2-(4-(Deciloxi) fenil)-1H-imidazo (4, 5-f) fenantrolina: estudo fotoquímico, acidocromismo e interação com cátions metálicos

Abstract

The study of fluorescent organic materials has been of great relevance due to their important applications in various areas. Within this context, the exploration of structures containing N-heterocyclic aromatic cores stands out, being particularly interesting for studies of acidochromism, which have significant implications in the field of sensors. This work presents a study of the photochemical and acidochromic properties of the compound 2-(4-(decyloxy) phenyl)-1H-imidazo[4,5-f]phenanthroline (10), which was synthesized with yields ranging from 50–65% through two multicomponent protocols. The photochemistry of compound 10 was studied in dichloromethane (DCM), tetrahydrofuran (THF), acetonitrile (ACN), dimethyl sulfoxide (DMSO), and methanol (MeOH). The maximum absorption wavelengths were observed between 307–317 nm, indicating the absence of pronounced solvatochromism. On the other hand, the fluorescence capacity of 10 varied considerably depending on the solvent, with higher emissions observed in THF (λEM = 430 nm) and DMSO (λEM = 450 nm), and quantum yield values of up to 31% in the former and 23% in the latter. In the other solvents, either emissions were low, or the material was characterized as non-emissive. The effect of water addition on the emissive behavior of compound 10 in polar solvents was evaluated. In MeOH, a slight enhancement in emission was observed at fw = 20%, likely due to the aggregation effect. In ACN, there was a reduction in emission starting from the initial water additions. In THF and DMSO, aqueous mixtures up to fw = 20% and fw = 10%, respectively, resulted in slight emission reductions, though the emissions remained intense and red-shifted (λEM = 450 nm for THF and λEM = 453 nm for DMSO). The acidochromism of 10 was evaluated in THF-H2O (fw = 20%) and DMSO-H2O (fw = 10%) mixtures using HCl and NaOH. In acidic medium, the aqueous THF mixture of 10 had its emission band at λEM = 450 nm completely suppressed, whereas the aqueous DMSO solution of 10 showed reduced emission at λEM = 453 nm, resulting in a new band at λEM = 389 nm. In basic medium, the THF-H2O system had its band at λEM = 467 nm completely suppressed. Conversely, a reduction in the band at λEM = 450 nm was observed, along with the appearance of another band at λEM = 525 nm. Acidochromism was also confirmed through 1H NMR analyses, which revealed significant spectral changes. Additionally, compound 10, when adsorbed on filter paper, demonstrated the ability to detect HCl and NH3 vapors. The interaction of compound 10 with 3,4,5- tridodecyloxybenzoic acid was evaluated via fluorescence (in DCM and DMSO solvents) and 1H NMR. The results are promising, as the interaction between the two compounds induced fluorescence enhancement, and changes were observed in the 1H NMR spectrum, indicating the formation of a molecular salt with good stability in aqueous DMSO solution. Compound 10 was also evaluated as a chemosensor for cations; however, it showed low selectivity toward metals.