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Characterization and decomposition mechanism of an unusual nickel, thiocyanate and 4-methylpyridine polymeric complex
Authors:Wagner J. Barreto   Henrique de Santana   Flaveli A. S. Almeida   Dilson N. Ishikawa  Yoshio Kawano
Affiliation:

a Laboratory of Environmental Physical Chemistry, Department of Chemistry, Londrina State University, Caixa Postal 6001, 86051-990, Londrina, PR, Brazil

b Department of Chemistry, Londrina State University, Caixa Postal 6001, 86051-990, Londrina, PR, Brazil

c Chemistry Institute, University of São Paulo, Caixa Postal 26077, 05513-970, São Paulo, SP, Brazil

Abstract:The synthesis, characterization, and thermal decomposition of the [Ni(SCN)2(H+SCN)2(4-mepy)2] compound with an octahedral structure in polymeric chain were reported, in which SCN groups form bridges among Ni(II) ions. The compound decomposes in water resulting in a pH<4 solution. The FT-IR spectrum presented doublet bands at 2117; 2128 cm−1, 788; 773 cm−1 assigned to ν(C---N) and ν(C---S) stretching modes, respectively, and δ(SCN) deformation modes at 468; 476 cm−1. The Raman spectrum of the compound presented the ν(C---N) stretching as a strong doublet at 2122; 2128 cm−1, ν(C---S) at 783; 770 cm−1, and δ(SCN) at 468; 477 cm−1. No significant changes were observed in the 4-mepy ligand bands compared with the vibrational frequencies of the pure compound or the compound in aqueous solution 0.2 mol l−1. The crystal UV–vis reflectance spectrum presented two bands centered in 626 and 424 nm tentatively assigned to the d→d type transitions, 3A2g3T1g and 3A2g3T1g, for a symmetry close to Oh. The TG curve showed a mass loss between 120 and 200 °C assigned to the loss of the two 4-mepy molecules; from 200 to 265 °C, the loss of the two H+SCN groups; and from 265 to 450 °C, the loss of the two SCN groups that formed the bridges among the nickel atoms. Based on these mass loss data, a mechanism of thermal decomposition for the compound was proposed.
Keywords:Nickel polymers   Nickel complex   4-Methylpyridine   Thiocynate   Thermal decomposition
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