FT-IR and Raman spectroscopic analysis of some Hofmann type complexes

Some new Hofmann type complexes with chemical formula of M(4pypp)2Ni(CN)4 (where 4pypp = 4-(1-pyrrolidinyl)piperidine and MNi or Co) were prepared and their FT-IR and Raman spectra were reported in the region of 4000–200 cm−1 and 4000–100 cm−1, respectively. The ligand molecule, polymeric sheet and metal–ligand bands of the compounds were assigned in detail. Vibrational spectra together with assignments of 4pypp (C9H18N2) were experimentally and theoretically studied in the region of 400–100 cm−1. Normal mode frequencies and corresponding vibrational assignments of Ni(CN)42- were theoretically examined by standard quantum chemical technique. Reliable vibrational assignments were made on the basis of potential energy distribution (PED) analysis. The results suggest that these compounds are similar in structure to the Hofmann type complexes and the 4phpy ligand molecule bonds to the metal (M) atom of |M–Ni(CN)4|∞ polymeric layers.

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► Synthesis and vibrational spectra of the Hofmann type complexes.
► 4-(1-Pyrrolidinyl)piperidine (4pypp) ligand molecule.
► 4pypp Molecules are coordinated in e-e form as a unidentate ligand.
► Presented compounds are further examples of the Hofmann type complexes.