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Piezochromism in Nickel Salicylaldoximato Complexes: Tuning Crystal-Field Splitting with High Pressure

DOI: 10.1002/chem.201200213 DOI Help
PMID: 22615125 PMID Help

Authors: Peter J. Byrne (University of Edinburgh, U.K.) , Patricia J. Richardson (University of Edinburgh, U.K.) , John Chang (University of Edinburgh, U.K.) , Anna F. Kusmartseva (University of Edinburgh, U.K.) , Dave Allan (Diamond Light Source) , Anita C. Jones (University of Edinburgh, U.K.) , Konstantin V. Kamenev (University of Edinburgh, U.K.) , Peter A. Tasker (University of Edinburgh, U.K.) , Simon Parsons (The University of Edinburgh)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Chemistry - A European Journal , VOL 18 (25) , PAGES 7738-7748

State: Published (Approved)
Published: June 2012

Abstract: The crystal structures of bis(3-fluoro-salicylaldoximato)nickel(II) and bis(3-methoxy-salicylaldoximato)nickel(II) have been determined at room temperature between ambient pressure and approximately 6 GPa. The principal effect of pressure is to reduce intermolecular contact distances. In the fluoro system molecules are stacked, and the Ni...Ni distance decreases from 3.19 angstrom at ambient pressure to 2.82 angstrom at 5.4 GPa. These data are similar to those observed in bis(dimethylglyoximato)nickel(II) over a similar pressure range, though contrary to that system, and in spite of their structural similarity, the salicyloximato does not become conducting at high pressure. Niligand distances also shorten, on average by 0.017 and 0.011 angstrom for the fluoro and methoxy complexes, respectively. Bond compression is small if the bond in question is directed towards an interstitial void. A band at 620 nm, which occurs in the visible spectrum of each derivative, can be assigned to a transition to an antibonding molecular orbital based on the metal 3d(x2-y2) orbital. Time-dependent density functional theory calculations show that the energy of this orbital is sensitive to pressure, increasing in energy as the Niligand distances are compressed, and consequently increasing the energy of the transition. The resulting blueshift of the UV-visible band leads to piezochromism, and crystals of both complexes, which are green at ambient pressure, become red at 5 GPa.

Journal Keywords: High-Pressure Chemistry; Nickel; Transition Metals; X-Ray Diffraction

Subject Areas: Chemistry

Instruments: I19-Small Molecule Single Crystal Diffraction

Added On: 08/10/2012 14:25

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