Ni(II) complex with sarcosine derived from in situ generated ligand: structural, spectroscopic, and DFT studies

Nickel(II) complex with sarcosine [Ni(sar)2(H2O)2] (1) has been obtained as a reaction product of a system: Ni(II)Cl2–1-methylhydantoin. Basic hydrolysis of the organic substrate leads to in situ formation of sarcosine ligand, which coordinates to the metal ion. The isolated complex has been characterized by means of single crystal X-ray diffraction and spectroscopic studies (IR, Raman, and NIR–UV–Vis) supported with DFT calculations. Single crystal X-ray diffraction revealed that the nickel environment in [NiN2O4] chromophore exhibited the geometry of a tetragonally elongated octahedron. Hydrogen bonds create two chain patterns which propagate along the main crystallographic directions a and b. It leads to the formation of a 2D network. Electronic spectra analysis showed that the nickel surroundings can be described as pseudooctahedral in solution and tetragonal in the solid state. Based on the calculated 10Dq parameter (10,990 cm−1), sarcosine ligand was located in the spectrochemical series close to ammonia. Comprehensive studies of the molecular structure and vibrational spectra of the title complex have been performed using UPBE0, unrestricted density functional method. The clear-cut assignment of the bands in FT-IR and Raman spectra of studied complex has been made on the basis of the calculated potential energy distribution. The Ni–L(sarcosine) stretching vibrations were assigned in Raman spectrum to the medium intensity band at 442 cm−1.