Anion- π interactions in hollow crystals of a copper(II)-cyamelurate coordination complex
Fecha
2018Resumen
A novel cyamelurate-based copper(II) coordination compound
has been designed from a computational approach to show anion−π
interactions between the s-heptazine core and perchlorate anions; therefore, a
complex of formula {[Cu(pmta)]3cyam}(ClO4)3 (1) [pmta = N,N,N′,N′′,N′′-
pentamethyl-diethylenetriamine and cyam = cyamelurate ligand] was
synthesized. The cationic molecule stabilizes in the solid state with two
perchlorate anions one above and the other below the cyamelurate aromatic
rings in a polar conformation, crystallizing in the R3c noncentrosymmetric space
group with a close cubic packing of the cations. The binding energies were
calculated to be ca. −175 kcal/mol for the two species 1:OClO3
− and
1:O3ClO−, and the anion-π contribution could also be calculated, being ca. −10
kcal/mol. The dielectric and magnetic properties were analyzed showing a
semiconductor behavior in the temperature range studied (300−458 K) and a
weak antiferromagnetic interaction among the three Cu(II) ions. The crystals of 1 show a hollowed hexagonal prismatic
morphology, with hollow diameters up to 300 μm. A mechanism based on oriented growth, dissolution, and recrystallization of
the outer shell was proposed to explain these hollowed structures.