Single-crystal electronic spectra of some quadrate chromium(III) complexes

Polarised electronic spectra of trans-[Cr(tmd)2F2](ClO4), trans-[Cr(en)2(dma)2](ClO4)3, trans-[Cr(en)2(dmf)Cl](ClO4)2 and trans-[Cr(en)2(dmf)Br](ClO4)2 have been measured at 77 K (tmd = trimethylenediamine; dma = N,N-dimethylacetamide; dmf = N,N-dimethylformamide; en = ethylenediamine, pn = propylenediamine). The observed quartet bands have been given definitive quadrate assignments based on polarisation characteristics. The four-component quadrate quartet bands have been uncovered and assigned also in the unpolarised crystal spectrum of trans-[Cr(en)2(dmf)2](ClO4)3 at 77 K and the solution spectrum of trans-[Cr(en)(pn)F2]+. The band maxima derived by gaussian analysis in these spectra have been fitted with the theoretical energy equations of d3 configuration in quadrate ligand fields including full configuration interaction. The ligand field parameters Dq, Dt, and Ds and the election correlation parameter, B, extracted by such a fitting, have been compared with those obtained for other similar systems earlier. The significance of the ligand field symmetry parameters and the translated angular overlap model parameters is discussed.

Graphical abstractPolarised, single-crystal, electronic spectra of a number of trans-disubstituted bis(ethylenediamine) chromium(III) complexes have been measured at 77 K. The observed quartet bands have been given definitive quadrate assignments based on polarisation characteristics. The significance of the ligand field symmetry parameters and the translated angular overlap model parameters is discussed.Figure optionsDownload full-size imageDownload as PowerPoint slide