Embracing ligands. Synthesis, characterisation and the correlation between⁵⁹Co NMR and ligand field parameters of Co(iii) complexes with a new class of nitrogen–thioether multidentate ligand

Abstract

The syntheses of the hexadentate ligands 2,2,10,10-tetra(methyleneamine)-4,8-dithiaundecane (PrN 4 S 2 amp), 2,2,11,11-tetra(methyleneamine)-4,9-dithiadodecane (BuN 4 S 2 amp), and 1,2-bis(4,4-methyleneamine)-2-thiapentyl)benzene (XyN 4 S 2 amp) are reported and the complexes [Co(RN 4 S 2 amp)] 3ϩ (R = Pr, Bu, Xy) characterised by single crystal X-ray study. The low-temperature (11 K) absorption spectra have been measured in Nafion films. From the observed positions of both spin-allowed 1 A 1g 1 T 1g and 1 A 1g 1 T 2g and spin forbidden 1 A 1g 3 T 1g and 1 A 1g 3 T 2g bands, octahedral ligand-field parameters (10D q , B and C ) have been determined. DFT calculations suggest that significant interaction between the d-d and CT excitations occurs for the complexes. The calculations offer an explanation for the observed deviations from linearity of the relationship between 59 Co magnetogyric ratio and β(∆E ) Ϫ1 (β = the nephelauxetic ratio; ∆E the energy of the 1 A 1g 1 T 1g transition) for a series of amine and mixed amine/thioether donor complexes.

A computational study of the electronic structure, bonding, and spectral properties of tripodal tetraamine Co(iii) carbonate complexes

“…A comparison of calculated (condensed phase) and observed values for bond distances and angles involving the Co, N, and O atoms is presented in Tables 3 and 4 for the two series of complexes studied in this work. As previously observed for other six-coordinate Co(III) complexes, 21,22 good agreement between computational and experimental results has been obtained for all structural parameters included in Tables 3 and 4, and in particular, longer than those observed in the crystal structures, but the deviations are small. As an additional test, 59 Co chemical shifts have also been calculated and are compared with experimental data in Table 5.…”

Synthesis, characterization and DFT studies of the cobalt(iii) complex of a tetrapodal pentadentate N4S donor ligand

“…The results of these calculations are summarized in Tables 2 and 3 (denoted LDA/TZP and PBE/ZORA/TZ2P). Both procedures have been previously shown 8 to satisfactorily reproduce the experimental structural parameters of Co complexes similar in size and ligand environment to those investigated in this work.…”

“…Our interest previously has been in the synthesis, electron transfer properties, 59 Co NMR and visible spectroscopy of mixed donor nitrogen-thioether cobalt() complexes. [7][8][9][10][11][12][13] We have also recently reported a potentially hexadentate N 3 OS 2 ligand which is able to give pentadentate chelation in a number of forms with Co(). 7 N 4 Samp arises from a deliberate synthetic strategy utilized previously to prepare a new set of hexadentate ligands known as amplectors.…”

“…7 N 4 Samp arises from a deliberate synthetic strategy utilized previously to prepare a new set of hexadentate ligands known as amplectors. 7,8 Results and discussion…”

13 Iron, cobalt and nickel

“…A series of cobalt(III) complexes of hexadentate embracing ligands (N 4 S 2 donors) show a correlation between 59 Co NMR and ligand field parameters of Co(III) complexes with a new class of nitrogen-thioether multidentate ligand. 49…”