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Speaker:
E W Meijer (Eindhoven University of Technology)
The intriguing prospects of molecular electronics, nanotechnology, biomaterials, and the aim to close the gap between synthetic and biological molecular systems are important ingredients to study the cooperative action of molecules in the self-assembly towards functional supramolecular systems. The design and synthesis of well-defined supramolecular architectures requires a balanced choice between covalent synthesis and the self-assembly of the fragments prepared. The current self-assembly processes are primarily controlled by solvent, temperature or concentration. For synthetic chemists, the non-covalent synthesis of these supramolecular architectures is regarded as one of the most challenging objectives in science: How far can we push chemical self-assembly and can we get control over the kinetic instabilities of the non-covalent architectures made? How can we go from self-assembly to self-organization? Where the number of different components is increasing the complexity of the system is increasing as well. Mastering this complexity is a prerequisite to achieve the challenges in creating functional systems. In the lecture we illustrate our approach using a number of examples out of our own laboratories, with the aim to come to new strategies for multi-step non-covalent synthesis of functional supramolecular systems.
Speaker:
Jeff Long (University of California, Berkeley)
Owing to their high surface
areas, tunable pore dimensions, and adjustable surface functionality,
metal-organic frameworks (MOFs) can offer advantages for a variety of gas
storage and gas separation applications.Â
In an effort to help curb greenhouse gas emissions from power plants, we
are developing new MOFs for use as solid adsorbents in post- and pre-combustion
CO2 capture, and for the separation of O2 from air, as
required for oxy-fuel combustion.1Â
In particular, MOFs with open metal cation sites or
diamine-functionalized surfaces are demonstrated to provide high selectivities
and working capacities for the adsorption of CO2 over N2
under dry flue gas conditions.2Â
Multicomponent adsorption measurements further show compounds of the
latter type to be effective in the presence of water,3 while
calorimetry and temperature swing cycling data reveal a low regeneration energy
compared to aqueous amine solutions.4Â MOFs with open metal sites, such as Mg2(dobdc)
(dobdc4– = 2,5-dioxido-1,4- benzenedicarboxylate), are highly
effective in the removal of CO2 under conditions relevant to H2
production, including in the presence of CH4 impurities.5Â Redox-active Fe2+ sites in the
isostructural compound Fe2(dobdc) allow the selective adsorption of
O2 over N2 via an electron transfer mechanism.6Â The same material is demonstrated to be
effective at 45 °C for the fractionation of mixtures of C1 and C2 hydrocarbons,
and for the high-purity separation of ethylene/ethane and propylene/propane
mixtures.7Â Finally, it will
be shown that certain structural features possible within MOFs, but not in
zeolites, can enable the fractionation of hexane isomers according to the
degree of branching or octane number.8
 References
1.    Â
Sumida, K.; Rogow, D. L.; Mason, J. A.; McDonald, T. M.; Bloch, E.
D.; Herm, Z. R.; Bae, T.-H.; Long, J. R. Chem.
Rev. 2012, 112, 724.
2.    Â
McDonald, T. M.; Lee, W. R.; Mason, J. A.; Wiers, B. M.; Hong, C.
S.; Long, J. R. J. Am. Chem. Soc. 2012, 134, 7056.
3.    Â
Mason, J. A.; McDonald, T. M.; Bae, T.-H.; Bachman, J. E.; Sumida,
K.; Dutton, J. J.; Kaye, S. S.; Long, J. R. J.
Am. Chem. Soc. 2015, 137, 4787.
4.    Â
McDonald, T. M.; Mason, J. A.; Kong, X.; Bloch, E. D.; Gygi, D.;
Dani, A.; Crocellà , V.; Giordano, F.; Odoh, S.; Drisdell, W.; Vlaisavljevich, B.;
Dzubak, A. L.; Poloni, R.; Schnell, S. K.; Planas, N.; Kyuho, L.; Pascal, T.;
Prendergast, D.; Neaton, J. B.; Smit, B.; Kortright, J. B.; Gagliardi, L.; Bordiga, S.; Reimer, J. A.;
Long, J. R. Nature 2015, 519, 303.
5.    Â
Herm, Z. R.; Swisher, J. A.;
Smit, B.; Krishna, R.; Long, J. R. J. Am.
Chem. Soc. 2011, 133, 5664.
6.    Â
Bloch, E. D.; Murray, L. J.;
Queen, W. L.; Maximoff, S. N.; Chavan, S.; Bigi, J. P.; Krishna, R.; Peterson,
V. K.; Grandjean, F.; Long, G. J.; Smit, B.; Bordiga, S.; Brown, C. M.; Long,
J. R. J. Am. Chem. Soc. 2011, 133, 14814.
7.    Â
Bloch, E. D.; Queen, W. L.;
Krishna, R.; Zadrozny, J. M.; Brown, C. M.; Long, J. R. Science 2012, 335, 1606.
8.    Â
Herm, Z. R.; Wiers, B. M.; Mason, J. A.; van Baten, J. M.; Hudson,
M. R.; Zajdel, P.; Brown, C. M.; Masciocchi, N.; Krishna, R.; Long, J. R. Science 2013, 340, 960.
Speaker:
Prof Andrew Beeby (The University of Durham)
After a long career making and studying a diverse range of luminescent materials my research turn an unexpected turn. I was asked “Could you use spectroscopy to analyse the paint in an old book?”. Surprisingly little is known about the paints and colours used to paint the vibrant illuminations in medieval manuscripts, some dating back as far as the 6th century. Analysing them is non-trivial: any methods have to be non-sampling and non-damaging and made in the library that owns the non-priceless books. Thus was born ’Team-Pigment’ a collaboration between chemists, historians, conservation scientists and librarians. Together we have studied over 250 manuscripts created between the 6th and 15th centuries and our systematic work has begun to reveal patterns in pigment use through the ages.
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.
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
Speaker:
Professor James McCusker (Michigan State University)
The information on this talk is not live. For up-to-date details please visit:https://www.strath.ac.uk/science/chemistry/events/
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