Structural investigation of the triaryl derivatives of the Group V elements. IX. Structure of triphenylamine, C18H15N

Vibrational spectrum and molecular structure of triphenylamine monomer: A combined matrix-isolation FTIR and theoretical study

“…In this structure, the central nitrogen and the three adjacent carbon atoms are co-planar, the planes of the three phenyl substituents being symmetrically twisted from the plane of the central NCCC moiety. Consistent with previously reported experimental data, 27 the molecule is predicted by the present calculations to have a propeller-like geometry, the phenyl substituents corresponding to the propeller blades. The minimum-energy structure of TPA, with the phenyl rings twisted with respect to the plane of the central NCCC moiety, can be rationalized in terms of the interplay between two opposing factors: (i) the energy-lowering conjugation of the p-electron systems of the phenyl groups and (ii) the energy-increasing repulsion between the protons of neighbouring phenyl rings.…”

“…50 for TPA in the gaseous phase 25 and 44 in crystalline TPA-average value for this parameter in the non equivalent molecules of the crystal unit cell. 27 Summarizing this section let us note that the theoretical calculations, performed without any restriction of symmetry, revealed that the central NCCC fragment of TPA molecule at the monomer level is planar. The molecule has overall D 3 symmetry and its total dipole moment is equal to zero.…”

“…Previous experimental [24][25][26][27][28]30 as well as theoretical [20][21][22] studies on the structure of TPA suggest a three-bladed propeller structure for the molecule ( Fig. 1) with a planar or nearly planar central NCCC moiety.…”

“…The dendrimer formation from TPA-based molecular systems 17,18 and their photocyclization to form carbazole derivatives 19 have also been the subject of intense research. Both their geometric [20][21][22][23][24][25][26][27][28] and electronic 29 structural characteristics have been addressed by several authors.…”

“…In the solid state, TPA forms crystals with four non-equivalent molecules per unit cell. 27 The average (over these four molecules) value of the CNC angle was determined as equal to 119. 6 , whereas the mean value of the dihedral angle between the planes of the central NCCC atoms and of a phenyl ring was found to be 44 .…”