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A SYSTEM WHICH CAN “TUNE” DRUGS
TO PERFECT THEM INTO MORE POTENCY

ABOUT THE PROJECT

Traditionally our research is focused to organic and hybrid systems used as dyes, indicators, sensing and NLO materials. Molecular spectroscopy (UV-Vis-NIR, IR/ Raman, fluorescence, NMR and mass spectrometry) and quantum chemistry are used as tools.In other words we are on the border between physical organic and organic analytical chemistry, depending on the viewpoint.

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SUPRAMOLECULAR CHEMISTRY

Two are the fields we work in:

Nonbonding interactions. We are interesting how the formation of aggregates influences the optical and tautomeric properties of dyes. The simplest case – monomer-dimer equilibrium – is usually considered in the frame of Kasha’s (exciton) theory. According to it two kinds of dimers are formed: sandwich (H-type, a/c in the picture below) and head-to-tail (J-type, b/d in the picture below). In the practice the usual problem is to find the spectrum of the dimer and to calculate the structural parameters (distance between the monomeric units R and angle between the monomer transition moments a). This can be solved by number of methods, one of them is our Fishing-Net-Algorithm. More complicated is to study how the dimer formation can influence the relative stability of the tautomers in a tautomeric mixture, which we do in the case of azodyes, Schiff bases and heterocyclic compounds.

 

Design of macrocyclic ligands. For couple of years we have tried to develop various aza-15-crown-5 based ligands. In most of the cases the azacrown was directly conjugated to the chromophore system, which leads to reduced electron density at the nitrogen atom (and as a result - low stability constants of the complexes obtained) and a blue shift of the absorption maximum under complexation (and as a result - limited applicability). Then we decided to exploit the tautomerism as signal converter using the fact that the tautomeric forms have different colors. The idea is shown below. The off-state is achieved through engagement of the tautomeric hydrogen using the hydrogen bonding ability of an antenna, which is connected to the tautomeric unit by a spacer. The engagement of this antenna by external stimuli (like addition of acid or metal ions) causes change in the tautomeric state, switching to the on-state. When the action of the stimuli is terminated the tautomeric equilibrium returns back to the off-state.

 

With this idea in mind we have developed a ligand, where an aza-15-crown-5 moiety is used as antenna and 1-phenylazo-4-naphthol as signaling unit. This compound gives red shift under complexation and the stability constants (alkali and alkaline-earth metal ions) are fairly high.

BASIC PAPERS:

Approach for increased information from the second-derivative spectra in UV-Vis absorption spectroscopy. L.Antonov & S.Stoyanov; Applied Spectroscopy, 47, 1712 (1993)

Step by step filter - an approach for noise reduction in the derivative UV-Vis spectra. L.Antonov & S.Stoyanov; Analytica Chimica Acta, 324, 77 (1996)

Drawbacks of the present standards for processing absorption spectra recorded linearly as a function of wavelength. L.Antonov; Trends in Analytical Chemistry, 16, 536 (1997)

Fourth derivative spectroscopy – a critical view. L.Antonov; Analytica Chimica Acta, 349, 295 (1997)

Step-by-step filter based program for calculations of highly informative derivatives curves. V.Petrov, L.Antonov, H.Ehara & N.Harada; Computers & Chemistry, 24, 561 (2000)

 

SOFTWARE

STEP BY STEP FILTER

Smart approach to increase the information, which can be extracted by using derivative spectroscopy

FISHING-NET ALGORITHM

Program for resolution of overlapping bands and quantitative spectral analysis of undefined (with unknown individual spectra of the components) mixtures

MARCUS FITTING

Program for resolution of charge transfer absorption/ emission bands