Chemical and photochemical properties of chloroharmine derivatives in aqueous solutions

Abstract

Thermal and photochemical stability (Φ(R)), room temperature UV-vis absorption and fluorescence spectra, fluorescence quantum yields (Φ(F)) and lifetimes (τ(F)), quantum yields of hydrogen peroxide (Φ(H2O2)) and singlet oxygen (Φ(Δ)) production, and triplet lifetimes (τ(T)) have been obtained for the neutral and protonated forms of 6-chloroharmine, 8-chloroharmine and 6,8-dichloroharmine, in aqueous media. When it was possible, the effect of pH and oxygen concentration was evaluated. The nature of electronic transitions of protonated and neutral species of the three investigated chloroharmines was established using Time-Dependent Density Functional Theory (TD-DFT) calculations. The impact of all the foregoing observations on the biological role of the studied compounds is discussed.

N-Methyl-β-carboline alkaloids: structure-dependent photosensitizing properties and localization in subcellular domains

“…59 Although the E T value of 3b was not determined, it was demonstrated that the unsubstituted derivative 3a has the required energy (274.4 kJ mol −1 ). 60 Considering that methylation at position N(2) induces an only small change in the relative energy of the electronic states (i.e., bathochromic shift ∼5 nm), it is expected that 3b also has the required energy for triplet-triplet sensitization. This hypothesis should be further investigated.…”

Photophysical and Photochemical Properties of Naturally Occurring normelinonine F and Melinonine F Alkaloids and Structurally Related N(2)‐ and/or N(9)‐methyl‐β‐carboline Derivatives

“…On the contrary to what was observed for other related β C derivatives ( i.e . chloro‐harmine derivatives) , aqueous solutions (2 < pH < 11) of the investigated compounds remained stable after more than 60 days kept in cool and dark conditions (Figs. ).…”

“…β Cs are able to photosensitize 1 O 2 formation, even upon two‐photon excitation. The efficiency of ROS production depends on the chemical nature of the β C (). In this context, the study of the capability of nor melinonine F, melinonine F and related N‐methyl‐ β ‐carbolinium derivatives to photosensitize 1 O 2 becomes relevant.Quantum yields of singlet oxygen production ( Φ Δ ) were determined for all 2‐methyl‐ and 2,9‐dimethyl‐ β C derivatives in D 2 O under physiologically relevant pH conditions (Table ).…”

“…bCs are able to photosensitize 1 O 2 formation, even upon two-photon excitation. The efficiency of ROS production depends on the chemical nature of the bC (45,(47)(48)(49)51,78). In this context, the study of the capability of normelinonine F, melinonine F and related N-methyl-b-carbolinium derivatives to photosensitize 1 O 2 becomes relevant.…”

“…If further insight is to be gained, then fundamental aspects related to spectroscopic, chemical and photophysical properties of N-methyl-bCs need to be addressed. It is known that for bCs, the latter properties strongly depend on molecular structure, as well as on the nature of the environment (solvent) and pH (47)(48)(49)(50)(51)(52). To the best of our knowledge, only partial information regarding the spectroscopic characteristics of few quaternary bCs has been reported (46,(53)(54)(55).…”