The electronic states and vibronic absorption spectrum of berberine in aqueous solution

Abstract

The time‐dependent density functional theory was used to calculate the vibronic absorption spectrum of berberine (BER) in an aqueous solution. The best agreement with the experimental spectrum gives the O3LYP functional. Functionals with long‐range correction showed poor agreement with experiment. The molecular orbitals of BER involved in the electronic transition during light absorption in the visible spectral region have been obtained. The dipole moments and atomic charges of the ground and excited states of the BER molecule have been calculated. Maps of BER electron density and electrostatic potential have been drawn. A significant photoinduced electron transfer from the outer di‐oxygen five‐membered heterocycle to the center of the BER chromophore has been found. According to our calculations, vibronic coupling and Boltzmann distribution play a significant role in the absorption spectrum of BER.

The Vibronic Absorption Spectrum and Electronic States of Nile Red in Aqueous Solution

“…Therefore, further analysis of the electronic states of the NR molecule was carried out at the O3LYP/6‐31G(d,p) level theory. Note that this level of theory gave an excellent agreement of TD‐DFT calculations with experiment for berberine [47] . For NR molecule, it gives 450 MOs, of which 84 are occupied and 366 are unoccupied.…”

Berberrubine Phosphate: A Selective Fluorescent Probe for Quadruplex DNA

“…At the same time, the derivative 2 has only a very weak emission with maxima between 531 nm (1-PrOH) and 558 nm (MeOH). The fluorescence quantum yields are generally higher in less polar solvents (e.g., 1-PrOH: Φ fl = 0.04) as compared to polar protic solvents (aqueous buffer: Φ fl < 0.01), which was also found for the parent berberine (1a) and may be interpreted as a result of a charge transfer (CT) in the excited state [41,42]. Usually, a CT is closely accompanied by conformational changes that may cause a symmetry-forbidden transition between the CT-excited state and the ground state [57].…”

“…Moreover, these compounds exhibit a light-up effect upon binding to polyanionic analytes like DNA, which is, however, rather unselective for the parent berberine [28,33,39,40]. Since the fluorescence of berberine is dependent on the polarity of the environment [41,42], the light-up effect upon complexation to DNA is significantly influenced by the binding mode of the ligand. As a result, the introduction of substituents that lead to particular binding modes of berberine derivatives to different DNA forms should enable a more selective light-up effect of the bound ligand.…”

Selective, pH‐Dependent Colorimetric and Fluorimetric Detection of Quadruplex DNA with 4‐Dimethylamino(phenyl)‐Substituted Berberine Derivatives

“…For comparison, the parent berberine ( 1 a ) gives essentially no ICD signal in the absorption range of the ligand under similar conditions (LDR=0.8) [53] . To clarify this aspect, the relevant transition dipole moments of 3 a were determined exemplarily by TD‐DFT calculations [54] and shown to be aligned parallel or slightly tilted along the long molecular axis of the isoquinolinium unit (Table S4, Figure S11) like it was already determined for the parent berberine ( 1 a ) [45] . Within this model, the positive ICD bands are likely the result of a roughly perpendicular orientation of the long molecular axis to the longitudinal axis of the DNA base pairs, with the sterically more demanding isoquinolinium unit protruding into the groove (Figure 6).…”