Tetracyanonickelate(II) has been a poster child of ligand field theory for several decades. We have revisited the literature assignments of the absorption spectrum of [Ni(CN) 4 ] 2− and the calculated ordering of orbitals with metal d character. Using lowtemperature single-crystal absorption spectroscopy and accurate ab initio and density functional quantum mechanical methods (NEVPT2-CASSCF, EOM-CCSD, TD-DFT), we find an ordering of the frontier d-and p-orbitals of xy < xz, yz < z 2 < z < x 2 −y 2 < x, y and assign the d-d bands in the absorption spectrum to 1 A
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