Nowadays a pronounced interest has been focused on the crystal engineering of supramolecular ensembles established by combination of coordinative and weaker non-covalent interactions (eg. hydrogen bonds, π–π stacking), which play an essential role in the fields from molecular biology to crystal engineering [1]. It is known that the introduction of polycyclic aromatic chelating ligands containing N-donors, like 1,10-phenanthroline (phen) into the metal-acetylacetonato systems prevent the formation of higher dimensional coordination networks and may provide supramolecular recognition sites for π–π, C–H–π stacking and C–H···O hydrogen bonding to form supramolecular structures [2]. Herein, we present three supramolecular systems constructed by π–π stacking interactions: Ni(acac)2(phen) (1), [Ni(phen)2(H2O)2] ·(ClO4)2 (2) and Cd(ClO4)2(phen)2 (3), where Hacac = acetylacetone. All compounds crystallize in centrosymmetric space groups: orthorhombic Pbcn, a=15.5235(10), b=10.2715(7), c=12.6198(7) Å for 1; monoclinic P21/c, a=17.6783(10), b=8.8563(4), c=17.5013(12) Å, β= 107.144(7) ° for 2; and triclinic P-1, a=8.2130(9), b=8.9194(10), c=9.4431(10) Å, α=108.185(10), β= 105.305(9), γ=104.568(10)° for 3. The structural determination revealed that the coordination geometry around the Ni/Cd centers is distorted octahedral in each complex. In the molecular unit 1 the metal atom has N2O4 environment, while in complexes 2 and 3, the metal atoms have N4O2 coordination cores. In the crystal structure of 2 the chelate phen ligands are stacked by the π–π interactions along the crystallographic a axis, giving supramolecular dimer, and these dimers are further linked into a 1D supramolecular polymer via weak π–π interactions (Fig1a). In the crystal structure of 3 π–π stacking interactions are noted between neighboring hydrophobic phen ligands, yielding 1D supramolecular chain along the c direction (Fig1b). 87 (a) (b) Fig.1. Supramolecular chains of the complexes 2 (a) and 3 (b) supported by π−π stacking interactions. [1] (a) A. Bauzá, P.M. Deyà, A. Frontera, in: S. Scheiner (Ed.), Noncovalent Forces, Challenges and Advances in Computational Chemistry and Physics, 19, Springer International Publishing, 2015, 471. [2] (a) P. Mahata, S. Natarajan, Eur. J. Inorg. Chem. 2005, 2156; (b) B. H. Ye, M. L. Tong, X. M. Chen, Coord. Chem. Rev. 249, 2005, 545; (c) E. Melnic, E. Tocana, A.V. Siminel, L. Croitor, Polyhedron 102, 2015, 410.