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We compare Raman and infrared spectra of the nuOH/OD modes in benzoic acid crystal powders at 7 K. The extremely sharp Raman bands contrast to the broad infrared profiles and suggest adiabatic separation of hydrogen (deuterium) dynamics from the crystal lattice. There is no evidence of any proton-proton coupling term. The assignment scheme is consistent with a quasisymmetric double-minimum potential, largely temperature independent. Tunnel splitting is a major band shaping mechanism, in addition to anharmonic coupling with lattice modes. The proton/deuteron dynamics are rationalized with nonlocal pseudoparticles and extended states. We propose a symmetry-related damping mechanism to account for the broad infrared profiles, as opposed to the sharp Raman bands. We assign spectral features to distinct interconversion mechanisms based on either pseudoparticle transfer or adiabatic pairwise transfer. We establish close contacts with theoretical models based on first-principles calculations.

We describe a convenient synthetic pathway to access the 12‐membered PCTA macrocycle, a polyaminocarboxylate ligand for which its M2+ and M3+ complexes are commonly associated with applications in biomedical diagnostics and radiotherapy. The synthetic pathway is based on the use of a linear tri‐N‐alkylated triamine synthon incorporating masked acetate arms and an efficient sodium template ion effect for the crucial macrocyclization step (87 % macrocyclization yield). This approach was then successfully applied to access three new PCTA[12] derivatives containing either a 4‐pyridol unit, an amide or a phosphinate coordinating function in the central arm. In all cases, the macrocyclization reactions were controlled by a sodium template ion effect, and the macrocyclization yields were in the range of 60 to 75 %. The luminescence and relaxometric properties of EuIII, TbIII, and GdIII complexes derived from PCTA derivatives with mixed coordinating arms were also investigated, making these complexes possible alternatives to PCTA[12]–LnIII complexes.