Naslov
Structural preferences and isomerism in nickel(II) and copper(II) complexes with 3- hydroxypicolinic acid

Autori
Kukovec, Boris-Marko ; Vaz, Pedro D. ; Calhorda, Maria Jose ; Popović, Zora

Izvornik
Polyhedron (0277-5387) 39 (2012), 1; 66-75

Vrsta, podvrsta i kategorija rada
Radovi u časopisima, članak, znanstveni

Ključne riječi
nickel(II); copper(II); 3-hydroxypicolinic acid; cis-trans isomerism; DFT calculations; solid-state structures

Sažetak
Recrystallyzation of [Ni(3-OHpic)2(H2O)2] (1) from pyridine (py) affords trans-[Ni(3- OHpic)2(py)2] (2), while cis-[Ni(3-OHpic)2(4-pic)2] (3) is obtained from 4-picoline (4-pic). The nickel(II) ion is octahedrally coordinated by two N, O-bidentate 3-hydroxypicolinate ligands in both 2 and 3, and by two pyridine molecules in trans position (2) or two 4-picoline molecules in cis position (3). [Cu(3-OHpic)2] reacted with 4-picoline to yield the pentacoordinated species [Cu(3-OHpic)2(4-pic)] (4), but in the presence of 3-picoline (3-pic) the octahedral trans-[Cu(3-OHpic)2(3-pic)2] (5), similar to 2, was isolated. The crystal structures of 2–5 exhibit strong intramolecular O–H...O hydrogen bonds, but the intermolecular interactions are weak (C–H...O hydrogen bonds, π–π and C–H...π interactions). DFT calculations showed a preference for octahedral coordination for both nickel(II) and copper(II) and a very small one for cis arrangement of the monodentate ligands, as observed in 2 and 5. The cooperative effect of weak intermolecular interactions should be responsible for reversing the preferences, but no major driving force could be identified. Calculated (DFT) and experimental IR spectra for 2–5 were compared and characteristic bands assigned. Thermogravimetric studies showed the initial loss of two coordinated pyridine, 4-picoline or 3-picoline molecules in 2, 3 and 5, respectively.

Izvorni jezik
Engleski

Znanstvena područja
Kemija

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