The ²H-NMR solid echo spectra of biphenyl molecules as guests in the mesopores of neat
and silylated SBA-15 have been measured as a function of temperature. At low temperatures
typical ²H-Pake patterns with parameters of (Qzz = 132 kHz, corresponding to Qcc = 176 kHz) and
(η = 0.04) are observed. All samples exhibit a strong reduction of the melting point from the bulk
value of 342.4 K to values between 222 K and 229 K, depending on both the pore diameter and the
surface state and a glass like behavior of the biphenyl molecules in the melting regime. Employing
the Roessler two-phase model of the modeling of glass-transitions by ²H-solid state NMR the
distribution of activation energies for the rotational motions has been determined. At temperatures
closely below the glass-transition temperature deviations from a static Pake pattern of an aromatic
deuteron are observed, which indicate a pre-melting motion of biphenyl, which could be caused
by C₂-ring flips of the phenyl rings
