Synthesis and Crystal Structure of [Zn(C14H12N2)(HCO2)2]•2H2O
Reactions of a freshly prepared Zn(OH)2-2x(CO3)x×yH2O precipitate, formic acid with 2,9’-dimethyl-1,10’-phenanthroline in CH3OH/H2O afforded [Zn(C14H12N2)(HCO2)2]·2H2O. The title compound was structurally characterized by X-ray diffraction methods. It consists of complex molecules [Zn(C14H12N2)(HCO2)2] in which Zn atoms are hexa-coordinated by two N atoms of one phenanthroline ligand and four O atoms of two bidentate formate groups. In the crystal, molecules are connected by O–H···O hydrogen bonds forming layers parallel to (010), and the resulting layers are further linked 3D framework along  by π-π packing interactions.
Fei Hu and Beibei Wang
S. L. Ni et al., "Synthesis and Crystal Structure of [Zn(C14H12N2)(HCO2)2]•2H2O", Advanced Materials Research, Vol. 279, pp. 174-178, 2011