Author: Son Chi Nguyen Publisher: ISBN: Category : Languages : en Pages : 102
Book Description
Vibrational spectroscopy is a powerful tool for structural characterization. Modern spectroscopy has been used ultrashort laser pulses in infrared region to monitor the structure evolution of species involving in chemical reaction. This spectroscopic technique can give dynamics of chemical reaction in ultrafast timescale, helping us understand the reaction mechanism in great detail. In this thesis, a wide range of ultrafast dynamics in solution triggered via photochemical reactions has been investigated: the photoisomerization mechanism of solar storage molecules (Fulvalene)tetracarbonyldiruthenium, the photo-inactive of analog molecules (Fulvalene)tetracarbonyldiiron, the spin state and reactivity of 14-electron species Fe(CO)3 and the heat transfer from various photochemical reaction to solvent. Finally, the dynamics of molecular rotational diffusion was also investigated to measure the effect of molecular mass on rotational motion of small solute in solution. The trends discovered from these prototypical complexes are expected to be applicable to other organometallics complexes. These results will have a great contribution to the ultrafast spectroscopy as well as the synthesis research community.
Author: Justin Lomont Publisher: ISBN: Category : Languages : en Pages : 186
Book Description
Ultrafast time-resolved infrared spectroscopy provides a powerful tool for studying the photochemistry of organometallic complexes. The studies described herein focus on the mechanisms of photochemically initiated organometallic reactions with a particular emphasis on two topics: the role of spin states and spin state changes in organometallic reactions, and the primary photochemical dynamics of complexes containing metal-metal bonds (e.g. transition metal dimers and clusters). Many of these studies seek to uncover trends in reactivity based on the spin states of organometallic reaction intermediates, with the goal of being able to offer some level of predictive insight into the reactivity of complexes as classified by their spin multiplicity. The reactivity of various coordinatively unsaturated reaction intermediates are studied with respect to bond activation, electron transfer, excited state photoisomerization, and other classes of reactions important to organometallic catalysis. A second focus, which shares some degree of overlap with the topic of spin state changes, is the primary photochemistry of complexes containing metal-metal bonds. Several of the studies reported herein use time-resolved infrared spectroscopy to examine the primary photochemical processes occurring upon excitation of transition metal dimers and clusters, and often spin state changes also found to play an important role. Results of computational chemistry calculations are frequently used to facilitate interpretation of the experimental results by computation of structures, relative energies, infrared spectra, and spin-orbit coupling for the complexes studied experimentally. Additional studies outside these two primary areas of focus also investigated the ring-slippage of cyclopentadienyl ligands and the CO-delivery properties of a popular CO-Releasing Molecule.
Author: Jacob Peter Schlegel Publisher: ISBN: Category : Languages : en Pages : 130
Book Description
Two systems were studied using either a pump-probe spectroscopic technique or a density functional theory computational method. Ultrafast time-resolved infrared spectroscopy has been used to investigate the reactivity of V(CO)5, a doublet species, with silicon-hydrogen and carbon-hydrogen bonds. Using a ultraviolet pump pulse, a carbonyl was dissociated from V(CO)6 while dissolved in triethylsilane; subsequently, a broad bandwidth infrared pulse interrogated the system. On timescales less than 1 ns, vanadium pentacarbonyl does not appear to react. The second study used the Growing String Method incorporating density functional theory to examine the possible reaction mechanisms for the fluxional rearrangement of Fe3(CO)12 and Ru3(CO)12. Fluxional mechanisms have structurally identical reactants and products; the atoms swap positions with other atoms of the same element. The concerted bridge-opening, bridge-closing mechanism for the Fe3(CO)12 was calculated to have the lowest barrier of those tested at 0.777 kcal/mol; in this mechanism, all twelve carbonyl change position and the final structure is equivalent to the initial structure. At 4.285 kcal/mol, the next lowest energy barrier was calculated for the Cotton's Merry-Go-Round mechanism.
Author: Publisher: ISBN: Category : Languages : en Pages : 228
Book Description
One and two dimensional time-resolved vibrational spectroscopy has been used to investigate the elementary reactions of several prototypical organometallic complexes in room temperature solution. The electron transfer and ligand substitution reactions of photogenerated 17-electron organometallic radicals CpW(CO)3 and CpFe(CO)2 have been examined with one dimensional spectroscopy on the picosecond through microsecond time-scales, revealing the importance of caging effects and odd-electron intermediates in these reactions. Similarly, an investigation of the photophysics of the simple Fischer carbene complex Cr(CO)5[CMe(OMe)] showed that this class of molecule undergoes an unusual molecular rearrangement on the picosecond time-scale, briefly forming a metal-ketene complex. Although time-resolved spectroscopy has long been used for these types of photoinitiated reactions, the advent of two dimensional vibrational spectroscopy (2D-IR) opens the possibility to examine the ultrafast dynamics of molecules under thermal equilibrium conditions. Using this method, the picosecond fluxional rearrangements of the model metal carbonyl Fe(CO)5 have been examined, revealing the mechanism, time-scale, and transition state of the fluxional reaction. The success of this experiment demonstrates that 2D-IR is a powerful technique to examine the thermally-driven, ultrafast rearrangements of organometallic molecules in solution.
Author: Son Chi Nguyen
Author: Justin Lomont
Author: Jacob Peter Schlegel
Author: Elizabeth Anne Glascoe
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Author: James Francis Cahoon
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Author: Steven Eric Bromberg
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Author: American Chemical Society. Committee on Professional Training