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

Abstract

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 Pc 2− – 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 F k and dipolar A 2 0 〈 r 2 〉 · G k 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 ( Δ δ k / 〈 S Z 〉 Ln ; Δ δ l / 〈 S Z 〉 Ln ) and three nuclei ( Δ δ k / 〈 S Z 〉 Ln ; Δ δ l / 〈 S Z 〉 Ln ; Δ δ m / 〈 S Z 〉 Ln ) crystal-field independent graphical analysis evidenced of isostructurality of the complete series, therefore variation of solely A 2 0 〈 r 2 〉 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 Δ δ k / Δ δ m versus Δ δ l / Δ δ m demonstrated that in studied complexes F k 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.