DOI: 10.5281/zenodo.5750748
title: Ultrafast Infrared Transient Absorption Spectroscopy of Gas-Phase Ni(CO)4 Photodissociation at 261 nm

description: This is the data repository for the following publication: Neil C. Cole-Filipiak, Jan Tross, Paul Schrader, Laura M. McCaslin, and Krupa Ramasesha, "Ultrafast infrared transient absorption spectroscopy of gas-phase Ni(CO)4 photodissociation at 261 nm," J. Chem. Phys. 156, 144306 (2022), https://doi.org/10.1063/5.0080844. <strong>Abstract:</strong> We employ ultrafast mid-infrared transient absorption spectroscopy to probe the rapid loss of carbonyl ligands from gas-phase nickel tetracarbonyl following ultraviolet photoexcitation at 261 nm. Here, nickel tetracarbonyl undergoes prompt dissociation to produce nickel tricarbonyl in a singlet excited state; this electronically excited tricarbonyl loses another CO group over tens of picoseconds. Our results also suggest the presence of a parallel, concerted dissociation mechanism to produce nickel dicarbonyl in a triplet excited state, which likely dissociates to nickel monocarbonyl. Mechanisms for the formation of these photoproducts in multiple electronic excited states are theoretically predicted with one-dimensional cuts through the potential energy surfaces and computation of spin–orbit coupling constants using equation of motion coupled cluster methods (EOM-CC) and coupled cluster theory with single and double excitations (CCSD). Bond dissociation energies are calculated with CCSD, and anharmonic frequencies of ground and excited state species are computed using density functional theory (DFT) and time-dependent density functional theory (TD-DFT). <strong>Experimental Data:</strong> All data are saved as a .csv file. The first column contains frequencies (in cm<sup>-1</sup>) while the first row indexes each time delay (in ps). High-resolution transient spectra at select time delays are similarly structured. Each transient .csv file is labeled according to molecule, pump wavelength, file contents, pump laser power, pressure, and a date (<em>e.g.</em> NT261_trans_1mW_1.5torr_17Feb2021.csv). <strong>Computational Data:</strong> This data repository consists of 7 directories, which contain the data used in the main paper. Computational data published in the supplementary material may be requested from the corresponding authors. Anharmonic frequencies and DFT energies can be obtained in the directory "VPT2", where the files are labelled nicoX_*_anharm.out, where X=3,2,1 (the compound) and * corresponds to the electronic state for which the calculation was performed. EOM-CC calculations of the spin-orbit coupling constants at the geometries reported are found within the "SOCC" directory using the naming convention nicoX_[]_so_*.out, where X=3,2, []=an indication of the geometry, and * corresponds to the electronic state for which the calculation was performed. Calculations of the minimum energy crossing points (MECPs) can be found in the directory "MECP" using the naming convention nicoX_min*.out, where X=4,3,2,1, and * corresponds to the two electronic states for which the MECP is calculated (e.g. s0s1). The following 4 directories contain all the EOM-CC output files needed to reproduce the curves from Figure 2: 4to3, 3to2, 4to2, and 2to1, corresponding to panels a, b, c, and d, respectively. The naming conventions for the files within these directories are X_yz.out, where X=the name of the directory, y=the value of the reaction coordiante, and z=s (singlet) or t (triplet).