The formation of hydrogen-bonded complexes in the mixtures of 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) with 4-tert-butylphenol and 4-cyanophenol has been studied as a function of the phenol concentration in chloroform and acetonitrile by FTIR spectroscopy. In chloroform, the formation of cyclic hydrogen-bonded structures between the TBD and phenol molecules was observed. These structures show large proton polarizability due to collective proton motion within these hydrogen bonds indicated by continuous absorptions in the FTIR spectra. In acetonitrile, the cyclic hydrogen-bonded structure is relatively stable in the 1:1 mixtures. With increasing concentration of phenol molecules the formation of non-cyclic hydrogen-bonded chains is much more favorable.