Complexation behavior of 6,6″-dimethyl-2,2′:6′,2″-terpyridine ligand with Co(II), Au(III), Ag(I), Zn(II) and Cd(II) ions: Synthesis, spectroscopic characterization and unusual structural motifs

Abstract

Despite the fact that the ‘tpy’ binding motif has been extensively documented, observation of the unusual coordination motifs makes the preprogrammed assembly of functional materials an up-to-date challenge. Drawing inspiration from our previous experience with 6,6″-dimethyl-2,2′:6′,2″-terpyridine ligand (L), we have thus focused on its complexation behavior with Co(II), Au(III), Ag(I), Zn(II) and Cd(II) metal ions, stemming from their applicative relevance. As a result, ten new coordination compounds were synthesized of the following molecular formulae: [CoL(NO3)2] (1), [CoL2]2(ClO4)4·5H2O (2), [CoL(MeOH)(CF3SO3)2] (3), [Co(Lox)(CH3SOCH3)(CF3SO3)]CF3SO3 (3a), [(LH2)2+·2AuCl4−·H2O] (4), [(Au(LH)Cl3)+·AuCl4−] (5), [AgL(O-NO2)]3[(AgL(O2-NO)] (6), [AgL(NCCH3)]BF4·CH3CN] (7), [ZnL(CF3SO3)2] (8), [CdL(NO3)2·CdLBr2] (9), as unambiguously confirmed by single-crystal X-ray diffraction studies. To our surprise, most of the presented structures are to the certain level unique; either considering incomplete tridentate coordination of the tpy ligand L (4, 5), its oxidative transformation (3a) or the formation of mixed solid state solutions (9). Each compound was fully characterized by a series of analytical techniques, including elementary analysis, FT-IR, ESI-MS and 1H NMR, the latter two of which allowed us to gain insight into their solution behavior.