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Steady-State and Pseudo-Steady-State Photocrystallographic Studies on Linkage Isomers of [Ni(Et4dien)(h2-O,ON)(h1-NO2)]: Identification of a New Linkage Isomer

DOI: 10.1002/chem.201304172 DOI Help
PMID: 24519880 PMID Help

Authors: Lauren Hatcher (University of Bath) , Jeppe Christensen (Lund University) , Michelle Hamilton , Jose Trincao (University of Bath) , Dave Allan (Diamond Light Source) , Ian P. Clarke (Central Laser Facility, STFC Rutherford Appleton Laboratory) , Mike Towrie (Research Complex at Harwell) , Sara Fuertes (University of Bath) , Charles C. Wilson (University of Bath) , Christopher Woodall (University of Bath) , Paul Raithby (University of Bath) , Mark Warren (Diamond Light Source)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Chemistry - A European Journal

State: Published (Approved)
Published: February 2014

Abstract: At temperatures below 150 K, 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 500 nm light, in the single crystal by steady-state photocrystallographic techniques. Kinetic studies show the system is no longer metastable above 150 K, decaying back to the ground state nitro-(η1-NO2) arrangement over several hours at 150 K. Variable-temperature kinetic measurements in the range of 150–160 K show that the rate of endo-nitrito decay is highly dependent on temperature, and an activation energy of Eact=+48.6(4) kJ mol−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. 140–190 K). 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.

Journal Keywords: Linkage Isomers · Metastable States · Nitro Complexes · Photocrystallography · Solid-State Kinetics

Subject Areas: Chemistry

Instruments: I19-Small Molecule Single Crystal Diffraction