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Issue 19, 2011
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Coordination-driven self-assembly of thiocyanate complexes of Co(ii), Ni(ii) and Cu(ii) with picolinamide: a structural and DFT study

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Abstract

The new heteroleptic complexes, [M(NCS)2(pia)2] M = Co(II) (1), Ni(II) (2), and [Cu(SCN)2(pia)2] (3), pia = pyridine-2-carboxamide, were synthesized and characterized. Their single crystal X-ray diffraction structures showed octahedral units, with the two thiocyanate ligands occupying cis-positions and binding through the nitrogen atom in Co(II) and Ni(II). In the Cu(II) complex, they were trans and S-bound. The crystal structures display a 2-d structure with NH⋯S hydrogen bonds for the Co(II) and Ni(II), forming tetrameric units, and are isomorphous with the Zn(II) complex, [Zn(NCS)2(pia)2], and a 2-d structure with NH⋯N for the Cu(II). DFT calculations were performed on the new complexes and the analogous polymorphs of [Zn(NCS)2(pia)2], including a second one containing dimeric motifs. The calculated vibrational modes of the thiocyanate ligands corroborate the experimental ones and reflect the coordination mode of the ligand. A comparison between the two Zn(II) polymorphs showed that the NH⋯S bond in the tetramer is stronger (−7.50 kcal mol−1 per metal) than the NH⋯O bond in the dimer (−4.01 kcal mol−1 per metal), indicating a preference for the formation of tetrameric units. The NH⋯N hydrogen bonds calculated in the Cu(II) crystal are stronger (−9.15 kcal mol−1 per metal) than the NH⋯S ones in Ni(II) and Zn(II).

Graphical abstract: Coordination-driven self-assembly of thiocyanate complexes of Co(ii), Ni(ii) and Cu(ii) with picolinamide: a structural and DFT study

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Supplementary files

Article information


Submitted
18 Mar 2011
Accepted
01 Jul 2011
First published
02 Aug 2011

CrystEngComm, 2011,13, 5863-5871
Article type
Paper

Coordination-driven self-assembly of thiocyanate complexes of Co(II), Ni(II) and Cu(II) with picolinamide: a structural and DFT study

M. Đaković, D. Vila-Viçosa, M. J. Calhorda and Z. Popović, CrystEngComm, 2011, 13, 5863
DOI: 10.1039/C1CE05332A

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