Indolino-Oxazolidine Acido- and Photochromic System Investigated by NMR and Density Functional Theory Calculations

Abstract

Three addressable indolino-oxazolidine units connected through an isomerizable double bond to a substituted thiophene represent a smart example of a multiaddressable system whose reversible responses could be selectively activated on demand. Experimental and theoretical approaches to push forward the understanding of the system mechanism and set pathways to design optimized compounds for suitable application are here presented. NMR and UV-visible spectroscopies are used for structural and kinetic studies, while density functional theory (DFT) calculations pave the way to highlight energetic and electronic processes that are involved. Substitution and solvent effects toward the reactivity of the compounds are experimentally studied and combined with theoretical calculations. The most efficient and selective stimuli to travel between the four possible states resulting from the ring-opening of indolino[2,1- b]oxazolidine (generally referenced as BOX) derivatives and the trans-cis isomerization of the ethylenic junction are elucidated.

Molecular Switches and Motors Powered by Orthogonal Stimuli

“…Other BOX hybrids that have been investigated [ 89 ] exhibit complications in their photoswitching processes similar to those found in 20 and 21 . Despite imperfect stimulus orthogonality and complicated electronic communication between the components, BOX‐based multistate molecular systems display a remarkable commutation ability that may be useful in the design of multifunctional molecular systems.…”

Rewritable acidochromic papers based on oxazolidine for anticounterfeiting and photosensing of polarity and pH of aqueous media

“…On the other hand, increasing of pH to alkaline conditions (in the range of 8–14) was led to increase of fluorescence emission intensity especially for pH in the range of 10–14, and maximum emission was calculated for the pH of 12, 13, and 14. This phenomenon can be attributed to the deprotonation of phenolate hydroxyl groups in alkaline solutions, which induced higher density of negative charges to OX 1 -OH structure and correspondingly increase of electron resonance in its conjugated structure 31 , 32 , 38 , 43 .The photography of colorimetric and fluorometric properties of OX 1 -OH at pH of 1–14 are presented in Fig. 8 C. The observations indicated different colors, fluorescence emissions, and also intensities for the OX 1 -OH solutions, which have potential applications for colorimetric and fluorometric photosensing of pH in aqueous solutions.…”

Development of highly sensitive metal-ion chemosensor and key-lock anticounterfeiting technology based on oxazolidine

“…In addition, a wide range of oxazolidine derivatives could be synthesized by using various aromatic aldehyde compounds substituted with different electron donor and electron withdrawing groups. Oxazolidine derivatives display various stimuli-chromism, such as hydrochromism, solvatochromism, acidochromism, and photochromism, depending on the functional groups on their chemical structure 45 , 47 – 50 . Oxazolidine displays various coloration and fluorescence emission in different media, depending on interactions of different functional groups on the indolenine ring or benzaldehyde structure with the surrounding media 45 , 51 – 55 .…”

“…Oxazolidine derivatives display various stimuli-chromism, such as hydrochromism, solvatochromism, acidochromism, and photochromism, depending on the functional groups on their chemical structure 45 , 47 – 50 . Oxazolidine displays various coloration and fluorescence emission in different media, depending on interactions of different functional groups on the indolenine ring or benzaldehyde structure with the surrounding media 45 , 51 – 55 . The color changes act as an alarm in response to stimulus that is detectable by naked eye, which is a significant requirement for development of highly selective colorimetric and fluorometric sensors without the need to high-cost materials or special equipment.…”