The13C Dipole-dipole relaxation time and the activation energies of internal motion of cyclic ether backbone were obtained for the 1,4,7,10-tetraoxacyclododecane(12. crown. 4) and its cationic complexes.13C dipolar relaxation time,TDD1of free tetraoxacyclododecane molecule and its Li,+Ca2+and Mg2+complexes were determined at various temperatures in DHO and CH3OD solutions at 15.0 MHz. The pseudorotation barriers of oxyethylene bridges were investigated throughout the temperature dependence of dipole-dipole relaxation times which verified that the TDD1values closely depend on the energy requirements of the particular dynamic processes of molecular systems as well as ion-dipole interactions of cation-cyclic ether. Namely, we concluded a simple analogy between the correlation times of the13C spins and the observed TDD1values in the vicinity of free and complexing systems. On the other hand our experimental results were correlated with the strain energy minimization calculations previously published, which have strongly proved our presented results.