: The unpolarized absorption and circular dichroism spectra of the fundamental vibrational transitions of the chiral molecule, 4-methyl-2-oxetanone, are calculated ab initio. Harmonic force fields are obtained using Density Functional Theory (DFT), MP2, and SCF methodologies and a 5S4P2D/3S2P (TZ2P) basis set. DFT calculations use the Local Spin Density Approximation (LSDA), BLYP, and Becke3LYP (B3LYP) density functionals. Mid-IR spectra predicted using LSDA, BLYP, and B3LYP force fields are of significantly different quality, the B3LYP force field yielding spectra in clearly superior, and overall excellent, agreement with experiment. The MP2 force field yields spectra in slightly worse agreement with experiment than the B3LYP force field. The SCF force field yields spectra in poor agreement with experiment.The basis set dependence of B3LYP force fields is also explored: the 6-31G* and TZ2P basis sets give very similar results while the 3-21G basis set yields spectra in substantially worse agreements with experiment. jg

Ab initio calculation of vibrational absorption and circular dichroism spectra using density functional force fields

Red emitting triphenylamine based rhodamine analogous with enhanced Stokes shift and viscosity sensitive emission

Retained fluorescence of aggregation-caused quenched Rhodamine grafted in the hierarchical mesopores of silica MCM-41 at solid-state

Spectroscopic and DFT approach for structure property relationship of red emitting rhodamine analogues: A study of linear and nonlinear optical properties

The absorption wavelengths of the two forms of Rhodamine B, cation and zwitterion, were investigated by Time-Dependent Density Functional Theory (TD-DFT) in combination with polarizable continuum model. The redshift in absorption spectrum of cation relative to zwitterion is attributed to strong inductive effect of carboxyphenyl group and weak electrostatic repulsion between xanthene ring and carboxyphenyl group. The absorption wavelengths of cation and zwitterion decrease linearly with increase of solvent polarity in normal alcohols since in high polar solvents electrostatic repulsion between xanthene ring and carboxyphenyl group increases and affects xanthene π conjugation system. The absorption wavelengths in water and formamide show a deviation from linear relationship because large dielectric constant hinders electrostatic repulsion between carboxyphenyl group and xanthene π system. The hydrogen bonds affect absorption wavelengths because hydrogen bonds could affect conjugation between amino N atoms and xanthene π system or electrostatic repulsion between carboxyphenyl group and xanthene ring. These results indicate electrostatic repulsion between carboxyphenyl group and xanthene ring plays a big role in determining absorption spectrum of Rhodamine B.

Qiying Xia

Papers

Theoretical investigation of the effect of the solvent, hydrogen bond and amino group on the isomerization of Rhodamines