembled monolayers}, series = {Physical chemistry, chemical physics : PCCP ; a journal of European Chemical Societies}, volume = {27}, journal = {Physical chemistry, chemical physics : PCCP ; a journal of European Chemical Societies}, number = {17}, publisher = {Royal Society of Chemistry}, address = {Cambridge}, issn = {1463-9076}, doi = {10.1039/c5cp03093e}, pages = {18079 -- 18086}, year = {2015}, abstract = {The combination of photochromic and nonlinear optical (NLO) properties of azobenzene-functionalized self-assembled monolayers (SAMs) constitutes an intriguing step towards novel photonic and optoelectronic devices. By utilizing the second-order NLO process of second harmonic generation (SHG), supported by density-functional theory and correlated wave function method calculations, we demonstrate that the photochromic interface provides the necessary prerequisites en route towards possible future technical applications: we find a high NLO contrast on the order of 16\% between the switching states. These are furthermore accessible reversibly and with high efficiencies in terms of cross sections on the order of 10-18 cm2 for both photoisomerization reactions, i.e., drivable by means of low-power LED light sources. Finally, both photostationary states (PSSs) are thermally stable at ambient conditions.}, language = {en} } @article{SchulzeUtechtHebertetal.2015, author = {Schulze, Michael and Utecht, Manuel Martin and Hebert, Andreas and R{\"u}ck-Braun, Karola and Saalfrank, Peter and Tegeder, Petra}, title = {Reversible Photoswitching of the Interfacial Nonlinear Optical Response}, series = {The journal of physical chemistry letters}, volume = {6}, journal = {The journal of physical chemistry letters}, number = {3}, publisher = {American Chemical Society}, address = {Washington}, issn = {1948-7185}, doi = {10.1021/jz502477m}, pages = {505 -- 509}, year = {2015}, abstract = {Incorporating photochromic molecules into organic/inorganic hybrid materials may lead to photoresponsive systems. In such systems, the second-order nonlinear properties can be controlled via external stimulation with light at an appropriate wavelength. By creating photochromic molecular switches containing self-assembled monolayers on Si(111), we can demonstrate efficient reversible switching, which is accompanied by a pronounced modulation of the nonlinear optical (NLO) response of the system. The concept of utilizing functionalized photoswitchable Si surfaces could be a way for the generation of two-dimensional NLO switching materials, which are promising for applications in photonic and optoelectronic devices.}, language = {en} } @misc{MatisSchoenbornSaalfrank2015, author = {Matis, Jochen Ren{\´e} and Sch{\"o}nborn, Jan Boyke and Saalfrank, Peter}, title = {A multi-reference study of the byproduct formation for a ring-closed dithienylethene photoswitch}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-89594}, pages = {14088 -- 14095}, year = {2015}, abstract = {Photodriven molecular switches are sometimes hindered in their performance by forming byproducts which act as dead ends in sequences of switching cycles, leading to rapid fatigue effects. Understanding the reaction pathways to unwanted byproducts is a prerequisite for preventing them. This article presents a study of the photochemical reaction pathways for byproduct formation in the photochromic switch 1,2-bis-(3-thienyl)-ethene. Specifically, using single- and multi-reference methods the post-deexcitation reaction towards the byproduct in the electronic ground state S0 when starting from the S1-S0 conical intersection (CoIn), is considered in detail. We find an unusual low-energy pathway, which offers the possibility for the formation of a dyotropic byproduct. Several high-energy pathways can be excluded with high probability.}, language = {en} } @article{MatisSchoenbornSaalfrank2015, author = {Matis, Jochen Ren{\´e} and Sch{\"o}nborn, Jan Boyke and Saalfrank, Peter}, title = {A multi-reference study of the byproduct formation for a ring-closed dithienylethene photoswitch}, series = {Physical chemistry, chemical physics : PCCP ; a journal of European Chemical Societies}, journal = {Physical chemistry, chemical physics : PCCP ; a journal of European Chemical Societies}, number = {17}, publisher = {The Royal Society of Chemistry}, address = {Cambridge}, issn = {1463-9076}, doi = {10.1039/C5CP00987A}, pages = {14088 -- 14095}, year = {2015}, abstract = {Photodriven molecular switches are sometimes hindered in their performance by forming byproducts which act as dead ends in sequences of switching cycles, leading to rapid fatigue effects. Understanding the reaction pathways to unwanted byproducts is a prerequisite for preventing them. This article presents a study of the photochemical reaction pathways for byproduct formation in the photochromic switch 1,2-bis-(3-thienyl)-ethene. Specifically, using single- and multi-reference methods the post-deexcitation reaction towards the byproduct in the electronic ground state S0 when starting from the S1-S0 conical intersection (CoIn), is considered in detail. We find an unusual low-energy pathway, which offers the possibility for the formation of a dyotropic byproduct. Several high-energy pathways can be excluded with high probability.}, language = {en} } @article{MatisSchoenbornSaalfrank2015, author = {Matis, Jochen Rene and Schoenborn, Jan Boyke and Saalfrank, Peter}, title = {A multi-reference study of the byproduct formation for a ring-closed dithienylethene photoswitch}, series = {Physical chemistry, chemical physics : a journal of European Chemical Societies}, volume = {17}, journal = {Physical chemistry, chemical physics : a journal of European Chemical Societies}, number = {21}, publisher = {Royal Society of Chemistry}, address = {Cambridge}, issn = {1463-9076}, doi = {10.1039/c5cp00987a}, pages = {14088 -- 14095}, year = {2015}, abstract = {Photodriven molecular switches are sometimes hindered in their performance by forming byproducts which act as dead ends in sequences of switching cycles, leading to rapid fatigue effects. Understanding the reaction pathways to unwanted byproducts is a prerequisite for preventing them. This article presents a study of the photochemical reaction pathways for byproduct formation in the photochromic switch 1,2-bis-(3-thienyl)-ethene. Specifically, using single-and multi-reference methods the post-deexcitation reaction towards the byproduct in the electronic ground state S-0 when starting from the S-1-S-0 conical intersection (CoIn), is considered in detail. We find an unusual low-energy pathway, which offers the possibility for the formation of a dyotropic byproduct. Several high-energy pathways can be excluded with high probability.}, language = {en} }