Monomer, dimer or cyclic helicate? Coordination diversity with hard–soft P,N-donor ligands

Abstract

We report the synthesis of copper(I) complexes of three ligands which contain a potential P,N,N,P-metal binding site. Elemental analysis confirms that the bulk products possess a composition of [CuL][PF6] where L = 1, 2 or 3. Electrospray mass spectrometry (ESI MS) provides evidence for speciation in MeCN or MeOH solutions and the formation of both [CuL]+ and [Cu2L2]2+; addition of NaCl to the ESI MS samples aids the observation of dinuclear species as [Cu2L2Cl]+ ions. NMR spectroscopic data for a CD3CN solution of [Cu(1)][PF6] were consistent with a mononuclear species, but more complex multinuclear spectra were observed for the same compound dissolved in CD2Cl2. In the solid state, dimeric species dominate. Crystals grown from CH2Cl2 solutions of [Cu(1)][PF6] are found to be [Cu2(1)2][PF6]2·6CH2Cl2; each Cu+ ion in the centrosymmetric cation is bound in an N,O,P,P-coordination sphere, the N-donor originating from the pyridine ring. In [Cu2(3)2][PF6]2, each bridging ligand in the centrosymmetric [Cu2(3)2]2+ ion acts as a P,N-chelate to each Cu+ ion. Competing with this dimeric assembly is that of a circular helicate in which each ligand 3 bridges adjacent pairs of copper(I) ions in a chiral, hexameric complex; both the Δ,Δ,Δ,Δ,Δ,Δ- and Λ,Λ,Λ,Λ,Λ,Λ-enantiomers are present in the crystal lattice; in [Cu6(3)6]6+, each ligand coordinates as a bis(P,N-chelate). The solution absorption spectra of [Cu(1)][PF6], [Cu(2)][PF6] and [Cu(3)][PF6] are dominated by ligand-based transitions and none of the copper(I) complexes exhibits emissive behaviour in solution.

Structural characterization of environmentally relevant ternary uranyl citrate complexes present in aqueous solutions and solid state materials

“…The soft ionization of an electrospray source has the ability to transfer material into the gas phase relatively intact which makes ESI-MS a desirable technique for the characterization of aqueous ionic species with high molecular weights. 14,35,36 Fragmentation of the molecular species occurs quite readily for these complexes; therefore, it is important to investigate the anionic species associated with U 2 Fe 4 , U 2 Fe 2 , and U 2 Al 2 compounds that can be observed with ESI-MS.…”

Temperature‐ and Voltage‐Induced Ligand Rearrangement of a Dynamic Electroluminescent Metallopolymer

“…The color change, shift in photoluminescence, and gel formation reversed upon cooling the sample to room temperature. This type of reversible gel formation upon temperature rise [4,[8][9][10] is the opposite behavior to that observed for most gelators, which undergo a sol-gel transition upon cooling. We had previously reported a similar effect in a series of related polymers, however, the high temperature of gel formation and poor solubility of the polymers inhibited further study or device fabrication.…”

“…The formation of polymer 1 was driven by the tendency of copper(I) to form heteroleptic complexes of the type Cu I P 2 N 2 . [8,16] Without the bulky phosphine groups and cationic charge of the copper, the polymers are inferred to aggregate into the fibrous structure of the gel matrix observed by scanning electron microscopy (SEM; Figure S19). In DMF, cooling of the solution appears to allow the [Cu(POP)] + groups to reattach to the vacant pyridyl imine sites, restoring the polymers and dissolving the gel.…”

Synthesis, structure, and characterization of a series of Ag(i), Cu(ii) and Ni(ii) complexes based on 2,5-dimethyl-1,3,4-thiodiazole

“…ESI-MS has proved to be a powerful tool for the analysis of ionic species in solution, several classes of chemical compounds having been characterized since its introduction. 23 Useful information regarding stoichiometry has also been achieved for the solution speciation of coordination compounds augmenting that available from spectroscopic techniques. In this context, ESI-MS spectra were recorded for complexes 1-2 and 4 by dissolving small quantities of crystals in DMSO solutions to assess the nature of the complexes in solution.…”