Naslov
Structural and DFT studies on the polymorphism of a cadmium(II) dipicolinate coordination polymer

Autori
Kukovec, Boris-Marko ; Venter, Gerhard A. ; Oliver, Clive L.

Izvornik
Crystal growth & design (1528-7483) 12 (2012), 1; 456-465

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

Ključne riječi
cadmium(II); dipicolinate; polymorphism; coordination polymer

Sažetak
The coordination polymer [Cd2(dipic)2(H2O)3]n was prepared by the reaction of cadmium(II) chloride or bromide and dipicolinic acid (dipicH2) at 60 °C under autogenous pressure. The C2/c polymorph (1) was almost exclusively obtained. However, a few crystals of the P2/c polymorph (2) were occasionally found in the mixture with C2/c polymorph, thus making it a disappearing and concomitant polymorph. The polymeric chains in 1 are connected into dimers by π–π interaction and O–H⋅⋅⋅O hydrogen bonds. These dimers are in turn connected by intermolecular O–H⋅⋅⋅O hydrogen bonds into 2D network. The polymeric chains in 2 are connected by intermolecular O–H⋅⋅⋅O hydrogen bonds into a zigzag chain along the [001] direction. According to DFT calculations, the hydrogen bonding is of similar order in both polymorphs (~7.5 kcal mol-1 per hydrogen bond). However, there is an additional stability, as shown by dispersion-corrected DFT, through π–π stacking between the polymeric chains in 1, making polymorph 1 the thermodynamically favored polymorph. Polymorph 1 was characterized by IR spectroscopy, PXRD analysis and TGA and DSC methods. The DSC analysis did not show any sign of phase transition between 1 and 2. This was also confirmed by variable temperature PXRD since the pattern of 1 remained unchanged until the decomposition of 1.

Izvorni jezik
Engleski

Znanstvena područja
Kemija

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