We have studied the dynamics of nano- to picosecond proton transfer processes in the ¹⁵N labeled polycrystalline TTAA molecule (1,8-dihydro-5,7,12,14-tetramethyldibenzo(b,i)-¹⁵N₄-(1,4,8,11)-tetraazacyclotetra-deca-4,6,11,13-tetraene) by a combination of 9.12 MHz ¹⁵N T₁ relaxation time measurements under CPMAS conditions (CP≡cross polarization and MAS≡magic angle spinning) and by 46 MHz ²H T₁ relaxation time measurements of a static sample of polycrystalline doubly deuterated TTAA-d₂. By an analysis of the temperature dependent isotropic ¹⁵N chemical shifts of the four inequivalent ¹⁵N atoms in TTAA evidence was obtained for a network of proton transfer steps between two trans-tautomers 1 and 2 and two cis-tautomers 3 and 4 which interconvert by single proton transfers. However, in the temperature range between 100 and 400 K tautomer 4 is not formed to an observable extent. Only a single spin diffusion averaged ¹⁵N T₁ relaxation time for all nitrogen atoms was observed, whereas the two deuterons in TTAA-¹⁵N₄ give rise to two different ²H T₁ relaxation times. An appropriate ¹⁵N and ²H relaxation theory in the presence of the reaction sequence 1⇄3⇄2 was developed and used to convert the relaxation data into the rate constants including the H/D isotope effects of the two reaction steps. Some ¹⁵N relaxation data obtained for TTAA at natural ¹⁵N abundance allowed us to assign a larger barrier to the reaction step 1⇄3 and a smaller barrier to the step 3⇄2 which dominates the longitudinal ¹⁵N and ²H relaxation. The Arrhenius diagram including the kinetic isotope effects showed that tunneling is operative at low temperatures. The results are discussed in comparison to those obtained previously for related intramolecular proton transfers in porphyrin, porphycene and the related DTAA molecule (1,8-dihydro-6,13-dimethyldibenzo(b,i)-¹⁵N₄-(1,4,8,11)-tetraazacyclotetra-deca-4,6,11,13- tetraene).