1H NMR spectral analysis in series of heteroleptic triple-decker lanthanide phthalocyaninato complexes: Contact and dipolar contributions of lanthanide-induced shifts

Model-free separation of lanthanide-induced shifts to contact and dipolar contributions was performed for the series of heteroleptic REE(III) trisphthalocyaninates, namely [(15C5)4Pc]M(Pc)M(Pc), where Pc2− – phthalocyaninato-dianion, [(15C5)4Pc]2− – 2,3,9,10,16,17,24,25-tetrakis(15-crown-5)phthalocyaninato-dianion, M = Nd, Sm, Eu, Tb, Dy, Er, Tm and Y as a diamagnetic reference. Application of one nucleus technique evidenced of abrupt changes of contact FkFk and dipolar A20〈r2〉·Gk terms between Tb and Dy. Not withstanding structural non-equivalence of lanthanide ions, they have virtually equal values of crystal-field parameters, which justified application of several crystal-field techniques for the further analysis of LIS data. Both two (Δδk/〈SZ〉LnΔδk/〈SZ〉Ln; Δδl/〈SZ〉LnΔδl/〈SZ〉Ln) and three nuclei (Δδk/〈SZ〉LnΔδk/〈SZ〉Ln; Δδl/〈SZ〉LnΔδl/〈SZ〉Ln; Δδm/〈SZ〉LnΔδm/〈SZ〉Ln) crystal-field independent graphical analysis evidenced of isostructurality of the complete series, therefore variation of solely A20〈r2〉 between Tb and Dy was responsible for changes of dipolar terms. To study the behavior of contact terms, another three nuclei technique was firstly applied to lanthanide phthalocyaninates. Plotting Δδk/ΔδmΔδk/Δδm versus Δδl/ΔδmΔδl/Δδm demonstrated that in studied complexes FkFk actually vary between Eu and Tb, therefore evidencing of non-simultaneous variations of contact and dipolar terms. Altogether, it let us refine the values of these terms, which would be subsequently applied for structural analysis of triple-decker crownphthalocyaninates and their supramolecular assemblies in solution.

Application of various model-free methods of lanthanide-induced shift analysis for the family of heteroleptic lanthanide (tetra-15-crown-5-phthalocyaninato)(phthalocyaninato) complexes [(15C5)4Pc]Ln(Pc)Ln(Pc) revealed non-simultaneous variations of contact and dipolar terms near the middle of lanthanide series. It afforded refinement of these terms, which would be further used for structural analysis of complexes and their supramolecular aggregates.Figure optionsDownload as PowerPoint slide