@article{13399, abstract = {Nature has long inspired scientists with its seemingly unlimited ability to harness solar energy and to utilize it to drive various physiological processes. With the help of man-made molecular photoswitches, we now have the potential to outperform natural systems in many ways, with the ultimate goal of fabricating multifunctional materials that operate at different light wavelengths. An important challenge in developing light-controlled artificial molecular machines lies in attaining a detailed understanding of the photoisomerization-coupled conformational changes that occur in macromolecules and molecular assemblies. In this issue of ACS Nano, Bléger, Rabe, and co-workers use force microscopy to provide interesting insights into the behavior of individual photoresponsive molecules and to identify contraction, extension, and crawling events accompanying light-induced isomerization.}, author = {Kundu, Pintu K. and Klajn, Rafal}, issn = {1936-086X}, journal = {ACS Nano}, keywords = {General Physics and Astronomy, General Engineering, General Materials Science}, number = {12}, pages = {11913--11916}, publisher = {American Chemical Society}, title = {{Watching single molecules move in response to light}}, doi = {10.1021/nn506656r}, volume = {8}, year = {2014}, } @article{13400, abstract = {Organizing inorganic nanocrystals into complex architectures is challenging and typically relies on preexisting templates, such as properly folded DNA or polypeptide chains. We found that under carefully controlled conditions, cubic nanocrystals of magnetite self-assemble into arrays of helical superstructures in a template-free manner with >99% yield. Computer simulations revealed that the formation of helices is determined by the interplay of van der Waals and magnetic dipole-dipole interactions, Zeeman coupling, and entropic forces and can be attributed to spontaneous formation of chiral nanocube clusters. Neighboring helices within their densely packed ensembles tended to adopt the same handedness in order to maximize packing, thus revealing a novel mechanism of symmetry breaking and chirality amplification.}, author = {Singh, Gurvinder and Chan, Henry and Baskin, Artem and Gelman, Elijah and Repnin, Nikita and Král, Petr and Klajn, Rafal}, issn = {1095-9203}, journal = {Science}, keywords = {Multidisciplinary}, number = {6201}, pages = {1149--1153}, publisher = {American Association for the Advancement of Science}, title = {{Self-assembly of magnetite nanocubes into helical superstructures}}, doi = {10.1126/science.1254132}, volume = {345}, year = {2014}, } @article{13401, abstract = {A compound combining the features of a molecular rotor and a photoswitch was synthesized and was shown to exist as three diastereomers, which interconvert via a reversible cyclic reaction scheme. Each of the three diastereomers was isolated, and by following the equilibration kinetics, activation barriers for all reactions were calculated. The results indicate that the properties of molecular switches depend heavily on their immediate chemical environment. The conclusions are important in the context of designing new switchable molecules and materials.}, author = {Kundu, Pintu K. and Lerner, Avishai and Kučanda, Kristina and Leitus, Gregory and Klajn, Rafal}, issn = {1520-5126}, journal = {Journal of the American Chemical Society}, keywords = {Colloid and Surface Chemistry, Biochemistry, General Chemistry, Catalysis}, number = {32}, pages = {11276--11279}, publisher = {American Chemical Society}, title = {{Cyclic kinetics during thermal equilibration of an axially chiral bis-spiropyran}}, doi = {10.1021/ja505948q}, volume = {136}, year = {2014}, } @article{13402, abstract = {Nanoporous frameworks are polymeric materials built from rigid molecules, which give rise to their nanoporous structures with applications in gas sorption and storage, catalysis and others. Conceptually new applications could emerge, should these beneficial properties be manipulated by external stimuli in a reversible manner. One approach to render nanoporous frameworks responsive to external signals would be to immobilize molecular switches within their nanopores. Although the majority of molecular switches require conformational freedom to isomerize, and switching in the solid state is prohibited, the nanopores may provide enough room for the switches to efficiently isomerize. Here we describe two families of nanoporous materials incorporating the spiropyran molecular switch. These materials exhibit a variety of interesting properties, including reversible photochromism and acidochromism under solvent-free conditions, light-controlled capture and release of metal ions, as well reversible chromism induced by solvation/desolvation.}, author = {Kundu, Pintu K. and Olsen, Gregory L. and Kiss, Vladimir and Klajn, Rafal}, issn = {2041-1723}, journal = {Nature Communications}, keywords = {General Physics and Astronomy, General Biochemistry, Genetics and Molecular Biology, General Chemistry, Multidisciplinary}, publisher = {Springer Nature}, title = {{Nanoporous frameworks exhibiting multiple stimuli responsiveness}}, doi = {10.1038/ncomms4588}, volume = {5}, year = {2014}, } @article{13403, abstract = {We show that bimolecular reactions between species confined to the surfaces of nanoparticles can be manipulated by the nature of the linker, as well as by the curvature of the underlying particles.}, author = {Zdobinsky, Tino and Sankar Maiti, Pradipta and Klajn, Rafal}, issn = {1520-5126}, journal = {Journal of the American Chemical Society}, keywords = {Colloid and Surface Chemistry, Biochemistry, General Chemistry, Catalysis}, number = {7}, pages = {2711--2714}, publisher = {American Chemical Society}, title = {{Support curvature and conformational freedom control chemical reactivity of immobilized species}}, doi = {10.1021/ja411573a}, volume = {136}, year = {2014}, } @article{13404, abstract = {In the past few years, spiropyran has emerged as the molecule-of-choice for the construction of novel dynamic materials. This unique molecular switch undergoes structural isomerisation in response to a variety of orthogonal stimuli, e.g. light, temperature, metal ions, redox potential, and mechanical stress. Incorporation of this switch onto macromolecular supports or inorganic scaffolds allows for the creation of robust dynamic materials. This review discusses the synthesis, switching conditions, and use of dynamic materials in which spiropyran has been attached to the surfaces of polymers, biomacromolecules, inorganic nanoparticles, as well as solid surfaces. The resulting materials show fascinating properties whereby the state of the switch intimately affects a multitude of useful properties of the support. The utility of the spiropyran switch will undoubtedly endow these materials with far-reaching applications in the near future.}, author = {Klajn, Rafal}, issn = {1460-4744}, journal = {Chemical Society Reviews}, keywords = {General Chemistry}, number = {1}, pages = {148--184}, publisher = {Royal Society of Chemistry}, title = {{Spiropyran-based dynamic materials}}, doi = {10.1039/c3cs60181a}, volume = {43}, year = {2014}, } @article{1375, abstract = {We consider directed graphs where each edge is labeled with an integer weight and study the fundamental algorithmic question of computing the value of a cycle with minimum mean weight. Our contributions are twofold: (1) First we show that the algorithmic question is reducible to the problem of a logarithmic number of min-plus matrix multiplications of n×n-matrices, where n is the number of vertices of the graph. (2) Second, when the weights are nonnegative, we present the first (1+ε)-approximation algorithm for the problem and the running time of our algorithm is Õ(nωlog3(nW/ε)/ε),1 where O(nω) is the time required for the classic n×n-matrix multiplication and W is the maximum value of the weights. With an additional O(log(nW/ε)) factor in space a cycle with approximately optimal weight can be computed within the same time bound.}, author = {Chatterjee, Krishnendu and Henzinger, Monika H and Krinninger, Sebastian and Loitzenbauer, Veronika and Raskin, Michael}, journal = {Theoretical Computer Science}, number = {C}, pages = {104 -- 116}, publisher = {Elsevier}, title = {{Approximating the minimum cycle mean}}, doi = {10.1016/j.tcs.2014.06.031}, volume = {547}, year = {2014}, } @inproceedings{1392, abstract = {Fault-tolerant distributed algorithms play an important role in ensuring the reliability of many software applications. In this paper we consider distributed algorithms whose computations are organized in rounds. To verify the correctness of such algorithms, we reason about (i) properties (such as invariants) of the state, (ii) the transitions controlled by the algorithm, and (iii) the communication graph. We introduce a logic that addresses these points, and contains set comprehensions with cardinality constraints, function symbols to describe the local states of each process, and a limited form of quantifier alternation to express the verification conditions. We show its use in automating the verification of consensus algorithms. In particular, we give a semi-decision procedure for the unsatisfiability problem of the logic and identify a decidable fragment. We successfully applied our framework to verify the correctness of a variety of consensus algorithms tolerant to both benign faults (message loss, process crashes) and value faults (message corruption).}, author = {Dragoi, Cezara and Henzinger, Thomas A and Veith, Helmut and Widder, Josef and Zufferey, Damien}, location = {San Diego, USA}, pages = {161 -- 181}, publisher = {Springer}, title = {{A logic-based framework for verifying consensus algorithms}}, doi = {10.1007/978-3-642-54013-4_10}, volume = {8318}, year = {2014}, } @inproceedings{1393, abstract = {Probabilistic programs are usual functional or imperative programs with two added constructs: (1) the ability to draw values at random from distributions, and (2) the ability to condition values of variables in a program via observations. Models from diverse application areas such as computer vision, coding theory, cryptographic protocols, biology and reliability analysis can be written as probabilistic programs. Probabilistic inference is the problem of computing an explicit representation of the probability distribution implicitly specified by a probabilistic program. Depending on the application, the desired output from inference may vary-we may want to estimate the expected value of some function f with respect to the distribution, or the mode of the distribution, or simply a set of samples drawn from the distribution. In this paper, we describe connections this research area called \Probabilistic Programming" has with programming languages and software engineering, and this includes language design, and the static and dynamic analysis of programs. We survey current state of the art and speculate on promising directions for future research.}, author = {Gordon, Andrew and Henzinger, Thomas A and Nori, Aditya and Rajamani, Sriram}, booktitle = {Proceedings of the on Future of Software Engineering}, location = {Hyderabad, India}, pages = {167 -- 181}, publisher = {ACM}, title = {{Probabilistic programming}}, doi = {10.1145/2593882.2593900}, year = {2014}, } @article{14018, abstract = {The sensitivities of high-harmonic generation (HHG) and strong-field ionization (SFI) to coupled electronic and nuclear dynamics are studied, using the nitric oxide (NO) molecule as an example. A coherent superposition of electronic and rotational states of NO is prepared by impulsive stimulated Raman scattering and probed by simultaneous detection of HHG and SFI yields. We observe a fourfold higher sensitivity of high-harmonic generation to electronic dynamics and attribute it to the presence of inelastic quantum paths connecting coherently related electronic states [Kraus et al., Phys. Rev. Lett.111, 243005 (2013)]. Whereas different harmonic orders display very different sensitivities to rotational or electronic dynamics, strong-field ionization is found to be most sensitive to electronic motion. We introduce a general theoretical formalism for high-harmonic generation from coupled nuclear-electronic wave packets. We show that the unequal sensitivities of different harmonic orders to electronic or rotational dynamics result from the angle dependence of the photorecombination matrix elements which encode several autoionizing and shape resonances in the photoionization continuum of NO. We further study the dependence of rotational and electronic coherences on the intensity of the excitation pulse and support the observations with calculations.}, author = {Baykusheva, Denitsa Rangelova and Kraus, Peter M. and Zhang, Song Bin and Rohringer, Nina and Wörner, Hans Jakob}, issn = {1364-5498}, journal = {Faraday Discussions}, keywords = {Physical and Theoretical Chemistry}, pages = {113--132}, publisher = {Royal Society of Chemistry}, title = {{The sensitivities of high-harmonic generation and strong-field ionization to coupled electronic and nuclear dynamics}}, doi = {10.1039/c4fd00018h}, volume = {171}, year = {2014}, } @article{14019, abstract = {The cyclopropene radical cation (c-C3H₄⁺) is an important but poorly characterized three-membered-ring hydrocarbon. We report on a measurement of the high-resolution photoelectron and photoionization spectra of cyclopropene and several deuterated isotopomers, from which we have determined the rovibrational energy level structure of the X⁺ (2)B2 ground electronic state of c-C3H₄⁺ at low energies for the first time. The synthesis of the partially deuterated isotopomers always resulted in mixtures of several isotopomers, differing in their number of D atoms and in the location of these atoms, so that the photoelectron spectra of deuterated samples are superpositions of the spectra of several isotopomers. The rotationally resolved spectra indicate a C(2v)-symmetric R0 structure for the ground electronic state of c-C3H₄⁺. Two vibrational modes of c-C3H₄⁺ are found to have vibrational wave numbers below 300 cm(-1), which is surprising for such a small cyclic hydrocarbon. The analysis of the isotopic shifts of the vibrational levels enabled the assignment of the lowest-frequency mode (fundamental wave number of ≈110 cm(-1) in c-C3H₄⁺) to the CH2 torsional mode (ν₈⁺, A2 symmetry) and of the second-lowest-frequency mode (≈210 cm(-1) in c-C3H₄⁺) to a mode combining a CH out-of-plane with a CH2 rocking motion (ν₁₅⁺, B2 symmetry). The potential energy along the CH2 torsional coordinate is flat near the equilibrium structure and leads to a pronounced anharmonicity.}, author = {Vasilatou, K. and Michaud, J. M. and Baykusheva, Denitsa Rangelova and Grassi, G. and Merkt, F.}, issn = {1089-7690}, journal = {The Journal of Chemical Physics}, keywords = {Physical and Theoretical Chemistry, General Physics and Astronomy}, number = {6}, publisher = {AIP Publishing}, title = {{The cyclopropene radical cation: Rovibrational level structure at low energies from high-resolution photoelectron spectra}}, doi = {10.1063/1.4890744}, volume = {141}, year = {2014}, } @article{14020, abstract = {We report the observation of macroscopic field-free orientation, i.e., more than 73% of CO molecules pointing in the same direction. This is achieved through an all-optical scheme operating at high particle densities (>10(17)  cm(-3)) that combines one-color (ω) and two-color (ω+2ω) nonresonant femtosecond laser pulses. We show that the achieved orientation solely relies on the hyperpolarizability interaction as opposed to an ionization-depletion mechanism, thus, opening a wide range of applications. The achieved strong orientation enables us to reveal the molecular-frame anisotropies of the photorecombination amplitudes and phases caused by a shape resonance. The resonance appears as a local maximum in the even-harmonic emission around 28 eV. In contrast, the odd-harmonic emission is suppressed in this spectral region through the combined effects of an asymmetric photorecombination phase and a subcycle Stark effect, generic for polar molecules, that we experimentally identify.}, author = {Kraus, P. M. and Baykusheva, Denitsa Rangelova and Wörner, H. J.}, issn = {1079-7114}, journal = {Physical Review Letters}, keywords = {General Physics and Astronomy}, number = {2}, publisher = {American Physical Society}, title = {{Two-pulse field-free orientation reveals anisotropy of molecular shape resonance}}, doi = {10.1103/physrevlett.113.023001}, volume = {113}, year = {2014}, } @article{14021, abstract = {We present the detailed analysis of a new two-pulse orientation scheme that achieves macroscopic field-free orientation at the high particle densities required for attosecond and high-harmonic spectroscopies (Kraus et al 2013 arXiv:1311.3923). Carbon monoxide molecules are oriented by combining one-colour and delayed two-colour non-resonant femtosecond laser pulses. High-harmonic generation is used to probe the oriented wave-packet dynamics and reveals that a very high degree of orientation (Nup/Ntotal = 0.73–0.82) is achieved. We further extend this approach to orienting carbonyl sulphide molecules. We show that the present two-pulse scheme selectively enhances orientation created by the hyperpolarizability interaction whereas the ionization-depletion mechanism plays no role. We further control and optimize orientation through the delay between the one- and two-colour pump pulses. Finally, we demonstrate a complementary encoding of electronic-structure features, such as shape resonances, in the even- and odd-harmonic spectrum. The achieved progress makes two-pulse field-free orientation an attractive tool for a broad class of time-resolved measurements.}, author = {Kraus, P M and Baykusheva, Denitsa Rangelova and Wörner, H J}, issn = {1361-6455}, journal = {Journal of Physics B: Atomic, Molecular and Optical Physics}, keywords = {Condensed Matter Physics, Atomic and Molecular Physics, and Optics}, number = {12}, publisher = {IOP Publishing}, title = {{Two-pulse orientation dynamics and high-harmonic spectroscopy of strongly-oriented molecules}}, doi = {10.1088/0953-4075/47/12/124030}, volume = {47}, year = {2014}, } @phdthesis{1403, abstract = {A variety of developmental and disease related processes depend on epithelial cell sheet spreading. In order to gain insight into the biophysical mechanism(s) underlying the tissue morphogenesis we studied the spreading of an epithelium during the early development of the zebrafish embryo. In zebrafish epiboly the enveloping cell layer (EVL), a simple squamous epithelium, spreads over the yolk cell to completely engulf it at the end of gastrulation. Previous studies have proposed that an actomyosin ring forming within the yolk syncytial layer (YSL) acts as purse string that through constriction along its circumference pulls on the margin of the EVL. Direct biophysical evidence for this hypothesis has however been missing. The aim of the thesis was to understand how the actomyosin ring may generate pulling forces onto the EVL and what cellular mechanism(s) may facilitate the spreading of the epithelium. Using laser ablation to measure cortical tension within the actomyosin ring we found an anisotropic tension distribution, which was highest along the circumference of the ring. However the low degree of anisotropy was incompatible with the actomyosin ring functioning as a purse string only. Additionally, we observed retrograde cortical flow from vegetal parts of the ring into the EVL margin. Interpreting the experimental data using a theoretical distribution that models the tissues as active viscous gels led us to proposen that the actomyosin ring has a twofold contribution to EVL epiboly. It not only acts as a purse string through constriction along its circumference, but in addition constriction along the width of the ring generates pulling forces through friction-resisted cortical flow. Moreover, when rendering the purse string mechanism unproductive EVL epiboly proceeded normally indicating that the flow-friction mechanism is sufficient to drive the process. Aiming to understand what cellular mechanism(s) may facilitate the spreading of the epithelium we found that tension-oriented EVL cell divisions limit tissue anisotropy by releasing tension along the division axis and promote epithelial spreading. Notably, EVL cells undergo ectopic cell fusion in conditions in which oriented-cell division is impaired or the epithelium is mechanically challenged. Taken together our study of EVL epiboly suggests a novel mechanism of force generation for actomyosin rings through friction-resisted cortical flow and highlights the importance of tension-oriented cell divisions in epithelial morphogenesis.}, author = {Behrndt, Martin}, pages = {91}, publisher = {IST Austria}, title = {{Forces driving epithelial spreading in zebrafish epiboly}}, year = {2014}, } @article{14301, abstract = {DNA has become a prime material for assembling complex three-dimensional objects that promise utility in various areas of application. However, achieving user-defined goals with DNA objects has been hampered by the difficulty to prepare them at arbitrary concentrations and in user-defined solution conditions. Here, we describe a method that solves this problem. The method is based on poly(ethylene glycol)-induced depletion of species with high molecular weight. We demonstrate that our method is applicable to a wide spectrum of DNA shapes and that it achieves excellent recovery yields of target objects up to 97 %, while providing efficient separation from non-integrated DNA strands. DNA objects may be prepared at concentrations up to the limit of solubility, including the possibility for bringing DNA objects into a solid phase. Due to the fidelity and simplicity of our method we anticipate that it will help to catalyze the development of new types of applications that use self-assembled DNA objects.}, author = {Stahl, Evi and Martin, Thomas and Praetorius, Florian M and Dietz, Hendrik}, issn = {1521-3773}, journal = {Angewandte Chemie International Edition}, number = {47}, pages = {12949--12954}, publisher = {Wiley}, title = {{Facile and scalable preparation of pure and dense DNA origami solutions}}, doi = {10.1002/ange.201405991}, volume = {126}, year = {2014}, } @article{1791, abstract = {Acute gene inactivation using short hairpin RNA (shRNA, knockdown) in developing brain is a powerful technique to study genetic function; however, discrepancies between knockdown and knockout murine phenotypes have left unanswered questions. For example, doublecortin (Dcx) knockdown but not knockout shows a neocortical neuronal migration phenotype. Here we report that in utero electroporation of shRNA, but not siRNA or miRNA, to Dcx demonstrates a migration phenotype in Dcx knockouts akin to the effect in wild-type mice, suggestingshRNA-mediated off-target toxicity. This effect wasnot limited to Dcx, as it was observed in Dclk1 knockouts, as well as with a fraction of scrambled shRNAs, suggesting a sequence-dependent but not sequence-specific effect. Profiling RNAs from electroporated cells showed a defect in endogenous let7 miRNA levels, and disruption of let7 or Dicer recapitulated the migration defect. The results suggest that shRNA-mediated knockdown can produce untoward migration effects by altering endogenous miRNA pathways.}, author = {Baek, SeungTae and Kerjan, Géraldine and Bielas, Stephanie L and Lee, Jieun and Fenstermaker, Ali G and Gaia Novarino and Gleeson, Joseph G}, journal = {Neuron}, number = {6}, pages = {1255 -- 1262}, publisher = {Elsevier}, title = {{Off-target effect of doublecortin family shRNA on neuronal migration associated with endogenous MicroRNA dysregulation}}, doi = {10.1016/j.neuron.2014.04.036}, volume = {82}, year = {2014}, } @article{17977, abstract = {Primary amines can interact with neighbor molecules or with a metal substrate via weak bonds involving the electron lone pair of their amino functional group. Near edge X-ray absorption spectra (NEXAFS) on the N 1s edge show that the structure of the empty molecular orbitals localized on the nitrogen atom is very sensitive to these interactions. Here we investigate the origin of these changes by means of theoretical calculations. NEXAFS spectra are simulated for the 1,4-benzenediamine (BDA) molecule in its free, crystalline, and monolayer on Au(111) forms. We identify the electronic states which are affected by these amino-based interactions. In the case of the molecular layer grown on the gold substrate, we show how the results of the calculations can be used to identify intermolecular interactions influencing adsorption geometries in molecular monolayers.}, author = {Balducci, Gabriele and Romeo, Michele and Stener, Mauro and Fronzoni, Giovanna and Cvetko, Dean and Cossaro, Albano and Dell’Angela, Martina and Kladnik, Gregor and Venkataraman, Latha and Morgante, Alberto}, issn = {1932-7455}, journal = {The Journal of Physical Chemistry C}, number = {4}, pages = {1988--1995}, publisher = {American Chemical Society}, title = {{Computational study of amino mediated molecular interaction evidenced in N 1s NEXAFS: 1,4-diaminobenzene on Au (111)}}, doi = {10.1021/jp512146t}, volume = {119}, year = {2014}, } @article{17978, abstract = {We studied the formation of graphene nanoribbons (GNRs) via the self-assembly of 10,10′-dibromo-9,9′-bianthryl precursor molecules on gold surfaces with different synchrotron spectroscopies. Through X-ray photoemission spectroscopy core-level shifts, we followed each step of the synthetic process, and could show that the Br–C bonds of the precursors cleave at temperatures as low as 100 °C on both Au(111) and Au(110). We established that the resulting radicals bind to Au, forming Au–C and Au–Br bonds. We show that the polymerization of the precursors follows Br desorption from Au, suggesting that the presence of halogens is the limiting factor in this step. Finally, with angle-resolved ultraviolet photoemission spectroscopy and density functional theory we show that the GNR/Au interaction results in an upshift of the Shockley surface state of Au(111) by ∼0.14 eV, together with an increased electron effective mass.}, author = {Batra, Arunabh and Cvetko, Dean and Kladnik, Gregor and Adak, Olgun and Cardoso, Claudia and Ferretti, Andrea and Prezzi, Deborah and Molinari, Elisa and Morgante, Alberto and Venkataraman, Latha}, issn = {2041-6539}, journal = {Chemical Science}, number = {11}, pages = {4419--4423}, publisher = {Royal Society of Chemistry}, title = {{Probing the mechanism for graphene nanoribbon formation on gold surfaces through X-ray spectroscopy}}, doi = {10.1039/c4sc01584c}, volume = {5}, year = {2014}, } @article{17979, abstract = {Using scanning tunneling microscope break-junction experiments and a new first-principles approach to conductance calculations, we report and explain low-bias charge transport behavior of four types of metal–porphyrin–gold molecular junctions. A nonequilibrium Green’s function approach based on self-energy corrected density functional theory and optimally tuned range-separated hybrid functionals is developed and used to understand experimental trends quantitatively. Importantly, due to the localized d states of the porphyrin molecules, hybrid functionals are essential for explaining measurements; standard semilocal functionals yield qualitatively incorrect results. Comparing directly with experiments, we show that the conductance can change by nearly a factor of 2 when different metal cations are used, counter to trends expected from gas-phase ionization energies which are relatively unchanged with the metal center. Our work explains the sensitivity of the porphyrin conductance with the metal center via a detailed and quantitative portrait of the interface electronic structure and provides a new framework for understanding transport quantitatively in complex junctions involving molecules with localized d states of relevance to light harvesting and energy conversion.}, author = {Liu, Zhen-Fei and Wei, Sujun and Yoon, Hongsik and Adak, Olgun and Ponce, Ingrid and Jiang, Yivan and Jang, Woo-Dong and Campos, Luis M. and Venkataraman, Latha and Neaton, Jeffrey B.}, issn = {1530-6992}, journal = {Nano Letters}, number = {9}, pages = {5365--5370}, publisher = {American Chemical Society}, title = {{Control of single-molecule junction conductance of porphyrins via a transition-metal center}}, doi = {10.1021/nl5025062}, volume = {14}, year = {2014}, } @article{17980, abstract = {We study the formation of covalent gold–carbon bonds in benzyltrimethylstannane (C10H16Sn) deposited on Au in ultra-high-vacuum conditions. Through X-ray photoemission spectroscopy and X-ray absorption measurements, we find that the molecule fragments at the Sn–benzyl bond when exposed to Au surfaces at temperatures as low as −110 °C. The resulting benzyl species is stabilized by the presence of Au(111) but only forms covalent Au–C bonds on more reactive Au surfaces like Au(110). We also present spectroscopic proof for the existence of an electronic “gateway” state localized on the Au–C bond that is responsible for its unique electronic properties. Finally, we use DFT-based nudged elastic band calculations to elucidate the crucial role played by the under-coordinated Au surface in the formation of Au–C bonds.}, author = {Batra, Arunabh and Kladnik, Gregor and Gorjizadeh, Narjes and Meisner, Jeffrey and Steigerwald, Michael and Nuckolls, Colin and Quek, Su Ying and Cvetko, Dean and Morgante, Alberto and Venkataraman, Latha}, issn = {1520-5126}, journal = {Journal of the American Chemical Society}, number = {36}, pages = {12556--12559}, publisher = {American Chemical Society}, title = {{Trimethyltin-mediated covalent Gold–Carbon bond formation}}, doi = {10.1021/ja5061406}, volume = {136}, year = {2014}, }