TAUTOMERIJA AZO PIRIDONSKIH BOJA: KRISTALNA STRUKTURA I SOLVATOHROMNA SVOJSTVA

Abstract

Azo boje ce poslednjih decenija primenjuju u različitim oblastima zbog izuzetnih svojstava. Njihova primena je u velikoj meri povezana sa fenomenom azo- hidrazon tautomerije. Naime, određivanje strukturnog oblika azo boja je značajno kako sa teorijskog stanovišta, tako i iz tehničke perspektive jer azo i hidrazon tautomeri poseduju različita fizička i hemijska svojstva. U ovom radu, sintetisana je azo boja (5-(2-hlorfenilazo)-3-cijano-1-etil-6- hidrokci-4-metil-2-piridon) i okarakterisana elementalnom analizom, NMR i ATR-FTIR spektroskopijom i rendgenskom strukturnom analizom (slika). Solvatohromna svojstva boje ispitana su UV-Vis spektroskopijom u različitim rastvaračima kako bi se utvrdio dominantan strukturni oblik boje. Kristalna struktura je pokazala da boja kristališe u obliku hidrzon tautomera. Stabilizacija kristalnog pakovanja ostvarena je posredstvom različitih nekovalentnih interakcija kao što cu C–H···O/N, π-π, slobodan elektronski par-π i Cl···O. Kristalografski podaci: C15H13ClN4O2, Mr = 316,74, trikliničan sistem, prostorna grupa P 1̅ , a = 7,9490(16), b = 8,9645(18), c = 11,697(2) Å, α = 72,92(3), β = 83,59(3), γ = 66,77(3) °, V = 732,1(3) Å3, Z = 2, F(000) = 328, ρx = 1,437 g cm–3, µ(MoKα) = 0,274 mm–1, R1 = 0,0447 i S = 1,018 za utačnjenih 219 parametara i 1941 primećenih reflekcija sa I ≥ 2σ(I).

Tremendous progress in the application of azo dyes in various fields has been achieved over the past few decades due to their intriguing properties. Their application is closely related to the phenomenon of azo-hydrazone tautomerism. Determination of the structural isomer of the azo dyes is not only important from the theoretical standpoint but also from the technical perspective since azo and hydrazone tautomers have distinctive physical and chemical properties. In this work, azo pyridone dye (5-(2-chlorophenylazo)-3-cyano-1-ethyl-6-hydroxy-4- methyl-2-pyridone) has been synthesized and characterized by elemental analysis, NMR and ATR-FTIR spectroscopy and single-crystal X-ray analysis (Figure). Solvatochromic properties of the dye have been investigated using UV-Vis spectroscopy in solvents of different polarity in order to determine the dominant form in solvents. The crystal structure of the dye shows that the dye crystallizes in the hydrazone form. The stabilization of the crystal packing is achieved by weak non- covalent interactions: C–H···O/N, π-π, lone pair-π and Cl O. Crystal data: C15H13ClN4O2, Mr = 316.74, triclinic, space group P1̅, a = 7.9490(16), b = 8.9645(18), c = 11.697(2) Å, a = 72.92(3), β = 83.59(3), γ = 66.77(3) °, V = 732.1(3) Å3, Z = 2, F(000) = 328, ρx = 1.437 g cm–3, µ(MoKa) = 0.274 mm–1, R1 = 0.0447 and S = 1.018 for 219 refined parameters and 1941 observed reflections with I ≥ 2σ(I).