Structural and Spectroscopic Properties of Metal Complexes with Ruhemann’s Purple Compounds Calculated Using Density Functional Theory

Abstract

Structural and spectroscopic properties of Ruhemann’s purple (RP) and its transition metal coordination complexes were calculated using theoretical chemistry techniques. The obtained information described RP and its coordination complexes with the transition metal ions [Cr(II), Mn(II), Fe(II), Co(II), Ni(II), Cu(II), Zn(II), Cd(II) and Hg(II)]. The procedures involved calculations of what are called density functional theory (DFT) and time-dependent DFT (TD-DFT). These methods optimized what is called, in the codes of theoretical chemistry, the hybrid density B3LYP function employing the 6‐311++G(d,p) and LANL2DZ basis sets. The RP geometries, bond lengths, angles, quantum chemical parameters, and excitation spectra indicate that the RP is well able to coordinate with a transition element ion. Then the correlation of these theoretical results with experimental observations provides a detailed description of the structural and spectroscopic properties of RP compounds. The inclusion of solvent effects causes a blue shift in all theoretical excitation spectra. In summary, this work leads to an understanding of the characteristics of transition metal complexes with Ruhemann’s purple. These materials can be applied in forensic chemistry as reagents in developing latent fingerprints.