NMR investigation of intramolecular dynamics of heteroleptic triple-decker (porphyrinato)(phthalocyaninato) lanthanides

Intramolecular dynamics of meso-aryl substituents of porphyrin deck in the triple-decker lanthanide (porphyrinato)(phthalocyaninates) of symmetrical type Br(4)TPP]Ln(15C5)(4)Pc]LnBr(4)TPP] (Ln = La, Nd, Eu; Br(4)TPP] = tetrakis-5,10,15,20-(4-bromophenyl)-porphyrinato-ligand; (15C5)(4)Pc] = tetrakis-(15-crown-5)-phthalocyaninato-ligand) are investigated. Attempts to achieve coalescence were not successful, although the trend of exchanging protons to coalescence point was observed in the case of Nd and Eu complexes. The analysis of NOESY cross-peaks between exchanging protons allowed to evaluate the rotation rate constants at different temperatures. The activation barrier of the meso-aryl substituent rotation was calculated with Arrhenius equation based on determined rate constants. The rate constants are lower and activation barriers are higher than ones found previously for related compounds.