STRUKTURNE I SOLVATOHROMNE KARAKTERISTIKE 5-(ARILAZO)-3-CIJANO-6-HIDROKSI-4-METIL-1-SUPSTITUISANIH-2-PIRIDONA: EKSPERIMENTALNA I KVANTNO-HEMIJSKA PROUČAVANJA

Abstract

U okviru disertacije, sintetisane su tri serije arilazo piridonskih boja: 5-(arilazo)-3-cijano-1-etil-6-hidroksi-4-metil-2-piridoni, 5-(arilazo)-3-cijano-6-hidroksi-4-metil-2-piridoni i 5-(4-arilazo)-3-cijano-6-hidroksi-1-hidroksietil-4-metil-2-piridoni. Predmet istraživanja je potpuna strukturna i solvatohromna karakterizacija sintetisanih jedinjenja kombinacijom eksperimentalnih tehnika i kvantno-hemijskih proračuna. Eksperimentalne metode podrazumevaju rendgensku strukturnu analizu i FT-IR, NMR i UV-Vis spektoskopiju. Energija, geometrijske strukture i vibracioni talasni brojevi 5-(metoksi supstituisanih fenilazo)-3-cijano-1-etil-6-hidroksi-4-metil-2-piridona dobijeni su kvantno-hemijskim proračunom, korišćenjem B3LYP, M06 i M06-2X modela, a stabilnost ovih molekula, kao posledica hiperkonjugativnih interakcija i delokalizacije naelektrisanja, izučavana je pomoću NBO analize. Optimizovane geometrije 5-(arilazo)-3-cijano-1-etil-6-hidroksi-4-metil-2-piridona u vakuumu dobijene su pomoću B3LYP/6-311++G(d,p) metode. UV-Vis apsorpcione energije za ista jedinjenja dobijene su pomoću vremenski zavisne DFT metode (TD-DFT). Simulacija je izvedena pomoću četiri modela: B3LYP, CAM-B3LYP, M06-2X i PBE0. UV-Vis spektralna svojstva jedinjenja i tautomerija detaljno su ispitani u dva rastvarača i to u etanolu i N,N-dimetilformamidu. Analizirani su UV-Vis apsorpcioni spektri u različitim rastvaračima i ispitivan je njihov uticaj na položaj apsorpcionih maksimuma. Takođe, ispitivan je uticaj prirode i položaja supstituenata u fenilnom jezgru i različitih supstituenata u položaju 1 piridonovog jezgra na apsorpcione spektre. Za kvantitativnu ocenu uticaja rastvarača na apsorpcione maksimume svih jedinjenja, primenjeni su principi LSER analize, i to Kamlet-Taft-ov i Catalán-ov model. Kvantitativna analiza uticaja supstituenata na apsorpcione maksimume 5-(4-arilazo)-3-cijano-6-hidroksi-1-hidroksietil-4-metil-2-piridona urađena je pomoću LFER modela i to primenom Hammett-ove jednačine. Pored toga, LFER model je primenjen i u ispitivanju uticaja elektronskih efekata supstituenata na 1H and 13C NMR pomeraje,primenom jednostavne i proširene Hammett-ove jednačine, kao i Swain-Lupton-ove jednačine. Elektrohemijska svojstva šest boja i njihovih 1:1 inkluzionih kompleksa sa (2-hidroksipropil)-β-ciklodekstrinom ispitivani su cikličnom voltametrijom i voltametrijom sa pravougaonim impulsima u 0,1 M rastvoru NaOH na elektrodi od zlata. Ispitivan je uticaj supstituenata koji se nalaze u položaju 1 piridonovog jezgra, kao i supstituenata na fenilnom jezgru azo boja. Njihov uticaj interpretiran je na osnovu promena u voltamogramima i predložen je mehanizam elektroksidacije ispitivanih arilazo piridonskih boja. Elektrokatalitičko obezbojavanje arilazo piridonskih boja ispitivano je u prisustvu natrijum-hlorida u razblaženom rastvoru natrijum-hidroksida korišćenjem DSA Ti/PtOx elektrode. Proces obezbojavanja je ispitivan variranjem uslova: koncentracije natrijum-hidroksida u opsegu od 40 mg dm–3 do 4 g dm–3, koncentracije natrijum-hlorida od 15 do 40 g dm–3, brzine mešanja od 150 do 500 ob min–1, jačine struje od 100 do 250 mA i koncentracije boje od 5 do 20 mg dm–3. Na osnovu dobijenih rezultata dobijeni su optimalni uslovi elektrolize. Pored toga, ispitivan je uticaj supstituenata na brzinu elektrohemijskog obezbojavanja arilazo piridonskih boja.

In this thesis, three series of arylazo pyridone dyes 5-(substituted phenylazo)-3-cyano-1-ethyl-6-hydroxy-4-methyl-2-pyridones, 5-(substituted phenylazo)-3-cyano-6-hydroxy-4-methyl-2-pyridone and 5-(4-substituted phenylazo)-3-cyano-6-hydroxy-1-hydroxyethyl-4-methyl-2-pyridone have been synthesized. The purpose of this research is a combined experimental and theoretical characterization of the synthesised dyes. Experimental methods include X-ray single-crystal analysis, as well as FT-IR, NMR and UV-Vis spectroscopy. Quantum chemical calculations of energies, geometrical structure and vibrational wavenumbers of 5-(methoxy substituted phenylazo)-3-cyano-1-ethyl-6-hydroxy-4-methyl-2-pyridones have been performed using B3LYP, M06 i M06-2X models. Stability of these molecules arising from hyperconjugative interactions and charge delocalization has been analyzed using natural bond orbital analysis. Optimized geometries in vacuum for 5-(substituted phenylazo)-3-cyano-1-ethyl-6-hydroxy-4-methyl-2-pyridones have been obtained using B3LYP/6-311++G(d,p) model. UV-Vis apsorbtion energies have been calculated using TD-DFT using B3LYP, CAM-B3LYP, M06-2X and PBE0 models. UV-Vis spectral properties and tautomerism have been throughly investigated in ethanol and N,N-dimethylformamide. The effects of the nature and the position of the substituents in phenyl ring on UV-Vis spectra in different solvents have been examined, as well as the impact of different substituents in the position 1 of pyridone ring. Furthermore, solvent effects on absorption spectra have been analysed. For quantitative evaluation of the solvent effects on the UV-Vis absorption maxima, the principles of the linear solvation energy relationships are used, i.e. models proposed by Kamlet–Taft and Catalán. Linear free energy relationships are applied to the UV-Vis absorption spectra and correlation of absorption frequencies with Hammett substituent constants are performed. Furthermore, the influence of the electronic nature of the substituents on 1H and 13C NMR shifts is investigated by simple and extended Hammett equations, as well as by Swain-Lupton equation. The electrochemical behavior of six arylazo pyridone dyes and their 1:1 inclusion complexes with (2-hydroxypropyl)-β-cyclodextrin have been studied using cyclic and square wave voltammetry in 0.1 M NaOH on a gold electrode. Substituent effects have been interpreted by changes in voltammograms. The electrooxidation mechanism of the investigated arylazo pyridone dyes have been also proposed. Electrocatalytic decolorization of the arylazo pyridone dyes has been investigated in the presence of sodium chloride using DSA Ti/PtOx electrode in the diluted sodium hydroxide. Electrochemical decolorization has been investigated for the different sodium hydroxide concentration in the range from 40 mg dm–3 to 4 g dm–3, sodium chloride concentration in the range from 15 to 40 g dm–3, agitation speed in the range from 150 to 500 rpm, currents in the range of 100 to 250 mA, and dye concentration from 5 to 20 mg dm–3. The optimum electrolysis conditions have been suggested. The effects of substituents on the reaction rate have also been studied.