Structural and spectroscopic study of the asymmetric 2-(2′-pyridyl)-1,8-naphthyridine ligand with closed-shell metals

Herein, we report the synthesis and characterization of a series of complexes of the asymmetric ligand 2-(2′-pyridyl)-1,8-naphthyridine (pyNP, 1) with different closed-shell metals. For the first time ligand pyNP has been structurally and vibrationally characterized. The geometry of the pyNP ligand, with 3 N donor sites, can favor metallophilic interaction in complexes, so we performed a study on its coordination chemistry with different metals (Ag(I), Hg(II) and Pb(II)). Twelve new complexes, namely [Ag2(pyNP)2(NO3)2] (2), [Hg(pyNP)X2](X = Cl(3), Br(4), I(5), CN(6), SCN(7, 8)), [Pb(pyNP)2(NO3)2] (9), [Pb(pyNP)(NO3)2]2 (10), [Cu(pyNP)Cl2(H2O)] (11), [Cu(pyNP)2(H2O)][Hg2(CN)4Cl2]-H2O (12) and [Cu(pyNP)(H2O)2(μ-CN)Hg2(CN)3Cl2]-H2O (13), have been synthesized and characterized by single crystal X-ray diffraction, Raman, FTIR and electronic spectroscopies. Structure of complex 2 shows a supported argentophilic interaction, and is the first structure in which pyNP bonds two previously unbounded metal centers.