Reflectance circular dichroism of solid‐state chiral coordination compounds

Solid-state diffuse reflectance circular dichroism (DRCD) spectra of some chiral lambda- and delta-M[(A--A)(n)](m+) coordination compounds [M(III) = Cr, Co; A--A = ethylendiamine (en), O,O'-2(R)3(R)dimethylethylene dithiophosphate ion, (R,R)bdtp(-), sepulchrate (Sep); n = 1, 3; m = 0, 3] were measured and compared with their solution, nujol mull, and KBr pellet spectra in the spectral region of 300-800 nm. The validity of the DRCD method to obtain reliable CD spectra which reflect a correct absolute configuration at the metal coordination center as well as subtle changes in the stereochemistry of the compound in the solid vs. solution states was proved. DRCD is the only spectroscopic method to examine randomly oriented chiral compounds without the effect of pressure, solvent, or diluting media such as KBr or nujol (which lends the sample irrecoverable and may interact with the sample), and directly relate to the structure that is revealed by X-ray diffractometry.