Shorena akhobadze

Perspectives of spiropyrans to design new photo controlled molecular equipment and biological materials, logic valves and sensors are not exhausted. Therefore, today, active investigation to design and study compounds with new properties are underway. The works appeared on photochromic compounds (spiro-compound and azo derivatives), which are combined with carbon nanoparticles and their use in technology is introduced due to their improved properties. A new azo- and spiro-group containing photochromic compound was synthesized according to the given scheme. Initially was synthesized starting compound - 5-nitro-2,3,3-trimethylindolenine by nitration of 2.3.3-trimethylindolenine (1). The quaternization of the compound 2 with CH3I was performed in a shallow ampoule at 80-82 ˚C in the acetonitrile area and quarternized salt 3 was isolated. With further reduction of compound 3 with LiAlH4 in tetrahydrofuran compound 4 was formed. By the treatment of obtained compound 4 with alkaline solutions forms compound 5, which reacts with 5-nitro salicylic aldehyde and gives a compound 6, the maximum absorption of which in the alcohol area is 660 nm (the maximum absorption of similar spiropyranes is 540 nm).  

New hybrid compounds, which molecule contain two photochromic fragments of different nature have been synthesized and investigated. The marriage of photocromic spiropyran and azobenzene can lead to the birth of novel hybrid materials SPAZ. Two typesof photochromic hybrid compounds were synthesized:by coupling azobenzene with (I) indoline spiropyran or (II) tetrahydroquinoline spiropyran with increased sensitivity to visible light. Bathochromic shift of the absorption bands, caused by elongation of the π -conjugation system, was observed in both types of samples. In sample II, in contrast to I, the thermodynamic equilibrium constant is greater than photochemical one and it is manifested in negative photochromism. In sample II, unlike I, due to the steric hindrance UV light does not affect the absorption band of the azobenzene moiety.

We have developed a novel UV radiation dosimeter that allows a real-time estimation of the dose of harmful ultraviolet UV-A, UV-B, and UV-C radiations emitted by the sun and artificial sources. When exposed to UV radiation, our UV Dosimeter visibly change color from the starting light-yellow to blue to dark violet. The color change correlates to levels of accumulated UV irradiation. The proposed UV dosimeter enables users to control a skin sunburn level caused by UV light from the sun and artificial sources, and visually monitor how much harmful radiation has been delivered to a surface, which helps them see if surfaces have received enough energy to kill bacteria, viruses, and spores – including Covid-19. The proposed UV dosimeter is environmentally safe, exhibits excellent photochromic properties, improved photosensitivity, high spatial resolution. It can be efficiently reused over 200 cycles without compromising its readability. 

The last few years have seen an explosion of interest in negative photochromic systems which are coloured in their ground state and reversibly photobleach upon exposure to electromagnetic radiation with a wavelength over 400 nm, for their applications in variable transmission devices, for the development of switches, logic gates, photoregulation of drug availability, to improve prospective photochromic recording media, and to design devices with new properties, in particular, clothing and camouflage coatings that change color depending on solar light intensity. The usefulness of these systems is only gradually coming with the advantages of low energy activation. The most interesting features in a photochromic species are the high stability and photosensitivitiy, fatigue resistance, and also numerous attempts have been made to achieve bathochromic shift long-wavelength absorption maximum of the colored form to radiation cheap diode laser (780 nm). In this regard, an appealing perspective is the possibility to tune or improve these properties. We have been able to increase the photosensitivity to visible light of tetrhydroquinolin spiropyran, and by extends π-conjugation system causes bathochromic shift of the absorption band of the coloured-zwitterionic form. The marriage of two photocromic molecule on the base of tetrhydroquinolin spiropyran and azobenzene can lead to the birth of novel hybrid material SPTHQAZ. By combining two photochromes: SP and electrophilic AZ, the length of the conjugation chain of a photoinduced form in one molecule increases resulting in the long-wave shift of the relevant absorption band.

The work proposes highly photosensitive and stable molecular switches created through the integration by the improved method of microcapsulating designed by us in the polymer of nemato-chiral liquid-crystal compositions doped with bistable, so called long-radical spiropyrans (II), which help economize the electrical power needed for the photoinduction occurring during the photochromic transformations. The work is based on an event of nanostructuring of merocyanine molecules into the spherical micelles, which are formed as a result of photoinduction with the ultraviolet (UV) light. Nanostructuring increases the effective photosensitivity of the composition.The merocyanine molecules formed photochemically are added by the molecules formed to restore the thermodynamic equilibrium i.e., from this moment, the process takes place at the expense of the internal energy and the coloration of the system continues without the consumption of the radial energy. This result was clearly seen, when recording the image on the polymer films.

New hybrid compounds, which molecule contain two photochromic fragments of different nature have been synthesized and investigated. The marriage of photocromic spiropyran and azobenzene can lead to the birth of novel hybrid materials SPAZ. Two types of photochromic hybrid compounds were synthesized: by coupling azobenzene with (I) indoline spiropyran or (II) tetrahydroquinoline spiropyran with increased sensitivity to visible light. Bathochromic shift of the absorption bands, caused by elongation of the π-conjugation system, was observed in both types of samples. In sample II, in contrast to I, the thermodynamic equilibrium constant is greater than photochemical one and it is manifested in negative photochromism. In sample II, unlike I, due to the steric hindrance UV light does not affect the absorption band of the azobenzene moiety.

The marriage of two photocromic molecules - spiropyran and azobenzene can lead to the birth of novel hybrid materials SPTHQAZ. The left fragment of hybrid molecule is indoline spiropyran modified by us with additional cyclic moiety which makes it rigid. Such compounds exhibits in polar solvents negative (inversion) photochromism. The colored MC form is more stable than the colorless SP form. In these cases, irradiation of visible light causes decoloration of MC to generate SP form. When SP form is placed in the dark, it returns to the colored MC form. Therefore, this thermally reversible photochromic system does not need the irradiation of UV light for its photochromism which may cause degradation of the compound. Studies have shown that such compounds are twice photosensitive to visible light than their indoline analogs. Due to the fact that thermodynamic equilibrium of the compounds with additional cyclic moiety in polar solutions is above photochemical - (KT>KPH) decoloration of system occurs with UV light too. The right side of the molecule - azobenzene extends π-conjugation system and causes bathochromic shift of the absorption band of the colored-zwitterionic form of SPTHQAZ. The molecule SPTHQAZ combines the beneficial characteristics and properties of both components. Consequently photochromic properties can be controlled by lasers with different frequencies.

Spiropyrans are one of the most popular class of photochromic bistable compounds that change their optical and structural properties in response to external inputs such as light, protons, metal ions, heat, mechanical stress, electric and magnetic fields, etc. The azobenzene derivatives attract particular interest due to their ability reversibly undergo to trans- cis-trans isomerization, which is accompanied with strong changes in some properties. We synthesized photobifunctional compounds SpAz based on spiropyran and azobenzen, which combine two photosensitive fragments in one molecule. The molecule of SpAz combines the spiropyran and azobenzene fragments in such a way that conjugation exists between the π– electronic systems of the indoline and azobenzene moieties. Practical application requires photochromic compounds to be incorporated by dissolution of the dye into a polymer. The spectra are shifted bathochromically with respect to model compounds due to conjugation chain.

Photochromic spiropyran doped nemato-chiralic liquidcrystallic compositions self-structuring as nanoparticles -micells, useful for targeting drug delivery founded by the authors is discussed. Nontoxic spiropyran's spherical micella is formed by amphiphilic molecules with zwitterionic head and nonpolar tail. Loaded by hidrophobic drug,

micella is moved by blood. Micella is unloaded shrank by UV irradiation, entered in the targeted place. The coat leaves the organism naturally. 

A quantum-chemical study of indoline spiropyrans during the transition from an uncolored state to a colored one at room temperature was carried out. To study the effect of substituents in the 3',3'-position of unsubstituted indoline spiropyrans, we performed quantum chemical calculations using the AM1 method. It can be seen from the calculation that in unsubstituted indoline spiropyrans in position 3',3', the replacement of methyl groups by phenyl ones causes an increase in the external bond angle, which in turn leads to a decrease in the internal angle of the five-membered ring and an increase in the C–O bond length of the pyran ring, and a decrease in the difference between heats of formation of closed and open forms from 4 Kcal/mol to 1 Kcal/mol. These data show that in unsubstituted indoline spiropyrans containing phenyl groups in the 3',3'-position, the transition from the uncolored state to the colored state occurs at room temperature. These calculations are in full agreement with the experimental data.

Spiropyrans, in comparison with other classes of organic photochromic materials, are distinguished by high photosensitivity, high two-photon absorption coefficient, etc. The relative ease of their structural modification makes it possible to control their photocharacteristics. One of the most common ways to control photochemical properties is to vary the substituents both in the indoline part and in the chromene fragment of the molecule. Photochromic properties depending on the electronic nature of the substituent in the chromene fragment were studied using spectroscopy and quantum chemical calculations. The same methods were used to study the effect of the indoline part of the molecule on the photochromic properties of spiropyrans. In the pyridine ring, the position of the electron-withdrawing nitrogen atom changed. The nitrogen atom has the greatest influence on the pyrene ring in the 7' position. Effective photosensitivity azaindoline spiropyrans are 1.5 higher than indoline analogues, and the thermodynamic equilibrium of the corresponding solutions is strongly shifted towards the uncolored form.

Doctoral Thesis Referee

Master Theses Supervisor

Doctoral Thesis Supervisor/Co-supervisor

Scientific editor of monographs in foreign languages

Scientific editor of a monograph in Georgian

Editor-in-Chief of a peer-reviewed or professional journal / proceedings

Review of a scientific professional journal / proceedings

Member of the editorial board of a peer-reviewed scientific or professional journal / proceedings

Participation in a project / grant funded by an international organization

Participation in a project / grant funded from the state budget

Patent authorship

Membership of the Georgian National Academy of Science or Georgian Academy of Agricultural Sciences

Membership of an international professional organization

Membership of the Conference Organizing / Program Committee

National Award / Sectoral Award, Order, Medal, etc.

Honorary title

Monograph

Handbook

Research articles in high impact factor and local Scientific Journals

Publication in Scientific Conference Proceedings Indexed in Web of Science and Scopus