Density functional methods have been applied to calculate the quadrupole splitting of a series of iron(II) spin crossover complexes. Experimental and calculated values are in reasonable agreement. In one case spin-orbit coupling is necessary to explain the very small quadrupole splitting value of 0.77 mm/s at 293 K for a high-spin isomer.
@article{arxiv.1206.3036,
title = {DFT Calculations as a Tool to Analyse Quadrupole Splittings of Spin Crossover Fe(II) complexes},
author = {Juliusz Adam Wolny and Hauke Paulsen and Heiner Winkler and Alfred Xaver Trautwein and Jean-Pierre Tuchagues},
journal= {arXiv preprint arXiv:1206.3036},
year = {2012}
}