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

Abstract

Theoretical optimization of triphenylamine geometry, carried out at DFT(B3LYP) level using 6-31G** and aug-cc-pVDZ basis sets, predicted a propeller-like structure of the compound with D 3 overall symmetry. In this structure, the central NCCC atoms are coplanar and the phenyl rings are symmetrically twisted from this plane by 41.5 (6-31G**) or 41.6 (aug-cc-pVDZ). The experimental FTIR spectrum of triphenylamine monomers isolated in an argon matrix was measured and interpreted by comparison with theoretical spectra calculated at the DFT(B3LYP) level with 6-31G** or aug-cc-pVDZ basis sets. The good agreement between the experimental and theoretical spectra allowed a positive assignment of the observed infrared absorption bands. Conformational flexibility of triphenylamine was investigated by carrying out a series of theoretical scans of the potential energy hypersurface of the system. Special attention was granted to the minimal energy pathway between the left-hand rotating and right-hand rotating symmetry identical structures of the compound. A route conserving a C 2 symmetry axis was identified as implying an energy barrier of 20 kJ mol À1 only, whereas the calculated barrier for the concerted twist of all the phenyl rings (the route with conservation of the C 3 symmetry axis) was as high as 54 kJ mol À1.

Photoinduced oxidation of triphenylphosphine isolated in a low-temperature oxygen matrix

“…This basis set was adopted from our previous study on triphenylamine [19], where it produced vibrational data quantitatively comparable with the augcc-pVDZ basis set. The scaling factor of 0.975, used in the present work for the calculated frequencies, was obtained from the least squares linear fit (R = 0.99985).…”

Cost-Effective Force Field Tailored for Solid-Phase Simulations of OLED Materials

“…In practice, only three types of torsion were reworked: phenyl-phenyl, phenylcarbazole, and the improper torsion involving the out-of-plane vibration of sp 2 nitrogen; the phenyl-nitrogen torsion in TPA being modeled with standard parameters, as it is dominated by steric repulsion which confers it a propeller-like structure. 45 Fully relaxed scans of the potential energy surface as a function of the dihedral angle were run in steps of 5 degrees, using BPH and PCZ as target fragments, with the obtained profiles shown in Figure 2. It is worth noting that these torsions are present also in the largest compounds of the training set, namely mCP and pCBP, and in many other OLED materials.…”

Molecular Structure of Triphenylamine in the Gas Phase

“…Closer values are provided by B3LYP methods. After we had completed our structural analysis, B3LYP/6-31G**-and aug-ccpDVZ computed spectra of triphenylamine became available [8]. These data are included in Table 1 for comparison.…”

“…Our longstanding experience on phenyl-containing compounds shows that various Hartree3Fock and density functional theory (DFT) calculations followed by normal-coordinate analysis provide reliable mean vibration amplitudes. This is ³ HNPh 2 [4] ÃÄÄÄÄÄÄÄÄÄÄÂÄÄÄÄÄÄÄÄÄÂÄÄÄÄÄÄÄÄÄÄÄÂÄÄÄÄÄÄÄÄÄÄÄÄÂÄÄÄÄÄÄÄÄÄ´³ ³ experiment ³ HF/6-31G* ³ aug-cc-pDVZ ³ B3LYP/631G** ³ crystal ³ ³ ³ ³ [7] ³ [8] ³ [8] ³ [5] …”