Viewing upcoming talks containing the keyword: 20
-
St Andrews
Multifunctional and Stimuli-responsive Coordination Cages
Speaker: Guido Clever (Dortmund)
Multifunctional and Stimuli-responsive Coordination Cages G. H. Clever * Department of Chemistry and Chemical Biology, TU Dortmund University, Germany guido.clever@tu -dortmund.de Banana -shaped bis-monodentate ligands react with Pd(II) cations to coordination compounds with a broad range of topologies from small Pd 2L4 cages, their interpenetrated dimers, rings of various size up to large Pd 24L48 spheres. 1 We introduce stimuli-responsive behaviour triggered by small molecules or light leading to the modulation of guest affinity 2 or complete structural reorganization (Figure a). 3 Interpenetrated double cages consisting of donor and acceptor moieties were shown to undergo light-induced charge separation but suffer from a lack of control over stoichiometry and stereochemistry (Figure b). 4 Therefore, we recently started to apply principles of geometric shape complementarity to control the structure and composition of heteroleptic cages (Figure c). 5 On the other hand, circularly polarized luminescence (CPL) was observed for chiral Pt(II) complexes (Figure d). 6 Advanced self -assembly strategies will enable the targeted synthesis of supra-molecular systems and materials with increasing structural and functional complexity. Figure 1 Light -responsive coordination cages and chiral organometallic luminophors 1. Reviews: a) M. Han, D. M. Engelhard, G. H. Clever, Chem. Soc. Rev. 2014, 43, 1848; b) M. Frank, M. D. Johnstone, G. H. Clever, Chem. Eur. J. 2016 , 22 , 14104. Recent examples: c) W. M. Bloch, J. J. Holstein, B. Dittrich, W. Hiller, G. H. Clever, Angew. Chem. Int. Ed. 2018, 57, 5534; d) R. Zhu, I. Regeni, J. J. Holstein, B. Dittrich, M. Simon, S. Prévost, M. Gradzielski, G. H. Clever, Angew. Chem. Int. Ed. 2018 , DOI: 10.1002/ani e.201806047. 2. a) S. Löffler, J. Lübben, L. Krause, D. Stalke, B. Dittrich, G. H. Clever, J. Am. Chem. Soc. 2015, 137, 1060; b) M. Han, R. Michel, B. He, Y. -S. Chen, D. Stalke, M. John, G. H. Clever, Angew. Chem. Int. Ed. 2013 , 52 , 1319. 3. a) R. Zhu, J. Lübben, B. Dittrich, G. H. Clever, Angew. Chem. Int. Ed. 2015, 54, 2796; b) M. Han, Y. Luo, B. Damaschke, L. Gómez, X. Ribas, A. Jose, P. Peretzki, M. Seibt, G. H. Clever, Angew. Chem. Int. Ed. 2016, 55 , 445 . 4. M. Frank, J. Ahrens, I. Bejenke, M. Krick, D. Schwarzer, G. H. Clever, J. Am. Chem. Soc. 2016 , 138 , 8279. 5. a) W. M. Bloch, Y. Abe, J. J. Holstein, C. M. Wandtke, B. Dittrich, G. H. Clever, J. Am. Chem. Soc. 2016, 138, 13750; b) W. M. Bloch, J. J. Holstein, W. Hiller, G. H. Clever, Angew. Chem. Int. Ed. 2017 , 56 , 8285. 6. T. R. Schulte, J. J. Holstein, L. Krause, R. Michel, D. Stalke, E. Sakuda, K. Umakoshi, G. Longhi, S. Abbate, G. H. Clever, J. Am. Chem. Soc. 2017 , 139 , 6863.On: November 28, 2018 From: 14h00 To: 15h00
View talk -
St Andrews
Photoswitchable Organometallics
Speaker: Zoraida Freixa (University of the Basque Country, San Sebastian, Spain)
PHOTO SWITCHABLE ORGANOMETALLICS. Zoraida Freixa 1,2 1 Department of Applied Chemistry, Faculty of Chemistry, University of the Basque Country (UPV -EHU), Donostia -San Sebastián, 20018, Spain 2 IKERBASQUE, Basque Foundation for Science, 48011, Bilbao, Spain Zoraida_freixa@ehu.eus In the last few decades, the development of photoresponsive materials has become an intensive area of research. These substances are intended for the production of “smart chemical systems”, whose properties — and eventually functionality — are controlled by changes of the environment (light irradiation). These systems have been already implemented in a wide range of modern materials and devices for daily applications such as sunglass lenses, memory devices, photochromic inks, etc. In spite of the importance and versatility of organometallic complexes, smart photoresponsive examples remain rather unexplored in comparison with the plethora of well known light -triggered organic switches. In principle, photoresponsive metal complexes can be obtained by incorporation of organic photochromic units in the structure of their ligands. These photosensitive ligands, rather than acting as conventional spectators that tune the properties of their complexes, transform them into dynamic smart entities able to offer a functional response to an external stimulus. 1 In our group, we work on the development of such photoresponsive organometallics for diverse applications. We have explored several areas of application exploding some of the most prominent properties of organometallics. Namely, their luminescence, catalytic activity or their potential use as metallodrugs. As will be discussed, the compatibility of the metal coordination and the photoresponse of the molecular switch is an issue that needs to be carefully addressed. 1. Crabtree, R. H., Multifunctional ligands in transition metal catalysis. New J. Chem. 2011, 35, 18 -23. Website: www.freixagroup.comOn: November 29, 2018 From: 14h00 To: 15h00
View talk -
St Andrews
Using ab initio approaches to model, predict and understand the optical properties of organic and inorganic dyes - Joint Chemistry/Physics Colloquium
Speaker: Denis Jacquemin (Nantes)
Using ab initio approaches to model, predict and understand the optical properties of organic and inorganic dyes Denis Jacquemin Laboratoire CEISAM, UMR CNRS n°6230, Université de Nantes, 2, rue de la Houssinière, 44322 Nantes, Cedex 3, France. Denis.Jacquemin@univ -nantes.fr During this lecture, I will illustrate some of the successes and failures of Time-Dependent Density Functional Theory (TD -DFT) in simulating the properties of electronically excited -states, with a specific interest on structures of interest for dye chemistry. 1-2 Notably, I will discuss the importance of calculating vibronic effects to obtain accurate comparisons with experimental data, including 0 -0 energies and band shapes, and illustrate this aspect with several examples. 3 I will also present examples of applications of TD -DFT to real-life structures used in LEDs focussing on two examples: ESIPT -based organic dyes for white OLEDs 4 and inorganic complexes used in blue/green/red phosphors. 5 1 D. Jacquemin, C. Adamo, Chem. Soc. Rev., 2013, 42, 845 . 2 D. Jacquemin, C. Adamo, Top. Curr. Chem.. , 2016 , 368 , 345 . 3 F. Santoro, D. Jacquemin, Wires. Comput. Mol. Sci. 2016, 6, 460. 4 A. Steffen, K. Costuas, A. Bouccekkine, M. H. Thibault, A. Beeby, A. S. Batsanov, D. Jacquemin, A. Charaf -Eddin, J. F. Halet, T. D. Marder Inorg. Chem. , 2014 , 53 , 7055 . 5 E. Heyer, K. Benelhadj, S. Budzak, D. Jacquemin, J. Massue, G. Ulrich Chem. Eur. J ., 2017, 23, 7324 . 6 D W . Zhang, D. Jacquemin, Q. Peng, Z. Suhai, D. Escudero, J. Phys. Chem. C, 2018 , 122 , 6340 .On: February 6, 2019 From: 14h00 To: 15h00
View talk -
St Andrews
Probing Ultrafast Chemical Dynamics Inspired by the Rhythms of Fireflies
Speaker: Greg Scholes (Princeton)
Probing Ultrafast Chemical Dynamics Inspired by the Rhythms of Fireflies Coherence phenomena arise from interference, or the addition, of wave -like amplitudes in phase [1] . While coherence has been shown to yield transformative new ways for improving function, advances have been limited to pristine matter, as quantum coherence is considered fragile. Here I will discuss how vibrational an d vibronic wavepackets entrain ensembles of molecules, like the synchronized flashing of fireflies . I will discuss how this can be used to probe mechanisms of ultrafast dynamics and how in -step vibrational motion might be employed to control function on ul trafast timescales. I will give examples that include light -harvesting in photosynthesis, energy flow in organometallic molecules that is ‘wired’ by Fermi resonance, and ultrafast electron transfer in molecular systems. [1] Scholes, et al. “Optimal Coherence in Chemical and Biophysical Dynamics” Nature 543, 647 – 656 (2017) .On: February 11, 2019 From: 13h00 To: 14h00
View talk -
St Andrews
Probing and harnessing the hydrophobic and Hofmeister Effects
Speaker: Prof Bruce Gibb (Tulane University)
Probing and harnessing the hydrophobic and Hofmeister Effect s A better understanding of how molecules interact in aqueous solutions has ramifications a cross the biosph ere, lithosphere, atmosphere, and hydrosphere . For example, aqueous solutions of dissolved organic molecul es and salts are central to all of biolo gy and biochemistry . Un surprisingly, documented studies of h ow organic solutes, dissolved sa lts, and water interact with each othe r arguably go back to at least the late 18 th Centur y with Franz Hoffmeister ’s seminal work on protein solubility . However, to date no comprehensive atomistic model of the interactions between this trinity of solute, s alt, and water has been forthcoming. For some time now , our research has focused on building up an atomistic view point of aqueous supramolecular chemistry. In doing so we envis age not only being able to subtly engineer and contro l specific molecular inte ractions at the atomistic level to engender un usu al phenomena , but also apply this information to build ing a better understanding of bulk phenomena such as solubility . This presentation will focus on o ur recent stu dies into aqueous supramolecular interact ions uti liz ing deep -cavity cavitands as models . We will discuss how these interactions control the bulk prop erties of the hosts, and how they can b e harnessed to yield novel supramolecular containers that function as yoctoliter reaction vess els and tools for bringing about separation protocols. 1 References 1. (a) Jordan, J. H.; Gibb, C. L. D.; Wishard, A.; Pham, T.; Gibb, B. C., J. Am. Chem. Soc. 2018, 140 (11), 4092 -4099; (b) Hill yer, M. B.; Ga n, H.; Gibb, B. C., ChemPhysC hem 2018, 19 (18), 2285 -2289; (c) Sokkalingam, P.; Shraberg, J.; Rick, S. W.; Gibb, B. C., J. Am. Chem. Soc. 2016, 138 (1), 48 -51; (d) Wa ng, K.; Gibb, B. C., J. Org. ChOn: February 19, 2019 From: 16h00 To: 16h30
View talk -
St Andrews
Tailoring the Photophysics of First-row Transition Metal-based Chromophores for Light Capture and Conversion: Challenges and Opportunities
Speaker: Jim McCusker (Michigan State)
https://talks.st-andrews.ac.uk/index.php?talks/talk_details/990
Figure 1. P lot of the ground state recovery dynamics of [Fe(bpy) 3 ](PF 6 ) 2 in CH 3 CN solution as a function of temperature following 1 A 1 ® 1 MLCT excitation . The solid line corresponds to a fit of the data to an Arrhenius mod el, indicating an activation energy of 310 ± 15 cm -1 and an intercept (i.e., the rate constant in the limit of no barrier) of 230 ± 20 ps -1 . An analysis of these data in the context of semiclassical non - radiative decay theory is providing new insights into the factors controlling ultrafast dynamics in such systems. Tailoring the Photophysics of First - row Transition Metal - based Chromophores for Light Capture and Conversion: Challenges and Opportunities James K. McCusker Department of Chemistry, Michigan State University The conversion of light to chemical energy is one of the most fundamental processes on Earth. It is the basis of photosynthesis, in which light absorption results in the separation of charge that ultimately creates the chemical potential needed to drive ATP synthesis; an advantageous by - product of th is process is, of course, O 2 production. Ironically, photosynthesis is also the source of the biomass from which the fossil fuels that constitute the basis of society’s energy infrastructure are derived. The overwhelming majority of climate scientists are in agreement that it is the burning of these fossil fuels – in effect the re - release of what was sequestered carbon into the atmosphere – that is driving global climate change. Options for shifting away from fossil fuels as our primary energy source genera lly revolve around renewables such as wind, solar, biomass, nuclear, geothermal, and hydro: of these, the only renewable energy source that is limitless and carbon - free (at least in principle) is solar. The energy flux hitting the Earth is 120,000 TW: inte grated over a 24 - hour period, this translates to humankind’s total energy budget for an entire year. Despite the progress that has been made in the implementation of solar energy (due primarily to reductions in the cost of silicon), the intermittent nature of solar energy, the balance of systems costs that continue to represent a significant economic obstacle, combined with the fact that electricity constitutes only ~30% of the global energy footprint all underscore the need for continued research in solar energy conversion science. Fundamental research on solar energy conversion – which will ultimately lead to the next generation of solar energy technologies – has sought to replicate Nature’s solution through the creation of artificial constructs that mimic va rious aspect of photosynthesis. When considering large - scale (i.e., global) implementation of any solar energy conversion scheme, material availability becomes a critically important consideration in the light - capture part of the problem, particularly w hen one considers the projected two - to three - fold increase in energy de mand over the next 30 - 40 years. Unfortunately, virtually all of the molecule - based approaches for solar energy conversion that have been proven successful rely on some of the least abu ndant elements on earth. An obvious alternative is to employ chromophores based on earth - abundant materials: for transition metal - based approaches, this means moving away from the second - and third - row transition series elements (e.g., ruthenium) and devel op photoredox - active chromophores based on first - row, widely available metals like iron and copper. As our group first demonstrated in 2000, the central problem with this approach is that the charge - transfer excited states that lie at the heart of photo - in duced electron transfer chemistry exhibit sub - picosecond lifetimes (as compared to the microsecond lifetimes of their 2 nd - and 3 rd - row congeners). Our research program therefore focuses on understanding the factors that determine the dynamics associated wi th the excited states of first - row transition metal - based chromophores, with the ultimate goal of circumventing and/or redefining their intrinsic photophysical properties in order to make feasible their use as light - harvesting components in solar energy co nversion schemes . This seminar will describe the key experimental results establishing this paradigm, as well as survey several approaches that we are pursuing in an effort to broaden the utility of this class of chromophores for a wide range of solar ener gy and chemical transformations
On: March 4, 2019 From: 13h00 To: 14h00
View talk