Synthesis, crystal structures and luminescence properties of new multi-component co-crystals of isostructural Co(II) and Zn(II) complexes

Abstract

Two novel isostructural compounds containing multi-component co-crystals [M(C6H4NO2)2(-H2O)2](C9H6O6)2 (M = Co (1), Zn (2), C6H4NO2 = Picolinic acid, C9H6O6 = Trimesic acid) have been synthesized. The compounds were characterized by elemental analysis, FT-IR, UVeVisible and 1H NMR spectroscopies as well as thermal and single crystal X-ray diffraction analyses. Single crystal X-ray diffraction analysis reveals that 1 and 2 are isostructural. Compound 1 crystallizes in triclinic space group (P-1, with a = 5.154(10) Å, b = 11.125(2) Å, c = 14.113(3) Å, a = 91.01(3)o, b = 100.54(3)o, and g = 102.71(3)o). In a similar fashion, compound 2 crystallizes in triclinic space group (P-1, with a = 5.1735(3) Å, b = 11.0930(10) Å, c = 14.1554(8) Å, a = 91.70(3)o, b = 100.26(3)o, g = 102.90(3)o). The metal (II) cation presents distorted MN2O4 octahedral geometry with H2O molecules coordinated to the metal in equatorial position while the picolinic acid molecules are axially coordinated through the pyridine N atom. The two trimesic acid molecules are not part of the first coordination sphere. Compounds 1 and 2 constitute an example of a class of coordination compound of multicomponent crystals having trimesic acid outside the coordination sphere where it is neither protonated or deprotonated. The two compounds were investigated for luminiscence properties.