The synthesis of heteroleptic cyanometallate aminopyridine complexes and an investigation into their structural properties with various spectroscopic methods

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In this study, three new transition metal(II) complexes consisting of zinc(II), mercury(II) atoms, cyanide group (CN), 3-aminopyridine (3AP) and 4-aminopyridine (4AP) ligand molecules were successfully synthesized in a single crystal form. The formulas of these newly synthesized heteroleptic cyanometalate aminopyridines complexes are given as [Zn(II)(3AP)2(CN)2], [Zn(II)(4AP)2(CN)2] and [Hg(II)(4AP)2(CN)2]. The crystal structures of these heteroleptic cyanometalate complexes were characterized by spectral analysis including single crystal X-ray diffraction techniques, FT-IR, and thermal analysis. The FT-IR and single crystal XRD spectra of these complexes were recorded in the 3750–250 cm−1 wavenumber range and in the region of about 3–29°, respectively. In addition, the thermal analysis curves of these complexes were recorded in the temperature range of 40–850 ℃ using TG, DTG, and DSC methods. The structural properties of these complexes are explained with reference to the changes in their characteristic peaks belonging to 3AP, 4AP ligand molecules and cyanide group in their FT-IR spectra. The most important feature of these new complexes is the presence of NH···N interactions between the H atom of the NH2 group of the 3AP and 4AP ligand molecules and the nitrogen atom of the CN group. These interactions play the most important role in the realization of the three-dimensional structure of the new heteroleptic cyanometalate complexes in crystal form. According to the spectral data of the newly obtained heteroleptic cyanometalate complexes, the complex with 3AP has the orthorhombic crystal system and the space group Pca21, whereas the other two heteroleptic cyanometalate complexes with 4AP have in the monoclinic crystal system and the C2/c space group. The asymmetric unit of [Zn(II)(3AP)2(CN)2] comprises one Zn(II) ion, two cyano groups, and two 3AP ligand molecules; the asymmetric unit of [Zn(II)(4AP)2(CN)2] comprises one Zn(II) ion, one cyano group and one 4AP ligand molecule. Similarly, the asymmetric unit of [Hg(II)(4AP)2(CN)2] comprises one Hg(II) ion, one cyano group and one 4AP ligand molecule.