A new supramolecular compound of Cr(III) atom was synthesized and characterized by using elemental analysis, FTIR spectroscopy, UV–vis, and single crystal X-ray diffraction method. The chemical formula and space group of the resulting compound is (2-apymH)[Cr(pydc)2]2H2O (1) (pydc = 2,6-pyridinedicarboxylate, 2-apym = 2-aminopyrimidine) and P21/c where the final R value is 0.0157 for 3896 reflections collected. The [Cr(pydc)2] anions and the (2-apymH)+ moiety form a three-dimensional solid state structure by a variety of noncovalent interactions such as ion pairing and hydrogen bonds interactions. On the basis of crystallographic data, it can be seen that Cr(III) atom is six-coordinated by two (pydc)2 groups. With respect to bond lengths and angles, it is observed that coordination sphere around Cr(III) atom is a distorted octahedral. Furthermore, DFT calculation and solution study have been completely performed on 1 where corresponding data showed that obtained results from DFT and solution studies have good agreement with X-ray crystallography results. The optimized geometry confirms that the C–O(bonded) bond length of (pydc)2 ligand in its complex form has been increased compared with the free ligand. The evidence shows that C–O(bonded) is weakened upon formation of complex, while C@O(free) converted to double bond. Anionic complex possesses 90 occupied molecular orbitals and 3 half-occupied ones (91– 93). A comparison between the stoichiometry of the crystalline complex in pydcH2–2-apym–Cr system and the results obtained from solution studies clearly revealed that the CrL2QH is the most abundant species existing in aqueous solution possesses a stoichiometry similar to that of the complex which was obtained in the solid state.

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