Steady-state and pseudo-steady-state photocrystallographic studies on linkage isomers of [Ni(Et4dien)(η2-O,ON)(η1-NO2)]: Identification of a new linkage isomer

Lauren E. Hatcher, Jeppe Christensen, Michelle L. Hamilton, Jose Trincao, David R. Allan, Mark R. Warren, Ian P. Clarke, Michael Towrie, D S Fuertes, Charles C. Wilson, Christopher H. Woodall, Paul R. Raithby

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Abstract

At temperatures below 150K, the photoactivated metastable endo-nitrito linkage isomer [Ni(Et4dien)(η2-O,ON)(η1-ONO)] (Et4dien=N,N,N',N'-tetraethyldiethylenetriamine) can be generated with 100% conversion from the ground state nitro-(η1-NO2) isomer on irradiation with 500nm light, in the single crystal by steady-state photocrystallographic techniques. Kinetic studies show the system is no longer metastable above 150K, decaying back to the ground state nitro-(η1-NO2) arrangement over several hours at 150K. Variable-temperature kinetic measurements in the range of 150-160K show that the rate of endo-nitrito decay is highly dependent on temperature, and an activation energy of Eact=+48.6(4)kJmol-1 is calculated for the decay process. Pseudo-steady-state experiments, where the crystal is continually pumped by the light source for the duration of the X-ray experiment, show the production of a previously unobserved, exo-nitrito-(η1-ONO) linkage isomer only at temperatures close to the metastable limit (ca. 140-190K). This exo isomer is considered to be a transient excited-state species, as it is only observed in data collected by pseudo-steady-state methods.
Original languageEnglish
Pages (from-to)3128-3134
Number of pages7
JournalChemistry - A European Journal
Volume20
Issue number11
Early online date12 Feb 2014
DOIs
Publication statusPublished - 10 Mar 2014

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