Charge transfer in trans-combretastatins

Abstract

The non-toxic trans isomer of combretastatin-A4 can be photoisomerised in physiological conditions to cis-CA4, a potential anticancer drug. Absorption at wavelengths with high tissue penetration can be achieved by functionalization with substituents influencing the degree of charge-transfer (CT) of the S 1 state, in which the isomerisation occurs. We present a TDDFT study of the excited state properties of a series of substituted combretastatins with various degrees of CT character. Increasing the CT character determines a redshift of absorption and an intensity enhancement, but it disfavours the isomerisation. An appropriate choice of substituents is therefore required to achieve optimal isomerisation conditions.

Influence of charge transfer on the isomerisation of stilbene derivatives for application in cancer therapy

“…[ 48 ] functional and kernel, which is known to typically yield accurate charge transfer excitation energies in molecular systems [ 49 , 50 ] and from which we obtained good qualitative agreement with experimental UV/VIS absorption and fluorescence spectra in our previous studies [ 17 ].…”

“…As a further step in the search of tuneable photo-isomerisable drug candidates, we recently have conducted a theoretical study on trans combretastatins and stilbene derivatives of different intramolecular charge transfer extent [ 17 ]. Consistent with our experimental results, we were able to confirm that the absorption wavelength redshifts and the oscillator strength increase for molecules with larger charge-transfer character.…”

“…We recently studied the experimental and calculated fluorescence red shifts in the spectra of the charge-transfer compounds 3t and 4t for polar solvents [17]. With the aim of tailoring chargetransfer stilbene combretastatins for cancer therapy, it is important to assess the influence of the solvent polarity on the charge-transfer character of these molecules, particularly since the anticancer activity must occur in physiological conditions, i.e.…”

Reversible photoswitching of the DNA-binding properties of styrylquinolizinium derivatives through photochromic [2 + 2] cycloaddition and cycloreversion

“…Notably, the amino-substituted derivative 3a did not react under these conditions, as indicated by only marginal changes of the absorption spectrum ( Figure 5A). Presumably, the strong donor-acceptor system in 3a led to an intramolecular charge-transfer (ICT) state that did not lead to a subsequent photoreaction [77]. In contrast, the absorption bands of the substrates 3b-d decreased relatively fast upon irradiation, but the maxima did not disappear completely ( Figure 5B-D).…”

Application of a definitive screening design for the synthesis of a charge-transfer complex of sparfloxacin with tetracyanoethylene: spectroscopic, thermodynamic, kinetics, and DFT computational studies

“…CTCs have become the target of considerable studies due to their various biological and physical properties. [20][21][22][23] Based on our previous research and preliminary studies, 22,24 several factors, both numerical and categorical, are known to inuence the CT reaction, including the reaction time (RT), reaction temperature (temp), reagent volume (RV) and the diluting solvent (DS).…”