Density Functional Theory Study of Vibrational Spectra of Fluorene

Abstract

Ab initio Hartree-Fock and density functional theory calculations using the 6-31G* basis set were carried out to study the molecular structure and vibrational spectrum of fluorene (FR). Two density functionals were employed: the (1) Becke-Lee-Yang-Parr (BLYP) functional and (2) the Becke 3-Lee-Yang-Parr (B3LYP) functional. Comparison of the calculated and experimental vibrational spectra reveals that the B3LYP calculations are quite accurate in predicting the vibrational frequencies and modes. We report the results of new assignments of the fundamental vibrational frequencies obtained on the basis of the calculations. The new assignments show a one-to-one correspondence between the observed and calculated fundamentals.

Understanding the Origin of the 535 nm Emission Band in Oxidized Poly(9,9‐dioctylfluorene): The Essential Role of Inter‐Chain/Inter‐Segment Interactions

“…The weaker band centered at 1612 cm ±1 in the fluorenone and pristine PFO samples, in particular, is assigned to an anti-symmetric stretching motion of a phenyl/phenylene ring. [73] The inset to Figure 2 shows the (open circles) for films that have been thermally oxidized in air. Oxidation was for a fixed period of 2 h but was undertaken at a range of different temperatures.…”

Three forms of squaric acid with pyrazine and pyridine derivatives: an experimental and theoretical study

“…Several authors have been reported that the HF methods under estimate some bond length and DFT/ B3LYP methods predicts bond lengths which are systematically too long, especially C-H bond lengths [32][33][34][35].…”

DFT Calculations on the Molecular Structure, Vibrational and Chemical Shift Assignments of 4-Allyl-2-(morpholin-4-ylmethyl)-5-(pyridin-4-yl)-2,4-Dihydro-3H-1,2,4-Triazole-3-Thione

“…We note that the experimental results were obtained in the solid phase and the theoretical calculations were obtained in the gaseous phase. For the optimized geometric parameters, the HF method is known to estimate some bond lengths well [33][34][35][36][37]. From our calculations, the B3LYP method gives good bond length correlations compared with the other methods ( Table 1).…”