The UV/Vis Spectrum of Potassium Heptacyanovanadate(III): A Theoretical Multi‐Reference Configuration Interaction Study Combined with Low‐Temperature Experiments

Abstract

The electronic spectrum of K 4 [V(CN) 7 ] has been calculated by means of a combined quantum chemical density functional and multi-reference configuration interaction scheme. In addition to the states known so far, our calculations predict the existence of two low-lying triplet electronic states with excitation energies of 13600 and 13700 cm -1 , respectively. Both result from d eЈЈ 1 Ǟ d eЈ 2 excitations in the slightly distorted pentagonal-bipyramidal ligand field. To validate these

Magnetostructural and EPR Studies of Anisotropic Vanadium trans-Dicyanide Molecules

“…The V(1)CN distance of 2.168(2) Å is slightly longer than the corresponding distances reported for (Et 4 N) 3 [V­(CN) 6 ] [2.127(3) Å], K 4 [V­(CN) 7 ]·2H 2 O [2.147(7) Å], (Et 4 N)­[Tp*V­(CN) 3 ] [2.085(7) Å], and [(cyclen)­V­(CN) 3 ] [2.160(6) Å]. The cyanide ligands are nearly linear with a VCN angle of 179.6(2)°; the CN bond distance of 1.150(3) Å is typical for vanadium cyanide complexes. − ,, The chelate ring of the acetylacetonate ligand is twisted out of the coordination plane with a dihedral angle of ∼19.2°.…”

“…49 The V(1)CN distance of 2.168(2) Å is slightly longer than the corresponding distances reported for (Et 16 3) Å is typical for vanadium cyanide complexes. [12][13][14][15][16]24,25 The chelate ring of the acetylacetonate ligand is twisted out of the coordination plane with a dihedral angle of ∼19.2°.…”

“…Surprisingly, the ν(CN) stretching mode for 1 is shifted to a lower frequency compared to the corresponding modes observed for simple cyanide salts, whereas for 2−4, the vibration shifts to higher frequencies and lies within the range of other reported vanadium cyanide precursors. [12][13][14][15][16]25 The presence of the coordinated Schiff base ligands in 2−4 is indicated by the ν(CN) stretching frequencies of the imine group at 1618−1666 cm −1 .…”

“…Despite the advantages that one could obtain by incorporating V III ions into molecular magnets containing cyanide, there are only a few well-known vanadium cyanide building blocks, − specifically K 4 [V­(CN) 6 ], K 3 [VO­(CN) 5 ], K 4 [V­(CN) 7 ]·2H 2 O, and (Et 4 N) 3 [V­(CN) 6 ], most likely due to the tendency for low valent vanadium complexes to decompose in the presence of oxygen and water. − Indeed, the incorporation of the hexacyano-vanadate­(III) anion [V III (CN) 6 ] 3– into PB-type materials has proven to be difficult because of the ease of oxidation of V III to V IV , but the room temperature cyanide-based magnet, V II 0.42 ­V III 0.58 ­[Cr III ­(CN) 6 ] 0.86 ·2.8H 2 O ( T C = 315 K), reported by Verdaguer’s group is a notable example of a vanadium containing molecule-based extended magnet . It is also important to point out that the first room temperature molecule-based magnet, V­(TCNE) 2 ( T C = 350 K), reported by Miller et al is also based on vanadium, albeit V II and not V III …”

Assessing the density functional theory-based multireference configuration interaction (DFT/MRCI) method for transition metal complexes

“…5 A parallel code has been recently developed 6 to facilitate the calculation of electronic spectra of larger molecules. However, there are yet only few DFT/MRCI applications to TM complexes, for example, tests for ferrocene, 3 heptacyanovanadate(III), 7 and the uranyl(VI) ion. 8 In this contribution, we present a DFT/MRCI study of the electronically excited states of several TM complexes, for which reliable highly accurate ab initio data have recently become available in the literature.…”