Self-Assembly of Quaterpyridine Ligands and Cu⁺ Cations into Helical Complexes of 2:2 Stoichiometry under Electrospray Ionisation Conditions

Abstract

Solutions containing quaterpyridine ligand 1 and Cu(2+) cation were analysed by electrospray ionisation mass spectrometry (ESI-MS). It was found that copper reduction under ESI conditions and self-assembly of 1 and Cu(I) led to the formation of the 2:2 stoichiometry complex. Such stoichiometry is characteristic of helical complex of quaterpyridine ligand with Cu(I). The isotope pattern characteristic of [Cu(2)1(2)](2+) ion and different from that of [Cu1](+) ion, is observed. When using methanol as solvent, only [Cu(2)1(2)](2+) ions are observed in mass spectrum obtained at low cone voltage. At higher cone voltage [Cu(2)1(2)](2+) ion easy dissociates producing [Cu1](+) ion. When using other solvents studied, water and acetonitrile, 2:2 stoichiometry complex is formed, but along with complexes of other stoichiometries. Helical complex was not observed for silver cation for which only 1:1 stoichiometry complex was observed (ion [Ag1](+)).

Full characterization and cytotoxic activity of new silver(i) and copper(i) helicates with quaterpyridine

“…S3, ESI †). 38 As well, FT-IR spectra are in good agreement with the solid state structures and are described in detail in Fig. S4, ESI †.…”

Quaterpyridines as Scaffolds for Functional Metallosupramolecular Materials

“…We have reported the syntheses of methyl ( 26 ) and ester ( 30 ) derivatives of qtpy 17 substituted in the 6 and 6‴ positions, of which the following dinuclear double helicates have been obtained and crystallographically characterized: [M 2 ( 26 ) 2 ]­X 2 {where M = Ag­(I), Cu­(I); X = PF 6 , OTf, BF 4 ), CuCl 4 , Cu­(NO 3 ) 4 and [Cu 2 ( 30 ) 2 ]­(PF 6 ) 2 . ,,, Intriguingly, [Cu 2 ( 26 ) 2 ]­(PF 6 ) 2 is one of the only two examples of qtpy helicates (see Table and subsection for the second example) that crystallize as racemic mixtures (Figure , red frame). It should be also noted that it is possible to form helical architectures of Cu­(I) from mononuclear Cu­(II) species even in the presence of strongly coordinating counterions (nitrate, chloride), provided metallic copper is used during the synthesis .…”

Unexpected Formation of Complexes between a Protonated Organic Ligand and a Neutral Salt Molecule Studied by Electrospray Ionization Mass Spectrometry

“…organic ligands containing pyridine moieties are able to form stable complexes with metal cations and also are prone to protonation. [15][16][17][18] the so-called bipyridine, terpyridine and quaterpyridine ligands have nitrogen donor atoms in such positions that they are "prepared" to form stable complexes with metal cations, especially transition metal cations (the metal cation is simultaneously coordinated by two or more nitrogen donor atoms). Ligands shown in Scheme 1 (L1 and L2) contain pyridine nitrogen donor atoms, but because of the number of degrees of freedom it cannot be expected that these atoms are "prepared" to form stable complexes with metal cations.…”